linux-kernel - [PATCH v2 4/7] perf intel-tpebs: Avoid race when evlist is being deleted

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Message-ID: <20250528032637.198960-5-irogers@google.com>
Date: Tue, 27 May 2025 20:26:34 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, Miguel Ojeda <ojeda@...nel.org>, 
	Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, 
	Gary Guo <gary@...yguo.net>, 
	"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>, 
	Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
	Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, 
	Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>, James Clark <james.clark@...aro.org>, 
	Howard Chu <howardchu95@...il.com>, Weilin Wang <weilin.wang@...el.com>, 
	Stephen Brennan <stephen.s.brennan@...cle.com>, Andi Kleen <ak@...ux.intel.com>, 
	Dmitry Vyukov <dvyukov@...gle.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 4/7] perf intel-tpebs: Avoid race when evlist is being deleted

Reading through the evsel->evlist may seg fault if a sample arrives
when the evlist is being deleted. Detect this case and ignore samples
arriving when the evlist is being deleted.

Fixes: bcfab08db7fb ("perf intel-tpebs: Filter non-workload samples")
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/intel-tpebs.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/intel-tpebs.c b/tools/perf/util/intel-tpebs.c
index 4ad4bc118ea5..3b92ebf5c112 100644
--- a/tools/perf/util/intel-tpebs.c
+++ b/tools/perf/util/intel-tpebs.c
@@ -162,9 +162,17 @@ static bool is_child_pid(pid_t parent, pid_t child)
 
 static bool should_ignore_sample(const struct perf_sample *sample, const struct tpebs_retire_lat *t)
 {
-	pid_t workload_pid = t->evsel->evlist->workload.pid;
-	pid_t sample_pid = sample->pid;
+	pid_t workload_pid, sample_pid = sample->pid;
 
+	/*
+	 * During evlist__purge the evlist will be removed prior to the
+	 * evsel__exit calling evsel__tpebs_close and taking the
+	 * tpebs_mtx. Avoid a segfault by ignoring samples in this case.
+	 */
+	if (t->evsel->evlist == NULL)
+		return true;
+
+	workload_pid = t->evsel->evlist->workload.pid;
 	if (workload_pid < 0 || workload_pid == sample_pid)
 		return false;
 
-- 
2.49.0.1238.gf8c92423fb-goog