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Message-ID: <20250805122312.1890951-1-chen.dylane@linux.dev>
Date: Tue, 5 Aug 2025 20:23:12 +0800
From: Tao Chen <chen.dylane@...ux.dev>
To: song@...nel.org,
jolsa@...nel.org,
ast@...nel.org,
daniel@...earbox.net,
andrii@...nel.org,
martin.lau@...ux.dev,
eddyz87@...il.com,
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
Cc: bpf@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org,
Tao Chen <chen.dylane@...ux.dev>
Subject: [PATCH bpf-next] bpf: Remove migrate_disable in kprobe_multi_link_prog_run
bpf program should run under migration disabled, kprobe_multi_link_prog_run
called the way from graph tracer, which disables preemption in
function_graph_enter_regs, as Jiri and Yonghong suggested, there is no
need to use migrate_disable. As a result, some overhead maybe will be
reduced.
Fixes: 0dcac2725406 ("bpf: Add multi kprobe link")
Signed-off-by: Tao Chen <chen.dylane@...ux.dev>
---
kernel/trace/bpf_trace.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 3ae52978cae..1993fc62539 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2734,14 +2734,19 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
goto out;
}
- migrate_disable();
+ /*
+ * bpf program should run under migration disabled, kprobe_multi_link_prog_run
+ * called the way from graph tracer, which disables preemption in
+ * function_graph_enter_regs, so there is no need to use migrate_disable.
+ * Accessing the above percpu data bpf_prog_active is also safe for the same
+ * reason.
+ */
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();
- migrate_enable();
out:
__this_cpu_dec(bpf_prog_active);
--
2.48.1
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