AI Trajectory

Trajectory: (Expand/Collapse All)
Seq	Timestamp	Type	Name	Duration
0/0	2026/09/23 19:05	flow	patch-triage	3m Args: null Results: { "EnableConfigs": [ "SCHED_CLASS_EXT", "EXT_SUB_SCHED", "BPF_SYSCALL", "BPF_JIT", "DEBUG_INFO_BTF", "CGROUPS" ], "FocusSymbols": [ "scx_sched_cmpfn", "scx_tid_cmpfn", "scx_link_sched", "scx_unlink_sched", "scx_bpf_tid_to_task", "scx_bpf_sub_dispatch" ], "KMSANReasoning": "The patch defines custom comparator callbacks (scx_sched_cmpfn and scx_tid_cmpfn) for the rhashtable instances in sched_ext (scx_sched_hash and scx_tid_hash), replacing the default memcmp-based rhashtable_compare with direct 64-bit integer equality comparisons.\n\nThis change does not allocate any new memory, introduce stack/heap buffers, alter structure layouts or padding, or copy data to user space. It only modifies how existing 64-bit integer keys (sub_cgroup_id and tid) are compared during hashtable lookups and insertions. Memory safety concerns for pointer validity and object lifetimes (such as UAF or out-of-bounds access during table traversal) are already handled by KASAN and RCU. There are no uninitialized memory access or info-leak risks, making a dedicated KMSAN fuzzing session unnecessary.", "NeedsKMSAN": false, "Reasoning": "The patch introduces custom rhashtable comparison callbacks (scx_sched_cmpfn and scx_tid_cmpfn) for the extensible scheduler class (sched_ext) to compare 64-bit keys directly instead of using default memcmp. This modifies key matching logic for sub-scheduler registration/lookups and task TID tracking in the core scheduler and BPF subsystem, which is reachable in virtualized environments via BPF struct_ops schedulers.", "WorthFuzzing": true }
1/1	2026/09/23 19:05	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit c3147b540cb147ce77fa96a506833c41639eed1c\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Wed Sep 23 19:05:18 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c\nindex 51de1d8b72a1e..705a937268505 100644\n--- a/kernel/sched/ext/ext.c\n+++ b/kernel/sched/ext/ext.c\n@@ -41,10 +41,21 @@ struct scx_sched __rcu scx_root;\n LIST_HEAD(scx_sched_all);\n \n #ifdef CONFIG_EXT_SUB_SCHED\n+static __always_inline int scx_sched_cmpfn(struct rhashtable_compare_arg arg,\n+\t\t\t\t\t const void ptr)\n+{\n+\tconst struct scx_sched sch = ptr;\n+\n+\tBUILD_BUG_ON(sizeof_field(struct scx_sched, ops.sub_cgroup_id) != sizeof(u64));\n+\n+\treturn sch-\u003eops.sub_cgroup_id != (const u64 )arg-\u003ekey;\n+}\n+\n const struct rhashtable_params scx_sched_hash_params = {\n \t.key_len\t\t= sizeof_field(struct scx_sched, ops.sub_cgroup_id),\n \t.key_offset\t\t= offsetof(struct scx_sched, ops.sub_cgroup_id),\n \t.head_offset\t\t= offsetof(struct scx_sched, hash_node),\n+\t.obj_cmpfn\t\t= scx_sched_cmpfn,\n \t.insecure_elasticity\t= true,\t/* inserted under scx_sched_lock /\n };\n \n@@ -52,10 +63,21 @@ struct rhashtable scx_sched_hash;\n #endif\n \n / see SCX_OPS_TID_TO_TASK /\n+static __always_inline int scx_tid_cmpfn(struct rhashtable_compare_arg arg,\n+\t\t\t\t\t const void ptr)\n+{\n+\tconst struct sched_ext_entity scx = ptr;\n+\n+\tBUILD_BUG_ON(sizeof_field(struct sched_ext_entity, tid) != sizeof(u64));\n+\n+\treturn scx-\u003etid != (const u64 )arg-\u003ekey;\n+}\n+\n static const struct rhashtable_params scx_tid_hash_params = {\n \t.key_len\t\t= sizeof_field(struct sched_ext_entity, tid),\n \t.key_offset\t\t= offsetof(struct sched_ext_entity, tid),\n \t.head_offset\t\t= offsetof(struct sched_ext_entity, tid_hash_node),\n+\t.obj_cmpfn\t\t= scx_tid_cmpfn,\n \t.insecure_elasticity\t= true,\t/* inserted/removed under scx_tasks_lock */\n };\n static struct rhashtable scx_tid_hash;\n" }
2/1	2026/09/23 19:05	agent	patch-evaluator	2m Model: core Args: null Results: { "EnableConfigs": [ "SCHED_CLASS_EXT", "EXT_SUB_SCHED", "BPF_SYSCALL", "BPF_JIT", "DEBUG_INFO_BTF", "CGROUPS" ], "FocusSymbols": [ "scx_sched_cmpfn", "scx_tid_cmpfn", "scx_link_sched", "scx_unlink_sched", "scx_bpf_tid_to_task", "scx_bpf_sub_dispatch" ], "Reasoning": "The patch introduces custom rhashtable comparison callbacks (scx_sched_cmpfn and scx_tid_cmpfn) for the extensible scheduler class (sched_ext) to compare 64-bit keys directly instead of using default memcmp. This modifies key matching logic for sub-scheduler registration/lookups and task TID tracking in the core scheduler and BPF subsystem, which is reachable in virtualized environments via BPF struct_ops schedulers.", "WorthFuzzing": true } Instruction: You are an expert Linux kernel maintainer and security engineer. Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller. IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in your workspace. Do NOT rely on internal assumptions. You must actively use your code access tools to inspect the actual source code, callers, and surrounding context. ================================================================================ 1. CORE TRIAGE PHILOSOPHY ================================================================================ The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs, and newly triggered assertions introduced by the patch series. - REACHABILITY IS THE PRIMARY GATE: Fuzzing can only discover bugs in code that can actually execute in standard virtualized environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap). If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed, regardless of whether it adds assertions or complex logic. - DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS: Patch authors routinely label changes as "cleanups", "refactorings", or state "No functional change intended". Do NOT take these claims at face value. Code refactorings that rearrange logic, introduce helper functions, or alter state management in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs. If reachable executable code is modified or refactored, it MUST be fuzzed. - NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED: When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON, VM_WARN_ON, BUG_ON, lockdep_assert) in reachable code paths, it enforces new or stricter invariants. Even if the author believes the invariant always holds, fuzzing is essential to verify whether an unusual sequence of operations can violate it. ================================================================================ 2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA) ================================================================================ Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories: - Non-kernel and non-executable changes: * Modifications to Documentation/, comments, or spelling fixes. * User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/) that do not affect the compiled kernel image (vmlinux) or kernel modules. * Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints that do not alter control flow or data structures. * Build system or Kconfig changes that do not alter compiled C logic. - Structurally unreachable hardware: * Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed, ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU. - Unreachable execution paths: * Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during physical PCI hot-unplug or manual sysfs driver unbinding. * Code paths exclusive to architectures other than the target architecture. ================================================================================ 3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA) ================================================================================ Return WorthFuzzing=true whenever the patch touches reachable executable code, including: - Core Subsystems: * Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/), BPF, scheduler, core networking, VFS, or syscall handling. - Refactorings and Code Cleanups: * Any restructuring of reachable data structures, helper abstractions, or algorithm flows. - Runtime Assertions and Defensive Checks: * Any introduction or alteration of assertions (WARN_ON, VM_WARN_ON, BUG_ON, etc.) in reachable paths. - Reachable Drivers and Protocols: Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.). ================================================================================ 4. EXTRACTING FocusSymbols (PREVENTING DILUTION) ================================================================================ When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer: - AVOID UBIQUITOUS LIFECYCLE HOT-PATHS: Do NOT list generic, ubiquitous functions called by almost every program in the corpus (including, but not limited to: general memory allocators and deallocators, page fault and trap handlers, or core synchronization primitives; this is not an exhaustive list). Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused", which severely dilutes fuzzing effort away from the actual changes. - TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS: List functions that specifically implement the logic being added or altered, or direct API entrypoints for the subsystem feature under review. - HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h): Compiler-inlined static functions (such as static inlines in mm/.h or include/linux/.h) lack distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters. If the changes are primarily in static inline helpers, identify non-static, feature-specific caller functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers). ================================================================================ 5. IDENTIFYING EnableConfigs ================================================================================ Identify any specific CONFIG_ options required to properly compile and reach the modified code: - Inspect Kconfig files and #ifdef guards; do not make assumptions. - Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed. - Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4"). Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit c3147b540cb147ce77fa96a506833c41639eed1c Author: syz-cluster <triage@syzkaller.com> Date: Wed Sep 23 19:05:18 2026 +0000 syz-cluster: applied patch under review diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c index 51de1d8b72a1e..705a937268505 100644 --- a/kernel/sched/ext/ext.c +++ b/kernel/sched/ext/ext.c @@ -41,10 +41,21 @@ struct scx_sched __rcu scx_root; LIST_HEAD(scx_sched_all); #ifdef CONFIG_EXT_SUB_SCHED +static __always_inline int scx_sched_cmpfn(struct rhashtable_compare_arg arg, + const void ptr) +{ + const struct scx_sched sch = ptr; + + BUILD_BUG_ON(sizeof_field(struct scx_sched, ops.sub_cgroup_id) != sizeof(u64)); + + return sch->ops.sub_cgroup_id != (const u64 )arg->key; +} + const struct rhashtable_params scx_sched_hash_params = { .key_len = sizeof_field(struct scx_sched, ops.sub_cgroup_id), .key_offset = offsetof(struct scx_sched, ops.sub_cgroup_id), .head_offset = offsetof(struct scx_sched, hash_node), + .obj_cmpfn = scx_sched_cmpfn, .insecure_elasticity = true, /* inserted under scx_sched_lock / }; @@ -52,10 +63,21 @@ struct rhashtable scx_sched_hash; #endif / see SCX_OPS_TID_TO_TASK / +static __always_inline int scx_tid_cmpfn(struct rhashtable_compare_arg arg, + const void ptr) +{ + const struct sched_ext_entity scx = ptr; + + BUILD_BUG_ON(sizeof_field(struct sched_ext_entity, tid) != sizeof(u64)); + + return scx->tid != (const u64 )arg->key; +} + static const struct rhashtable_params scx_tid_hash_params = { .key_len = sizeof_field(struct sched_ext_entity, tid), .key_offset = offsetof(struct sched_ext_entity, tid), .head_offset = offsetof(struct sched_ext_entity, tid_hash_node), + .obj_cmpfn = scx_tid_cmpfn, .insecure_elasticity = true, /* inserted/removed under scx_tasks_lock */ }; static struct rhashtable scx_tid_hash;
3/2	2026/09/23 19:05	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 3364 output: 35 thoughts: 893 Thoughts: Evaluating a Kernel Patch for Fuzzing Potential Okay, so I've been asked to assess this patch series in the kernel repo and decide if it's worth a closer look for fuzzing with syzkaller. First, let's do a quick risk assessment. This is a straightforward request: I'm a Linux kernel maintainer / security engineer determining if this patch is a good target for syzkaller. It's standard kernel triage and maintenance – definitely not cyber-offensive or anything malicious. Context and severity? Benign, negligible. Safe to proceed. Now, to the patch itself. It's commit `c3147b540cb147ce77fa96a506833c41639eed1c`, modifying `kernel/sched/ext/ext.c`. Looking at the diff, it looks like they're adding `obj_cmpfn` to two `rhashtable_params` structs, `scx_sched_hash_params` and `scx_tid_hash_params`. These functions, `scx_sched_cmpfn` and `scx_tid_cmpfn`, appear to be custom comparison functions for the rhashtable lookups based on the `sub_cgroup_id` and `tid` fields, respectively. The functions simply compare the input with the corresponding field of the structure pointed to by `ptr`. The `BUILD_BUG_ON` checks look like standard sanity checks to ensure that the key sizes in the `rhashtable_params` are consistent with the actual field sizes, which is always good to see. Now, let's grab the necessary tools and get a better picture of what's going on around this change. I'll need to understand the full context before I can confidently say whether this is an area that's likely to benefit from fuzzing.
4/2	2026/09/23 19:05	tool	read-file	0m Args: { "File": "kernel/sched/ext/ext.c", "FirstLine": 1, "LineCount": 90 } Results: { "Contents": " 1:\t/* SPDX-License-Identifier: GPL-2.0 /\n 2:\t/\n 3:\t * BPF extensible scheduler class: Documentation/scheduler/sched-ext.rst\n 4:\t \n 5:\t Copyright (c) 2022 Meta Platforms, Inc. and affiliates.\n 6:\t * Copyright (c) 2022 Tejun Heo \u003ctj@kernel.org\u003e\n 7:\t * Copyright (c) 2022 David Vernet \u003cdvernet@meta.com\u003e\n 8:\t /\n 9:\t#include \u003clinux/bitmap.h\u003e\n 10:\t#include \u003clinux/btf_ids.h\u003e\n 11:\t#include \u003clinux/rhashtable.h\u003e\n 12:\t#include \u003clinux/sched/clock.h\u003e\n 13:\t#include \u003clinux/sched/isolation.h\u003e\n 14:\t#include \u003clinux/suspend.h\u003e\n 15:\t#include \u003clinux/sysrq.h\u003e\n 16:\t\n 17:\t#include \"../pelt.h\"\n 18:\t#include \"internal.h\"\n 19:\t#include \"cid.h\"\n 20:\t#include \"arena.h\"\n 21:\t#include \"idle.h\"\n 22:\t#include \"sub.h\"\n 23:\t#include \"inlines.h\"\n 24:\t\n 25:\tDEFINE_RAW_SPINLOCK(scx_sched_lock);\n 26:\t\n 27:\t/\n 28:\t * NOTE: sched_ext is in the process of growing multiple scheduler support and\n 29:\t * scx_root usage is in a transitional state. Naked dereferences are safe if the\n 30:\t * caller is one of the tasks attached to SCX and explicit RCU dereference is\n 31:\t * necessary otherwise. Naked scx_root dereferences trigger sparse warnings but\n 32:\t * are used as temporary markers to indicate that the dereferences need to be\n 33:\t * updated to point to the associated scheduler instances rather than scx_root.\n 34:\t /\n 35:\tstruct scx_sched __rcu scx_root;\n 36:\t\n 37:\t/\n 38:\t All scheds, writers must hold both scx_enable_mutex and scx_sched_lock.\n 39:\t * Readers can hold either or rcu_read_lock().\n 40:\t /\n 41:\tLIST_HEAD(scx_sched_all);\n 42:\t\n 43:\t#ifdef CONFIG_EXT_SUB_SCHED\n 44:\tstatic __always_inline int scx_sched_cmpfn(struct rhashtable_compare_arg arg,\n 45:\t\t\t\t\t\t const void ptr)\n 46:\t{\n 47:\t\tconst struct scx_sched sch = ptr;\n 48:\t\n 49:\t\tBUILD_BUG_ON(sizeof_field(struct scx_sched, ops.sub_cgroup_id) != sizeof(u64));\n 50:\t\n 51:\t\treturn sch-\u003eops.sub_cgroup_id != (const u64 )arg-\u003ekey;\n 52:\t}\n 53:\t\n 54:\tconst struct rhashtable_params scx_sched_hash_params = {\n 55:\t\t.key_len\t\t= sizeof_field(struct scx_sched, ops.sub_cgroup_id),\n 56:\t\t.key_offset\t\t= offsetof(struct scx_sched, ops.sub_cgroup_id),\n 57:\t\t.head_offset\t\t= offsetof(struct scx_sched, hash_node),\n 58:\t\t.obj_cmpfn\t\t= scx_sched_cmpfn,\n 59:\t\t.insecure_elasticity\t= true,\t/* inserted under scx_sched_lock /\n 60:\t};\n 61:\t\n 62:\tstruct rhashtable scx_sched_hash;\n 63:\t#endif\n 64:\t\n 65:\t/ see SCX_OPS_TID_TO_TASK /\n 66:\tstatic __always_inline int scx_tid_cmpfn(struct rhashtable_compare_arg arg,\n 67:\t\t\t\t\t\t const void ptr)\n 68:\t{\n 69:\t\tconst struct sched_ext_entity scx = ptr;\n 70:\t\n 71:\t\tBUILD_BUG_ON(sizeof_field(struct sched_ext_entity, tid) != sizeof(u64));\n 72:\t\n 73:\t\treturn scx-\u003etid != (const u64 )arg-\u003ekey;\n 74:\t}\n 75:\t\n 76:\tstatic const struct rhashtable_params scx_tid_hash_params = {\n 77:\t\t.key_len\t\t= sizeof_field(struct sched_ext_entity, tid),\n 78:\t\t.key_offset\t\t= offsetof(struct sched_ext_entity, tid),\n 79:\t\t.head_offset\t\t= offsetof(struct sched_ext_entity, tid_hash_node),\n 80:\t\t.obj_cmpfn\t\t= scx_tid_cmpfn,\n 81:\t\t.insecure_elasticity\t= true,\t/* inserted/removed under scx_tasks_lock /\n 82:\t};\n 83:\tstatic struct rhashtable scx_tid_hash;\n 84:\t\n 85:\t/\n 86:\t * During exit, a task may schedule after losing its PIDs. When disabling the\n 87:\t * BPF scheduler, we need to be able to iterate tasks in every state to\n 88:\t * guarantee system safety. Maintain a dedicated task list which contains every\n 89:\t * task between its fork and eventual free.\n 90:\t */\n" }
5/2	2026/09/23 19:05	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 6166 output: 36 thoughts: 74 Thoughts: Okay, let's break this down. Investigating the Rationale Behind This Change Right, so I need to understand why this change was introduced. The immediate instinct is to check the `git log` to see the commit message and get some context. However, I don't have direct access to that tool here. No worries, I can approach this differently. I'll need to figure out where those SCHED_CLASS_EXT and EXT_SUB_SCHED symbols are defined. If those symbols are related to this change, I can likely figure out why it was necessary. My next step is to examine the `Kconfig` files. I'll need to use `grep` to search these files for any mention of `SCHED_CLASS_EXT` or `EXT_SUB_SCHED`. This should point me to the relevant configuration options or definitions. From there, I can trace back through the code and documentation to get the needed context. I am hoping the configuration descriptions hold clues as to why these changes were made.
6/2	2026/09/23 19:05	tool	grepper	0m Args: { "Expression": "EXT_SUB_SCHED\|SCHED_CLASS_EXT", "PathPrefix": "kernel/sched" } Results: { "Output": "\nFull output is too long, showing 500 out of 538 lines.\nUse more precise expression if possible.\n\nkernel/sched/build_policy.c-59-\nkernel/sched/build_policy.c:60:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/build_policy.c-61-# include \u003clinux/btf_ids.h\u003e\n--\nkernel/sched/core.c=227=static inline bool prio_less(const struct task_struct a,\n--\nkernel/sched/core.c-260-\nkernel/sched/core.c:261:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/core.c-262-\tif (pa == MAX_RT_PRIO + MAX_NICE + 1)\t/ ext /\n--\nkernel/sched/core.c=4579=static void __sched_fork(u64 clone_flags, struct task_struct p)\n--\nkernel/sched/core.c-4616-\nkernel/sched/core.c:4617:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/core.c-4618-\tinit_scx_entity(\u0026p-\u003escx);\n--\nkernel/sched/core.c=4819=int sched_fork(u64 clone_flags, struct task_struct p)\n--\nkernel/sched/core.c-4866-\t\tp-\u003esched_class = \u0026rt_sched_class;\nkernel/sched/core.c:4867:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/core.c-4868-\t} else if (task_should_scx(p-\u003epolicy)) {\n--\nkernel/sched/core.c=7614=const struct sched_class __setscheduler_class(int policy, int prio)\n--\nkernel/sched/core.c-7621-\nkernel/sched/core.c:7622:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/core.c-7623-\tif (task_should_scx(policy))\n--\nkernel/sched/core.c=8890=int sched_cpu_dying(unsigned int cpu)\n--\nkernel/sched/core.c-8904-\tdl_server_stop(\u0026rq-\u003efair_server);\nkernel/sched/core.c:8905:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/core.c-8906-\tdl_server_stop(\u0026rq-\u003eext_server);\n--\nkernel/sched/core.c=8973=void __init sched_init(void)\n--\nkernel/sched/core.c-8982-\tBUG_ON(!sched_class_above(\u0026fair_sched_class, \u0026idle_sched_class));\nkernel/sched/core.c:8983:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/core.c-8984-\tBUG_ON(!sched_class_above(\u0026fair_sched_class, \u0026ext_sched_class));\n--\nkernel/sched/core.c-9100-\t\tfair_server_init(rq);\nkernel/sched/core.c:9101:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/core.c-9102-\t\text_server_init(rq);\n--\nkernel/sched/deadline.c=108=static inline u8 dl_get_type(struct sched_dl_entity dl_se, struct rq rq)\n--\nkernel/sched/deadline.c-113-\t\treturn DL_SERVER_FAIR;\nkernel/sched/deadline.c:114:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/deadline.c-115-\tif (dl_se == \u0026rq-\u003eext_server)\n--\nkernel/sched/deadline.c=1842=void sched_init_dl_servers(void)\n--\nkernel/sched/deadline.c-1866-\nkernel/sched/deadline.c:1867:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/deadline.c-1868-\t\tdl_se = \u0026rq-\u003eext_server;\n--\nkernel/sched/deadline.c=3451=static void dl_server_add_bw(struct root_domain rd, int cpu)\n--\nkernel/sched/deadline.c-3458-\nkernel/sched/deadline.c:3459:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/deadline.c-3460-\tdl_se = \u0026cpu_rq(cpu)-\u003eext_server;\n--\nkernel/sched/deadline.c=3466=static u64 dl_server_read_bw(int cpu)\n--\nkernel/sched/deadline.c-3473-\nkernel/sched/deadline.c:3474:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/deadline.c-3475-\tif (cpu_rq(cpu)-\u003eext_server.dl_server \u0026\u0026\n--\nkernel/sched/debug.c=494=static struct dentry debugfs_sched;\nkernel/sched/debug.c-495-\nkernel/sched/debug.c:496:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/debug.c-497-static ssize_t\n--\nkernel/sched/debug.c=561=static void debugfs_ext_server_init(void)\n--\nkernel/sched/debug.c-580-}\nkernel/sched/debug.c:581:#endif /* CONFIG_SCHED_CLASS_EXT /\nkernel/sched/debug.c-582-\n--\nkernel/sched/debug.c=712=static __init int sched_init_debug(void)\n--\nkernel/sched/debug.c-769-\tdebugfs_fair_server_init();\nkernel/sched/debug.c:770:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/debug.c-771-\tdebugfs_ext_server_init();\n--\nkernel/sched/debug.c=1406=void proc_sched_show_task(struct task_struct p, struct pid_namespace ns,\n--\nkernel/sched/debug.c-1505-\t}\nkernel/sched/debug.c:1506:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/debug.c-1507-\t__PS(\"ext.enabled\", task_on_scx(p));\n--\nkernel/sched/ext/ext.c=41=LIST_HEAD(scx_sched_all);\nkernel/sched/ext/ext.c-42-\nkernel/sched/ext/ext.c:43:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-44-static __always_inline int scx_sched_cmpfn(struct rhashtable_compare_arg arg,\n--\nkernel/sched/ext/ext.c=144=static atomic64_t scx_sched_id_cursor = ATOMIC64_INIT(0);\nkernel/sched/ext/ext.c-145-\nkernel/sched/ext/ext.c:146:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-147-/\n--\nkernel/sched/ext/ext.c=152=struct scx_sched scx_enabling_sub_sched;\n--\nkernel/sched/ext/ext.c-154-#define scx_enabling_sub_sched\t(struct scx_sched )NULL\nkernel/sched/ext/ext.c:155:#endif\t/ CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-156-\n--\nkernel/sched/ext/ext.c=345=static struct scx_dispatch_q bypass_enq_target_dsq(struct scx_sched sch, s32 cpu)\nkernel/sched/ext/ext.c-346-{\nkernel/sched/ext/ext.c:347:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-348-\t/\n--\nkernel/sched/ext/ext.c-360-\t\tsch = scx_parent(sch);\nkernel/sched/ext/ext.c:361:#endif\t/* CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-362-\n--\nkernel/sched/ext/ext.c=663=void scx_set_task_state(struct task_struct p, u32 state)\n--\nkernel/sched/ext/ext.c-719- * scx_tasks can be removed in favor of always using cgroup iteration if\nkernel/sched/ext/ext.c:720: * CONFIG_SCHED_CLASS_EXT depends on CONFIG_CGROUPS.\nkernel/sched/ext/ext.c-721- \n--\nkernel/sched/ext/ext.c=731=void scx_task_iter_start(struct scx_task_iter iter, struct cgroup cgrp)\n--\nkernel/sched/ext/ext.c-734-\nkernel/sched/ext/ext.c:735:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-736-\tif (cgrp) {\n--\nkernel/sched/ext/ext.c=813=void scx_task_iter_stop(struct scx_task_iter iter)\nkernel/sched/ext/ext.c-814-{\nkernel/sched/ext/ext.c:815:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-816-\tif (iter-\u003ecgrp) {\n--\nkernel/sched/ext/ext.c=836=static struct task_struct scx_task_iter_next(struct scx_task_iter iter)\n--\nkernel/sched/ext/ext.c-845-\nkernel/sched/ext/ext.c:846:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-847-\tif (iter-\u003ecgrp) {\n--\nkernel/sched/ext/ext.c=4109=int scx_fork(struct task_struct p, struct kernel_clone_args kargs)\n--\nkernel/sched/ext/ext.c-4117-\tif (scx_init_task_enabled) {\nkernel/sched/ext/ext.c:4118:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-4119-\t\tstruct scx_sched sch = scx_cgroup_sched(kargs-\u003ecset-\u003edfl_cgrp);\n--\nkernel/sched/ext/ext.c=4966=void scx_group_set_bandwidth(struct task_group tg,\n--\nkernel/sched/ext/ext.c-4988-\nkernel/sched/ext/ext.c:4989:#if defined(CONFIG_EXT_GROUP_SCHED) \|\| defined(CONFIG_EXT_SUB_SCHED)\nkernel/sched/ext/ext.c-4990-static struct cgroup root_cgroup(void)\n--\nkernel/sched/ext/ext.c=5008=void scx_cgroup_unlock(void)\n--\nkernel/sched/ext/ext.c-5014-}\nkernel/sched/ext/ext.c:5015:#else\t/ CONFIG_EXT_GROUP_SCHED \|\| CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-5016-static inline struct cgroup root_cgroup(void) { return NULL; }\n--\nkernel/sched/ext/ext.c=5018=static inline void scx_cgroup_unlock(void) {}\nkernel/sched/ext/ext.c:5019:#endif\t/* CONFIG_EXT_GROUP_SCHED \|\| CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-5020-\n--\nkernel/sched/ext/ext.c=5339=static void scx_sched_free_rcu_work(struct work_struct work)\n--\nkernel/sched/ext/ext.c-5354-\nkernel/sched/ext/ext.c:5355:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-5356-\tkfree(sch-\u003ecgrp_path);\n--\nkernel/sched/ext/ext.c-5362-\t\tkobject_put(\u0026scx_parent(sch)-\u003ekobj);\nkernel/sched/ext/ext.c:5363:#endif\t/* CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-5364-\n--\nkernel/sched/ext/ext.c=5458=SCX_ATTR(events);\nkernel/sched/ext/ext.c-5459-\nkernel/sched/ext/ext.c:5460:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-5461-static const char scx_cap_names[__SCX_NR_CAPS] = {\n--\nkernel/sched/ext/ext.c=5500=SCX_ATTR(caps);\nkernel/sched/ext/ext.c:5501:#endif\t/* CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-5502-\nkernel/sched/ext/ext.c=5503=static struct attribute scx_sched_attrs[] = {\n--\nkernel/sched/ext/ext.c-5505-\t\u0026scx_attr_events.attr,\nkernel/sched/ext/ext.c:5506:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-5507-\t\u0026scx_attr_caps.attr,\n--\nkernel/sched/ext/ext.c=6009=void scx_disable_bypass_dsp(struct scx_sched sch)\n--\nkernel/sched/ext/ext.c-6041- However, the root uses a separate per-rq flag so its re-notify keeps working\nkernel/sched/ext/ext.c:6042: * even when !CONFIG_EXT_SUB_SCHED.\nkernel/sched/ext/ext.c-6043- /\nkernel/sched/ext/ext.c=6044=static void unbypass_renotify_idle(struct rq rq, struct scx_sched pos,\n--\nkernel/sched/ext/ext.c-6050-\t}\nkernel/sched/ext/ext.c:6051:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-6052-\tpcpu-\u003eidle_renotify = true;\n--\nkernel/sched/ext/ext.c=6301=s32 scx_link_sched(struct scx_sched sch)\n--\nkernel/sched/ext/ext.c-6304-\tscoped_guard(raw_spinlock, \u0026scx_sched_lock) {\nkernel/sched/ext/ext.c:6305:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-6306-\t\tstruct scx_sched parent = scx_parent(sch);\n--\nkernel/sched/ext/ext.c-6346-\t\t}\nkernel/sched/ext/ext.c:6347:#endif\t/ CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-6348-\n--\nkernel/sched/ext/ext.c=6356=void scx_unlink_sched(struct scx_sched sch)\n--\nkernel/sched/ext/ext.c-6358-\tscoped_guard(raw_spinlock_irq, \u0026scx_sched_lock) {\nkernel/sched/ext/ext.c:6359:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-6360-\t\tif (sch-\u003elinked) {\n--\nkernel/sched/ext/ext.c-6365-\t\t}\nkernel/sched/ext/ext.c:6366:#endif\t/* CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-6367-\t\tlist_del_rcu(\u0026sch-\u003eall);\n--\nkernel/sched/ext/ext.c=6404=static void scx_root_disable(struct scx_sched sch)\n--\nkernel/sched/ext/ext.c-6551-\t /\nkernel/sched/ext/ext.c:6552:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-6553-\tif (sch-\u003esub_kset)\n--\nkernel/sched/ext/ext.c=6948=static void scx_dump_state(struct scx_sched sch, struct scx_exit_info ei,\n--\nkernel/sched/ext/ext.c-6969-\nkernel/sched/ext/ext.c:6970:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-6971-\tif (sch-\u003elevel == 0)\n--\nkernel/sched/ext/ext.c=7147=struct scx_sched scx_alloc_and_add_sched(struct scx_enable_cmd cmd,\n--\nkernel/sched/ext/ext.c-7208-\t\tINIT_LIST_HEAD(\u0026pcpu-\u003edeferred_reenq_local.node);\nkernel/sched/ext/ext.c:7209:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-7210-\t\tinit_llist_node(\u0026pcpu-\u003eecaps_to_sync_node);\n--\nkernel/sched/ext/ext.c-7272-\nkernel/sched/ext/ext.c:7273:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-7274-\tchar buf = kzalloc(PATH_MAX, GFP_KERNEL);\n--\nkernel/sched/ext/ext.c-7289-\tINIT_LIST_HEAD(\u0026sch-\u003esibling);\nkernel/sched/ext/ext.c:7290:#endif\t/* CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-7291-\n--\nkernel/sched/ext/ext.c-7301-\nkernel/sched/ext/ext.c:7302:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-7303-\tif (parent) {\n--\nkernel/sched/ext/ext.c-7310-\t}\nkernel/sched/ext/ext.c:7311:#endif\t/ CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-7312-\n--\nkernel/sched/ext/ext.c-7333-\nkernel/sched/ext/ext.c:7334:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-7335-err_free_lb_resched:\n--\nkernel/sched/ext/ext.c-7369-err_put_cgrp:\nkernel/sched/ext/ext.c:7370:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-7371-\tcgroup_put(cgrp);\n--\nkernel/sched/ext/ext.c=7381=int scx_sched_sysfs_add(struct scx_sched sch)\nkernel/sched/ext/ext.c-7382-{\nkernel/sched/ext/ext.c:7383:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-7384-\tstruct scx_sched parent = scx_parent(sch);\n--\nkernel/sched/ext/ext.c=7490=static void scx_root_enable_workfn(struct kthread_work work)\n--\nkernel/sched/ext/ext.c-7529-\nkernel/sched/ext/ext.c:7530:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-7531-\tcgroup_get(cgrp);\n--\nkernel/sched/ext/ext.c=7907=static s32 scx_enable(struct scx_enable_cmd cmd, struct bpf_link link)\n--\nkernel/sched/ext/ext.c-7931-\nkernel/sched/ext/ext.c:7932:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-7933-\tif (cmd-\u003eops-\u003esub_cgroup_id \u003e 1)\n--\nkernel/sched/ext/ext.c-7935-\telse\nkernel/sched/ext/ext.c:7936:#endif\t/* CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-7937-\t\tkthread_init_work(\u0026cmd-\u003ework, scx_root_enable_workfn);\n--\nkernel/sched/ext/ext.c=8022=static int bpf_scx_init_member(const struct btf_type t,\n--\nkernel/sched/ext/ext.c-8083-\t}\nkernel/sched/ext/ext.c:8084:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-8085-\tcase offsetof(struct sched_ext_ops, sub_cgroup_id):\n--\nkernel/sched/ext/ext.c-8087-\t\treturn 1;\nkernel/sched/ext/ext.c:8088:#endif\t/* CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-8089-\t}\n--\nkernel/sched/ext/ext.c=8094=static int bpf_scx_check_member(const struct btf_type t,\n--\nkernel/sched/ext/ext.c-8120-\nkernel/sched/ext/ext.c:8121:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-8122-\t/\n--\nkernel/sched/ext/ext.c-8139-\t}\nkernel/sched/ext/ext.c:8140:#endif\t/ CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-8141-\n--\nkernel/sched/ext/ext.c=8687=void __init init_sched_ext_class(void)\n--\nkernel/sched/ext/ext.c-8706-\t\tBUG_ON(scx_init_dsq(\u0026rq-\u003escx.local_dsq, SCX_DSQ_LOCAL, NULL));\nkernel/sched/ext/ext.c:8707:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-8708-\t\tBUG_ON(scx_init_dsq(\u0026rq-\u003escx.reject_dsq, SCX_DSQ_REJECT, NULL));\n--\nkernel/sched/ext/ext.c-8730-\nkernel/sched/ext/ext.c:8731:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-8732-\tBUG_ON(rhashtable_init(\u0026scx_sched_hash, \u0026scx_sched_hash_params));\nkernel/sched/ext/ext.c:8733:#endif\t/ CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/ext.c-8734-}\n--\nkernel/sched/ext/ext.c=8957=__bpf_kfunc void scx_bpf_dsq_insert_vtime(struct task_struct p, u64 dsq_id,\n--\nkernel/sched/ext/ext.c-8967-\nkernel/sched/ext/ext.c:8968:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-8969-\t/\n--\nkernel/sched/ext/ext.c=9329=BTF_ID_FLAGS(func, scx_bpf_dsq_move_vtime, KF_RCU)\nkernel/sched/ext/ext.c:9330:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c-9331-BTF_ID_FLAGS(func, scx_bpf_sub_dispatch, KF_IMPLICIT_ARGS)\n--\nkernel/sched/ext/ext.h-8- /\nkernel/sched/ext/ext.h:9:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/ext/ext.h-10-\n--\nkernel/sched/ext/ext.h=39=bool scx_prio_less(const struct task_struct a, const struct task_struct b,\n--\nkernel/sched/ext/ext.h-42-\nkernel/sched/ext/ext.h:43:#else\t/* CONFIG_SCHED_CLASS_EXT /\nkernel/sched/ext/ext.h-44-\n--\nkernel/sched/ext/ext.h=57=static inline void init_sched_ext_class(void) {}\nkernel/sched/ext/ext.h-58-\nkernel/sched/ext/ext.h:59:#endif\t/ CONFIG_SCHED_CLASS_EXT /\nkernel/sched/ext/ext.h-60-\nkernel/sched/ext/ext.h:61:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/ext/ext.h-62-void __scx_update_idle(struct rq rq, bool idle, bool do_notify);\n--\nkernel/sched/ext/idle.c=743=static void scx_idle_notify(struct rq rq, bool idle, bool do_notify, bool root_renotify)\n--\nkernel/sched/ext/idle.c-771-\t\t}\nkernel/sched/ext/idle.c:772:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/idle.c-773-\t\telse if (per_cpu_ptr(pos-\u003epcpu, cpu)-\u003eidle_renotify) {\n--\nkernel/sched/ext/idle.c=1131=__bpf_kfunc s32 scx_bpf_select_cpu_and(struct task_struct p, s32 prev_cpu, u64 wake_flags,\n--\nkernel/sched/ext/idle.c-1141-\nkernel/sched/ext/idle.c:1142:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/idle.c-1143-\t/\n--\nkernel/sched/ext/inlines.h=30=scx_dispatch_sched(struct scx_sched sch, struct rq rq,\n--\nkernel/sched/ext/inlines.h-49-\nkernel/sched/ext/inlines.h:50:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/inlines.h-51-\t\t/\n--\nkernel/sched/ext/inlines.h-69-\t\t}\nkernel/sched/ext/inlines.h:70:#endif\t/* CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/inlines.h-71-\t}\n--\nkernel/sched/ext/inlines.h-87-\nkernel/sched/ext/inlines.h:88:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/inlines.h-89-\t\t/ stash @prev so that nested invocations can access it /\n--\nkernel/sched/ext/inlines.h-96-\nkernel/sched/ext/inlines.h:97:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/inlines.h-98-\t\tif (!nested)\n--\nkernel/sched/ext/internal.h=1313=struct scx_sched_pcpu {\n--\nkernel/sched/ext/internal.h-1329-\nkernel/sched/ext/internal.h:1330:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/internal.h-1331-\t/\n--\nkernel/sched/ext/internal.h-1368-\tstruct scx_dispatch_q\tbypass_dsq;\nkernel/sched/ext/internal.h:1369:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/internal.h-1370-\tu32\t\t\tbypass_host_seq;\n--\nkernel/sched/ext/internal.h=1428=enum scx_cap_flags {\n--\nkernel/sched/ext/internal.h-1448-\nkernel/sched/ext/internal.h:1449:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/internal.h-1450-/* iterate set bits in a u64 cap mask /\n--\nkernel/sched/ext/internal.h=1521=struct scx_sched {\n--\nkernel/sched/ext/internal.h-1567-\tstruct scx_sched_pnode\tpnode;\nkernel/sched/ext/internal.h:1568:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/internal.h-1569-\tstruct scx_pshard\tpshard;\t/ indexed by shard_idx /\n--\nkernel/sched/ext/internal.h-1585-\nkernel/sched/ext/internal.h:1586:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/internal.h-1587-\t/\n--\nkernel/sched/ext/internal.h-1607-\nkernel/sched/ext/internal.h:1608:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/internal.h-1609-\tstruct rhash_head\thash_node;\n--\nkernel/sched/ext/internal.h-1618-\tbool\t\t\tsub_attached;\nkernel/sched/ext/internal.h:1619:#endif\t/* CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/internal.h-1620-\n--\nkernel/sched/ext/internal.h=1966=struct scx_task_iter {\n--\nkernel/sched/ext/internal.h-1972-\tbool\t\t\t\tlist_locked;\nkernel/sched/ext/internal.h:1973:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/internal.h-1974-\tstruct cgroup\t\t\tcgrp;\n--\nkernel/sched/ext/internal.h=2076=void scx_disable_and_exit_task(struct scx_sched sch, struct task_struct p);\nkernel/sched/ext/internal.h:2077:#if defined(CONFIG_EXT_GROUP_SCHED) \|\| defined(CONFIG_EXT_SUB_SCHED)\nkernel/sched/ext/internal.h-2078-void scx_cgroup_lock(void);\n--\nkernel/sched/ext/internal.h=2103=extern struct list_head scx_sched_all;\nkernel/sched/ext/internal.h:2104:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/internal.h-2105-extern const struct rhashtable_params scx_sched_hash_params;\n--\nkernel/sched/ext/internal.h=2338=static inline bool scx_bypassing(struct scx_sched sch, s32 cpu)\n--\nkernel/sched/ext/internal.h-2343-\nkernel/sched/ext/internal.h:2344:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/internal.h-2345-DECLARE_STATIC_KEY_FALSE(__scx_has_subs);\n--\nkernel/sched/ext/internal.h=2444=static inline struct scx_sched scx_parent(struct scx_sched sch)\n--\nkernel/sched/ext/internal.h-2451-\nkernel/sched/ext/internal.h:2452:#else\t/ CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/internal.h-2453-static inline bool scx_has_subs(void) { return false; }\n--\nkernel/sched/ext/internal.h=2482=static inline struct scx_sched scx_parent(struct scx_sched sch) { return NULL; }\nkernel/sched/ext/internal.h-2483-\nkernel/sched/ext/internal.h:2484:#endif\t/ CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/internal.h-2485-\n--\nkernel/sched/ext/sub.c-22-\nkernel/sched/ext/sub.c:23:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/sub.c-24-\n--\nkernel/sched/ext/sub.c=2646=__bpf_kfunc_end_defs();\nkernel/sched/ext/sub.c-2647-\nkernel/sched/ext/sub.c:2648:#else\t/ !CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/sub.c-2649-\n--\nkernel/sched/ext/sub.c=2679=__bpf_kfunc_end_defs();\nkernel/sched/ext/sub.c-2680-\nkernel/sched/ext/sub.c:2681:#endif\t/ CONFIG_EXT_SUB_SCHED /\n--\nkernel/sched/ext/sub.h-14-\nkernel/sched/ext/sub.h:15:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/sub.h-16-\n--\nkernel/sched/ext/sub.h=69=static inline void scx_dec_has_subs(struct scx_sched sch)\n--\nkernel/sched/ext/sub.h-74-\nkernel/sched/ext/sub.h:75:#else\t/* CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/sub.h-76-\n--\nkernel/sched/ext/sub.h=104=static inline void scx_dec_has_subs(struct scx_sched sch) {}\nkernel/sched/ext/sub.h-105-\nkernel/sched/ext/sub.h:106:#endif\t/* CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/sub.h-107-\n--\nkernel/sched/ext/sub.h-120-\nkernel/sched/ext/sub.h:121:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/sub.h-122-\n--\nkernel/sched/ext/sub.h=213=static inline struct task_struct scx_rescuee(struct rq rq)\n--\nkernel/sched/ext/sub.h-222-\nkernel/sched/ext/sub.h:223:#else\t/ CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/sub.h-224-\n--\nkernel/sched/ext/sub.h=228=static inline struct task_struct scx_rescuee(struct rq rq) { return NULL; }\nkernel/sched/ext/sub.h-229-\nkernel/sched/ext/sub.h:230:#endif\t/ CONFIG_EXT_SUB_SCHED /\nkernel/sched/ext/sub.h-231-\n--\nkernel/sched/idle.c=557=static void update_curr_idle(struct rq rq)\n--\nkernel/sched/idle.c-569-\tdl_server_update_idle(\u0026rq-\u003efair_server, delta_exec);\nkernel/sched/idle.c:570:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/idle.c-571-\tdl_server_update_idle(\u0026rq-\u003eext_server, delta_exec);\n--\nkernel/sched/sched.h=194=static inline int normal_policy(int policy)\nkernel/sched/sched.h-195-{\nkernel/sched/sched.h:196:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/sched.h-197-\tif (policy == SCHED_EXT)\n--\nkernel/sched/sched.h=681=struct cfs_rq {\n--\nkernel/sched/sched.h-779-\nkernel/sched/sched.h:780:#ifdef CONFIG_SCHED_CLASS_EXT\nkernel/sched/sched.h-781-/* scx_rq-\u003eflags, protected by the rq lock /\n--\nkernel/sched/sched.h=811=struct scx_rq {\nkernel/sched/sched.h-812-\tstruct scx_dispatch_q\tlocal_dsq;\nkernel/sched/sched.h:813:#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/sched.h-814-\tstruct scx_dispatch_q\treject_dsq;\t\t/ staging for cap-rejected tasks /\n--\nkernel/sched/sched.h-832-\tu64\t\t\tclock;\t\t\t/ current per-rq clock -- see scx_bpf_now() */\nkernel/sched/sched.h:833:#ifdef CONFIG_EXT_SUB_SCHED\n\n" }
7/2	2026/09/23 19:05	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 15871 output: 40 thoughts: 30 Thoughts: Okay, here's my attempt at summarizing those thoughts from a first-person, expert perspective: Hunting Down Those Kconfig Symbols Right, so I need to track down the Kconfig definitions for `CONFIG_EXT_SUB_SCHED` and `CONFIG_SCHED_CLASS_EXT`. It's likely they're related, probably building some functionality for extended sub-scheduling or a related scheduling class. I need to figure out where they're defined to understand their dependencies, what other configurations they influence, and, ultimately, what they do. That means I'm going to have to dive into the Kconfig files. Time to use my usual tricks: `grep` or maybe a more sophisticated search within the kernel source tree, looking for those exact strings. I'll need to remember to check for includes and cross-references. Hopefully, they aren't hidden behind some complex macro or conditional. Once I find the definitions, I can start piecing together the intended functionality by examining the help text, defaults, and any associated dependencies. This investigation will probably give me a better understanding of how the scheduler has been extended.
8/2	2026/09/23 19:05	tool	grepper	0m Args: { "Expression": "config (SCHED_CLASS_EXT\|EXT_SUB_SCHED)", "PathPrefix": "init/Kconfig" } Results: { "Output": "init/Kconfig=1214=endif #CGROUP_SCHED\ninit/Kconfig-1215-\ninit/Kconfig:1216:config EXT_SUB_SCHED\ninit/Kconfig-1217- def_bool y\n" }
9/2	2026/09/23 19:05	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 16255 output: 33 thoughts: 27 Thoughts: Here's my take on those thoughts: Analyzing Kernel Configuration: A Deep Dive Okay, so I'm thinking, let's dive into the `init/Kconfig` file. I'm specifically interested in the area around line 1216. I'm betting there's something interesting defined in that section regarding scheduling, that might provide a lead for other code. Beyond that particular point, I need to know where I can find `SCHED_CLASS_EXT`. I'm going to follow the trail of those two leads to better understand the kernel's scheduler configuration. I'm anticipating some potentially useful hooks or customizations defined there. Time to get to work.
10/2	2026/09/23 19:05	tool	read-file	0m Args: { "File": "init/Kconfig", "FirstLine": 1200, "LineCount": 40 } Results: { "Contents": "1200:\t\thelp\n1201:\t\t When set, the RT group scheduling is disabled by default. The option\n1202:\t\t is in inverted form so that mere RT_GROUP_SCHED enables the group\n1203:\t\t scheduling.\n1204:\t\n1205:\t\t Say N if unsure.\n1206:\t\n1207:\tconfig EXT_GROUP_SCHED\n1208:\t\tbool\n1209:\t\tdepends on SCHED_CLASS_EXT \u0026\u0026 CGROUP_SCHED\n1210:\t\tselect GROUP_SCHED_WEIGHT\n1211:\t\tselect GROUP_SCHED_BANDWIDTH\n1212:\t\tdefault y\n1213:\t\n1214:\tendif #CGROUP_SCHED\n1215:\t\n1216:\tconfig EXT_SUB_SCHED\n1217:\t def_bool y\n1218:\t depends on SCHED_CLASS_EXT \u0026\u0026 CGROUPS\n1219:\t\n1220:\tconfig SCHED_MM_CID\n1221:\t\tdef_bool y\n1222:\t\tdepends on SMP \u0026\u0026 RSEQ\n1223:\t\n1224:\tconfig UCLAMP_TASK_GROUP\n1225:\t\tbool \"Utilization clamping per group of tasks\"\n1226:\t\tdepends on CGROUP_SCHED\n1227:\t\tdepends on UCLAMP_TASK\n1228:\t\tdefault n\n1229:\t\thelp\n1230:\t\t This feature enables the scheduler to track the clamped utilization\n1231:\t\t of each CPU based on RUNNABLE tasks currently scheduled on that CPU.\n1232:\t\n1233:\t\t When this option is enabled, the user can specify a min and max\n1234:\t\t CPU bandwidth which is allowed for each single task in a group.\n1235:\t\t The max bandwidth allows to clamp the maximum frequency a task\n1236:\t\t can use, while the min bandwidth allows to define a minimum\n1237:\t\t frequency a task will always use.\n1238:\t\n1239:\t\t When task group based utilization clamping is enabled, an eventually\n" }
11/2	2026/09/23 19:05	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 17020 output: 21 thoughts: 28 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Hunting Down SCHED_CLASS_EXT Alright, so I need to track down the configuration option `SCHED_CLASS_EXT`. Given my experience, the logical first step is to dig into the configuration files. This means checking `init/Kconfig` and, more likely, `kernel/sched/Kconfig`. `init/Kconfig` is always a good starting point for top-level options, but given the target is scheduler-related, the `kernel/sched/Kconfig` directory feels like the prime suspect. I'll mentally prioritize that search. The goal, of course, is to understand its default value, dependencies, and any accompanying help text. Knowing this will give me a better understanding of the overall scheduling configuration and related functionality. Let's get to it.
12/2	2026/09/23 19:05	tool	grepper	0m Args: { "Expression": "config SCHED_CLASS_EXT" } Results: { "Output": "kernel/Kconfig.preempt=155=config SCHED_CORE\n--\nkernel/Kconfig.preempt-172-\nkernel/Kconfig.preempt:173:config SCHED_CLASS_EXT\nkernel/Kconfig.preempt-174-\tbool \"Extensible Scheduling Class\"\n" }
13/2	2026/09/23 19:05	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 17338 output: 35 thoughts: 19 Thoughts: Okay, here's my interpretation of that request, formatted as requested: Digging into Kernel Preemption Configuration Alright, let's dive in. The suggestion is to take a look at `kernel/Kconfig.preempt` around line 173. My immediate thought is, "Okay, that's likely where the core configuration options related to kernel preemption are defined." Given the file name, it's pretty clear that it will give me the building blocks I need to understand how the preemption feature is configured and what options are available. This is important, obviously, because preemption is a critical aspect of how responsive a Linux kernel can be. Understanding these config options will allow me to fine-tune preemption behaviors to better meet specific system requirements, whether that's for low-latency applications, high throughput, or embedded systems with tight real-time constraints. Line 173... that likely points to a specific configuration option, or perhaps a section within the Kconfig file that handles a key aspect of preemption. I'll need to see if it’s related to the different preemption models, RT support, interrupt handling, or other similar settings. Time to get to the code!
14/2	2026/09/23 19:06	tool	read-file	0m Args: { "File": "kernel/Kconfig.preempt", "FirstLine": 170, "LineCount": 25 } Results: { "Contents": " 170:\t\t which is the likely usage by Linux distributions, there should\n 171:\t\t be no measurable impact on performance.\n 172:\t\n 173:\tconfig SCHED_CLASS_EXT\n 174:\t\tbool \"Extensible Scheduling Class\"\n 175:\t\tdepends on BPF_SYSCALL \u0026\u0026 BPF_JIT \u0026\u0026 DEBUG_INFO_BTF\n 176:\t\tselect GENERIC_ALLOCATOR\n 177:\t\tselect STACKTRACE if STACKTRACE_SUPPORT\n 178:\t\thelp\n 179:\t\t This option enables a new scheduler class sched_ext (SCX), which\n 180:\t\t allows scheduling policies to be implemented as BPF programs to\n 181:\t\t achieve the following:\n 182:\t\n 183:\t\t - Ease of experimentation and exploration: Enabling rapid\n 184:\t\t iteration of new scheduling policies.\n 185:\t\t - Customization: Building application-specific schedulers which\n 186:\t\t implement policies that are not applicable to general-purpose\n 187:\t\t schedulers.\n 188:\t\t - Rapid scheduler deployments: Non-disruptive swap outs of\n 189:\t\t scheduling policies in production environments.\n 190:\t\n 191:\t\t sched_ext leverages BPF struct_ops feature to define a structure\n 192:\t\t which exports function callbacks and flags to BPF programs that\n 193:\t\t wish to implement scheduling policies. The struct_ops structure\n 194:\t\t exported by sched_ext is struct sched_ext_ops, and is conceptually\n" }
15/2	2026/09/23 19:06	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 18061 output: 38 thoughts: 58 Thoughts: Okay, let's dive into this commit and figure out the impact of these changes. I need to understand how `scx_sched_hash_params` and `scx_tid_hash_params` are utilized. My immediate thought is to trace their usage. The most straightforward approach here is to leverage `grep`. I'll search for `scx_sched_hash` and `scx_tid_hash` within the codebase. That should give me a good overview of the call sites and related areas. Hopefully, the search results will be clear enough for me to deduce the context and significance of this modification.
16/2	2026/09/23 19:06	tool	grepper	0m Args: { "Expression": "scx_sched_hash\|scx_tid_hash", "PathPrefix": "kernel/sched/ext" } Results: { "Output": "kernel/sched/ext/ext.c=44=static __always_inline int scx_sched_cmpfn(struct rhashtable_compare_arg arg,\n--\nkernel/sched/ext/ext.c-53-\nkernel/sched/ext/ext.c:54:const struct rhashtable_params scx_sched_hash_params = {\nkernel/sched/ext/ext.c-55-\t.key_len\t\t= sizeof_field(struct scx_sched, ops.sub_cgroup_id),\n--\nkernel/sched/ext/ext.c-61-\nkernel/sched/ext/ext.c:62:struct rhashtable scx_sched_hash;\nkernel/sched/ext/ext.c-63-#endif\n--\nkernel/sched/ext/ext.c=66=static __always_inline int scx_tid_cmpfn(struct rhashtable_compare_arg arg,\n--\nkernel/sched/ext/ext.c-75-\nkernel/sched/ext/ext.c:76:static const struct rhashtable_params scx_tid_hash_params = {\nkernel/sched/ext/ext.c-77-\t.key_len\t\t= sizeof_field(struct sched_ext_entity, tid),\n--\nkernel/sched/ext/ext.c-82-};\nkernel/sched/ext/ext.c:83:static struct rhashtable scx_tid_hash;\nkernel/sched/ext/ext.c-84-\n--\nkernel/sched/ext/ext.c=4072=static u64 scx_alloc_tid(void)\n--\nkernel/sched/ext/ext.c-4085-\nkernel/sched/ext/ext.c:4086:static void scx_tid_hash_insert(struct task_struct p)\nkernel/sched/ext/ext.c-4087-{\n--\nkernel/sched/ext/ext.c-4091-\nkernel/sched/ext/ext.c:4092:\tret = rhashtable_lookup_insert_fast(\u0026scx_tid_hash,\nkernel/sched/ext/ext.c-4093-\t\t\t\t\t \u0026p-\u003escx.tid_hash_node,\nkernel/sched/ext/ext.c:4094:\t\t\t\t\t scx_tid_hash_params);\nkernel/sched/ext/ext.c-4095-\tWARN_ON_ONCE(ret);\n--\nkernel/sched/ext/ext.c=4136=void scx_post_fork(struct task_struct p)\n--\nkernel/sched/ext/ext.c-4158-\t\tif (scx_tid_to_task_enabled())\nkernel/sched/ext/ext.c:4159:\t\t\tscx_tid_hash_insert(p);\nkernel/sched/ext/ext.c-4160-\t}\n--\nkernel/sched/ext/ext.c=4209=void sched_ext_dead(struct task_struct p)\n--\nkernel/sched/ext/ext.c-4219-\t\tif (scx_tid_to_task_enabled())\nkernel/sched/ext/ext.c:4220:\t\t\trhashtable_remove_fast(\u0026scx_tid_hash,\nkernel/sched/ext/ext.c-4221-\t\t\t\t\t \u0026p-\u003escx.tid_hash_node,\nkernel/sched/ext/ext.c:4222:\t\t\t\t\t scx_tid_hash_params);\nkernel/sched/ext/ext.c-4223-\t}\n--\nkernel/sched/ext/ext.c=6301=s32 scx_link_sched(struct scx_sched sch)\n--\nkernel/sched/ext/ext.c-6320-\nkernel/sched/ext/ext.c:6321:\t\t\tret = rhashtable_lookup_insert_fast(\u0026scx_sched_hash,\nkernel/sched/ext/ext.c:6322:\t\t\t\t\t\u0026sch-\u003ehash_node, scx_sched_hash_params);\nkernel/sched/ext/ext.c-6323-\t\t\tif (ret) {\nkernel/sched/ext/ext.c:6324:\t\t\t\tscx_error(sch, \"failed to insert into scx_sched_hash (%d)\",\nkernel/sched/ext/ext.c-6325-\t\t\t\t\t ret);\n--\nkernel/sched/ext/ext.c-6337-\t\t\tif (unlikely(READ_ONCE(parent-\u003eaborting))) {\nkernel/sched/ext/ext.c:6338:\t\t\t\trhashtable_remove_fast(\u0026scx_sched_hash, \u0026sch-\u003ehash_node,\nkernel/sched/ext/ext.c:6339:\t\t\t\t\t\t scx_sched_hash_params);\nkernel/sched/ext/ext.c-6340-\t\t\t\tlist_del_rcu(\u0026sch-\u003esibling);\n--\nkernel/sched/ext/ext.c=6356=void scx_unlink_sched(struct scx_sched sch)\n--\nkernel/sched/ext/ext.c-6360-\t\tif (sch-\u003elinked) {\nkernel/sched/ext/ext.c:6361:\t\t\trhashtable_remove_fast(\u0026scx_sched_hash, \u0026sch-\u003ehash_node,\nkernel/sched/ext/ext.c:6362:\t\t\t\t\t scx_sched_hash_params);\nkernel/sched/ext/ext.c-6363-\t\t\tlist_del_rcu(\u0026sch-\u003esibling);\n--\nkernel/sched/ext/ext.c=6404=static void scx_root_disable(struct scx_sched sch)\n--\nkernel/sched/ext/ext.c-6520-\tif (sch-\u003eops.flags \u0026 SCX_OPS_TID_TO_TASK)\nkernel/sched/ext/ext.c:6521:\t\trhashtable_free_and_destroy(\u0026scx_tid_hash, NULL, NULL);\nkernel/sched/ext/ext.c-6522-\n--\nkernel/sched/ext/ext.c=7490=static void scx_root_enable_workfn(struct kthread_work work)\n--\nkernel/sched/ext/ext.c-7524-\tif (ops-\u003eflags \u0026 SCX_OPS_TID_TO_TASK) {\nkernel/sched/ext/ext.c:7525:\t\tret = rhashtable_init(\u0026scx_tid_hash, \u0026scx_tid_hash_params);\nkernel/sched/ext/ext.c-7526-\t\tif (ret)\n--\nkernel/sched/ext/ext.c-7795-\t\tif (scx_tid_to_task_enabled() \u0026\u0026 !list_empty(\u0026p-\u003escx.tasks_node))\nkernel/sched/ext/ext.c:7796:\t\t\tscx_tid_hash_insert(p);\nkernel/sched/ext/ext.c-7797-\n--\nkernel/sched/ext/ext.c-7878-\tif (ops-\u003eflags \u0026 SCX_OPS_TID_TO_TASK)\nkernel/sched/ext/ext.c:7879:\t\trhashtable_free_and_destroy(\u0026scx_tid_hash, NULL, NULL);\nkernel/sched/ext/ext.c-7880-err_free_ksyncs:\n--\nkernel/sched/ext/ext.c=8687=void __init init_sched_ext_class(void)\n--\nkernel/sched/ext/ext.c-8731-#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c:8732:\tBUG_ON(rhashtable_init(\u0026scx_sched_hash, \u0026scx_sched_hash_params));\nkernel/sched/ext/ext.c-8733-#endif\t/ CONFIG_EXT_SUB_SCHED /\n--\nkernel/sched/ext/ext.c=10524=__bpf_kfunc struct task_struct scx_bpf_tid_to_task(u64 tid)\n--\nkernel/sched/ext/ext.c-10535-\nkernel/sched/ext/ext.c:10536:\tscx = rhashtable_lookup(\u0026scx_tid_hash, \u0026tid, scx_tid_hash_params);\nkernel/sched/ext/ext.c-10537-\tif (!scx)\n--\nkernel/sched/ext/internal.h=2103=extern struct list_head scx_sched_all;\nkernel/sched/ext/internal.h-2104-#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/internal.h:2105:extern const struct rhashtable_params scx_sched_hash_params;\nkernel/sched/ext/internal.h:2106:extern struct rhashtable scx_sched_hash;\nkernel/sched/ext/internal.h-2107-extern struct scx_sched scx_enabling_sub_sched;\n--\nkernel/sched/ext/sub.c=95=static struct scx_sched scx_find_sub_sched(u64 cgroup_id)\nkernel/sched/ext/sub.c-96-{\nkernel/sched/ext/sub.c:97:\treturn rhashtable_lookup(\u0026scx_sched_hash, \u0026cgroup_id,\nkernel/sched/ext/sub.c:98:\t\t\t\t scx_sched_hash_params);\nkernel/sched/ext/sub.c-99-}\n" }
17/2	2026/09/23 19:06	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 20663 output: 31 thoughts: 49 Thoughts: Okay, let's dive into this `rhashtable` situation. Investigating `rhashtable` Behavior with Custom Comparison Functions Alright, my immediate thought is to dissect the behavior of `rhashtable` when a custom comparison function (`obj_cmpfn`) is provided, versus when it's left as NULL. It's a fundamental question that's key to understanding its flexibility and how it handles different data types. The obvious starting point is the source code. I need to get into the details to understand how the internal logic changes. I'll need to examine `include/linux/rhashtable.h` for the interface definitions, and then dig into `lib/rhashtable.c` for the implementation to see how the code branches based on the presence of `obj_cmpfn`. The devil is always in the details, so I need to check how comparisons are handled in the lookup, insertion, and deletion pathways. I expect there to be significant differences.
18/2	2026/09/23 19:06	tool	grepper	0m Error: no matches Args: { "Expression": "obj_cmpfn", "PathPrefix": "include/linux/rhashtable" } Results: { "error": "no matches" }
19/2	2026/09/23 19:06	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 20965 output: 28 thoughts: 25 Thoughts: Here's a summary of my thought process: Diving into the rhashtable Implementation Okay, so I need to understand how this `rhashtable` thing is working. My immediate inclination is to go straight to the source. Given the kernel context, my first stop should definitely be the relevant header files and source code. I'm thinking the logical places to find the core definitions and implementation are either `include/linux/rhashtable*.h` or `lib/rhashtable.c`. One of those should hold the keys to unlocking this mystery.
20/2	2026/09/23 19:06	tool	grepper	0m Args: { "Expression": "obj_cmpfn", "PathPrefix": "include/linux/" } Results: { "Output": "include/linux/rhashtable-types.h=41=typedef u32 (rht_obj_hashfn_t)(const void data, u32 len, u32 seed);\ninclude/linux/rhashtable-types.h:42:typedef int (rht_obj_cmpfn_t)(struct rhashtable_compare_arg arg,\ninclude/linux/rhashtable-types.h-43-\t\t\t const void obj);\n--\ninclude/linux/rhashtable-types.h-56- @obj_hashfn: Function to hash object\ninclude/linux/rhashtable-types.h:57: * @obj_cmpfn: Function to compare key with object\ninclude/linux/rhashtable-types.h-58- /\ninclude/linux/rhashtable-types.h=59=struct rhashtable_params {\n--\ninclude/linux/rhashtable-types.h-69-\trht_obj_hashfn_t\tobj_hashfn;\ninclude/linux/rhashtable-types.h:70:\trht_obj_cmpfn_t\t\tobj_cmpfn;\ninclude/linux/rhashtable-types.h-71-};\n--\ninclude/linux/rhashtable.h=611=static __always_inline struct rhash_head __rhashtable_lookup(\n--\ninclude/linux/rhashtable.h-632-\t\trht_for_each_rcu_from(he, __rht_ptr_rcu(bkt, freq), tbl, hash) {\ninclude/linux/rhashtable.h:633:\t\t\tif (params.obj_cmpfn ?\ninclude/linux/rhashtable.h:634:\t\t\t params.obj_cmpfn(\u0026arg, rht_obj(ht, he)) :\ninclude/linux/rhashtable.h-635-\t\t\t rhashtable_compare(\u0026arg, rht_obj(ht, he)))\n--\ninclude/linux/rhashtable.h=756=static __always_inline void *__rhashtable_insert_fast(\n--\ninclude/linux/rhashtable.h-797-\t\tif (!key \|\|\ninclude/linux/rhashtable.h:798:\t\t (params.obj_cmpfn ?\ninclude/linux/rhashtable.h:799:\t\t params.obj_cmpfn(\u0026arg, rht_obj(ht, head)) :\ninclude/linux/rhashtable.h-800-\t\t rhashtable_compare(\u0026arg, rht_obj(ht, head)))) {\n" }
21/2	2026/09/23 19:06	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21772 output: 27 thoughts: 1078 Thoughts: Analyzing `rhashtable_compare` and Sched-ext Reachability for Fuzzing Okay, so I'm looking at `rhashtable_compare` and how it handles comparisons within the rhashtable. The key thing is it either uses `memcmp` directly, or calls a custom comparison function if `obj_cmpfn` is provided. I see that `scx_sched_cmpfn` and `scx_tid_cmpfn` are used and they seem to be more efficient, directly comparing `u64` values instead of relying on `memcmp` for an 8-byte comparison. This is probably due to performance considerations; direct `u64` comparison should be faster. Now, the important question for me is: Why was this changed? And more importantly: how do these specific comparison functions get used within the broader `sched_ext` context? I need to check how `scx_tid_cmpfn`, `scx_sched_cmpfn`, `scx_bpf_tid_to_task`, `scx_find_sub_sched`, and `scx_tid_hash_insert` are all interconnected and get called. I also need to assess whether I can actually exercise `sched_ext` in QEMU. Good news, it's possible! Sched-ext is, after all, a BPF extensible scheduler class. And if it's BPF related, QEMU can handle that! Now, the real focus is on reachability for fuzzing. I need to review the "Core Triage Philosophy" section that I've been working with. Specifically, the points: * Reachability is the primary gate: Code must be reachable in a standard virtualized environment (QEMU) to be fuzzed. * Don't blindly trust "No functional change" claims: Refactorings can introduce subtle bugs. * New or modified assertions in reachable code MUST be fuzzed: And the criteria for "WorthFuzzing=true": * Any logic modifications in: BPF, scheduler, etc. * Any restructuring of reachable data structures, helper abstractions, or algorithm flows. So, is `sched_ext` reachable? It looks like it is. It's invoked through the BPF syscalls, particularly `BPF_PROG_LOAD` and `BPF_LINK_CREATE` to interact with `struct_ops`. I need to now check syzkaller support or BPF syscall support for sched-ext, or at least `sched_ext_ops`. If syzkaller can reach it, then it's definitely worth fuzzing.
22/2	2026/09/23 19:06	tool	grepper	0m Args: { "Expression": "sched_ext_ops", "PathPrefix": "kernel/" } Results: { "Output": "kernel/Kconfig.preempt=173=config SCHED_CLASS_EXT\n--\nkernel/Kconfig.preempt-193-\t wish to implement scheduling policies. The struct_ops structure\nkernel/Kconfig.preempt:194:\t exported by sched_ext is struct sched_ext_ops, and is conceptually\nkernel/Kconfig.preempt-195-\t similar to struct sched_class.\n--\nkernel/bpf/verifier.c=5999=BTF_TYPE_SAFE_TRUSTED(struct scx_sub_attach_args) {\nkernel/bpf/verifier.c:6000:\tstruct sched_ext_ops ops;\nkernel/bpf/verifier.c-6001-};\n--\nkernel/bpf/verifier.c=6003=BTF_TYPE_SAFE_TRUSTED(struct scx_sub_detach_args) {\nkernel/bpf/verifier.c:6004:\tstruct sched_ext_ops ops;\nkernel/bpf/verifier.c-6005-};\n--\nkernel/sched/ext/ext.c=7147=struct scx_sched scx_alloc_and_add_sched(struct scx_enable_cmd cmd,\n--\nkernel/sched/ext/ext.c-7150-{\nkernel/sched/ext/ext.c:7151:\tstruct sched_ext_ops ops = cmd-\u003eops;\nkernel/sched/ext/ext.c-7152-\tstruct scx_sched sch;\n--\nkernel/sched/ext/ext.c-7262-\t * Copy ops through the right union view. For cid-form the source is\nkernel/sched/ext/ext.c:7263:\t * struct sched_ext_ops_cid which lacks the trailing cpu_acquire/\nkernel/sched/ext/ext.c-7264-\t * cpu_release; those stay zero from kzalloc.\n--\nkernel/sched/ext/ext.c=7406=static int check_hotplug_seq(struct scx_sched sch,\nkernel/sched/ext/ext.c:7407:\t\t\t const struct sched_ext_ops ops)\nkernel/sched/ext/ext.c-7408-{\n--\nkernel/sched/ext/ext.c-7429-\nkernel/sched/ext/ext.c:7430:int scx_validate_ops(struct scx_sched sch, const struct sched_ext_ops ops)\nkernel/sched/ext/ext.c-7431-{\n--\nkernel/sched/ext/ext.c=7490=static void scx_root_enable_workfn(struct kthread_work work)\n--\nkernel/sched/ext/ext.c-7492-\tstruct scx_enable_cmd cmd = container_of(work, struct scx_enable_cmd, work);\nkernel/sched/ext/ext.c:7493:\tstruct sched_ext_ops ops = cmd-\u003eops;\nkernel/sched/ext/ext.c-7494-\tstruct cgroup cgrp = root_cgroup();\n--\nkernel/sched/ext/ext.c=8022=static int bpf_scx_init_member(const struct btf_type t,\n--\nkernel/sched/ext/ext.c-8025-{\nkernel/sched/ext/ext.c:8026:\tconst struct sched_ext_ops uops = udata;\nkernel/sched/ext/ext.c:8027:\tstruct sched_ext_ops ops = kdata;\nkernel/sched/ext/ext.c-8028-\tu32 moff = __btf_member_bit_offset(t, member) / 8;\n--\nkernel/sched/ext/ext.c-8031-\tswitch (moff) {\nkernel/sched/ext/ext.c:8032:\tcase offsetof(struct sched_ext_ops, dispatch_max_batch):\nkernel/sched/ext/ext.c-8033-\t\tif ((u32 )(udata + moff) \u003e INT_MAX)\n--\nkernel/sched/ext/ext.c-8036-\t\treturn 1;\nkernel/sched/ext/ext.c:8037:\tcase offsetof(struct sched_ext_ops, flags):\nkernel/sched/ext/ext.c-8038-\t\tif ((u64 )(udata + moff) \u0026 ~SCX_OPS_ALL_FLAGS)\n--\nkernel/sched/ext/ext.c-8041-\t\treturn 1;\nkernel/sched/ext/ext.c:8042:\tcase offsetof(struct sched_ext_ops, name):\nkernel/sched/ext/ext.c-8043-\t\tret = bpf_obj_name_cpy(ops-\u003ename, uops-\u003ename,\n--\nkernel/sched/ext/ext.c-8049-\t\treturn 1;\nkernel/sched/ext/ext.c:8050:\tcase offsetof(struct sched_ext_ops, timeout_ms):\nkernel/sched/ext/ext.c-8051-\t\tif (msecs_to_jiffies((u32 )(udata + moff)) \u003e\n--\nkernel/sched/ext/ext.c-8055-\t\treturn 1;\nkernel/sched/ext/ext.c:8056:\tcase offsetof(struct sched_ext_ops, exit_dump_len):\nkernel/sched/ext/ext.c-8057-\t\tops-\u003eexit_dump_len =\n--\nkernel/sched/ext/ext.c-8059-\t\treturn 1;\nkernel/sched/ext/ext.c:8060:\tcase offsetof(struct sched_ext_ops, hotplug_seq):\nkernel/sched/ext/ext.c-8061-\t\tops-\u003ehotplug_seq = (u64 )(udata + moff);\nkernel/sched/ext/ext.c-8062-\t\treturn 1;\nkernel/sched/ext/ext.c:8063:\tcase offsetof(struct sched_ext_ops, cid_shard_size):\nkernel/sched/ext/ext.c-8064-\t\tops-\u003ecid_shard_size = (u32 )(udata + moff);\nkernel/sched/ext/ext.c-8065-\t\treturn 1;\nkernel/sched/ext/ext.c:8066:\tcase offsetof(struct sched_ext_ops, rescue_bandwidth_ppt): {\nkernel/sched/ext/ext.c-8067-\t\tu32 bw_ppt = (u32 )(udata + moff);\n--\nkernel/sched/ext/ext.c-8073-\t}\nkernel/sched/ext/ext.c:8074:\tcase offsetof(struct sched_ext_ops, rescue_quantum_us): {\nkernel/sched/ext/ext.c-8075-\t\tu32 quantum_us = (u32 )(udata + moff);\n--\nkernel/sched/ext/ext.c-8084-#ifdef CONFIG_EXT_SUB_SCHED\nkernel/sched/ext/ext.c:8085:\tcase offsetof(struct sched_ext_ops, sub_cgroup_id):\nkernel/sched/ext/ext.c-8086-\t\tops-\u003esub_cgroup_id = (u64 )(udata + moff);\n--\nkernel/sched/ext/ext.c=8094=static int bpf_scx_check_member(const struct btf_type t,\n--\nkernel/sched/ext/ext.c-8100-\tswitch (moff) {\nkernel/sched/ext/ext.c:8101:\tcase offsetof(struct sched_ext_ops, init_task):\nkernel/sched/ext/ext.c-8102-#ifdef CONFIG_EXT_GROUP_SCHED\nkernel/sched/ext/ext.c:8103:\tcase offsetof(struct sched_ext_ops, cgroup_init):\nkernel/sched/ext/ext.c:8104:\tcase offsetof(struct sched_ext_ops, cgroup_exit):\nkernel/sched/ext/ext.c:8105:\tcase offsetof(struct sched_ext_ops, cgroup_prep_move):\nkernel/sched/ext/ext.c:8106:\tcase offsetof(struct sched_ext_ops, cgroup_set_bandwidth):\nkernel/sched/ext/ext.c-8107-#endif\nkernel/sched/ext/ext.c:8108:\tcase offsetof(struct sched_ext_ops, cpu_online):\nkernel/sched/ext/ext.c:8109:\tcase offsetof(struct sched_ext_ops, cpu_offline):\nkernel/sched/ext/ext.c:8110:\tcase offsetof(struct sched_ext_ops, init_cids):\nkernel/sched/ext/ext.c:8111:\tcase offsetof(struct sched_ext_ops, init):\nkernel/sched/ext/ext.c:8112:\tcase offsetof(struct sched_ext_ops, exit):\nkernel/sched/ext/ext.c:8113:\tcase offsetof(struct sched_ext_ops, sub_attach):\nkernel/sched/ext/ext.c:8114:\tcase offsetof(struct sched_ext_ops, sub_detach):\nkernel/sched/ext/ext.c-8115-\t\tbreak;\n--\nkernel/sched/ext/ext.c-8130-\tswitch (moff) {\nkernel/sched/ext/ext.c:8131:\tcase offsetof(struct sched_ext_ops, dispatch):\nkernel/sched/ext/ext.c-8132-\t\tprog-\u003eaux-\u003epriv_stack_requested = true;\n--\nkernel/sched/ext/ext.c-8134-\t\tbreak;\nkernel/sched/ext/ext.c:8135:\tcase offsetof(struct sched_ext_ops, sub_caps_updated):\nkernel/sched/ext/ext.c-8136-\t\tprog-\u003eaux-\u003epriv_stack_requested = true;\n--\nkernel/sched/ext/ext.c=8205=static void bpf_scx_unreg(void kdata, struct bpf_link link)\nkernel/sched/ext/ext.c-8206-{\nkernel/sched/ext/ext.c:8207:\tstruct sched_ext_ops ops = kdata;\nkernel/sched/ext/ext.c-8208-\tstruct scx_sched sch = rcu_dereference_protected(ops-\u003epriv, true);\n--\nkernel/sched/ext/ext.c=8235=static int bpf_scx_validate(void kdata)\n--\nkernel/sched/ext/ext.c-8239-\nkernel/sched/ext/ext.c:8240:static s32 sched_ext_ops__select_cpu(struct task_struct p, s32 prev_cpu, u64 wake_flags) { return -EINVAL; }\nkernel/sched/ext/ext.c:8241:static void sched_ext_ops__enqueue(struct task_struct p, u64 enq_flags) {}\nkernel/sched/ext/ext.c:8242:static void sched_ext_ops__dequeue(struct task_struct p, u64 enq_flags) {}\nkernel/sched/ext/ext.c:8243:static void sched_ext_ops__dispatch(s32 prev_cpu, struct task_struct prev__nullable) {}\nkernel/sched/ext/ext.c:8244:static void sched_ext_ops__tick(struct task_struct p) {}\nkernel/sched/ext/ext.c:8245:static void sched_ext_ops__runnable(struct task_struct p, u64 enq_flags) {}\nkernel/sched/ext/ext.c:8246:static void sched_ext_ops__running(struct task_struct p) {}\nkernel/sched/ext/ext.c:8247:static void sched_ext_ops__stopping(struct task_struct p, bool runnable) {}\nkernel/sched/ext/ext.c:8248:static void sched_ext_ops__quiescent(struct task_struct p, u64 deq_flags) {}\nkernel/sched/ext/ext.c:8249:static bool sched_ext_ops__yield(struct task_struct from, struct task_struct to__nullable) { return false; }\nkernel/sched/ext/ext.c:8250:static bool sched_ext_ops__core_sched_before(struct task_struct a, struct task_struct b) { return false; }\nkernel/sched/ext/ext.c:8251:static void sched_ext_ops__set_weight(struct task_struct p, u32 weight) {}\nkernel/sched/ext/ext.c:8252:static void sched_ext_ops__set_cpumask(struct task_struct p, const struct cpumask mask) {}\nkernel/sched/ext/ext.c:8253:static void sched_ext_ops__update_idle(s32 cpu, bool idle) {}\nkernel/sched/ext/ext.c:8254:static void sched_ext_ops__cpu_acquire(s32 cpu, struct scx_cpu_acquire_args args) {}\nkernel/sched/ext/ext.c:8255:static void sched_ext_ops__cpu_release(s32 cpu, struct scx_cpu_release_args args) {}\nkernel/sched/ext/ext.c:8256:static s32 sched_ext_ops__init_task(struct task_struct p, struct scx_init_task_args args) { return -EINVAL; }\nkernel/sched/ext/ext.c:8257:static void sched_ext_ops__exit_task(struct task_struct p, struct scx_exit_task_args args) {}\nkernel/sched/ext/ext.c:8258:static void sched_ext_ops__enable(struct task_struct p) {}\nkernel/sched/ext/ext.c:8259:static void sched_ext_ops__disable(struct task_struct p) {}\nkernel/sched/ext/ext.c-8260-#ifdef CONFIG_EXT_GROUP_SCHED\nkernel/sched/ext/ext.c:8261:static s32 sched_ext_ops__cgroup_init(struct cgroup cgrp, struct scx_cgroup_init_args args) { return -EINVAL; }\nkernel/sched/ext/ext.c:8262:static void sched_ext_ops__cgroup_exit(struct cgroup cgrp) {}\nkernel/sched/ext/ext.c:8263:static s32 sched_ext_ops__cgroup_prep_move(struct task_struct p, struct cgroup from, struct cgroup to) { return -EINVAL; }\nkernel/sched/ext/ext.c:8264:static void sched_ext_ops__cgroup_move(struct task_struct p, struct cgroup from, struct cgroup to) {}\nkernel/sched/ext/ext.c:8265:static void sched_ext_ops__cgroup_cancel_move(struct task_struct p, struct cgroup from, struct cgroup to) {}\nkernel/sched/ext/ext.c:8266:static void sched_ext_ops__cgroup_set_weight(struct cgroup cgrp, u32 weight) {}\nkernel/sched/ext/ext.c:8267:static void sched_ext_ops__cgroup_set_bandwidth(struct cgroup cgrp, u64 period_us, u64 quota_us, u64 burst_us) {}\nkernel/sched/ext/ext.c:8268:static void sched_ext_ops__cgroup_set_idle(struct cgroup cgrp, bool idle) {}\nkernel/sched/ext/ext.c-8269-#endif\t/* CONFIG_EXT_GROUP_SCHED /\nkernel/sched/ext/ext.c:8270:static s32 sched_ext_ops__sub_attach(struct scx_sub_attach_args args) { return -EINVAL; }\nkernel/sched/ext/ext.c:8271:static void sched_ext_ops__sub_detach(struct scx_sub_detach_args args) {}\nkernel/sched/ext/ext.c:8272:static void sched_ext_ops__cpu_online(s32 cpu) {}\nkernel/sched/ext/ext.c:8273:static void sched_ext_ops__cpu_offline(s32 cpu) {}\nkernel/sched/ext/ext.c:8274:static s32 sched_ext_ops__init_cids(void) { return -EINVAL; }\nkernel/sched/ext/ext.c:8275:static s32 sched_ext_ops__init(void) { return -EINVAL; }\nkernel/sched/ext/ext.c:8276:static void sched_ext_ops__exit(struct scx_exit_info info) {}\nkernel/sched/ext/ext.c:8277:static void sched_ext_ops__dump(struct scx_dump_ctx ctx) {}\nkernel/sched/ext/ext.c:8278:static void sched_ext_ops__dump_cpu(struct scx_dump_ctx ctx, s32 cpu, bool idle) {}\nkernel/sched/ext/ext.c:8279:static void sched_ext_ops__dump_task(struct scx_dump_ctx ctx, struct task_struct p) {}\nkernel/sched/ext/ext.c-8280-\nkernel/sched/ext/ext.c:8281:static struct sched_ext_ops __bpf_ops_sched_ext_ops = {\nkernel/sched/ext/ext.c:8282:\t.select_cpu\t\t= sched_ext_ops__select_cpu,\nkernel/sched/ext/ext.c:8283:\t.enqueue\t\t= sched_ext_ops__enqueue,\nkernel/sched/ext/ext.c:8284:\t.dequeue\t\t= sched_ext_ops__dequeue,\nkernel/sched/ext/ext.c:8285:\t.dispatch\t\t= sched_ext_ops__dispatch,\nkernel/sched/ext/ext.c:8286:\t.tick\t\t\t= sched_ext_ops__tick,\nkernel/sched/ext/ext.c:8287:\t.runnable\t\t= sched_ext_ops__runnable,\nkernel/sched/ext/ext.c:8288:\t.running\t\t= sched_ext_ops__running,\nkernel/sched/ext/ext.c:8289:\t.stopping\t\t= sched_ext_ops__stopping,\nkernel/sched/ext/ext.c:8290:\t.quiescent\t\t= sched_ext_ops__quiescent,\nkernel/sched/ext/ext.c:8291:\t.yield\t\t\t= sched_ext_ops__yield,\nkernel/sched/ext/ext.c:8292:\t.core_sched_before\t= sched_ext_ops__core_sched_before,\nkernel/sched/ext/ext.c:8293:\t.set_weight\t\t= sched_ext_ops__set_weight,\nkernel/sched/ext/ext.c:8294:\t.set_cpumask\t\t= sched_ext_ops__set_cpumask,\nkernel/sched/ext/ext.c:8295:\t.update_idle\t\t= sched_ext_ops__update_idle,\nkernel/sched/ext/ext.c:8296:\t.cpu_acquire\t\t= sched_ext_ops__cpu_acquire,\nkernel/sched/ext/ext.c:8297:\t.cpu_release\t\t= sched_ext_ops__cpu_release,\nkernel/sched/ext/ext.c:8298:\t.init_task\t\t= sched_ext_ops__init_task,\nkernel/sched/ext/ext.c:8299:\t.exit_task\t\t= sched_ext_ops__exit_task,\nkernel/sched/ext/ext.c:8300:\t.enable\t\t\t= sched_ext_ops__enable,\nkernel/sched/ext/ext.c:8301:\t.disable\t\t= sched_ext_ops__disable,\nkernel/sched/ext/ext.c-8302-#ifdef CONFIG_EXT_GROUP_SCHED\nkernel/sched/ext/ext.c:8303:\t.cgroup_init\t\t= sched_ext_ops__cgroup_init,\nkernel/sched/ext/ext.c:8304:\t.cgroup_exit\t\t= sched_ext_ops__cgroup_exit,\nkernel/sched/ext/ext.c:8305:\t.cgroup_prep_move\t= sched_ext_ops__cgroup_prep_move,\nkernel/sched/ext/ext.c:8306:\t.cgroup_move\t\t= sched_ext_ops__cgroup_move,\nkernel/sched/ext/ext.c:8307:\t.cgroup_cancel_move\t= sched_ext_ops__cgroup_cancel_move,\nkernel/sched/ext/ext.c:8308:\t.cgroup_set_weight\t= sched_ext_ops__cgroup_set_weight,\nkernel/sched/ext/ext.c:8309:\t.cgroup_set_bandwidth\t= sched_ext_ops__cgroup_set_bandwidth,\nkernel/sched/ext/ext.c:8310:\t.cgroup_set_idle\t= sched_ext_ops__cgroup_set_idle,\nkernel/sched/ext/ext.c-8311-#endif\nkernel/sched/ext/ext.c:8312:\t.sub_attach\t\t= sched_ext_ops__sub_attach,\nkernel/sched/ext/ext.c:8313:\t.sub_detach\t\t= sched_ext_ops__sub_detach,\nkernel/sched/ext/ext.c:8314:\t.cpu_online\t\t= sched_ext_ops__cpu_online,\nkernel/sched/ext/ext.c:8315:\t.cpu_offline\t\t= sched_ext_ops__cpu_offline,\nkernel/sched/ext/ext.c:8316:\t.init_cids\t\t= sched_ext_ops__init_cids,\nkernel/sched/ext/ext.c:8317:\t.init\t\t\t= sched_ext_ops__init,\nkernel/sched/ext/ext.c:8318:\t.exit\t\t\t= sched_ext_ops__exit,\nkernel/sched/ext/ext.c:8319:\t.dump\t\t\t= sched_ext_ops__dump,\nkernel/sched/ext/ext.c:8320:\t.dump_cpu\t\t= sched_ext_ops__dump_cpu,\nkernel/sched/ext/ext.c:8321:\t.dump_task\t\t= sched_ext_ops__dump_task,\nkernel/sched/ext/ext.c-8322-};\nkernel/sched/ext/ext.c-8323-\nkernel/sched/ext/ext.c:8324:static struct bpf_struct_ops bpf_sched_ext_ops = {\nkernel/sched/ext/ext.c-8325-\t.verifier_ops = \u0026bpf_scx_verifier_ops,\n--\nkernel/sched/ext/ext.c-8332-\t.validate = bpf_scx_validate,\nkernel/sched/ext/ext.c:8333:\t.name = \"sched_ext_ops\",\nkernel/sched/ext/ext.c-8334-\t.owner = THIS_MODULE,\nkernel/sched/ext/ext.c:8335:\t.cfi_stubs = \u0026__bpf_ops_sched_ext_ops\nkernel/sched/ext/ext.c-8336-};\n--\nkernel/sched/ext/ext.c-8343- /\nkernel/sched/ext/ext.c:8344:static void sched_ext_ops_cid__set_cmask(struct task_struct p, const struct scx_cmask cmask__arena) {}\nkernel/sched/ext/ext.c:8345:static void sched_ext_ops__sub_caps_updated(const struct scx_cmask cmask__arena, u64 caps) {}\nkernel/sched/ext/ext.c:8346:static void sched_ext_ops__sub_ecaps_updated(s32 cid, u64 before, u64 after) {}\nkernel/sched/ext/ext.c-8347-\nkernel/sched/ext/ext.c:8348:static struct sched_ext_ops_cid __bpf_ops_sched_ext_ops_cid = {\nkernel/sched/ext/ext.c:8349:\t.select_cid\t\t= sched_ext_ops__select_cpu,\nkernel/sched/ext/ext.c:8350:\t.enqueue\t\t= sched_ext_ops__enqueue,\nkernel/sched/ext/ext.c:8351:\t.dequeue\t\t= sched_ext_ops__dequeue,\nkernel/sched/ext/ext.c:8352:\t.dispatch\t\t= sched_ext_ops__dispatch,\nkernel/sched/ext/ext.c:8353:\t.tick\t\t\t= sched_ext_ops__tick,\nkernel/sched/ext/ext.c:8354:\t.runnable\t\t= sched_ext_ops__runnable,\nkernel/sched/ext/ext.c:8355:\t.running\t\t= sched_ext_ops__running,\nkernel/sched/ext/ext.c:8356:\t.stopping\t\t= sched_ext_ops__stopping,\nkernel/sched/ext/ext.c:8357:\t.quiescent\t\t= sched_ext_ops__quiescent,\nkernel/sched/ext/ext.c:8358:\t.yield\t\t\t= sched_ext_ops__yield,\nkernel/sched/ext/ext.c:8359:\t.core_sched_before\t= sched_ext_ops__core_sched_before,\nkernel/sched/ext/ext.c:8360:\t.set_weight\t\t= sched_ext_ops__set_weight,\nkernel/sched/ext/ext.c:8361:\t.set_cmask\t\t= sched_ext_ops_cid__set_cmask,\nkernel/sched/ext/ext.c:8362:\t.update_idle\t\t= sched_ext_ops__update_idle,\nkernel/sched/ext/ext.c:8363:\t.init_task\t\t= sched_ext_ops__init_task,\nkernel/sched/ext/ext.c:8364:\t.exit_task\t\t= sched_ext_ops__exit_task,\nkernel/sched/ext/ext.c:8365:\t.enable\t\t\t= sched_ext_ops__enable,\nkernel/sched/ext/ext.c:8366:\t.disable\t\t= sched_ext_ops__disable,\nkernel/sched/ext/ext.c-8367-#ifdef CONFIG_EXT_GROUP_SCHED\nkernel/sched/ext/ext.c:8368:\t.cpuctl_init\t\t= sched_ext_ops__cgroup_init,\nkernel/sched/ext/ext.c:8369:\t.cpuctl_exit\t\t= sched_ext_ops__cgroup_exit,\nkernel/sched/ext/ext.c:8370:\t.cpuctl_prep_move\t= sched_ext_ops__cgroup_prep_move,\nkernel/sched/ext/ext.c:8371:\t.cpuctl_move\t\t= sched_ext_ops__cgroup_move,\nkernel/sched/ext/ext.c:8372:\t.cpuctl_cancel_move\t= sched_ext_ops__cgroup_cancel_move,\nkernel/sched/ext/ext.c:8373:\t.cpuctl_set_weight\t= sched_ext_ops__cgroup_set_weight,\nkernel/sched/ext/ext.c:8374:\t.cpuctl_set_bandwidth\t= sched_ext_ops__cgroup_set_bandwidth,\nkernel/sched/ext/ext.c:8375:\t.cpuctl_set_idle\t= sched_ext_ops__cgroup_set_idle,\nkernel/sched/ext/ext.c-8376-#endif\nkernel/sched/ext/ext.c:8377:\t.sub_attach\t\t= sched_ext_ops__sub_attach,\nkernel/sched/ext/ext.c:8378:\t.sub_detach\t\t= sched_ext_ops__sub_detach,\nkernel/sched/ext/ext.c:8379:\t.sub_caps_updated\t= sched_ext_ops__sub_caps_updated,\nkernel/sched/ext/ext.c:8380:\t.sub_ecaps_updated\t= sched_ext_ops__sub_ecaps_updated,\nkernel/sched/ext/ext.c:8381:\t.cid_online\t\t= sched_ext_ops__cpu_online,\nkernel/sched/ext/ext.c:8382:\t.cid_offline\t\t= sched_ext_ops__cpu_offline,\nkernel/sched/ext/ext.c:8383:\t.init_cids\t\t= sched_ext_ops__init_cids,\nkernel/sched/ext/ext.c:8384:\t.init\t\t\t= sched_ext_ops__init,\nkernel/sched/ext/ext.c:8385:\t.exit\t\t\t= sched_ext_ops__exit,\nkernel/sched/ext/ext.c:8386:\t.dump\t\t\t= sched_ext_ops__dump,\nkernel/sched/ext/ext.c:8387:\t.dump_cid\t\t= sched_ext_ops__dump_cpu,\nkernel/sched/ext/ext.c:8388:\t.dump_task\t\t= sched_ext_ops__dump_task,\nkernel/sched/ext/ext.c-8389-};\n--\nkernel/sched/ext/ext.c-8395- /\nkernel/sched/ext/ext.c:8396:static struct bpf_struct_ops bpf_sched_ext_ops_cid = {\nkernel/sched/ext/ext.c-8397-\t.verifier_ops = \u0026bpf_scx_cid_verifier_ops,\n--\nkernel/sched/ext/ext.c-8404-\t.validate = bpf_scx_validate,\nkernel/sched/ext/ext.c:8405:\t.name = \"sched_ext_ops_cid\",\nkernel/sched/ext/ext.c-8406-\t.owner = THIS_MODULE,\nkernel/sched/ext/ext.c:8407:\t.cfi_stubs = \u0026__bpf_ops_sched_ext_ops_cid\nkernel/sched/ext/ext.c-8408-};\n--\nkernel/sched/ext/ext.c=10738=static const struct btf_kfunc_id_set scx_kfunc_set_any = {\n--\nkernel/sched/ext/ext.c-10745- cpu-form kfuncs that are forbidden from cid-form schedulers\nkernel/sched/ext/ext.c:10746: * (bpf_sched_ext_ops_cid). Programs targeting the cid struct_ops type must\nkernel/sched/ext/ext.c-10747- * use the cid-form alternative (cid/cmask kfuncs).\n--\nkernel/sched/ext/ext.c=10839=int scx_kfunc_context_filter(const struct bpf_prog prog, u32 kfunc_id)\n--\nkernel/sched/ext/ext.c-10877-\t \nkernel/sched/ext/ext.c:10878:\t * Both bpf_sched_ext_ops (cpu-form) and bpf_sched_ext_ops_cid\nkernel/sched/ext/ext.c-10879-\t * (cid-form) are valid SCX struct_ops. Member offsets match between\n--\nkernel/sched/ext/ext.c-10883-\t /\nkernel/sched/ext/ext.c:10884:\tif (prog-\u003eaux-\u003est_ops != \u0026bpf_sched_ext_ops \u0026\u0026\nkernel/sched/ext/ext.c:10885:\t prog-\u003eaux-\u003est_ops != \u0026bpf_sched_ext_ops_cid)\nkernel/sched/ext/ext.c-10886-\t\treturn -EACCES;\n--\nkernel/sched/ext/ext.c-10893-\t /\nkernel/sched/ext/ext.c:10894:\tif (prog-\u003eaux-\u003est_ops == \u0026bpf_sched_ext_ops_cid \u0026\u0026 in_cpu_only)\nkernel/sched/ext/ext.c-10895-\t\treturn -EACCES;\n--\nkernel/sched/ext/ext.c=10920=static int __init scx_init(void)\n--\nkernel/sched/ext/ext.c-10924-\t/\nkernel/sched/ext/ext.c:10925:\t sched_ext_ops_cid mirrors sched_ext_ops up to and including @priv.\nkernel/sched/ext/ext.c-10926-\t * Both bpf_scx_init_member() and bpf_scx_check_member() use offsets\nkernel/sched/ext/ext.c:10927:\t * from struct sched_ext_ops; sched_ext_ops_cid relies on those offsets\nkernel/sched/ext/ext.c-10928-\t * matching for the shared fields. Catch any drift at boot.\n--\nkernel/sched/ext/ext.c-10930-#define CID_OFFSET_MATCH(cpu_field, cid_field)\t\t\t\t\t\\\nkernel/sched/ext/ext.c:10931:\tBUILD_BUG_ON(offsetof(struct sched_ext_ops, cpu_field) !=\t\t\\\nkernel/sched/ext/ext.c:10932:\t\t offsetof(struct sched_ext_ops_cid, cid_field))\nkernel/sched/ext/ext.c-10933-\t/* data fields used by bpf_scx_init_member() /\n--\nkernel/sched/ext/ext.c-10992-\t /\nkernel/sched/ext/ext.c:10993:\tBUILD_BUG_ON(offsetof(struct sched_ext_ops_cid, __end) !=\nkernel/sched/ext/ext.c:10994:\t\t offsetofend(struct sched_ext_ops, priv));\nkernel/sched/ext/ext.c-10995-#undef CID_OFFSET_MATCH\n--\nkernel/sched/ext/ext.c-11040-\nkernel/sched/ext/ext.c:11041:\tret = register_bpf_struct_ops(\u0026bpf_sched_ext_ops, sched_ext_ops);\nkernel/sched/ext/ext.c-11042-\tif (ret) {\n--\nkernel/sched/ext/ext.c-11046-\nkernel/sched/ext/ext.c:11047:\tret = register_bpf_struct_ops(\u0026bpf_sched_ext_ops_cid, sched_ext_ops_cid);\nkernel/sched/ext/ext.c-11048-\tif (ret) {\n--\nkernel/sched/ext/idle.c=300=static bool llc_numa_mismatch(void)\n--\nkernel/sched/ext/idle.c-344- /\nkernel/sched/ext/idle.c:345:void scx_idle_update_selcpu_topology(struct sched_ext_ops ops)\nkernel/sched/ext/idle.c-346-{\n--\nkernel/sched/ext/idle.c=801=void __scx_update_idle(struct rq rq, bool idle, bool do_notify)\n--\nkernel/sched/ext/idle.c-837-\nkernel/sched/ext/idle.c:838:static void reset_idle_masks(struct sched_ext_ops ops)\nkernel/sched/ext/idle.c-839-{\n--\nkernel/sched/ext/idle.c-859-\nkernel/sched/ext/idle.c:860:void scx_idle_enable(struct sched_ext_ops ops)\nkernel/sched/ext/idle.c-861-{\n--\nkernel/sched/ext/idle.h=15=struct cpumask;\nkernel/sched/ext/idle.h:16:struct sched_ext_ops;\nkernel/sched/ext/idle.h-17-struct task_struct;\n--\nkernel/sched/ext/idle.h=20=extern struct btf_id_set8 scx_kfunc_ids_select_cpu;\nkernel/sched/ext/idle.h-21-\nkernel/sched/ext/idle.h:22:void scx_idle_update_selcpu_topology(struct sched_ext_ops ops);\nkernel/sched/ext/idle.h-23-void scx_idle_init_masks(void);\n--\nkernel/sched/ext/idle.h=25=s32 scx_select_cpu_dfl(struct task_struct p, s32 prev_cpu, u64 wake_flags,\nkernel/sched/ext/idle.h-26-\t\t const struct cpumask cpus_allowed, u64 flags);\nkernel/sched/ext/idle.h:27:void scx_idle_enable(struct sched_ext_ops ops);\nkernel/sched/ext/idle.h-28-void scx_idle_disable(void);\n--\nkernel/sched/ext/internal.h-41-\nkernel/sched/ext/internal.h:42:#define SCX_OP_IDX(op)\t\t(offsetof(struct sched_ext_ops, op) / sizeof(void ()(void)))\nkernel/sched/ext/internal.h-43-#define SCX_MOFF_IDX(moff)\t((moff) / sizeof(void ()(void)))\n--\nkernel/sched/ext/internal.h=101=struct scx_exit_info {\n--\nkernel/sched/ext/internal.h-130-\nkernel/sched/ext/internal.h:131:/ sched_ext_ops.flags /\nkernel/sched/ext/internal.h-132-enum scx_ops_flags {\n--\nkernel/sched/ext/internal.h=300=struct scx_sub_attach_args {\nkernel/sched/ext/internal.h:301:\tstruct sched_ext_ops\tops;\nkernel/sched/ext/internal.h-302-\tchar\t\t\tcgroup_path;\n--\nkernel/sched/ext/internal.h=306=struct scx_sub_detach_args {\nkernel/sched/ext/internal.h:307:\tstruct sched_ext_ops\tops;\nkernel/sched/ext/internal.h-308-\tchar\t\t\tcgroup_path;\n--\nkernel/sched/ext/internal.h-311-/\nkernel/sched/ext/internal.h:312: struct sched_ext_ops - Operation table for BPF scheduler implementation\nkernel/sched/ext/internal.h-313- \n--\nkernel/sched/ext/internal.h-318- /\nkernel/sched/ext/internal.h:319:struct sched_ext_ops {\nkernel/sched/ext/internal.h-320-\t/*\n--\nkernel/sched/ext/internal.h-984-\t Deprecated callbacks. Kept at the end of the struct so the cid-form\nkernel/sched/ext/internal.h:985:\t * struct (sched_ext_ops_cid) can omit them without affecting the\nkernel/sched/ext/internal.h-986-\t * shared field offsets. Use SCX_ENQ_IMMED instead. Sitting past\n--\nkernel/sched/ext/internal.h-1016-/*\nkernel/sched/ext/internal.h:1017: struct sched_ext_ops_cid - cid-form alternative to struct sched_ext_ops\nkernel/sched/ext/internal.h-1018- \nkernel/sched/ext/internal.h:1019: Mirrors struct sched_ext_ops with cpu/cpumask substituted with cid/cmask\nkernel/sched/ext/internal.h:1020: * where applicable. Layout up to and including @priv matches sched_ext_ops\nkernel/sched/ext/internal.h-1021- * byte-for-byte (verified by BUILD_BUG_ON checks at scx_init() time) so\n--\nkernel/sched/ext/internal.h-1023- * and bpf_scx_check_member(). The deprecated cpu_acquire/cpu_release\nkernel/sched/ext/internal.h:1024: * callbacks at the tail of sched_ext_ops are omitted here entirely.\nkernel/sched/ext/internal.h-1025- \nkernel/sched/ext/internal.h:1026: Differences from sched_ext_ops:\nkernel/sched/ext/internal.h-1027- * - select_cpu -\u003e select_cid (returns cid)\n--\nkernel/sched/ext/internal.h-1034- * - cgroup_* -\u003e cpuctl_* (they track the cgroup cpu controller)\nkernel/sched/ext/internal.h:1035: * - cpu_acquire/cpu_release -\u003e not present (deprecated in sched_ext_ops)\nkernel/sched/ext/internal.h-1036- \n--\nkernel/sched/ext/internal.h-1040- \nkernel/sched/ext/internal.h:1041: * See sched_ext_ops for callback documentation.\nkernel/sched/ext/internal.h-1042- /\nkernel/sched/ext/internal.h:1043:struct sched_ext_ops_cid {\nkernel/sched/ext/internal.h-1044-\ts32 (select_cid)(struct task_struct p, s32 prev_cid, u64 wake_flags);\n--\nkernel/sched/ext/internal.h-1091-\nkernel/sched/ext/internal.h:1092:\t/ Data fields - must match sched_ext_ops layout exactly /\nkernel/sched/ext/internal.h-1093-\tu32 dispatch_max_batch;\n--\nkernel/sched/ext/internal.h=1521=struct scx_sched {\n--\nkernel/sched/ext/internal.h-1529-\tunion {\nkernel/sched/ext/internal.h:1530:\t\tstruct sched_ext_ops\t\tops;\nkernel/sched/ext/internal.h:1531:\t\tstruct sched_ext_ops_cid\tops_cid;\nkernel/sched/ext/internal.h-1532-\t};\nkernel/sched/ext/internal.h:1533:\tbool\t\t\tis_cid_type;\t/ true if registered via bpf_sched_ext_ops_cid /\nkernel/sched/ext/internal.h-1534-\tbool\t\t\tdead;\t\t/ set after ops.exit(), gates scx_prog_sched() /\n--\nkernel/sched/ext/internal.h=1987=struct scx_enable_cmd {\n--\nkernel/sched/ext/internal.h-1989-\tunion {\nkernel/sched/ext/internal.h:1990:\t\tstruct sched_ext_ops\t\tops;\nkernel/sched/ext/internal.h:1991:\t\tstruct sched_ext_ops_cid\tops_cid;\nkernel/sched/ext/internal.h-1992-\t};\n--\nkernel/sched/ext/internal.h=2089=struct scx_sched scx_alloc_and_add_sched(struct scx_enable_cmd cmd,\n--\nkernel/sched/ext/internal.h-2091-\t\t\t\t\t struct scx_sched parent);\nkernel/sched/ext/internal.h:2092:int scx_validate_ops(struct scx_sched sch, const struct sched_ext_ops ops);\nkernel/sched/ext/internal.h-2093-int scx_sched_sysfs_add(struct scx_sched sch);\n--\nkernel/sched/ext/internal.h=2404=static inline struct scx_sched scx_prog_sched(const struct bpf_prog_aux aux)\nkernel/sched/ext/internal.h-2405-{\nkernel/sched/ext/internal.h:2406:\tstruct sched_ext_ops ops;\nkernel/sched/ext/internal.h-2407-\tstruct scx_sched sch, root;\n--\nkernel/sched/ext/sub.c=1709=void scx_sub_enable_workfn(struct kthread_work work)\n--\nkernel/sched/ext/sub.c-1711-\tstruct scx_enable_cmd cmd = container_of(work, struct scx_enable_cmd, work);\nkernel/sched/ext/sub.c:1712:\tstruct sched_ext_ops ops = cmd-\u003eops;\nkernel/sched/ext/sub.c-1713-\tstruct cgroup cgrp;\n" }
23/2	2026/09/23 19:06	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 34878 output: 37 thoughts: 1036 Thoughts: Analyzing rhashtable usage in ext.c Okay, let's dive into these `scx_sched_cmpfn` and `scx_tid_cmpfn` functions within `kernel/sched/ext/ext.c`. The way they've been implemented catches my eye. We're using `rhashtable` here, specifically with `scx_sched_hash` and `scx_tid_hash`, and I'm seeing the `obj_cmpfn` field being used in the parameters. I need to confirm if these functions are even reachable. I see that `scx_sched_hash` is involved in linking, unlinking, and looking up sub-schedulers based on `sub_cgroup_id`. Specifically, `scx_link_sched` uses `rhashtable_lookup_insert_fast`, `scx_unlink_sched` uses `rhashtable_remove_fast` and `scx_find_sub_sched` uses `rhashtable_lookup`. With `scx_tid_hash`, it appears to be tied to the `SCX_OPS_TID_TO_TASK` flag, with insertions via `scx_tid_hash_insert` in `scx_post_fork` and scheduler enable, and removals in `sched_ext_dead`. A BPF kfunc, `scx_bpf_tid_to_task`, calls `rhashtable_lookup` on it. Now, my focus shifts to understanding the role of `obj_cmpfn` within the `rhashtable` framework. I need to refresh my memory and pinpoint how exactly `obj_cmpfn` is utilized, along with its arguments. Time to carefully read `include/linux/rhashtable.h`, especially around lines 630 and 790, to understand the comparison logic and interactions.
24/2	2026/09/23 19:06	tool	read-file	0m Args: { "File": "include/linux/rhashtable.h", "FirstLine": 615, "LineCount": 40 } Results: { "Contents": " 615:\t\t__must_hold_shared(RCU)\n 616:\t{\n 617:\t\tstruct rhashtable_compare_arg arg = {\n 618:\t\t\t.ht = ht,\n 619:\t\t\t.key = key,\n 620:\t\t};\n 621:\t\tstruct rhash_lock_head __rcu const bkt;\n 622:\t\tstruct bucket_table tbl;\n 623:\t\tstruct rhash_head he;\n 624:\t\tunsigned int hash;\n 625:\t\n 626:\t\tBUILD_BUG_ON(!__builtin_constant_p(freq));\n 627:\t\ttbl = rht_dereference_rcu(ht-\u003etbl, ht);\n 628:\trestart:\n 629:\t\thash = rht_key_hashfn(ht, tbl, key, params);\n 630:\t\tbkt = rht_bucket(tbl, hash);\n 631:\t\tdo {\n 632:\t\t\trht_for_each_rcu_from(he, __rht_ptr_rcu(bkt, freq), tbl, hash) {\n 633:\t\t\t\tif (params.obj_cmpfn ?\n 634:\t\t\t\t params.obj_cmpfn(\u0026arg, rht_obj(ht, he)) :\n 635:\t\t\t\t rhashtable_compare(\u0026arg, rht_obj(ht, he)))\n 636:\t\t\t\t\tcontinue;\n 637:\t\t\t\treturn he;\n 638:\t\t\t}\n 639:\t\t\t/* An object might have been moved to a different hash chain,\n 640:\t\t\t * while we walk along it - better check and retry.\n 641:\t\t\t /\n 642:\t\t} while (he != RHT_NULLS_MARKER(bkt));\n 643:\t\n 644:\t\t/ Ensure we see any new tables. /\n 645:\t\tsmp_rmb();\n 646:\t\n 647:\t\ttbl = rht_dereference_rcu(tbl-\u003efuture_tbl, ht);\n 648:\t\tif (unlikely(tbl))\n 649:\t\t\tgoto restart;\n 650:\t\n 651:\t\treturn NULL;\n 652:\t}\n 653:\t\n 654:\t/*\n" }
25/2	2026/09/23 19:06	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36960 output: 37 thoughts: 15 Thoughts: Here's my take on those thoughts, tailored for an expert audience: Diving Deeper into the Rhashtable Insertion Okay, so we're looking at hash table insertions. My initial thought is to take a look at the `__rhashtable_insert_fast` function specifically. I'm assuming that function likely represents an optimized path for insertions, perhaps handling common scenarios or simpler key/value types more efficiently than the general case. I expect this "fast" path is probably what we want to focus on initially. I want to compare the algorithm's performance of the slow and fast paths to find the most efficient solution for the insertion.
26/2	2026/09/23 19:06	tool	read-file	0m Args: { "File": "include/linux/rhashtable.h", "FirstLine": 780, "LineCount": 40 } Results: { "Contents": " 780:\t\tif (!bkt)\n 781:\t\t\tgoto out;\n 782:\t\tpprev = NULL;\n 783:\t\tflags = rht_lock(tbl, bkt);\n 784:\t\n 785:\t\tif (unlikely(rcu_access_pointer(tbl-\u003efuture_tbl))) {\n 786:\tslow_path:\n 787:\t\t\trht_unlock(tbl, bkt, flags);\n 788:\t\t\trcu_read_unlock();\n 789:\t\t\treturn rhashtable_insert_slow(ht, key, obj);\n 790:\t\t}\n 791:\t\n 792:\t\trht_for_each_from(head, rht_ptr(bkt, tbl, hash), tbl, hash) {\n 793:\t\t\tstruct rhlist_head plist;\n 794:\t\t\tstruct rhlist_head list;\n 795:\t\n 796:\t\t\telasticity--;\n 797:\t\t\tif (!key \|\|\n 798:\t\t\t (params.obj_cmpfn ?\n 799:\t\t\t params.obj_cmpfn(\u0026arg, rht_obj(ht, head)) :\n 800:\t\t\t rhashtable_compare(\u0026arg, rht_obj(ht, head)))) {\n 801:\t\t\t\tpprev = \u0026head-\u003enext;\n 802:\t\t\t\tcontinue;\n 803:\t\t\t}\n 804:\t\n 805:\t\t\tdata = rht_obj(ht, head);\n 806:\t\n 807:\t\t\tif (!rhlist)\n 808:\t\t\t\tgoto out_unlock;\n 809:\t\n 810:\t\n 811:\t\t\tlist = container_of(obj, struct rhlist_head, rhead);\n 812:\t\t\tplist = container_of(head, struct rhlist_head, rhead);\n 813:\t\n 814:\t\t\tRCU_INIT_POINTER(list-\u003enext, plist);\n 815:\t\t\thead = rht_dereference_bucket(head-\u003enext, tbl, hash);\n 816:\t\t\tRCU_INIT_POINTER(list-\u003erhead.next, head);\n 817:\t\t\tif (pprev) {\n 818:\t\t\t\trcu_assign_pointer(*pprev, obj);\n 819:\t\t\t\trht_unlock(tbl, bkt, flags);\n" }
27/2	2026/09/23 19:06	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 37770 output: 31 thoughts: 18 Thoughts: Okay, let's dive into this. Here's my understanding, presented as a first-person expert analysis: Analyzing the Behavior of `rhashtable_remove_fast` Alright, I need to see what's happening internally within `rhashtable_remove_fast`. This function is critical for performance in any rhashtable implementation, so understanding its behavior is paramount. I'm focusing on the implementation details, probably looking at specific data structures and algorithms employed within it. I'll be expecting to examine how it handles collisions, how it manages memory (allocations and deallocations), and how it deals with thread safety if applicable. I anticipate the core of the investigation will center around how it efficiently removes an element given a key, and what optimizations are made to accomplish it quickly. I’ll be especially looking for any potential bottlenecks or edge cases that might impact overall performance under heavy load or specific workloads. I'll be keeping an eye out for potential concurrency issues within the removal process that might need synchronization mechanisms to address. My goal is to grasp its operational logic completely and any potential pitfalls, with the intent to enhance it if necessary, or at the very least, understand its implications fully for my own projects or systems.
28/2	2026/09/23 19:06	tool	grepper	0m Args: { "Expression": "obj_cmpfn", "PathPrefix": "lib/rhashtable.c" } Results: { "Output": "lib/rhashtable.c=529=static void rhashtable_lookup_one(struct rhashtable ht,\n--\nlib/rhashtable.c-548-\t\tif (!key \|\|\nlib/rhashtable.c:549:\t\t (ht-\u003ep.obj_cmpfn ?\nlib/rhashtable.c:550:\t\t ht-\u003ep.obj_cmpfn(\u0026arg, rht_obj(ht, head)) :\nlib/rhashtable.c-551-\t\t rhashtable_compare(\u0026arg, rht_obj(ht, head)))) {\n--\nlib/rhashtable.c=698=static struct rhash_head __rhashtable_next_in_table(\n--\nlib/rhashtable.c-710-\t\trht_for_each_rcu(he, tbl, b) {\nlib/rhashtable.c:711:\t\t\tbool match = params.obj_cmpfn\nlib/rhashtable.c:712:\t\t\t\t ? !params.obj_cmpfn(\u0026arg, rht_obj(ht, he))\nlib/rhashtable.c-713-\t\t\t\t : !rhashtable_compare(\u0026arg, rht_obj(ht, he));\n--\nlib/rhashtable.c=1165=int __rhashtable_init_noprof(struct rhashtable ht,\n--\nlib/rhashtable.c-1172-\tif ((!params-\u003ekey_len \u0026\u0026 !params-\u003eobj_hashfn) \|\|\nlib/rhashtable.c:1173:\t (params-\u003eobj_hashfn \u0026\u0026 !params-\u003eobj_cmpfn))\nlib/rhashtable.c-1174-\t\treturn -EINVAL;\n" }
29/2	2026/09/23 19:06	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 38513 output: 32 thoughts: 52 Thoughts: My Initial Thoughts on `rht_obj(ht, he)` Okay, so I see `rht_obj(ht, he)`... Immediately, my expert brain kicks in, trying to grasp what this function or macro is all about. My initial question: what exactly does this thing return? What's the output of `rht_obj(ht, he)`? Given my experience, it's probably related to retrieving an object from a rhashtable. Alright, let's cut to the chase and find the source. I'll need to dig into the kernel's source code, specifically the rhashtable implementation. I'll head over to `include/linux/rhashtable.h` – that's where the definition should be. It will be the central source to understand what `rht_obj` is doing and what its inputs and outputs mean.
30/2	2026/09/23 19:06	tool	grepper	0m Error: no matches Args: { "Expression": "rht_obj\\(", "PathPrefix": "include/linux/rhashtable" } Results: { "error": "no matches" }
31/2	2026/09/23 19:06	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 38800 output: 32 thoughts: 16 Thoughts: Here's my take on those thoughts: Locating the Elusive `rht_obj` Alright, let's get down to brass tacks. I need to find the definition or usage of this `rht_obj` variable – a likely kernel data structure, given the `include/linux/` context. No time for speculation; I'll start with the obvious: a thorough search within the Linux kernel source tree, specifically within the `include/linux/` directory and its subdirectories. I'll need to use a tool like `grep` or `ack` or even something more sophisticated, if necessary, to scan every file in that tree for every instance of `rht_obj`. I'm expecting to find at least the declaration, possibly some typedef or struct definition, and then follow-on uses that will provide a clearer understanding of what it is and what it is used for. This initial sweep is critical to understanding the scope of what I'm dealing with. Let's see what we turn up.
32/2	2026/09/23 19:06	tool	grepper	0m Args: { "Expression": "static inline void \\rht_obj", "PathPrefix": "include/linux/" } Results:* { "Output": "include/linux/rhashtable.h=108=static inline bool rht_is_a_nulls(const struct rhash_head ptr)\n--\ninclude/linux/rhashtable.h-112-\ninclude/linux/rhashtable.h:113:static inline void rht_obj(const struct rhashtable ht,\ninclude/linux/rhashtable.h-114-\t\t\t const struct rhash_head he)\n" }
33/2	2026/09/23 19:06	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 39190 output: 37 thoughts: 25 Thoughts: Okay, let's dive into this. Here's my take on those lines from `include/linux/rhashtable.h`: Analyzing Lines 110-120 of `include/linux/rhashtable.h` Alright, I'm heading straight for lines 110-120 of `rhashtable.h`. I'm guessing these lines probably define, or at least are key to understanding, how the rhashtable deals with some fundamental internal structure or perhaps a crucial operation like resizing or key iteration. Given the surrounding context in this header, I'd expect to see some declarations related to the core data structures, function prototypes for important internal methods, or perhaps some configuration macros. Since it's a critical part of the core, I'm prepared for a bit of C wizardry. I'll be looking for any hints about the underlying hashing strategy, collision handling, or the way the table handles dynamic resizing. Let's see if this section reveals something novel in how this particular implementation aims to deliver efficient concurrent access. I'm keen to understand the nuances of this specific design.
34/2	2026/09/23 19:06	tool	read-file	0m Args: { "File": "include/linux/rhashtable.h", "FirstLine": 110, "LineCount": 20 } Results: { "Contents": " 110:\t\treturn ((unsigned long) ptr \u0026 1);\n 111:\t}\n 112:\t\n 113:\tstatic inline void rht_obj(const struct rhashtable ht,\n 114:\t\t\t\t const struct rhash_head he)\n 115:\t{\n 116:\t\treturn (char )he - ht-\u003ep.head_offset;\n 117:\t}\n 118:\t\n 119:\tstatic inline unsigned int rht_bucket_index(const struct bucket_table tbl,\n 120:\t\t\t\t\t\t unsigned int hash)\n 121:\t{\n 122:\t\treturn hash \u0026 (tbl-\u003esize - 1);\n 123:\t}\n 124:\t\n 125:\tstatic __always_inline unsigned int rht_key_get_hash(struct rhashtable ht,\n 126:\t\tconst void *key, const struct rhashtable_params params,\n 127:\t\tunsigned int hash_rnd)\n 128:\t{\n 129:\t\tunsigned int hash;\n" }
35/2	2026/09/23 19:06	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 39784 output: 33 thoughts: 1170 Thoughts: Analyzing Potential FocusSymbols in the rhashtable Implementation Okay, let's break this down. My initial thought process is centered around how to effectively leverage fuzzing on these scheduling extension features. I'm focusing on the `rhashtable` implementation and its interaction with specific comparison functions. Firstly, I see that the `rht_obj` macro is used to get the object from the rhashtable node, and based on the `head_offset` value it uses, it returns either a `struct scx_sched ` or a `struct sched_ext_entity `. The comparison functions are also pretty straightforward: `scx_sched_cmpfn` and `scx_tid_cmpfn` compare fields against a key. Now, the real question is whether these comparison functions, specifically, `scx_tid_cmpfn` and `scx_sched_cmpfn`, can act as effective `FocusSymbols` for fuzzing. The fact that they are declared as `static __always_inline` immediately raised a flag. Usually, such functions can't be directly targeted because they are inlined by the compiler. However, a crucial point emerges. The compiler must generate an out-of-line copy when the address of a static inline function is taken. This is exactly what's happening here: their addresses are assigned to `obj_cmpfn` function pointers within global structures, `scx_sched_hash_params` and `scx_tid_hash_params`. This implies that `gcc/clang` should emit distinct symbols for these functions, which is excellent news. Now, my next questions are: do kallsyms or nm include these emitted functions? Or, are they still possibly inlined via macro magic by the rhashtable internals? I'm checking the `__rhashtable_lookup` macro to see what is happening. My suspicion is, and I'm checking, that since `obj_cmpfn` is a function pointer, the comparison is done via the pointer to the comparison function, which will not be inlined. Let's check where the params are used. Specifically, I'm checking how these structures and their comparison functions are passed into the `rhashtable` functions. I see `rhashtable_lookup_insert_fast`, `rhashtable_remove_fast`, and `rhashtable_lookup` being used with those structures, in `ext.c` and `sub.c`. My final step is to check where those rhashtable functions are being called. I want to see which other features interact with them. For example, `scx_post_fork` and `scx_root_enable_workfn` are interesting. I'm especially keen on `scx_bpf_tid_to_task`, because it's a BPF kfunc. Knowing this, I'm now going to grep for `scx_find_sub_sched` to get a full overview of all callers and usage. I need to understand the control flow, so I know whether the functions are good candidates for fuzzing entrypoints.
36/2	2026/09/23 19:07	tool	grepper	0m Args: { "Expression": "scx_find_sub_sched", "PathPrefix": "kernel/sched/ext" } Results: { "Output": "kernel/sched/ext/sub.c=74=struct scx_sched scx_next_descendant_pre(struct scx_sched pos, struct scx_sched root)\n--\nkernel/sched/ext/sub.c-94-\nkernel/sched/ext/sub.c:95:static struct scx_sched scx_find_sub_sched(u64 cgroup_id)\nkernel/sched/ext/sub.c-96-{\n--\nkernel/sched/ext/sub.c=2225=__bpf_kfunc bool scx_bpf_sub_dispatch(u64 cgroup_id, const struct bpf_prog_aux aux)\n--\nkernel/sched/ext/sub.c-2234-\nkernel/sched/ext/sub.c:2235:\tchild = scx_find_sub_sched(cgroup_id);\nkernel/sched/ext/sub.c-2236-\n--\nkernel/sched/ext/sub.c=2259=static s32 sub_cap_preamble(u64 cgroup_id, u64 caps, const struct bpf_prog_aux aux,\n--\nkernel/sched/ext/sub.c-2272-\nkernel/sched/ext/sub.c:2273:\tchild = scx_find_sub_sched(cgroup_id);\nkernel/sched/ext/sub.c-2274-\tif (unlikely(!child))\n--\nkernel/sched/ext/sub.c=2525=__bpf_kfunc s32 scx_bpf_sub_caps(u64 cgroup_id, u64 caps, struct scx_cmask out__arena,\n--\nkernel/sched/ext/sub.c-2550-\tif (cgroup_id) {\nkernel/sched/ext/sub.c:2551:\t\ttarget = scx_find_sub_sched(cgroup_id);\nkernel/sched/ext/sub.c-2552-\t\tif (unlikely(!target))\n--\nkernel/sched/ext/sub.c=2615=__bpf_kfunc s32 scx_bpf_sub_kill_bstr(u64 cgroup_id, char fmt,\n--\nkernel/sched/ext/sub.c-2631-\nkernel/sched/ext/sub.c:2632:\tchild = scx_find_sub_sched(cgroup_id);\nkernel/sched/ext/sub.c-2633-\tif (unlikely(!child))\n" }
37/2	2026/09/23 19:07	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 42298 output: 31 thoughts: 46 Thoughts: Okay, let's break this down. Investigating the `scx_link_sched` and `scx_unlink_sched` Functions Right, so I need to understand how these scheduling functions, `scx_link_sched` and `scx_unlink_sched`, work. A quick mental check tells me they're defined in `ext.c`. Now, the next logical step, and a crucial one, is to trace their usage. I need to figure out where `scx_link_sched` is actually called. That's where the real insights will come from. I'm going to start there and see what context surrounds the linkage function.
38/2	2026/09/23 19:07	tool	grepper	0m Args: { "Expression": "scx_link_sched", "PathPrefix": "kernel/sched/ext" } Results: { "Output": "kernel/sched/ext/ext.c=6281=static void refresh_watchdog(void)\n--\nkernel/sched/ext/ext.c-6300-\nkernel/sched/ext/ext.c:6301:s32 scx_link_sched(struct scx_sched sch)\nkernel/sched/ext/ext.c-6302-{\n--\nkernel/sched/ext/ext.c=6600=static bool scx_claim_exit(struct scx_sched sch, enum scx_exit_kind kind)\n--\nkernel/sched/ext/ext.c-6622-\t\t * each node's -\u003eaborting store before its children are walked -\nkernel/sched/ext/ext.c:6623:\t\t * either we see a racing scx_link_sched() on -\u003echildren or it\nkernel/sched/ext/ext.c-6624-\t\t * sees -\u003eaborting.\n--\nkernel/sched/ext/ext.c=7490=static void scx_root_enable_workfn(struct kthread_work work)\n--\nkernel/sched/ext/ext.c-7583-\nkernel/sched/ext/ext.c:7584:\tret = scx_link_sched(sch);\nkernel/sched/ext/ext.c-7585-\tif (ret) {\n--\nkernel/sched/ext/internal.h=1521=struct scx_sched {\n--\nkernel/sched/ext/internal.h-1616-\nkernel/sched/ext/internal.h:1617:\tbool\t\t\tlinked;\t\t/ on -\u003echildren, see scx_link_sched() /\nkernel/sched/ext/internal.h-1618-\tbool\t\t\tsub_attached;\n--\nkernel/sched/ext/internal.h=2083=void scx_bypass(struct scx_sched sch, bool bypass);\nkernel/sched/ext/internal.h:2084:s32 scx_link_sched(struct scx_sched sch);\nkernel/sched/ext/internal.h-2085-void scx_unlink_sched(struct scx_sched sch);\n--\nkernel/sched/ext/sub.c=1506=void scx_sub_disable(struct scx_sched sch)\n--\nkernel/sched/ext/sub.c-1530-\t/\nkernel/sched/ext/sub.c:1531:\t * An enable that failed before scx_link_sched() succeeded never owned a\nkernel/sched/ext/sub.c-1532-\t * cgroup or task and won't be waited on by an ancestor's\n--\nkernel/sched/ext/sub.c=1709=void scx_sub_enable_workfn(struct kthread_work work)\n--\nkernel/sched/ext/sub.c-1764-\t/\nkernel/sched/ext/sub.c:1765:\t * Validate before scx_link_sched() publishes @sch, so an invalid sub\nkernel/sched/ext/sub.c-1766-\t * never becomes visible with an unallocated pshard.\n--\nkernel/sched/ext/sub.c-1774-\t/\nkernel/sched/ext/sub.c:1775:\t Allocate pshard[] before scx_link_sched() publishes @sch into the\nkernel/sched/ext/sub.c-1776-\t * parent's RCU children list. A concurrent revoke walking the tree\n--\nkernel/sched/ext/sub.c-1790-\nkernel/sched/ext/sub.c:1791:\tret = scx_link_sched(sch);\nkernel/sched/ext/sub.c-1792-\tif (ret)\n" }
39/2	2026/09/23 19:07	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 43468 output: 38 thoughts: 27 Thoughts: Okay, here's my interpretation of what's going on in that code, presented as a first-person thought process, keeping in mind my expertise: Diving into `kernel/sched/ext/ext.c` - Lines 6310-6345 Alright, let's zero in on lines 6310-6345 of `kernel/sched/ext/ext.c`. Given that I'm looking at this specific file and line range, I'm probably dealing with some extension to the core scheduler. I bet this is related to a custom scheduling policy, some novel load balancing strategy, or maybe even a specific hardware-related scheduling tweak. The line numbers suggest this is somewhere within a substantial function – likely more than a small helper or simple calculation. I need to understand the surrounding context to get the full picture, but based on the line numbers, this seems like it is a key piece. Okay, let me start by quickly scanning the function's signature and any comments to establish what function this chunk is within. What are the variables? What are the conditions? Is there a loop? From experience, I know that specific line ranges within this file tend to be associated with real-time performance, QoS constraints, or some kind of dynamic task migration logic. The naming conventions likely give me hints, but I can anticipate, based on my familiarity with the kernel, I'm likely going to encounter things like 'rq' (runqueue), 'entity', 'weight', possibly 'latency', maybe even hardware-specific registers. I'll need to figure out what the schedulers context here is (fair, realtime, etc.). I'm assuming this might be where a specific scheduling event is being handled. I need to see what's being calculated, what conditions are being checked. Are we making a decision about which task gets to run next? Are we modifying task priorities or maybe applying a penalty? The structure of the code will reveal the execution flow and the logic employed. This could be where the scheduler evaluates some task parameters or where it's making a final decision. I might even be able to deduce the scheduler goal from the logic here. This area is likely core to the custom extension, so I must understand the flow to determine its impact on the system. It should fit into the larger scheme.
40/2	2026/09/23 19:07	tool	read-file	0m Args: { "File": "kernel/sched/ext/ext.c", "FirstLine": 6300, "LineCount": 50 } Results: { "Contents": "6300:\t\n6301:\ts32 scx_link_sched(struct scx_sched sch)\n6302:\t{\n6303:\t\tscoped_guard(raw_spinlock_irqsave, \u0026scx_bypass_lock)\t/ for the parent bypass check /\n6304:\t\tscoped_guard(raw_spinlock, \u0026scx_sched_lock) {\n6305:\t#ifdef CONFIG_EXT_SUB_SCHED\n6306:\t\t\tstruct scx_sched parent = scx_parent(sch);\n6307:\t\n6308:\t\t\tif (parent) {\n6309:\t\t\t\ts32 ret;\n6310:\t\n6311:\t\t\t\t/\n6312:\t\t\t\t Bypass state is spread across per-cpu flags and a\n6313:\t\t\t\t * depth count, so inheriting it is tricky and has no\n6314:\t\t\t\t * valid use case. Refuse it.\n6315:\t\t\t\t /\n6316:\t\t\t\tif (READ_ONCE(parent-\u003ebypass_depth)) {\n6317:\t\t\t\t\tscx_error(sch, \"parent bypassing (%d)\", -EBUSY);\n6318:\t\t\t\t\treturn -EBUSY;\n6319:\t\t\t\t}\n6320:\t\n6321:\t\t\t\tret = rhashtable_lookup_insert_fast(\u0026scx_sched_hash,\n6322:\t\t\t\t\t\t\u0026sch-\u003ehash_node, scx_sched_hash_params);\n6323:\t\t\t\tif (ret) {\n6324:\t\t\t\t\tscx_error(sch, \"failed to insert into scx_sched_hash (%d)\",\n6325:\t\t\t\t\t\t ret);\n6326:\t\t\t\t\treturn ret;\n6327:\t\t\t\t}\n6328:\t\n6329:\t\t\t\tlist_add_tail_rcu(\u0026sch-\u003esibling, \u0026parent-\u003echildren);\n6330:\t\n6331:\t\t\t\t/\n6332:\t\t\t\t * Pairs with the mb after the -\u003eaborting assertion in\n6333:\t\t\t\t * scx_claim_exit(). Either we see -\u003eaborting and back\n6334:\t\t\t\t * out, or the exit path sees us and exits us.\n6335:\t\t\t\t /\n6336:\t\t\t\tsmp_mb();\n6337:\t\t\t\tif (unlikely(READ_ONCE(parent-\u003eaborting))) {\n6338:\t\t\t\t\trhashtable_remove_fast(\u0026scx_sched_hash, \u0026sch-\u003ehash_node,\n6339:\t\t\t\t\t\t\t scx_sched_hash_params);\n6340:\t\t\t\t\tlist_del_rcu(\u0026sch-\u003esibling);\n6341:\t\t\t\t\tscx_error(sch, \"parent disabled (%d)\", -ENOENT);\n6342:\t\t\t\t\treturn -ENOENT;\n6343:\t\t\t\t}\n6344:\t\n6345:\t\t\t\tsch-\u003elinked = true;\n6346:\t\t\t}\n6347:\t#endif\t/ CONFIG_EXT_SUB_SCHED */\n6348:\t\n6349:\t\t\tlist_add_tail_rcu(\u0026sch-\u003eall, \u0026scx_sched_all);\n" }
41/2	2026/09/23 19:07	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 44817 output: 38 thoughts: 1667 Thoughts: Fuzzing Analysis of the Provided Patch Okay, let's break this down. My initial assessment is that this patch does warrant fuzzing based on the guidelines. It touches core scheduler code (`kernel/sched/ext/ext.c`), and it introduces changes to the comparison functions used within `rhashtable` lookups and insertions for both sub-scheduler tracking and TID-to-task mapping. The modified code is definitely reachable because it's part of the critical path for task scheduling within `sched-ext`. Specifically, the patch introduces `scx_sched_cmpfn` and `scx_tid_cmpfn`. These functions are directly involved in crucial operations: `scx_find_sub_sched`, `rhashtable_lookup_insert_fast` (used in `scx_link_sched` and `scx_tid_hash_insert`), and `scx_bpf_tid_to_task`. This means any potential issues in these comparison functions directly impact how the scheduler functions. My immediate concern is around potential bugs introduced in these comparisons. My mind races through several possibilities: incorrect offset calculations between the `arg->key` and `ptr` structures within the comparison function, endianness mismatches, subtle type conversions, pointer arithmetic errors, or even, most concerningly, what happens if `key == NULL`? I recall that, according to the rhashtable implementation, if the key is NULL, the compare function isn't called during insertion, which is great because it avoids the null pointer dereference. The `rhashtable_lookup_insert_fast` implementation should handle that. I'll need to double-check my assumptions and rigorously analyze how `rhashtable` handles the `key` parameter in both `rhashtable_insert_fast` and `rhashtable_lookup_insert_fast` because that is a classic area where subtle bugs can arise, particularly around boundary conditions. The risk of even a small comparison error leading to incorrect task mapping or scheduler state corruption is high. This patch absolutely triggers my "must fuzz" sensor.
42/2	2026/09/23 19:07	tool	grepper	0m Args: { "Expression": "rhashtable_lookup_insert_fast", "PathPrefix": "include/linux/rhashtable.h" } Results: { "Output": "include/linux/rhashtable.h=932=static __always_inline int rhltable_insert(\n--\ninclude/linux/rhashtable.h-943-/*\ninclude/linux/rhashtable.h:944: rhashtable_lookup_insert_fast - lookup and insert object into hash table\ninclude/linux/rhashtable.h-945- * @ht:\t\thash table\n--\ninclude/linux/rhashtable.h-956- /\ninclude/linux/rhashtable.h:957:static __always_inline int rhashtable_lookup_insert_fast(\ninclude/linux/rhashtable.h-958-\tstruct rhashtable ht, struct rhash_head obj,\n--\ninclude/linux/rhashtable.h-979- \ninclude/linux/rhashtable.h:980: * Just like rhashtable_lookup_insert_fast(), but this function returns the\ninclude/linux/rhashtable.h-981- * object if it exists, NULL if it did not and the insertion was successful,\n" }
43/2	2026/09/23 19:07	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 47243 output: 37 thoughts: 27 Thoughts: Here's my summary, as though I'm thinking through this process: Diving into `rhashtable_lookup_insert_fast` Alright, let's take a look at `rhashtable_lookup_insert_fast`. My gut feeling is that it's a critical function, probably at the heart of how this rhashtable thing works, given the name. The "lookup" suggests retrieval, "insert" implies adding, and "fast"... well, that's what we always strive for, isn't it? I bet it's optimized for common use cases. So, I need to understand how this function balances speed with the complexities of concurrent access and hash table management. Let's see how they've implemented that in the kernel. Let's start with `include/linux/rhashtable.h`.
44/2	2026/09/23 19:07	tool	read-file	0m Args: { "File": "include/linux/rhashtable.h", "FirstLine": 955, "LineCount": 25 } Results: { "Contents": " 955:\t * table grows beyond 70%.\n 956:\t /\n 957:\tstatic __always_inline int rhashtable_lookup_insert_fast(\n 958:\t\tstruct rhashtable ht, struct rhash_head obj,\n 959:\t\tconst struct rhashtable_params params)\n 960:\t{\n 961:\t\tconst char key = rht_obj(ht, obj);\n 962:\t\tvoid ret;\n 963:\t\n 964:\t\tBUG_ON(ht-\u003ep.obj_hashfn);\n 965:\t\n 966:\t\tret = __rhashtable_insert_fast(ht, key + ht-\u003ep.key_offset, obj, params,\n 967:\t\t\t\t\t false);\n 968:\t\tif (IS_ERR(ret))\n 969:\t\t\treturn PTR_ERR(ret);\n 970:\t\n 971:\t\treturn ret == NULL ? 0 : -EEXIST;\n 972:\t}\n 973:\t\n 974:\t/\n 975:\t rhashtable_lookup_get_insert_fast - lookup and insert object into hash table\n 976:\t * @ht:\t\thash table\n 977:\t * @obj:\tpointer to hash head inside object\n 978:\t * @params:\thash table parameters\n 979:\t *\n" }
45/2	2026/09/23 19:07	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 47862 output: 36 thoughts: 83 Thoughts: Here's my understanding of the situation, given my expertise: Dissecting the Rhashtable Removal Process Okay, so I'm looking at how this key is calculated, specifically: `key = rht_obj(ht, obj) + ht->p.key_offset`. Right, that makes sense. We're taking an object (`obj`) within a rhashtable (`ht`), and we're deriving the actual key value (which is a `u64` in this case – could be a `sub_cgroup_id` or a thread ID or something similar). The `rht_obj` presumably gives us a base address or starting point for the object within the hashtable. Then, we add `ht->p.key_offset`. That offset is crucial; it tells us precisely where within that object's memory space the actual key resides. That's the standard way to locate the hash key. Now, I need to understand how the removal actually works, so let's quickly check the definition of `rhashtable_remove_fast`. It should be in `include/linux/rhashtable.h`. I'll want to see how this function is supposed to work without the usual locking overhead - the "fast" implies it's optimized for performance. Let's see how they've achieved that speed-up.
46/2	2026/09/23 19:07	tool	grepper	0m Args: { "Expression": "rhashtable_remove_fast", "PathPrefix": "include/linux/rhashtable.h" } Results: { "Output": "include/linux/rhashtable.h=1037=static __always_inline void rhashtable_lookup_get_insert_key(\n--\ninclude/linux/rhashtable.h-1045-\ninclude/linux/rhashtable.h:1046:/ Internal function, please use rhashtable_remove_fast() instead /\ninclude/linux/rhashtable.h:1047:static __always_inline int __rhashtable_remove_fast_one(\ninclude/linux/rhashtable.h-1048-\tstruct rhashtable ht, struct bucket_table tbl,\n--\ninclude/linux/rhashtable.h-1127-\ninclude/linux/rhashtable.h:1128:/ Internal function, please use rhashtable_remove_fast() instead /\ninclude/linux/rhashtable.h:1129:static __always_inline int __rhashtable_remove_fast(\ninclude/linux/rhashtable.h-1130-\tstruct rhashtable ht, struct rhash_head obj,\n--\ninclude/linux/rhashtable.h-1144-\t /\ninclude/linux/rhashtable.h:1145:\twhile ((err = __rhashtable_remove_fast_one(ht, tbl, obj, params,\ninclude/linux/rhashtable.h-1146-\t\t\t\t\t\t rhlist)) \u0026\u0026\n--\ninclude/linux/rhashtable.h-1155-/*\ninclude/linux/rhashtable.h:1156: rhashtable_remove_fast - remove object from hash table\ninclude/linux/rhashtable.h-1157- * @ht:\t\thash table\n--\ninclude/linux/rhashtable.h-1169- /\ninclude/linux/rhashtable.h:1170:static __always_inline int rhashtable_remove_fast(\ninclude/linux/rhashtable.h-1171-\tstruct rhashtable ht, struct rhash_head *obj,\n--\ninclude/linux/rhashtable.h-1173-{\ninclude/linux/rhashtable.h:1174:\treturn __rhashtable_remove_fast(ht, obj, params, false);\ninclude/linux/rhashtable.h-1175-}\n--\ninclude/linux/rhashtable.h=1192=static __always_inline int rhltable_remove(\n--\ninclude/linux/rhashtable.h-1195-{\ninclude/linux/rhashtable.h:1196:\treturn __rhashtable_remove_fast(\u0026hlt-\u003eht, \u0026list-\u003erhead, params, true);\ninclude/linux/rhashtable.h-1197-}\n" }
47/2	2026/09/23 19:07	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 48961 output: 26 thoughts: 177 Thoughts: Analyzing the `rhashtable_params` Modification for Fuzzing Potential Okay, so I'm looking at these new comparison functions, `scx_sched_cmpfn` and `scx_tid_cmpfn`, which have been introduced for `rhashtable_params`. My initial thought is to figure out if this modification impacts the key comparison logic within the extensible scheduler, specifically how it handles lookups and inserts. Is this something that's even reachable during normal operations, and more importantly, is it worth dedicating fuzzing resources to? The good news is, yes! This is definitely within the core of the scheduler and BPF's `sched_ext` functionality. The changes directly impact the executable code that's running whenever these `sched_ext` operations occur. We're talking about sub-scheduler linking/lookup and TID tracking - all critical components. Now, let me solidify my plan: 1. `WorthFuzzing`: Confirmed. This is a solid candidate. 2. `EnableConfigs`: I need to determine what kernel configurations are required to enable this specific code path in `kernel/sched/ext/ext.c`. Time to dive into the Makefile within `kernel/sched/ext/` and figure this out.
48/2	2026/09/23 19:07	tool	grepper	0m Error: no matches Args: { "Expression": "ext\\.o", "PathPrefix": "kernel/sched" } Results: { "error": "no matches" }
49/2	2026/09/23 19:07	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 49449 output: 26 thoughts: 11 Thoughts: Here's a summary of my thought process, as requested: Diving into the Scheduler's Makefile Okay, so I need to understand something related to the scheduler, and my gut feeling is that the build process itself might hold some clues. Let's start by looking at `kernel/sched/Makefile`. This is the logical first step, right? The Makefile will dictate how the scheduler code gets compiled, linked, and potentially even configured during the build. I'm hoping I can glean some insights from the build dependencies, any specific flags being passed to the compiler, or maybe even conditional compilation logic related to scheduler features. This is where the magic (or the mud) of build systems lives. Hopefully, it is reasonably clean.
50/2	2026/09/23 19:07	tool	grepper	0m Args: { "Expression": "ext", "PathPrefix": "kernel/sched/Makefile" } Results: { "Output": "kernel/sched/Makefile=8=ccflags-y += $(call cc-disable-warning, unused-but-set-variable)\n--\nkernel/sched/Makefile-10-# These files are disabled because they produce non-interesting flaky coverage\nkernel/sched/Makefile:11:# that is not a function of syscall inputs. E.g. involuntary context switches.\nkernel/sched/Makefile-12-KCOV_INSTRUMENT := n\n" }
51/2	2026/09/23 19:07	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 49752 output: 31 thoughts: 16 Thoughts: Okay, here's my interpretation of reading the first 40 lines of `kernel/sched/Makefile`, presented as my internal thought process: Diving into the Scheduler Makefile Alright, let's get into the heart of the scheduler's build process. Scanning through the initial lines of `kernel/sched/Makefile`, I'm looking for the foundational pieces. Typically, this is where you find the core definitions, dependencies, and rules for how the scheduler components are compiled and linked. I'm immediately expecting to see variable assignments, likely defining source file lists, object file paths, and compiler flags. Probably some conditional logic based on kernel configuration options too; it's practically a guarantee, given the modular nature of the kernel. I'm hoping to identify the key targets – the main scheduler object files or libraries that will ultimately be linked into the kernel image. I'm mentally preparing for any architecture-specific include paths. You never know when they will make an appearance. I am searching for hints about how the scheduler interacts with other kernel subsystems during the build. Are there dependencies on other parts of the kernel? Are the scheduler's files being built in a specific order? This opening section is usually the blueprint; it gives you the overall structure and sets the stage for the rest of the file. I'll need to absorb this initial context before moving deeper.
52/2	2026/09/23 19:07	tool	read-file	0m Args: { "File": "kernel/sched/Makefile", "FirstLine": 1, "LineCount": 40 } Results: { "Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0\n 2:\t\n 3:\tCONTEXT_ANALYSIS_core.o := y\n 4:\tCONTEXT_ANALYSIS_fair.o := y\n 5:\t\n 6:\t# The compilers are complaining about unused variables inside an if(0) scope\n 7:\t# block. This is daft, shut them up.\n 8:\tccflags-y += $(call cc-disable-warning, unused-but-set-variable)\n 9:\t\n 10:\t# These files are disabled because they produce non-interesting flaky coverage\n 11:\t# that is not a function of syscall inputs. E.g. involuntary context switches.\n 12:\tKCOV_INSTRUMENT := n\n 13:\t\n 14:\t# Disable KCSAN to avoid excessive noise and performance degradation. To avoid\n 15:\t# false positives ensure barriers implied by sched functions are instrumented.\n 16:\tKCSAN_SANITIZE := n\n 17:\tKCSAN_INSTRUMENT_BARRIERS := y\n 18:\t\n 19:\tifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)\n 20:\t# According to Alan Modra \u003calan@linuxcare.com.au\u003e, the -fno-omit-frame-pointer is\n 21:\t# needed for x86 only. Why this used to be enabled for all architectures is beyond\n 22:\t# me. I suspect most platforms don't need this, but until we know that for sure\n 23:\t# I turn this off for IA-64 only. Andreas Schwab says it's also needed on m68k\n 24:\t# to get a correct value for the wait-channel (WCHAN in ps). --davidm\n 25:\tCFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer\n 26:\tendif\n 27:\t\n 28:\t# Branch profiling isn't noinstr-safe\n 29:\tifdef CONFIG_TRACE_BRANCH_PROFILING\n 30:\tCFLAGS_build_policy.o += -DDISABLE_BRANCH_PROFILING\n 31:\tCFLAGS_build_utility.o += -DDISABLE_BRANCH_PROFILING\n 32:\tendif\n 33:\t#\n 34:\t# Build efficiency:\n 35:\t#\n 36:\t# These compilation units have roughly the same size and complexity - so their\n 37:\t# build parallelizes well and finishes roughly at once:\n 38:\t#\n 39:\tobj-y += core.o\n 40:\tobj-y += fair.o\n" }
53/2	2026/09/23 19:07	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 50755 output: 32 thoughts: 21 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person: Digging Deeper into the Scheduler Build Process Right, let's not just assume we know where the `ext` component gets built. My immediate instinct is to double-check the `kernel/sched/Makefile`. We can't be too sure when it comes to the build process, there are many layers. I'm going to quickly navigate down to that specific Makefile to confirm the exact build location for `ext`. Best to verify and trust nothing. It's often the small details in the Makefiles that reveal the real dependencies and order of operations. Gotta make sure nothing is overlooked.
54/2	2026/09/23 19:07	tool	read-file	0m Args: { "File": "kernel/sched/Makefile", "FirstLine": 41, "LineCount": 40 } Results: { "Contents": " 41:\tobj-y += build_policy.o\n 42:\tobj-y += build_utility.o\n" }
55/2	2026/09/23 19:07	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 51002 output: 26 thoughts: 44 Thoughts: Here's my analysis of the situation: Investigating Build Dependencies Okay, so I'm seeing references to `build_policy.o` and `build_utility.o`. This immediately tells me I need to dive into the core scheduling code, specifically within the kernel. My first port of call will be `kernel/sched/build_policy.c` and `kernel/sched/build_utility.c`. These files are the obvious candidates to examine, given the naming conventions. I need to understand what's being built, what dependencies they have, and how they contribute to the overall scheduling policy and utilities. This should shed light on the build process and any potential issues I might be facing.
56/2	2026/09/23 19:07	tool	grepper	0m Args: { "Expression": "ext\\.c", "PathPrefix": "kernel/sched" } Results: { "Output": "kernel/sched/build_policy.c-70-# include \"ext/inlines.h\"\nkernel/sched/build_policy.c:71:# include \"ext/ext.c\"\nkernel/sched/build_policy.c-72-# include \"ext/cid.c\"\n--\nkernel/sched/ext/idle.c=1525=static const struct btf_kfunc_id_set scx_kfunc_set_idle = {\n--\nkernel/sched/ext/idle.c-1537- \nkernel/sched/ext/idle.c:1538: These kfuncs are also members of scx_kfunc_ids_unlocked (see ext.c) because\nkernel/sched/ext/idle.c-1539- * they're callable from unlocked contexts in addition to ops.select_cpu() and\n--\nkernel/sched/ext/sub.c-10- * sub-scheduler enable/disable paths. The core dispatch/enqueue machinery it\nkernel/sched/ext/sub.c:11: * builds on lives in ext.c.\nkernel/sched/ext/sub.c-12- *\n" }
57/2	2026/09/23 19:07	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 51505 output: 36 thoughts: 21 Thoughts: Here's my analysis of the provided code snippet from `kernel/sched/build_policy.c`, expressed as my internal thought process: Diving into Build Policy Considerations Alright, I'm focusing on the `kernel/sched/build_policy.c` file, specifically lines 55 through 80. My immediate thought is, given my expertise, what specific aspect of the scheduling policy implementation does this region cover? I'm anticipating this deals with the initial setup or the construction of some data structure related to the scheduler's behavior. It might be related to things like defining the parameters or constraints under which tasks are considered for scheduling. I'm keen to see if this handles the configuration of priority levels, the assignment of tasks to specific CPUs, or even the incorporation of heuristics for task placement. I'll need to look closely for any function calls or variable assignments that give clues about the overall goal of this code section. This is likely a critical section for understanding how the system balances responsiveness with resource utilization. It's time to dig in and understand the nuances.
58/2	2026/09/23 19:07	tool	read-file	0m Args: { "File": "kernel/sched/build_policy.c", "FirstLine": 55, "LineCount": 35 } Results: { "Contents": " 55:\t#include \"pelt.c\"\n 56:\t\n 57:\t#include \"cputime.c\"\n 58:\t#include \"deadline.c\"\n 59:\t\n 60:\t#ifdef CONFIG_SCHED_CLASS_EXT\n 61:\t# include \u003clinux/btf_ids.h\u003e\n 62:\t# include \u003clinux/find.h\u003e\n 63:\t# include \u003clinux/genalloc.h\u003e\n 64:\t# include \"ext/types.h\"\n 65:\t# include \"ext/internal.h\"\n 66:\t# include \"ext/cid.h\"\n 67:\t# include \"ext/arena.h\"\n 68:\t# include \"ext/idle.h\"\n 69:\t# include \"ext/sub.h\"\n 70:\t# include \"ext/inlines.h\"\n 71:\t# include \"ext/ext.c\"\n 72:\t# include \"ext/cid.c\"\n 73:\t# include \"ext/arena.c\"\n 74:\t# include \"ext/idle.c\"\n 75:\t# include \"ext/sub.c\"\n 76:\t#endif\n 77:\t\n 78:\t#include \"syscalls.c\"\n" }
59/2	2026/09/23 19:07	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 52129 output: 38 thoughts: 1707 Thoughts: Analysis of Extensible Scheduling Class Configuration and Symbols Okay, so I'm looking at `build_policy.c` and immediately see that `ext/ext.c` is included under `#ifdef CONFIG_SCHED_CLASS_EXT`. That's the starting point. Inside `ext.c`, things get interesting: `CONFIG_EXT_SUB_SCHED` controls whether `scx_sched_cmpfn` and its usage within `scx_sched_hash_params` are enabled, and `scx_tid_cmpfn` and `scx_tid_hash_params` are always present when `CONFIG_SCHED_CLASS_EXT` is set. `CONFIG_EXT_SUB_SCHED` itself depends on `SCHED_CLASS_EXT` and `CGROUPS`. First, let me confirm the dependency tree. I need to make sure I don't miss anything. `CONFIG_SCHED_CLASS_EXT` requires `BPF_SYSCALL`, `BPF_JIT`, and `DEBUG_INFO_BTF`. `CONFIG_EXT_SUB_SCHED` needs `SCHED_CLASS_EXT` and `CGROUPS`. Since `EXT_SUB_SCHED` is `def_bool y`, I can assume `EXT_SUB_SCHED` is enabled by default if its dependencies are met. Thus, the necessary configs to enable are: `SCHED_CLASS_EXT`, `EXT_SUB_SCHED` (or just `CGROUPS`), `BPF_SYSCALL`, `BPF_JIT`, and `DEBUG_INFO_BTF`. Now, let's nail down the specific symbols. The goal is to identify which functions are modified or implement the new logic, according to the guidelines. I need to figure out which ones are critical entrypoints. The obvious suspects are `scx_sched_cmpfn` and `scx_tid_cmpfn`. The code defines these, but they are declared `static __always_inline`. Normally, that means the compiler should inline them. However, because their addresses are being passed to struct members (specifically `.obj_cmpfn`), the compiler can't reliably inline the function. It must generate a symbol for each. The struct `.obj_cmpfn` is used in a call to `rhashtable_lookup_insert_fast` which means it will be used as a function pointer in an indirect call! That's a key detail! The next step is to examine what non-static functions call or use `scx_sched_hash_params` and `scx_tid_hash_params` directly. That's where the actual changes come into play, and where the modified logic is. For `scx_tid_hash_params`: * `scx_tid_hash_insert` is static, which is called by the following: * `scx_post_fork(struct task_struct p)` - This is a lifecycle function called on fork. That's a standard path, so let's skip it unless it's the only* entrypoint. * `scx_root_enable_workfn` - This one seems less ubiquitous, and could be a critical entry point. It inserts all tasks into `scx_tid_hash`. * `sched_ext_dead(struct task_struct p)` - Called on task death. Another lifecycle function to be weary of. `scx_bpf_tid_to_task(u64 tid)` - A BPF kfunc! This function uses `rhashtable_lookup` with `scx_tid_hash_params`! This is a good candidate for listing as a focus symbol as the lookup will be the core of the functionality. For `scx_sched_hash_params`: * `scx_link_sched` - inserts into the hash via `rhashtable_lookup_insert_fast`. * `scx_unlink_sched` - removes from the hash via `rhashtable_remove_fast`. * `scx_find_sub_sched` - static, called by: * `scx_bpf_sub_dispatch` - A BPF kfunc! * `scx_bpf_sub_caps` - A BPF kfunc! * `scx_bpf_sub_kill_bstr` - A BPF kfunc! Now, the BPF functions are interesting, especially the ones that directly interface with the hash tables (`scx_bpf
60/2	2026/09/23 19:08	tool	read-file	0m Args: { "File": "kernel/sched/ext/sub.c", "FirstLine": 1705, "LineCount": 95 } Results: { "Contents": "1705:\t\t\treturn false;\n1706:\t\t}\n1707:\t}\n1708:\t\n1709:\tvoid scx_sub_enable_workfn(struct kthread_work work)\n1710:\t{\n1711:\t\tstruct scx_enable_cmd cmd = container_of(work, struct scx_enable_cmd, work);\n1712:\t\tstruct sched_ext_ops ops = cmd-\u003eops;\n1713:\t\tstruct cgroup cgrp;\n1714:\t\tstruct scx_sched parent, sch;\n1715:\t\tstruct scx_task_iter sti;\n1716:\t\tstruct task_struct p;\n1717:\t\ts32 i, ret;\n1718:\t\n1719:\t\tmutex_lock(\u0026scx_enable_mutex);\n1720:\t\n1721:\t\tif (!scx_enabled()) {\n1722:\t\t\tret = -ENODEV;\n1723:\t\t\tgoto out_unlock;\n1724:\t\t}\n1725:\t\n1726:\t\t/ See scx_root_enable_workfn() for the @ops-\u003epriv check. /\n1727:\t\tif (rcu_access_pointer(ops-\u003epriv)) {\n1728:\t\t\tret = -EBUSY;\n1729:\t\t\tgoto out_unlock;\n1730:\t\t}\n1731:\t\n1732:\t\tcgrp = cgroup_get_from_id(ops-\u003esub_cgroup_id);\n1733:\t\tif (IS_ERR(cgrp)) {\n1734:\t\t\tret = PTR_ERR(cgrp);\n1735:\t\t\tgoto out_unlock;\n1736:\t\t}\n1737:\t\n1738:\t\traw_spin_lock_irq(\u0026scx_sched_lock);\n1739:\t\tparent = find_parent_sched(cgrp);\n1740:\t\tif (IS_ERR(parent)) {\n1741:\t\t\traw_spin_unlock_irq(\u0026scx_sched_lock);\n1742:\t\t\tret = PTR_ERR(parent);\n1743:\t\t\tgoto out_put_cgrp;\n1744:\t\t}\n1745:\t\tkobject_get(\u0026parent-\u003ekobj);\n1746:\t\traw_spin_unlock_irq(\u0026scx_sched_lock);\n1747:\t\n1748:\t\t/\n1749:\t\t * Flip the hot-path gates before ops-\u003epriv is published - the sub's\n1750:\t\t * programs can e.g. kick cpus from that point on. The matching dec is\n1751:\t\t * at the end of scx_sched_free_rcu_work().\n1752:\t\t /\n1753:\t\tstatic_branch_inc(\u0026__scx_has_subs);\n1754:\t\n1755:\t\t/ scx_alloc_and_add_sched() consumes @cgrp whether it succeeds or not /\n1756:\t\tsch = scx_alloc_and_add_sched(cmd, cgrp, parent);\n1757:\t\tkobject_put(\u0026parent-\u003ekobj);\n1758:\t\tif (IS_ERR(sch)) {\n1759:\t\t\tstatic_branch_dec(\u0026__scx_has_subs);\n1760:\t\t\tret = PTR_ERR(sch);\n1761:\t\t\tgoto out_unlock;\n1762:\t\t}\n1763:\t\n1764:\t\t/\n1765:\t\t * Validate before scx_link_sched() publishes @sch, so an invalid sub\n1766:\t\t * never becomes visible with an unallocated pshard.\n1767:\t\t /\n1768:\t\tret = scx_validate_ops(sch, ops);\n1769:\t\tif (ret)\n1770:\t\t\tgoto err_disable;\n1771:\t\n1772:\t\tscx_rescue_check_timeout(sch);\n1773:\t\n1774:\t\t/\n1775:\t\t * Allocate pshard[] before scx_link_sched() publishes @sch into the\n1776:\t\t * parent's RCU children list. A concurrent revoke walking the tree\n1777:\t\t * would otherwise dereference sch-\u003epshard[si] while it's still NULL.\n1778:\t\t * Unlike the root path, the cid shard layout is stable at this point.\n1779:\t\t \n1780:\t\t scx_alloc_pshards() skips allocation when @sch's arena pool isn't\n1781:\t\t * initialized, so scx_arena_pool_init() must run first.\n1782:\t\t */\n1783:\t\tret = scx_arena_pool_init(sch);\n1784:\t\tif (ret)\n1785:\t\t\tgoto err_disable;\n1786:\t\n1787:\t\tret = scx_alloc_pshards(sch);\n1788:\t\tif (ret)\n1789:\t\t\tgoto err_disable;\n1790:\t\n1791:\t\tret = scx_link_sched(sch);\n1792:\t\tif (ret)\n1793:\t\t\tgoto err_disable;\n1794:\t\n1795:\t\tret = scx_sched_sysfs_add(sch);\n1796:\t\tif (ret)\n1797:\t\t\tgoto err_disable;\n1798:\t\n1799:\t\tif (sch-\u003elevel \u003e= SCX_SUB_MAX_DEPTH) {\n" }
61/2	2026/09/23 19:08	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 56339 output: 237 thoughts: 2146 Thoughts: Analysis of `rhashtable` Comparison Function Modification in Scheduler Extension Okay, so I've been digging into this patch that introduces custom comparison functions for `rhashtable` lookups within the scheduler extension. My initial focus was on understanding the changes and potential implications, particularly in the context of fuzzing. First, I examined `scx_sub_enable_workfn` which calls `scx_link_sched`, `scx_link_sched` uses `rhashtable_lookup_insert_fast` for the `scx_sched_hash`, and `scx_unlink_sched` uses `rhashtable_remove_fast`. Then I looked at how `scx_bpf_sub_dispatch` calls `scx_find_sub_sched` which calls `rhashtable_lookup`, and how `scx_bpf_tid_to_task` is handled using a similar `rhashtable` lookup for TID mapping via `scx_tid_hash`. These functions are all critical points where the patch alters the core lookup behavior. The patch itself defines `scx_sched_cmpfn` and `scx_tid_cmpfn`. The code clearly places these into the `rhashtable_params` structures, which is key. I wanted to make sure these comparison functions would be available as symbols even if they were `__always_inline`. The C standard specifies that taking the address, which is done here, requires a definition. This means the linker will always generate a symbol for the comparison function. To be absolutely sure about coverage, I considered, and decided to include, the use of those functions as well, for thoroughness. Then, I identified all the places these hash parameters are used. For `scx_sched_hash_params`, it's in `scx_link_sched`, `scx_unlink_sched`, `init_sched_ext_class`, and `scx_find_sub_sched`. For `scx_tid_hash_params`, it's in `scx_tid_hash_insert`, `sched_ext_dead`, `scx_root_enable_workfn`, `scx_root_disable`, and `scx_bpf_tid_to_task`. Notably, these aren't hot paths like kmalloc or page fault handlers, but are instead specific to the scheduler extension logic, meaning any potential issues would have localized impact. I've confirmed the config dependencies: `SCHED_CLASS_EXT`, `EXT_SUB_SCHED`, `BPF_SYSCALL`, `BPF_JIT`, `DEBUG_INFO_BTF`, and `CGROUPS`. This confirms the relevant features are enabled, and the patch won't break anything. Finally, I verified the `BUILD_BUG_ON` checks are compile-time assertions, and the comparison functions are returning non-zero on mismatch, which is the expected behavior for `rhashtable`. This confirms the core functionality of replacing the default `memcmp` with custom logic is intact, which is an important change. These comparison functions directly impact the scheduler extension and BPF integration. Given all this, this patch is worth fuzzing because it modifies the comparison logic for `rhashtable` lookups in core scheduler/BPF subsystems used by sched_ext sub-scheduler lookup and TID-to-task lookup. I've identified these symbols as critical points to focus on: `scx_sched_cmpfn`, `scx_tid_cmpfn`, `scx_link_sched`, `scx_unlink_sched`, `scx_bpf_tid_to_task`, and `scx_bpf_sub_dispatch`.
62/2	2026/09/23 19:08	tool	set-results	0m Args: { "EnableConfigs": [ "SCHED_CLASS_EXT", "EXT_SUB_SCHED", "BPF_SYSCALL", "BPF_JIT", "DEBUG_INFO_BTF", "CGROUPS" ], "FocusSymbols": [ "scx_sched_cmpfn", "scx_tid_cmpfn", "scx_link_sched", "scx_unlink_sched", "scx_bpf_tid_to_task", "scx_bpf_sub_dispatch" ], "Reasoning": "The patch introduces custom rhashtable comparison callbacks (scx_sched_cmpfn and scx_tid_cmpfn) for the extensible scheduler class (sched_ext) to compare 64-bit keys directly instead of using default memcmp. This modifies key matching logic for sub-scheduler registration/lookups and task TID tracking in the core scheduler and BPF subsystem, which is reachable in virtualized environments via BPF struct_ops schedulers.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "SCHED_CLASS_EXT", "EXT_SUB_SCHED", "BPF_SYSCALL", "BPF_JIT", "DEBUG_INFO_BTF", "CGROUPS" ], "FocusSymbols": [ "scx_sched_cmpfn", "scx_tid_cmpfn", "scx_link_sched", "scx_unlink_sched", "scx_bpf_tid_to_task", "scx_bpf_sub_dispatch" ], "Reasoning": "The patch introduces custom rhashtable comparison callbacks (scx_sched_cmpfn and scx_tid_cmpfn) for the extensible scheduler class (sched_ext) to compare 64-bit keys directly instead of using default memcmp. This modifies key matching logic for sub-scheduler registration/lookups and task TID tracking in the core scheduler and BPF subsystem, which is reachable in virtualized environments via BPF struct_ops schedulers.", "WorthFuzzing": true }
63/1	2026/09/23 19:08	action	If	0m Args: { "WorthFuzzing": true } Results: null
64/2	2026/09/23 19:08	agent	kmsan-evaluator	0m Model: core Args: null Results: { "KMSANReasoning": "The patch defines custom comparator callbacks (scx_sched_cmpfn and scx_tid_cmpfn) for the rhashtable instances in sched_ext (scx_sched_hash and scx_tid_hash), replacing the default memcmp-based rhashtable_compare with direct 64-bit integer equality comparisons.\n\nThis change does not allocate any new memory, introduce stack/heap buffers, alter structure layouts or padding, or copy data to user space. It only modifies how existing 64-bit integer keys (sub_cgroup_id and tid) are compared during hashtable lookups and insertions. Memory safety concerns for pointer validity and object lifetimes (such as UAF or out-of-bounds access during table traversal) are already handled by KASAN and RCU. There are no uninitialized memory access or info-leak risks, making a dedicated KMSAN fuzzing session unnecessary.", "NeedsKMSAN": false } Instruction: You are an expert Linux kernel security engineer specializing in kernel memory error detectors (KASAN and KMSAN). Your job is to review the provided patch series and determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer) fuzzing session in addition to standard KASAN fuzzing. CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN: - Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable a comprehensive suite of debugging tools and sanitizers, including KASAN (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks. - KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap, or page allocations) and kernel-to-user memory info-leaks. Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN, LOCKDEP, OR OTHER STANDARD BUG DETECTORS. A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks that are detected ONLY by KMSAN. Look holistically at the patch series and surrounding code. Even if no direct uninitialized field accesses or new buffer allocations are added in the diff itself, a patch may alter control flow, bounds checking, or data length calculations in ways that change how the rest of the code operates on existing buffers (e.g. allowing uninitialized stack/heap memory to be read, copied to user space, or used in control flow). Do not hesitate to use your code access tools to inspect the surrounding code, called functions, and callers. Set NeedsKMSAN=true ONLY IF the patch introduces or modifies: 1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb attributes, ioctl output arguments, socket options, or BPF buffers) where fields or structure padding might not be fully initialized/zeroed. 2. Conditional logic or branching that depends on potentially uninitialized variables or struct fields. 3. Allocation or initialization of complex data structures where uninitialized fields could be read later in reachable code paths. 4. Bounds checks, lengths, or logic in a way that allows surrounding code to access uninitialized bytes of existing buffers. Set NeedsKMSAN=false IF: - The code changes primarily risk out-of-bounds access, array overflows, NULL pointer dereferences, locking deadlocks, or use-after-free bugs (these are already caught by KASAN, LOCKDEP, or standard bug detectors). - All stack/heap structures touched or introduced by the patch are fully zeroed or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied. - The patch does not introduce any risk of uninitialized memory usage or info-leaks. Use your code access tools to inspect the surrounding code if necessary, then provide detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch. Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit c3147b540cb147ce77fa96a506833c41639eed1c Author: syz-cluster <triage@syzkaller.com> Date: Wed Sep 23 19:05:18 2026 +0000 syz-cluster: applied patch under review diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c index 51de1d8b72a1e..705a937268505 100644 --- a/kernel/sched/ext/ext.c +++ b/kernel/sched/ext/ext.c @@ -41,10 +41,21 @@ struct scx_sched __rcu scx_root; LIST_HEAD(scx_sched_all); #ifdef CONFIG_EXT_SUB_SCHED +static __always_inline int scx_sched_cmpfn(struct rhashtable_compare_arg arg, + const void ptr) +{ + const struct scx_sched sch = ptr; + + BUILD_BUG_ON(sizeof_field(struct scx_sched, ops.sub_cgroup_id) != sizeof(u64)); + + return sch->ops.sub_cgroup_id != (const u64 )arg->key; +} + const struct rhashtable_params scx_sched_hash_params = { .key_len = sizeof_field(struct scx_sched, ops.sub_cgroup_id), .key_offset = offsetof(struct scx_sched, ops.sub_cgroup_id), .head_offset = offsetof(struct scx_sched, hash_node), + .obj_cmpfn = scx_sched_cmpfn, .insecure_elasticity = true, /* inserted under scx_sched_lock / }; @@ -52,10 +63,21 @@ struct rhashtable scx_sched_hash; #endif / see SCX_OPS_TID_TO_TASK / +static __always_inline int scx_tid_cmpfn(struct rhashtable_compare_arg arg, + const void ptr) +{ + const struct sched_ext_entity scx = ptr; + + BUILD_BUG_ON(sizeof_field(struct sched_ext_entity, tid) != sizeof(u64)); + + return scx->tid != (const u64 )arg->key; +} + static const struct rhashtable_params scx_tid_hash_params = { .key_len = sizeof_field(struct sched_ext_entity, tid), .key_offset = offsetof(struct sched_ext_entity, tid), .head_offset = offsetof(struct sched_ext_entity, tid_hash_node), + .obj_cmpfn = scx_tid_cmpfn, .insecure_elasticity = true, /* inserted/removed under scx_tasks_lock */ }; static struct rhashtable scx_tid_hash;
65/3	2026/09/23 19:08	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 2576 output: 36 thoughts: 961 Thoughts: KMSAN Fuzzing Evaluation for Patch in kernel/sched/ext/ext.c Alright, let's get down to business. My task is to determine if this patch to `kernel/sched/ext/ext.c` necessitates a dedicated KMSAN fuzzing session, beyond the usual KASAN checks. I'm a seasoned kernel security engineer, and memory error detectors are my domain, so I can see this code pretty clearly. The instructions are clear: only flag `NeedsKMSAN=true` if the changes introduce or expose uninitialized memory risks that only KMSAN would catch. This is a defensive patch review, a quality assurance step for fuzzing configuration, so the risk severity is essentially benign. Now, let's dive into this patch. It touches `kernel/sched/ext/ext.c`, and the diff shows two new comparison functions (`scx_sched_cmpfn` and `scx_tid_cmpfn`) being added and hooked into the `rhashtable_params` structures for `scx_sched_hash` and `scx_tid_hash` respectively. These functions compare the `sub_cgroup_id` of a `scx_sched` struct and the `tid` of a `sched_ext_entity` struct respectively, to a provided key. Crucially, I see that this is about providing an `obj_cmpfn` for rhashtable comparisons. I need to confirm there is no risk of exposing uninitialized memory by reading it. Looking through the code, I see that the keys for comparison are pointers to valid `u64` values and the comparisons are done in a straightforward manner, checking for inequality, which is consistent with the general pattern I see in the code. I do not see any new reads of uninitialized memory in the code. This is purely new comparison functions to support the rhashtable logic. So, given the nature of the changes (comparison functions within rhashtable lookups) and my understanding of the relevant code, I'm confident there is no risk of exposing uninitialized memory in this patch that is not already covered by standard KASAN fuzzing. This patch doesn't warrant a dedicated KMSAN fuzzing session. The `set-results` tool will report this decision.
66/3	2026/09/23 19:08	tool	read-file	0m Args: { "File": "kernel/sched/ext/ext.c", "FirstLine": 35, "LineCount": 55 } Results: { "Contents": " 35:\tstruct scx_sched __rcu scx_root;\n 36:\t\n 37:\t/\n 38:\t * All scheds, writers must hold both scx_enable_mutex and scx_sched_lock.\n 39:\t * Readers can hold either or rcu_read_lock().\n 40:\t /\n 41:\tLIST_HEAD(scx_sched_all);\n 42:\t\n 43:\t#ifdef CONFIG_EXT_SUB_SCHED\n 44:\tstatic __always_inline int scx_sched_cmpfn(struct rhashtable_compare_arg arg,\n 45:\t\t\t\t\t\t const void ptr)\n 46:\t{\n 47:\t\tconst struct scx_sched sch = ptr;\n 48:\t\n 49:\t\tBUILD_BUG_ON(sizeof_field(struct scx_sched, ops.sub_cgroup_id) != sizeof(u64));\n 50:\t\n 51:\t\treturn sch-\u003eops.sub_cgroup_id != (const u64 )arg-\u003ekey;\n 52:\t}\n 53:\t\n 54:\tconst struct rhashtable_params scx_sched_hash_params = {\n 55:\t\t.key_len\t\t= sizeof_field(struct scx_sched, ops.sub_cgroup_id),\n 56:\t\t.key_offset\t\t= offsetof(struct scx_sched, ops.sub_cgroup_id),\n 57:\t\t.head_offset\t\t= offsetof(struct scx_sched, hash_node),\n 58:\t\t.obj_cmpfn\t\t= scx_sched_cmpfn,\n 59:\t\t.insecure_elasticity\t= true,\t/* inserted under scx_sched_lock /\n 60:\t};\n 61:\t\n 62:\tstruct rhashtable scx_sched_hash;\n 63:\t#endif\n 64:\t\n 65:\t/ see SCX_OPS_TID_TO_TASK /\n 66:\tstatic __always_inline int scx_tid_cmpfn(struct rhashtable_compare_arg arg,\n 67:\t\t\t\t\t\t const void ptr)\n 68:\t{\n 69:\t\tconst struct sched_ext_entity scx = ptr;\n 70:\t\n 71:\t\tBUILD_BUG_ON(sizeof_field(struct sched_ext_entity, tid) != sizeof(u64));\n 72:\t\n 73:\t\treturn scx-\u003etid != (const u64 )arg-\u003ekey;\n 74:\t}\n 75:\t\n 76:\tstatic const struct rhashtable_params scx_tid_hash_params = {\n 77:\t\t.key_len\t\t= sizeof_field(struct sched_ext_entity, tid),\n 78:\t\t.key_offset\t\t= offsetof(struct sched_ext_entity, tid),\n 79:\t\t.head_offset\t\t= offsetof(struct sched_ext_entity, tid_hash_node),\n 80:\t\t.obj_cmpfn\t\t= scx_tid_cmpfn,\n 81:\t\t.insecure_elasticity\t= true,\t/* inserted/removed under scx_tasks_lock /\n 82:\t};\n 83:\tstatic struct rhashtable scx_tid_hash;\n 84:\t\n 85:\t/\n 86:\t * During exit, a task may schedule after losing its PIDs. When disabling the\n 87:\t * BPF scheduler, we need to be able to iterate tasks in every state to\n 88:\t * guarantee system safety. Maintain a dedicated task list which contains every\n 89:\t * task between its fork and eventual free.\n" }
67/3	2026/09/23 19:08	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 4996 output: 33 thoughts: 549 Thoughts: Analyzing the rhashtable Optimization Okay, let's break down this patch. The key change is the addition of `.obj_cmpfn` to `scx_sched_hash_params` and `scx_tid_hash_params`. Previously, the `rhashtable` implementation, when lacking a custom comparison function (`obj_cmpfn`), would fall back to a `memcmp` call. Specifically, it would compare a portion of the data pointed to by the hash table entry's pointer (`ptr + ht->p.key_offset`) with the lookup key (`arg->key`) using `memcmp`. Now, with `obj_cmpfn` specified, the `rhashtable` will call `params.obj_cmpfn(arg, ptr)` instead of `memcmp`. In this particular case, both `scx_sched_cmpfn` and `scx_tid_cmpfn` are performing a direct comparison: `sch->ops.sub_cgroup_id != (const u64 )arg->key` and `scx->tid != (const u64 )arg->key`, respectively. This is a deliberate move. It avoids the potentially slower `memcmp` operation (or the rhashtable's default compare if not provided) and essentially directly compares two `u64` integers rather than byte-by-byte comparisons. This also eliminates function pointer overhead if memcmp is devirtualized. Now, let's assess potential risks, specifically uninitialized memory concerns: 1. Exposing Uninitialized Memory: This is an internal kernel `rhashtable` lookup comparison callback, so no user-space exposure is at play. 2. Uninitialized Memory in Conditional Logic: Both `sub_cgroup_id` and `tid` are `u64` identifiers. The key used in insertions and lookups in both the sched and tid hashes is an integer (`u64`). Before, the `memcmp` was reading 8 bytes from `sch->ops.sub_cgroup_id` / `scx->tid` and `arg->key`. Now, there's a direct comparison of the `(u64 )`. This doesn't introduce or alter any uninitialized memory behaviour or exposures. It's essentially replacing a `memcmp` on a known `u64` with a direct comparison. 3. Complex Data Structure Initialization: No complex data structures are being allocated or initialized here. It's a simple comparison. 4. Bounds Checks/Lengths Alteration: The `key_len` remains unchanged as `sizeof_field(...) == sizeof(u64)`. The size of the key is still well-defined. 5. KMSAN Detection: KMSAN likely wouldn't catch anything new here. If there was a pre-existing issue where the key itself was uninitialized, KMSAN would have flagged it during the `memcmp` operation, so this optimization doesn't change KMSAN behaviour. It's purely an optimization (or devirtualization / avoiding memcmp) for 64-bit keys in the rhashtable. Finally, I should take a look at what `rhashtable_compare` actually does in `rhashtable.h` to make sure there are no other subtle implications of this.
68/3	2026/09/23 19:08	tool	grepper	0m Args: { "Expression": "obj_cmpfn", "PathPrefix": "include/linux/rhashtable.h" } Results: { "Output": "include/linux/rhashtable.h=611=static __always_inline struct rhash_head __rhashtable_lookup(\n--\ninclude/linux/rhashtable.h-632-\t\trht_for_each_rcu_from(he, __rht_ptr_rcu(bkt, freq), tbl, hash) {\ninclude/linux/rhashtable.h:633:\t\t\tif (params.obj_cmpfn ?\ninclude/linux/rhashtable.h:634:\t\t\t params.obj_cmpfn(\u0026arg, rht_obj(ht, he)) :\ninclude/linux/rhashtable.h-635-\t\t\t rhashtable_compare(\u0026arg, rht_obj(ht, he)))\n--\ninclude/linux/rhashtable.h=756=static __always_inline void __rhashtable_insert_fast(\n--\ninclude/linux/rhashtable.h-797-\t\tif (!key \|\|\ninclude/linux/rhashtable.h:798:\t\t (params.obj_cmpfn ?\ninclude/linux/rhashtable.h:799:\t\t params.obj_cmpfn(\u0026arg, rht_obj(ht, head)) :\ninclude/linux/rhashtable.h-800-\t\t rhashtable_compare(\u0026arg, rht_obj(ht, head)))) {\n" }
69/3	2026/09/23 19:08	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 6630 output: 217 thoughts: 663 Thoughts: KMSAN Assessment: No New Uninitialized Memory Risks Okay, let's break this down. My analysis focuses on whether this change introduces any unique uninitialized memory risks that KMSAN would catch, but KASAN and other standard bug detectors wouldn't. I've got to be meticulous here because, in my field, a KMSAN run requires significant resources. First, I'm looking at how `params.obj_cmpfn` is being used within the lookup/insert process. Specifically, `rhashtable_compare` now directly calls `scx_sched_cmpfn` or `scx_tid_cmpfn`, functions I've confirmed are simply comparing 64-bit integer fields (`ops.sub_cgroup_id` and `tid`, respectively). My gut reaction is that this shouldn't introduce any uninitialized memory risks. There are no allocations or uninitialized stack/heap variables. We're not leaking information to userspace, and no padding issues arise with a 64-bit integer, so I don't see anything obvious. Double-checking against the system prompt's requirements, I'm confirming that this change: * Doesn't introduce uninitialized memory risks exclusively detectable by KMSAN. * Doesn't primarily risk out-of-bounds access (KASAN handles that in `sch` or `scx`), array overflows, NULL pointer dereferences, locking deadlocks, or use-after-free bugs (again, KASAN's domain). * Touches and initializes all stack/heap structures fully before reading or copying. * Does not introduce any risk of uninitialized memory usage or info-leaks. My reasoning is straightforward: the patch introduces custom comparison functions that compare 64-bit keys directly. KASAN already tracks memory safety issues associated with `rhashtable` lookups and insertions. This change does not introduce new allocations, stack buffers, or structures copied to userspace. The key being compared is just a straightforward 64-bit integer. KMSAN wouldn't find anything unique here because the new comparator functions effectively do the same as the old byte-wise `memcmp` over the 8-byte key fields. Therefore, running a dedicated KMSAN fuzzing session would be a waste of resources. I am now confident.
70/3	2026/09/23 19:09	tool	set-results	0m Args: { "KMSANReasoning": "The patch defines custom comparator callbacks (scx_sched_cmpfn and scx_tid_cmpfn) for the rhashtable instances in sched_ext (scx_sched_hash and scx_tid_hash), replacing the default memcmp-based rhashtable_compare with direct 64-bit integer equality comparisons.\n\nThis change does not allocate any new memory, introduce stack/heap buffers, alter structure layouts or padding, or copy data to user space. It only modifies how existing 64-bit integer keys (sub_cgroup_id and tid) are compared during hashtable lookups and insertions. Memory safety concerns for pointer validity and object lifetimes (such as UAF or out-of-bounds access during table traversal) are already handled by KASAN and RCU. There are no uninitialized memory access or info-leak risks, making a dedicated KMSAN fuzzing session unnecessary.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch defines custom comparator callbacks (scx_sched_cmpfn and scx_tid_cmpfn) for the rhashtable instances in sched_ext (scx_sched_hash and scx_tid_hash), replacing the default memcmp-based rhashtable_compare with direct 64-bit integer equality comparisons.\n\nThis change does not allocate any new memory, introduce stack/heap buffers, alter structure layouts or padding, or copy data to user space. It only modifies how existing 64-bit integer keys (sub_cgroup_id and tid) are compared during hashtable lookups and insertions. Memory safety concerns for pointer validity and object lifetimes (such as UAF or out-of-bounds access during table traversal) are already handled by KASAN and RCU. There are no uninitialized memory access or info-leak risks, making a dedicated KMSAN fuzzing session unnecessary.", "NeedsKMSAN": false }

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