From: Tao Chen <chen.dylane@linux.dev>
To: peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
namhyung@kernel.org, mark.rutland@arm.com,
alexander.shishkin@linux.intel.com, jolsa@kernel.org,
irogers@google.com, adrian.hunter@intel.com,
kan.liang@linux.intel.com
Cc: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
bpf@vger.kernel.org, Tao Chen <chen.dylane@linux.dev>,
Yonghong Song <yonghong.song@linux.dev>
Subject: [PATCH bpf-next v5 2/3] perf: Add atomic operation in get_recursion_context
Date: Mon, 10 Nov 2025 00:35:58 +0800 [thread overview]
Message-ID: <20251109163559.4102849-3-chen.dylane@linux.dev> (raw)
In-Reply-To: <20251109163559.4102849-1-chen.dylane@linux.dev>
From BPF side, preemption usually is enabled. Yonghong said, it is
possible that both tasks (at process level) may reach right before
"recursion[rctx]++;". In such cases, both tasks will be able to get
buffer and this is not right.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Tao Chen <chen.dylane@linux.dev>
---
kernel/events/internal.h | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index d9cc5708309..684bde972ba 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -214,12 +214,9 @@ static inline int get_recursion_context(u8 *recursion)
{
unsigned char rctx = interrupt_context_level();
- if (recursion[rctx])
+ if (cmpxchg(&recursion[rctx], 0, 1) != 0)
return -1;
- recursion[rctx]++;
- barrier();
-
return rctx;
}
--
2.48.1
next prev parent reply other threads:[~2025-11-09 16:36 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-09 16:35 [PATCH bpf-next v5 0/3] Pass external callchain entry to get_perf_callchain Tao Chen
2025-11-09 16:35 ` [PATCH bpf-next v5 1/3] perf: Refactor get_perf_callchain Tao Chen
2025-11-09 16:58 ` bot+bpf-ci
2025-11-10 9:31 ` Tao Chen
2025-11-09 16:35 ` Tao Chen [this message]
2025-11-10 8:52 ` [PATCH bpf-next v5 2/3] perf: Add atomic operation in get_recursion_context Peter Zijlstra
2025-11-10 9:26 ` Tao Chen
2025-11-09 16:35 ` [PATCH bpf-next v5 3/3] bpf: Hold the perf callchain entry until used completely Tao Chen
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