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

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Message-Id: <20091109.121836.719610044276873093.mitake@dcl.info.waseda.ac.jp>
Date:	Mon, 09 Nov 2009 12:18:36 +0900 (JST)
From:	Hitoshi Mitake <mitake@....info.waseda.ac.jp>
To:	mingo@...e.hu, linux-kernel@...r.kernel.org
Cc:	mitake@....info.waseda.ac.jp, rusty@...tcorp.com.au,
	a.p.zijlstra@...llo.nl, paulus@...ba.org, efault@....de,
	acme@...hat.com, fweisbec@...il.com, jkosina@...e.cz
Subject: Re: [PATCH] perf bench:Fix bench/sched-pipe.c to wait child process

From: Hitoshi Mitake <mitake@....info.waseda.ac.jp>
Subject: [PATCH] perf bench:Fix bench/sched-pipe.c to wait child process
Date: Mon,  9 Nov 2009 12:13:08 +0900

Sorry, the title lacks space after "perf bench:".
I'll send new fixed one, please discard this.

> 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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