linux-kernel - [PATCH bpf-next v2 7/7] bpf: use rcu_read_lock_dont

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Message-ID: <20250819093424.1011645-8-dongml2@chinatelecom.cn>
Date: Tue, 19 Aug 2025 17:34:24 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: ast@...nel.org,
	paulmck@...nel.org
Cc: frederic@...nel.org,
	neeraj.upadhyay@...nel.org,
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Subject: [PATCH bpf-next v2 7/7] bpf: use rcu_read_lock_dont_migrate() for trampoline.c

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 <dongml2@...natelecom.cn>
---
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