linux-kernel - [PATCH bpf-next] bpf: remove unnecessary rcu_read_lock in kprobe_multi_link_prog

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Message-ID: <20250827123814.60217-1-dongml2@chinatelecom.cn>
Date: Wed, 27 Aug 2025 20:38:14 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: jolsa@...nel.org
Cc: ast@...nel.org,
	daniel@...earbox.net,
	andrii@...nel.org,
	martin.lau@...ux.dev,
	eddyz87@...il.com,
	song@...nel.org,
	yonghong.song@...ux.dev,
	john.fastabend@...il.com,
	kpsingh@...nel.org,
	sdf@...ichev.me,
	haoluo@...gle.com,
	mattbobrowski@...gle.com,
	rostedt@...dmis.org,
	mhiramat@...nel.org,
	mathieu.desnoyers@...icios.com,
	bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH bpf-next] bpf: remove unnecessary rcu_read_lock in kprobe_multi_link_prog_run

Preemption is disabled in ftrace graph, which indicate rcu_read_lock. So
the rcu_read_lock is not needed in fprobe_entry(), and it is not needed
in kprobe_multi_link_prog_run() neither.

Signed-off-by: Menglong Dong <dongml2@...natelecom.cn>
---
 kernel/trace/bpf_trace.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 606007c387c5..0e79fa84a634 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2741,12 +2741,10 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
 		goto out;
 	}
 
-	rcu_read_lock();
 	regs = ftrace_partial_regs(fregs, bpf_kprobe_multi_pt_regs_ptr());
 	old_run_ctx = bpf_set_run_ctx(&run_ctx.session_ctx.run_ctx);
 	err = bpf_prog_run(link->link.prog, regs);
 	bpf_reset_run_ctx(old_run_ctx);
-	rcu_read_unlock();
 
  out:
 	__this_cpu_dec(bpf_prog_active);
-- 
2.51.0