AI Trajectory

null

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "KMSANReasoning": "",
  "NeedsKMSAN": false,
  "Reasoning": "All changes in the patch series are strictly confined to the user-space 'tools/' directory (tools/sched_ext/). They add an example sched_ext BPF scheduler tool and documentation, and do not modify the compiled kernel image (vmlinux) or kernel modules. Therefore, fuzzing is not warranted.",
  "WorthFuzzing": false
}

null

{
  "PatchDiff": "commit ff62a136def69c04147f598af6344878d1f294bc\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Thu Sep 24 10:38:47 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/tools/sched_ext/Makefile b/tools/sched_ext/Makefile\nindex 21554f0896923..41b80e164cda1 100644\n--- a/tools/sched_ext/Makefile\n+++ b/tools/sched_ext/Makefile\n@@ -191,7 +191,7 @@ $(INCLUDE_DIR)/%.bpf.skel.h: $(SCXOBJ_DIR)/%.bpf.o $(INCLUDE_DIR)/vmlinux.h $(BP\n \n SCX_COMMON_DEPS := include/scx/common.h include/scx/user_exit_info.h | $(BINDIR)\n \n-c-sched-targets = scx_simple scx_cpu0 scx_qmap scx_central scx_flatcg scx_userland scx_pair scx_sdt\n+c-sched-targets = scx_simple scx_cpu0 scx_qmap scx_central scx_flatcg scx_userland scx_pair scx_sdt scx_priority\n \n $(addprefix $(BINDIR)/,$(c-sched-targets)): \\\n \t$(BINDIR)/%: \\\ndiff --git a/tools/sched_ext/README.md b/tools/sched_ext/README.md\nindex 0ee5a3d997e5d..18b80eacc28ae 100644\n--- a/tools/sched_ext/README.md\n+++ b/tools/sched_ext/README.md\n@@ -164,6 +164,13 @@ scx_simple can be run in either global weighted vtime mode, or FIFO mode.\n Though very simple, in limited scenarios, this scheduler can perform reasonably\n well on single-socket systems with a unified L3 cache.\n \n+## scx_priority\n+\n+A dual-queue priority scheduler that separates latency-sensitive and interactive\n+tasks from normal/batch tasks. Tasks with higher priority (nice \u003c 0) are queued\n+to a dedicated high-priority DSQ with boosted time slices and drained first upon\n+dispatch.\n+\n ## scx_qmap\n \n Another simple, yet slightly more complex scheduler that provides an example of\ndiff --git a/tools/sched_ext/scx_priority.bpf.c b/tools/sched_ext/scx_priority.bpf.c\nnew file mode 100644\nindex 0000000000000..816b197c40193\n--- /dev/null\n+++ b/tools/sched_ext/scx_priority.bpf.c\n@@ -0,0 +1,117 @@\n+// SPDX-License-Identifier: GPL-2.0\n+/*\n+ * A dual-queue priority scheduler based on sched_ext.\n+ *\n+ * Dispatches latency-sensitive / interactive tasks (nice \u003c 0) to a high-priority\n+ * DSQ, and batch / normal tasks to a standard DSQ. When a CPU core becomes\n+ * available, the high-priority queue is drained first before serving normal tasks.\n+ *\n+ * Copyright (c) 2026 Rahad Bhuiya \u003crahadbhuiya2021@gmail.com\u003e\n+ */\n+#include \u003cscx/common.bpf.h\u003e\n+\n+char _license[] SEC(\"license\") = \"GPL\";\n+\n+#define PRIO_DSQ_HIGH\t0\n+#define PRIO_DSQ_LOW\t1\n+\n+/*\n+ * Stats tracking:\n+ * [0] - High priority / interactive tasks queued\n+ * [1] - Standard / batch tasks queued\n+ */\n+struct {\n+\t__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);\n+\t__uint(key_size, sizeof(u32));\n+\t__uint(value_size, sizeof(u64));\n+\t__uint(max_entries, 2);\n+} stats SEC(\".maps\");\n+\n+static void stat_inc(u32 idx)\n+{\n+\tu64 *cnt_p = bpf_map_lookup_elem(\u0026stats, \u0026idx);\n+\n+\tif (cnt_p)\n+\t\t(*cnt_p)++;\n+}\n+\n+static bool is_high_prio(const struct task_struct *p)\n+{\n+\t/*\n+\t * In the Linux kernel, static_prio maps nice -20..19 to 100..139.\n+\t * Default nice 0 corresponds to static_prio 120. Tasks with nice \u003c 0\n+\t * (static_prio \u003c 120) or real-time policies are prioritized.\n+\t */\n+\treturn p-\u003estatic_prio \u003c 120;\n+}\n+\n+s32 BPF_STRUCT_OPS(prio_select_cpu, struct task_struct *p, s32 prev_cpu, u64 wake_flags)\n+{\n+\tbool is_idle = false;\n+\ts32 cpu;\n+\n+\tcpu = scx_bpf_select_cpu_dfl(p, prev_cpu, wake_flags, \u0026is_idle);\n+\tif (is_idle) {\n+\t\tu64 slice = is_high_prio(p) ? (2 * SCX_SLICE_DFL) : SCX_SLICE_DFL;\n+\n+\t\tstat_inc(is_high_prio(p) ? 0 : 1);\n+\t\tscx_bpf_dsq_insert(p, SCX_DSQ_LOCAL, slice, 0);\n+\t}\n+\n+\treturn cpu;\n+}\n+\n+void BPF_STRUCT_OPS(prio_enqueue, struct task_struct *p, u64 enq_flags)\n+{\n+\tif (is_high_prio(p)) {\n+\t\tstat_inc(0);\n+\t\tscx_bpf_dsq_insert(p, PRIO_DSQ_HIGH, 2 * SCX_SLICE_DFL, enq_flags);\n+\t} else {\n+\t\tstat_inc(1);\n+\t\tscx_bpf_dsq_insert(p, PRIO_DSQ_LOW, SCX_SLICE_DFL, enq_flags);\n+\t}\n+}\n+\n+void BPF_STRUCT_OPS(prio_dispatch, s32 cpu, struct task_struct *prev)\n+{\n+\t/* First drain high-priority tasks if any are waiting */\n+\tif (scx_bpf_dsq_move_to_local(PRIO_DSQ_HIGH, 0))\n+\t\treturn;\n+\n+\t/* Otherwise drain standard priority tasks */\n+\tscx_bpf_dsq_move_to_local(PRIO_DSQ_LOW, 0);\n+}\n+\n+s32 BPF_STRUCT_OPS_SLEEPABLE(prio_init)\n+{\n+\tint ret;\n+\n+\tret = scx_bpf_create_dsq(PRIO_DSQ_HIGH, -1);\n+\tif (ret) {\n+\t\tscx_bpf_error(\"failed to create high priority DSQ (%d)\", ret);\n+\t\treturn ret;\n+\t}\n+\n+\tret = scx_bpf_create_dsq(PRIO_DSQ_LOW, -1);\n+\tif (ret) {\n+\t\tscx_bpf_error(\"failed to create low priority DSQ (%d)\", ret);\n+\t\treturn ret;\n+\t}\n+\n+\treturn 0;\n+}\n+\n+UEI_DEFINE(uei);\n+\n+void BPF_STRUCT_OPS(prio_exit, struct scx_exit_info *ei)\n+{\n+\tUEI_RECORD(uei, ei);\n+}\n+\n+SCX_OPS_DEFINE(priority_ops,\n+\t       .select_cpu\t= (void *)prio_select_cpu,\n+\t       .enqueue\t\t= (void *)prio_enqueue,\n+\t       .dispatch\t= (void *)prio_dispatch,\n+\t       .init\t\t= (void *)prio_init,\n+\t       .exit\t\t= (void *)prio_exit,\n+\t       .name\t\t= \"priority\");\ndiff --git a/tools/sched_ext/scx_priority.c b/tools/sched_ext/scx_priority.c\nnew file mode 100644\nindex 0000000000000..3cf975be3a1e6\n--- /dev/null\n+++ b/tools/sched_ext/scx_priority.c\n@@ -0,0 +1,128 @@\n+// SPDX-License-Identifier: GPL-2.0\n+/*\n+ * Userspace controller and monitor for scx_priority scheduler.\n+ *\n+ * Copyright (c) 2026 Rahad Bhuiya \u003crahadbhuiya2021@gmail.com\u003e\n+ */\n+#include \u003cstdio.h\u003e\n+#include \u003cstdlib.h\u003e\n+#include \u003cunistd.h\u003e\n+#include \u003csignal.h\u003e\n+#include \u003cassert.h\u003e\n+#include \u003clibgen.h\u003e\n+#include \u003cbpf/bpf.h\u003e\n+#include \u003cscx/common.h\u003e\n+#include \"scx_priority.bpf.skel.h\"\n+\n+const char help_fmt[] =\n+\"A dual-queue priority sched_ext scheduler.\\n\"\n+\"\\n\"\n+\"Usage: %s [-i INTERVAL] [-v] [-h]\\n\"\n+\"\\n\"\n+\"  -i INTERVAL   Stats monitoring interval in seconds (default: 1)\\n\"\n+\"  -v            Print libbpf debug messages\\n\"\n+\"  -h            Display this help and exit\\n\";\n+\n+static bool verbose;\n+static sig_atomic_t exit_req;\n+\n+static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)\n+{\n+\tif (level == LIBBPF_DEBUG \u0026\u0026 !verbose)\n+\t\treturn 0;\n+\treturn vfprintf(stderr, format, args);\n+}\n+\n+static void sigint_handler(int sig)\n+{\n+\texit_req = 1;\n+}\n+\n+static void read_stats(struct scx_priority *skel, __u64 *stats)\n+{\n+\tint nr_cpus = libbpf_num_possible_cpus();\n+\t__u64 *cnts[2];\n+\t__u32 idx;\n+\n+\tassert(nr_cpus \u003e 0);\n+\tcnts[0] = calloc(nr_cpus, sizeof(__u64));\n+\tcnts[1] = calloc(nr_cpus, sizeof(__u64));\n+\tif (!cnts[0] || !cnts[1]) {\n+\t\tfree(cnts[0]);\n+\t\tfree(cnts[1]);\n+\t\treturn;\n+\t}\n+\n+\tmemset(stats, 0, sizeof(stats[0]) * 2);\n+\n+\tfor (idx = 0; idx \u003c 2; idx++) {\n+\t\tint ret, cpu;\n+\n+\t\tret = bpf_map_lookup_elem(bpf_map__fd(skel-\u003emaps.stats),\n+\t\t\t\t\t  \u0026idx, cnts[idx]);\n+\t\tif (ret \u003c 0)\n+\t\t\tcontinue;\n+\t\tfor (cpu = 0; cpu \u003c nr_cpus; cpu++)\n+\t\t\tstats[idx] += cnts[idx][cpu];\n+\t}\n+\n+\tfree(cnts[0]);\n+\tfree(cnts[1]);\n+}\n+\n+int main(int argc, char **argv)\n+{\n+\tstruct scx_priority *skel;\n+\tstruct bpf_link *link;\n+\t__s32 opt;\n+\t__u64 ecode;\n+\tint interval = 1;\n+\n+\tlibbpf_set_print(libbpf_print_fn);\n+\tsignal(SIGINT, sigint_handler);\n+\tsignal(SIGTERM, sigint_handler);\n+\n+restart:\n+\toptind = 1;\n+\tskel = SCX_OPS_OPEN(priority_ops, scx_priority);\n+\n+\twhile ((opt = getopt(argc, argv, \"i:vh\")) != -1) {\n+\t\tswitch (opt) {\n+\t\tcase 'i':\n+\t\t\tinterval = atoi(optarg);\n+\t\t\tif (interval \u003c= 0)\n+\t\t\t\tinterval = 1;\n+\t\t\tbreak;\n+\t\tcase 'v':\n+\t\t\tverbose = true;\n+\t\t\tbreak;\n+\t\tdefault:\n+\t\t\tfprintf(stderr, help_fmt, basename(argv[0]));\n+\t\t\treturn opt != 'h';\n+\t\t}\n+\t}\n+\n+\tSCX_OPS_LOAD(skel, priority_ops, scx_priority, uei);\n+\tlink = SCX_OPS_ATTACH(skel, priority_ops, scx_priority);\n+\n+\tprintf(\"scx_priority started (interval: %ds). Press Ctrl-C to stop.\\n\", interval);\n+\tprintf(\"%-15s %-15s %-15s\\n\", \"HIGH_PRIO(UI)\", \"LOW_PRIO(BATCH)\", \"TOTAL_DISPATCH\");\n+\n+\twhile (!exit_req \u0026\u0026 !UEI_EXITED(skel, uei)) {\n+\t\t__u64 stats[2];\n+\n+\t\tread_stats(skel, stats);\n+\t\tprintf(\"%-15llu %-15llu %-15llu\\n\",\n+\t\t       stats[0], stats[1], stats[0] + stats[1]);\n+\t\tfflush(stdout);\n+\t\tsleep(interval);\n+\t}\n+\n+\tbpf_link__destroy(link);\n+\tecode = UEI_REPORT(skel, uei);\n+\tscx_priority__destroy(skel);\n+\n+\tif (!exit_req \u0026\u0026 UEI_ECODE_RESTART(ecode))\n+\t\tgoto restart;\n+\treturn 0;\n+}\n"
}

core

null

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "Reasoning": "All changes in the patch series are strictly confined to the user-space 'tools/' directory (tools/sched_ext/). They add an example sched_ext BPF scheduler tool and documentation, and do not modify the compiled kernel image (vmlinux) or kernel modules. Therefore, fuzzing is not warranted.",
  "WorthFuzzing": false
}

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.

Target architecture: amd64

For your convenience, here is the diff of the changes:
commit ff62a136def69c04147f598af6344878d1f294bc
Author: syz-cluster <triage@syzkaller.com>
Date:   Thu Sep 24 10:38:47 2026 +0000

    syz-cluster: applied patch under review

diff --git a/tools/sched_ext/Makefile b/tools/sched_ext/Makefile
index 21554f0896923..41b80e164cda1 100644
--- a/tools/sched_ext/Makefile
+++ b/tools/sched_ext/Makefile
@@ -191,7 +191,7 @@ $(INCLUDE_DIR)/%.bpf.skel.h: $(SCXOBJ_DIR)/%.bpf.o $(INCLUDE_DIR)/vmlinux.h $(BP
 
 SCX_COMMON_DEPS := include/scx/common.h include/scx/user_exit_info.h | $(BINDIR)
 
-c-sched-targets = scx_simple scx_cpu0 scx_qmap scx_central scx_flatcg scx_userland scx_pair scx_sdt
+c-sched-targets = scx_simple scx_cpu0 scx_qmap scx_central scx_flatcg scx_userland scx_pair scx_sdt scx_priority
 
 $(addprefix $(BINDIR)/,$(c-sched-targets)): \
 	$(BINDIR)/%: \
diff --git a/tools/sched_ext/README.md b/tools/sched_ext/README.md
index 0ee5a3d997e5d..18b80eacc28ae 100644
--- a/tools/sched_ext/README.md
+++ b/tools/sched_ext/README.md
@@ -164,6 +164,13 @@ scx_simple can be run in either global weighted vtime mode, or FIFO mode.
 Though very simple, in limited scenarios, this scheduler can perform reasonably
 well on single-socket systems with a unified L3 cache.
 
+## scx_priority
+
+A dual-queue priority scheduler that separates latency-sensitive and interactive
+tasks from normal/batch tasks. Tasks with higher priority (nice < 0) are queued
+to a dedicated high-priority DSQ with boosted time slices and drained first upon
+dispatch.
+
 ## scx_qmap
 
 Another simple, yet slightly more complex scheduler that provides an example of
diff --git a/tools/sched_ext/scx_priority.bpf.c b/tools/sched_ext/scx_priority.bpf.c
new file mode 100644
index 0000000000000..816b197c40193
--- /dev/null
+++ b/tools/sched_ext/scx_priority.bpf.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * A dual-queue priority scheduler based on sched_ext.
+ *
+ * Dispatches latency-sensitive / interactive tasks (nice < 0) to a high-priority
+ * DSQ, and batch / normal tasks to a standard DSQ. When a CPU core becomes
+ * available, the high-priority queue is drained first before serving normal tasks.
+ *
+ * Copyright (c) 2026 Rahad Bhuiya <rahadbhuiya2021@gmail.com>
+ */
+#include <scx/common.bpf.h>
+
+char _license[] SEC("license") = "GPL";
+
+#define PRIO_DSQ_HIGH	0
+#define PRIO_DSQ_LOW	1
+
+/*
+ * Stats tracking:
+ * [0] - High priority / interactive tasks queued
+ * [1] - Standard / batch tasks queued
+ */
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__uint(key_size, sizeof(u32));
+	__uint(value_size, sizeof(u64));
+	__uint(max_entries, 2);
+} stats SEC(".maps");
+
+static void stat_inc(u32 idx)
+{
+	u64 *cnt_p = bpf_map_lookup_elem(&stats, &idx);
+
+	if (cnt_p)
+		(*cnt_p)++;
+}
+
+static bool is_high_prio(const struct task_struct *p)
+{
+	/*
+	 * In the Linux kernel, static_prio maps nice -20..19 to 100..139.
+	 * Default nice 0 corresponds to static_prio 120. Tasks with nice < 0
+	 * (static_prio < 120) or real-time policies are prioritized.
+	 */
+	return p->static_prio < 120;
+}
+
+s32 BPF_STRUCT_OPS(prio_select_cpu, struct task_struct *p, s32 prev_cpu, u64 wake_flags)
+{
+	bool is_idle = false;
+	s32 cpu;
+
+	cpu = scx_bpf_select_cpu_dfl(p, prev_cpu, wake_flags, &is_idle);
+	if (is_idle) {
+		u64 slice = is_high_prio(p) ? (2 * SCX_SLICE_DFL) : SCX_SLICE_DFL;
+
+		stat_inc(is_high_prio(p) ? 0 : 1);
+		scx_bpf_dsq_insert(p, SCX_DSQ_LOCAL, slice, 0);
+	}
+
+	return cpu;
+}
+
+void BPF_STRUCT_OPS(prio_enqueue, struct task_struct *p, u64 enq_flags)
+{
+	if (is_high_prio(p)) {
+		stat_inc(0);
+		scx_bpf_dsq_insert(p, PRIO_DSQ_HIGH, 2 * SCX_SLICE_DFL, enq_flags);
+	} else {
+		stat_inc(1);
+		scx_bpf_dsq_insert(p, PRIO_DSQ_LOW, SCX_SLICE_DFL, enq_flags);
+	}
+}
+
+void BPF_STRUCT_OPS(prio_dispatch, s32 cpu, struct task_struct *prev)
+{
+	/* First drain high-priority tasks if any are waiting */
+	if (scx_bpf_dsq_move_to_local(PRIO_DSQ_HIGH, 0))
+		return;
+
+	/* Otherwise drain standard priority tasks */
+	scx_bpf_dsq_move_to_local(PRIO_DSQ_LOW, 0);
+}
+
+s32 BPF_STRUCT_OPS_SLEEPABLE(prio_init)
+{
+	int ret;
+
+	ret = scx_bpf_create_dsq(PRIO_DSQ_HIGH, -1);
+	if (ret) {
+		scx_bpf_error("failed to create high priority DSQ (%d)", ret);
+		return ret;
+	}
+
+	ret = scx_bpf_create_dsq(PRIO_DSQ_LOW, -1);
+	if (ret) {
+		scx_bpf_error("failed to create low priority DSQ (%d)", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+UEI_DEFINE(uei);
+
+void BPF_STRUCT_OPS(prio_exit, struct scx_exit_info *ei)
+{
+	UEI_RECORD(uei, ei);
+}
+
+SCX_OPS_DEFINE(priority_ops,
+	       .select_cpu	= (void *)prio_select_cpu,
+	       .enqueue		= (void *)prio_enqueue,
+	       .dispatch	= (void *)prio_dispatch,
+	       .init		= (void *)prio_init,
+	       .exit		= (void *)prio_exit,
+	       .name		= "priority");
diff --git a/tools/sched_ext/scx_priority.c b/tools/sched_ext/scx_priority.c
new file mode 100644
index 0000000000000..3cf975be3a1e6
--- /dev/null
+++ b/tools/sched_ext/scx_priority.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Userspace controller and monitor for scx_priority scheduler.
+ *
+ * Copyright (c) 2026 Rahad Bhuiya <rahadbhuiya2021@gmail.com>
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <signal.h>
+#include <assert.h>
+#include <libgen.h>
+#include <bpf/bpf.h>
+#include <scx/common.h>
+#include "scx_priority.bpf.skel.h"
+
+const char help_fmt[] =
+"A dual-queue priority sched_ext scheduler.\n"
+"\n"
+"Usage: %s [-i INTERVAL] [-v] [-h]\n"
+"\n"
+"  -i INTERVAL   Stats monitoring interval in seconds (default: 1)\n"
+"  -v            Print libbpf debug messages\n"
+"  -h            Display this help and exit\n";
+
+static bool verbose;
+static sig_atomic_t exit_req;
+
+static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
+{
+	if (level == LIBBPF_DEBUG && !verbose)
+		return 0;
+	return vfprintf(stderr, format, args);
+}
+
+static void sigint_handler(int sig)
+{
+	exit_req = 1;
+}
+
+static void read_stats(struct scx_priority *skel, __u64 *stats)
+{
+	int nr_cpus = libbpf_num_possible_cpus();
+	__u64 *cnts[2];
+	__u32 idx;
+
+	assert(nr_cpus > 0);
+	cnts[0] = calloc(nr_cpus, sizeof(__u64));
+	cnts[1] = calloc(nr_cpus, sizeof(__u64));
+	if (!cnts[0] || !cnts[1]) {
+		free(cnts[0]);
+		free(cnts[1]);
+		return;
+	}
+
+	memset(stats, 0, sizeof(stats[0]) * 2);
+
+	for (idx = 0; idx < 2; idx++) {
+		int ret, cpu;
+
+		ret = bpf_map_lookup_elem(bpf_map__fd(skel->maps.stats),
+					  &idx, cnts[idx]);
+		if (ret < 0)
+			continue;
+		for (cpu = 0; cpu < nr_cpus; cpu++)
+			stats[idx] += cnts[idx][cpu];
+	}
+
+	free(cnts[0]);
+	free(cnts[1]);
+}
+
+int main(int argc, char **argv)
+{
+	struct scx_priority *skel;
+	struct bpf_link *link;
+	__s32 opt;
+	__u64 ecode;
+	int interval = 1;
+
+	libbpf_set_print(libbpf_print_fn);
+	signal(SIGINT, sigint_handler);
+	signal(SIGTERM, sigint_handler);
+
+restart:
+	optind = 1;
+	skel = SCX_OPS_OPEN(priority_ops, scx_priority);
+
+	while ((opt = getopt(argc, argv, "i:vh")) != -1) {
+		switch (opt) {
+		case 'i':
+			interval = atoi(optarg);
+			if (interval <= 0)
+				interval = 1;
+			break;
+		case 'v':
+			verbose = true;
+			break;
+		default:
+			fprintf(stderr, help_fmt, basename(argv[0]));
+			return opt != 'h';
+		}
+	}
+
+	SCX_OPS_LOAD(skel, priority_ops, scx_priority, uei);
+	link = SCX_OPS_ATTACH(skel, priority_ops, scx_priority);
+
+	printf("scx_priority started (interval: %ds). Press Ctrl-C to stop.\n", interval);
+	printf("%-15s %-15s %-15s\n", "HIGH_PRIO(UI)", "LOW_PRIO(BATCH)", "TOTAL_DISPATCH");
+
+	while (!exit_req && !UEI_EXITED(skel, uei)) {
+		__u64 stats[2];
+
+		read_stats(skel, stats);
+		printf("%-15llu %-15llu %-15llu\n",
+		       stats[0], stats[1], stats[0] + stats[1]);
+		fflush(stdout);
+		sleep(interval);
+	}
+
+	bpf_link__destroy(link);
+	ecode = UEI_REPORT(skel, uei);
+	scx_priority__destroy(skel);
+
+	if (!exit_req && UEI_ECODE_RESTART(ecode))
+		goto restart;
+	return 0;
+}

gemini-3.8-flash

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							input: 6081
							output: 23
							thoughts: 851
						

**Fuzzing Triage Evaluation: Sched_ext Example**

Okay, let's break this down. The request is to evaluate a patch series related to `tools/sched_ext` for fuzzing with syzkaller. From a safety perspective, this looks straightforward. It's a code review/maintenance task, specifically an example/tool scheduler. No red flags here – no immediate risks of exploits or malicious intent.

Now, let's dive into the patch itself. The diff points to changes in: `tools/sched_ext/Makefile`, `tools/sched_ext/README.md`, `tools/sched_ext/scx_priority.bpf.c`, and `tools/sched_ext/scx_priority.c`. All in the `tools/sched_ext/` directory.

We need to apply the rules. The question is: does this patch fall under the "NEGATIVE CRITERIA" – specifically, is the modified code strictly confined to non-kernel, non-executable changes?  We have a checklist:  Documentation, comments, user-space tools, build system changes etc.

Aha! `tools/` is a user-space directory. It's in the "samples, scripts, etc." category and, as long as it doesn't affect the compiled kernel image (`vmlinux`) or kernel modules, we're good. Even `scx_priority.bpf.c`, despite being a BPF program, is within `tools/sched_ext/` (an example scheduler tool) and the rules state this is ok. The question becomes, is it strictly inside `tools/sched_ext/`?  We need to confirm that.

Alright, let's use the tools at our disposal. We can use the information provided to verify with our "grepper", or "codesearch-dir-index".  It looks like we can't directly use git diff but that's not needed, based on the provided diff.  Let's verify our initial analysis.

Let's check `tools/sched_ext/` using `codesearch-dir-index` to confirm. Based on the diff provided, nothing outside the `tools/sched_ext` directory was modified.

{
  "Dir": "tools/sched_ext"
}

{
  "Files": [
    "README.md",
    "scx_central.bpf.c",
    "scx_central.c",
    "scx_cpu0.bpf.c",
    "scx_cpu0.c",
    "scx_flatcg.bpf.c",
    "scx_flatcg.c",
    "scx_flatcg.h",
    "scx_pair.bpf.c",
    "scx_pair.c",
    "scx_pair.h",
    "scx_priority.bpf.c",
    "scx_priority.c",
    "scx_qmap.bpf.c",
    "scx_qmap.c",
    "scx_qmap.h",
    "scx_sdt.bpf.c",
    "scx_sdt.c",
    "scx_sdt.h",
    "scx_simple.bpf.c",
    "scx_simple.c",
    "scx_userland.bpf.c",
    "scx_userland.c",
    "scx_userland.h"
  ],
  "Subdirs": [
    "include"
  ]
}

gemini-3.8-flash

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							input: 7705
							output: 18
							thoughts: 15
						

Okay, here's my summary, tailored for an expert audience, as if I'm thinking these thoughts myself:

**Investigating the `scx_priority` References**

Alright, let's dive in. I need to quickly ascertain the scope of any potential changes related to the system. Specifically, I need to know where, if anywhere, the `scx_priority` keyword is being used in any of the kernel files. This is a critical first step. Understanding the contexts in which this is used is fundamental to avoid introducing unintended side effects or regressions. So, let's get a handle on the landscape. A comprehensive search is the starting point here. Let's see what turns up, and then we can analyze the results.

{
  "Expression": "scx_priority"
}

{
  "Output": "tools/sched_ext/Makefile=192=SCX_COMMON_DEPS := include/scx/common.h include/scx/user_exit_info.h | $(BINDIR)\ntools/sched_ext/Makefile-193-\ntools/sched_ext/Makefile:194:c-sched-targets = scx_simple scx_cpu0 scx_qmap scx_central scx_flatcg scx_userland scx_pair scx_sdt scx_priority\ntools/sched_ext/Makefile-195-\n--\ntools/sched_ext/README.md=165=well on single-socket systems with a unified L3 cache.\ntools/sched_ext/README.md-166-\ntools/sched_ext/README.md:167:## scx_priority\ntools/sched_ext/README.md-168-\n--\ntools/sched_ext/scx_priority.c-2-/*\ntools/sched_ext/scx_priority.c:3: * Userspace controller and monitor for scx_priority scheduler.\ntools/sched_ext/scx_priority.c-4- *\n--\ntools/sched_ext/scx_priority.c-14-#include \u003cscx/common.h\u003e\ntools/sched_ext/scx_priority.c:15:#include \"scx_priority.bpf.skel.h\"\ntools/sched_ext/scx_priority.c-16-\n--\ntools/sched_ext/scx_priority.c=36=static void sigint_handler(int sig)\n--\ntools/sched_ext/scx_priority.c-40-\ntools/sched_ext/scx_priority.c:41:static void read_stats(struct scx_priority *skel, __u64 *stats)\ntools/sched_ext/scx_priority.c-42-{\n--\ntools/sched_ext/scx_priority.c=73=int main(int argc, char **argv)\ntools/sched_ext/scx_priority.c-74-{\ntools/sched_ext/scx_priority.c:75:\tstruct scx_priority *skel;\ntools/sched_ext/scx_priority.c-76-\tstruct bpf_link *link;\n--\ntools/sched_ext/scx_priority.c-86-\toptind = 1;\ntools/sched_ext/scx_priority.c:87:\tskel = SCX_OPS_OPEN(priority_ops, scx_priority);\ntools/sched_ext/scx_priority.c-88-\n--\ntools/sched_ext/scx_priority.c-104-\ntools/sched_ext/scx_priority.c:105:\tSCX_OPS_LOAD(skel, priority_ops, scx_priority, uei);\ntools/sched_ext/scx_priority.c:106:\tlink = SCX_OPS_ATTACH(skel, priority_ops, scx_priority);\ntools/sched_ext/scx_priority.c-107-\ntools/sched_ext/scx_priority.c:108:\tprintf(\"scx_priority started (interval: %ds). Press Ctrl-C to stop.\\n\", interval);\ntools/sched_ext/scx_priority.c-109-\tprintf(\"%-15s %-15s %-15s\\n\", \"HIGH_PRIO(UI)\", \"LOW_PRIO(BATCH)\", \"TOTAL_DISPATCH\");\n--\ntools/sched_ext/scx_priority.c-122-\tecode = UEI_REPORT(skel, uei);\ntools/sched_ext/scx_priority.c:123:\tscx_priority__destroy(skel);\ntools/sched_ext/scx_priority.c-124-\n"
}

gemini-3.8-flash

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							input: 8845
							output: 95
							thoughts: 254
						

**Patch Analysis: WorthFuzzing=false**

Okay, let's break this down. This patch is *completely* contained within `tools/sched_ext/`. Time to re-check that section 2 criteria: specifically, the bit about "Non-kernel and non-executable changes." Right. That includes docs, comments, spelling fixes, and user-space stuff like tools, samples, and scripts *that don't* touch the compiled kernel image or modules.

Let's see… looking at the modified files, it's all: `tools/sched_ext/Makefile`, `tools/sched_ext/README.md`, `tools/sched_ext/scx_priority.bpf.c`, and `tools/sched_ext/scx_priority.c`. Yep, they are all in `tools/` and *definitely* don't build into `vmlinux` or a kernel module.

Therefore, this is a clear-cut case for `WorthFuzzing=false`. Consequently, my `FocusSymbols` and `EnableConfigs` should be empty: `[]` and `[]`. The reasoning needs to be concise and accurate. Let's call `set-results`.

{
  "EnableConfigs": [],
  "FocusSymbols": [],
  "Reasoning": "All changes in the patch series are strictly confined to the user-space 'tools/' directory (tools/sched_ext/). They add an example sched_ext BPF scheduler tool and documentation, and do not modify the compiled kernel image (vmlinux) or kernel modules. Therefore, fuzzing is not warranted.",
  "WorthFuzzing": false
}

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "Reasoning": "All changes in the patch series are strictly confined to the user-space 'tools/' directory (tools/sched_ext/). They add an example sched_ext BPF scheduler tool and documentation, and do not modify the compiled kernel image (vmlinux) or kernel modules. Therefore, fuzzing is not warranted.",
  "WorthFuzzing": false
}

{
  "WorthFuzzing": false
}

null