linux-kernel - [PATCH 3/3] perf ftrace: Use atomic inc to update histogram in BPF

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Message-ID: <20250227191223.1288473-3-namhyung@kernel.org>
Date: Thu, 27 Feb 2025 11:12:23 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Kan Liang <kan.liang@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org,
	bpf@...r.kernel.org,
	Gabriele Monaco <gmonaco@...hat.com>
Subject: [PATCH 3/3] perf ftrace: Use atomic inc to update histogram in BPF

It should use an atomic instruction to update even if the histogram is
keyed by delta as it's also used for stats.

Cc: Gabriele Monaco <gmonaco@...hat.com>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/bpf_skel/func_latency.bpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/bpf_skel/func_latency.bpf.c b/tools/perf/util/bpf_skel/func_latency.bpf.c
index ad70547446786c54..e731a79a753a4d2d 100644
--- a/tools/perf/util/bpf_skel/func_latency.bpf.c
+++ b/tools/perf/util/bpf_skel/func_latency.bpf.c
@@ -142,7 +142,7 @@ int BPF_PROG(func_end)
 		if (!hist)
 			return 0;
 
-		*hist += 1;
+		__sync_fetch_and_add(hist, 1);
 
 		__sync_fetch_and_add(&total, delta); // always in nsec
 		__sync_fetch_and_add(&count, 1);
-- 
2.48.1.711.g2feabab25a-goog