linux-kernel - [tip:perf/core] perf record: Fix race where process can disappear while reading its /proc/pid/tasks

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Message-ID: <tip-7f3bedcc93f935631d2363f23de1cc80f04fdf3e@git.kernel.org>
Date:	Tue, 27 Oct 2009 13:03:32 GMT
From:	tip-bot for Arnaldo Carvalho de Melo <acme@...hat.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, paulus@...ba.org, acme@...hat.com,
	hpa@...or.com, mingo@...hat.com, efault@....de,
	peterz@...radead.org, fweisbec@...il.com, tglx@...utronix.de,
	mingo@...e.hu
Subject: [tip:perf/core] perf record: Fix race where process can disappear while reading its /proc/pid/tasks

Commit-ID:  7f3bedcc93f935631d2363f23de1cc80f04fdf3e
Gitweb:     http://git.kernel.org/tip/7f3bedcc93f935631d2363f23de1cc80f04fdf3e
Author:     Arnaldo Carvalho de Melo <acme@...hat.com>
AuthorDate: Mon, 26 Oct 2009 19:23:17 -0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Tue, 27 Oct 2009 13:51:53 +0100

perf record: Fix race where process can disappear while reading its /proc/pid/tasks

Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Mike Galbraith <efault@....de>
LKML-Reference: <1256592199-9608-1-git-send-email-acme@...hat.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 tools/perf/builtin-record.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index ac5ddff..9e1638c 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -206,6 +206,7 @@ static pid_t pid_synthesize_comm_event(pid_t pid, int full)
 
 	fp = fopen(filename, "r");
 	if (fp == NULL) {
+out_race:	
 		/*
 		 * We raced with a task exiting - just return:
 		 */
@@ -247,6 +248,9 @@ static pid_t pid_synthesize_comm_event(pid_t pid, int full)
 	snprintf(filename, sizeof(filename), "/proc/%d/task", pid);
 
 	tasks = opendir(filename);
+	if (tasks == NULL)
+		goto out_race;
+
 	while (!readdir_r(tasks, &dirent, &next) && next) {
 		char *end;
 		pid = strtol(dirent.d_name, &end, 10);
--
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