linux-kernel - [PATCH] perf bench: Fix bench/sched-pipe.c to wait child process

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Date:	Mon,  9 Nov 2009 12:31:05 +0900
From:	Hitoshi Mitake <mitake@....info.waseda.ac.jp>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org,
	Hitoshi Mitake <mitake@....info.waseda.ac.jp>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Mike Galbraith <efault@....de>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Kosina <jkosina@...e.cz>
Subject: [PATCH] perf bench: Fix bench/sched-pipe.c to wait child process

Fixed bench/sched-pipe.c to avoid the below case
notified by Ingo Molnar,

---

$ ./perf bench sched pipe
(executing 1000000 pipe operations between two tasks)

	Total time:4.898 sec
$ 		4.898586 usecs/op
		204140 ops/sec

the shell prompt came back before the usecs/op and ops/sec line was
printed. Process teardown race, lack of wait() or so?

---

This caused by lack of calling waitpid() by parent process,
so I added it.

Signed-off-by: Hitoshi Mitake <mitake@....info.waseda.ac.jp>
Cc: Rusty Russell <rusty@...tcorp.com.au>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Mike Galbraith <efault@....de>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Jiri Kosina <jkosina@...e.cz>
---
 tools/perf/bench/sched-pipe.c |   10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/tools/perf/bench/sched-pipe.c b/tools/perf/bench/sched-pipe.c
index 3214ed2..6a29100 100644
--- a/tools/perf/bench/sched-pipe.c
+++ b/tools/perf/bench/sched-pipe.c
@@ -26,6 +26,7 @@
 #include <errno.h>
 #include <assert.h>
 #include <sys/time.h>
+#include <sys/types.h>
 
 #define LOOPS_DEFAULT 1000000
 static int loops = LOOPS_DEFAULT;
@@ -58,8 +59,8 @@ int bench_sched_pipe(int argc, const char **argv,
 	 * discarding returned value of read(), write()
 	 * causes error in building environment for perf
 	 */
-	int ret;
-	pid_t pid;
+	int ret, wait_stat;
+	pid_t pid, retpid;
 
 	argc = parse_options(argc, argv, options,
 			     bench_sched_pipe_usage, 0);
@@ -87,8 +88,11 @@ int bench_sched_pipe(int argc, const char **argv,
 	gettimeofday(&stop, NULL);
 	timersub(&stop, &start, &diff);
 
-	if (pid)
+	if (pid) {
+		retpid = waitpid(pid, &wait_stat, 0);
+		assert((retpid == pid) && WIFEXITED(wait_stat));
 		return 0;
+	}
 
 	if (simple)
 		printf("%lu.%03lu\n",
-- 
1.6.5.2

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