linux-kernel - [PATCH 2/2] perf tools: Ignore dead threads during event synthesis

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Date:   Fri,  1 Jul 2022 13:54:58 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>,
        linux-perf-users@...r.kernel.org
Subject: [PATCH 2/2] perf tools: Ignore dead threads during event synthesis

When it synthesize various task events, it scans the list of task
first and then accesses later.  There's a window threads can die
between the two and proc entries may not be available.

Instead of bailing out, we can ignore that thread and move on.

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/synthetic-events.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index a068f42833c3..84d17bd4efae 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -767,11 +767,12 @@ static int __event__synthesize_thread(union perf_event *comm_event,
 		if (*end)
 			continue;
 
-		rc = -1;
+		/* some threads may exit just after scan, ignore it */
 		if (perf_event__prepare_comm(comm_event, pid, _pid, machine,
 					     &tgid, &ppid, &kernel_thread) != 0)
-			break;
+			continue;
 
+		rc = -1;
 		if (perf_event__synthesize_fork(tool, fork_event, _pid, tgid,
 						ppid, process, machine) < 0)
 			break;
-- 
2.37.0.rc0.161.g10f37bed90-goog