migrate_disable() is called to disable migration in the kernel, and it is often used together with rcu_read_lock(). However, with PREEMPT_RCU disabled, it's unnecessary, as rcu_read_lock() will always disable preemption, which will also disable migration. Introduce rcu_read_lock_dont_migrate() and rcu_read_unlock_migrate(), which will do the migration enable and disable only when PREEMPT_RCU. Signed-off-by: Menglong Dong --- v3: - make rcu_read_lock_dont_migrate() more compact v2: - introduce rcu_read_lock_dont_migrate() instead of rcu_migrate_disable() --- include/linux/rcupdate.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 120536f4c6eb..9691ca380a4f 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -962,6 +962,20 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) preempt_enable_notrace(); } +static __always_inline void rcu_read_lock_dont_migrate(void) +{ + if (IS_ENABLED(CONFIG_PREEMPT_RCU)) + migrate_disable(); + rcu_read_lock(); +} + +static inline void rcu_read_unlock_migrate(void) +{ + rcu_read_unlock(); + if (IS_ENABLED(CONFIG_PREEMPT_RCU)) + migrate_enable(); +} + /** * RCU_INIT_POINTER() - initialize an RCU protected pointer * @p: The pointer to be initialized. -- 2.50.1 Use rcu_read_lock_dont_migrate() and rcu_read_unlock_migrate() in bpf_cgrp_storage_free to obtain better performance when PREEMPT_RCU is not enabled. Signed-off-by: Menglong Dong --- v2: - use rcu_read_lock_dont_migrate() instead of rcu_migrate_disable() --- kernel/bpf/bpf_cgrp_storage.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/bpf_cgrp_storage.c b/kernel/bpf/bpf_cgrp_storage.c index 148da8f7ff36..0687a760974a 100644 --- a/kernel/bpf/bpf_cgrp_storage.c +++ b/kernel/bpf/bpf_cgrp_storage.c @@ -45,8 +45,7 @@ void bpf_cgrp_storage_free(struct cgroup *cgroup) { struct bpf_local_storage *local_storage; - migrate_disable(); - rcu_read_lock(); + rcu_read_lock_dont_migrate(); local_storage = rcu_dereference(cgroup->bpf_cgrp_storage); if (!local_storage) goto out; @@ -55,8 +54,7 @@ void bpf_cgrp_storage_free(struct cgroup *cgroup) bpf_local_storage_destroy(local_storage); bpf_cgrp_storage_unlock(); out: - rcu_read_unlock(); - migrate_enable(); + rcu_read_unlock_migrate(); } static struct bpf_local_storage_data * -- 2.50.1 Use rcu_read_lock_dont_migrate() and rcu_read_unlock_migrate() in bpf_inode_storage_free to obtain better performance when PREEMPT_RCU is not enabled. Signed-off-by: Menglong Dong --- v2: - use rcu_read_lock_dont_migrate() instead of rcu_migrate_disable() --- kernel/bpf/bpf_inode_storage.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c index 15a3eb9b02d9..e54cce2b9175 100644 --- a/kernel/bpf/bpf_inode_storage.c +++ b/kernel/bpf/bpf_inode_storage.c @@ -62,8 +62,7 @@ void bpf_inode_storage_free(struct inode *inode) if (!bsb) return; - migrate_disable(); - rcu_read_lock(); + rcu_read_lock_dont_migrate(); local_storage = rcu_dereference(bsb->storage); if (!local_storage) @@ -71,8 +70,7 @@ void bpf_inode_storage_free(struct inode *inode) bpf_local_storage_destroy(local_storage); out: - rcu_read_unlock(); - migrate_enable(); + rcu_read_unlock_migrate(); } static void *bpf_fd_inode_storage_lookup_elem(struct bpf_map *map, void *key) -- 2.50.1 Use rcu_read_lock_dont_migrate() and rcu_read_unlock_migrate() in bpf_iter_run_prog to obtain better performance when PREEMPT_RCU is not enabled. Signed-off-by: Menglong Dong --- v2: - use rcu_read_lock_dont_migrate() instead of rcu_migrate_disable() --- kernel/bpf/bpf_iter.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c index 0cbcae727079..6ac35430c573 100644 --- a/kernel/bpf/bpf_iter.c +++ b/kernel/bpf/bpf_iter.c @@ -705,13 +705,11 @@ int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx) migrate_enable(); rcu_read_unlock_trace(); } else { - rcu_read_lock(); - migrate_disable(); + rcu_read_lock_dont_migrate(); old_run_ctx = bpf_set_run_ctx(&run_ctx); ret = bpf_prog_run(prog, ctx); bpf_reset_run_ctx(old_run_ctx); - migrate_enable(); - rcu_read_unlock(); + rcu_read_unlock_migrate(); } /* bpf program can only return 0 or 1: -- 2.50.1 Use rcu_read_lock_dont_migrate() and rcu_read_unlock_migrate() in bpf_task_storage_free to obtain better performance when PREEMPT_RCU is not enabled. Signed-off-by: Menglong Dong --- v2: - use rcu_read_lock_dont_migrate() instead of rcu_migrate_disable() --- kernel/bpf/bpf_task_storage.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c index 1109475953c0..a1dc1bf0848a 100644 --- a/kernel/bpf/bpf_task_storage.c +++ b/kernel/bpf/bpf_task_storage.c @@ -70,8 +70,7 @@ void bpf_task_storage_free(struct task_struct *task) { struct bpf_local_storage *local_storage; - migrate_disable(); - rcu_read_lock(); + rcu_read_lock_dont_migrate(); local_storage = rcu_dereference(task->bpf_storage); if (!local_storage) @@ -81,8 +80,7 @@ void bpf_task_storage_free(struct task_struct *task) bpf_local_storage_destroy(local_storage); bpf_task_storage_unlock(); out: - rcu_read_unlock(); - migrate_enable(); + rcu_read_unlock_migrate(); } static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key) -- 2.50.1 Use rcu_read_lock_dont_migrate() and rcu_read_unlock_migrate() in bpf_prog_run_array_cg to obtain better performance when PREEMPT_RCU is not enabled. Signed-off-by: Menglong Dong --- v2: - use rcu_read_lock_dont_migrate() instead of rcu_migrate_disable() --- kernel/bpf/cgroup.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 180b630279b9..9912c7b9a266 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -71,8 +71,7 @@ bpf_prog_run_array_cg(const struct cgroup_bpf *cgrp, u32 func_ret; run_ctx.retval = retval; - migrate_disable(); - rcu_read_lock(); + rcu_read_lock_dont_migrate(); array = rcu_dereference(cgrp->effective[atype]); item = &array->items[0]; old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx); @@ -88,8 +87,7 @@ bpf_prog_run_array_cg(const struct cgroup_bpf *cgrp, item++; } bpf_reset_run_ctx(old_run_ctx); - rcu_read_unlock(); - migrate_enable(); + rcu_read_unlock_migrate(); return run_ctx.retval; } -- 2.50.1 Use rcu_read_lock_dont_migrate() and rcu_read_unlock_migrate() in trampoline.c to obtain better performance when PREEMPT_RCU is not enabled. Signed-off-by: Menglong Dong --- v2: - use rcu_read_lock_dont_migrate() instead of rcu_migrate_disable() --- kernel/bpf/trampoline.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index 0e364614c3a2..5949095e51c3 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -899,8 +899,7 @@ static __always_inline u64 notrace bpf_prog_start_time(void) static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx) __acquires(RCU) { - rcu_read_lock(); - migrate_disable(); + rcu_read_lock_dont_migrate(); run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx); @@ -949,8 +948,7 @@ static void notrace __bpf_prog_exit_recur(struct bpf_prog *prog, u64 start, update_prog_stats(prog, start); this_cpu_dec(*(prog->active)); - migrate_enable(); - rcu_read_unlock(); + rcu_read_unlock_migrate(); } static u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog, @@ -960,8 +958,7 @@ static u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog, /* Runtime stats are exported via actual BPF_LSM_CGROUP * programs, not the shims. */ - rcu_read_lock(); - migrate_disable(); + rcu_read_lock_dont_migrate(); run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx); @@ -974,8 +971,7 @@ static void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start, { bpf_reset_run_ctx(run_ctx->saved_run_ctx); - migrate_enable(); - rcu_read_unlock(); + rcu_read_unlock_migrate(); } u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog, @@ -1033,8 +1029,7 @@ static u64 notrace __bpf_prog_enter(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx) __acquires(RCU) { - rcu_read_lock(); - migrate_disable(); + rcu_read_lock_dont_migrate(); run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx); @@ -1048,8 +1043,7 @@ static void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start, bpf_reset_run_ctx(run_ctx->saved_run_ctx); update_prog_stats(prog, start); - migrate_enable(); - rcu_read_unlock(); + rcu_read_unlock_migrate(); } void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr) -- 2.50.1