linux-kernel - [RFC,PATCH 1/2] cputimers/proc: do_task_stat()->task

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Message-ID: <20100324204550.GA31777@redhat.com>
Date:	Wed, 24 Mar 2010 21:45:50 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Americo Wang <xiyou.wangcong@...il.com>,
	Balbir Singh <balbir@...ibm.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Roland McGrath <roland@...hat.com>,
	Spencer Candland <spencer@...ehost.com>,
	Stanislaw Gruszka <sgruszka@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: [RFC,PATCH 1/2] cputimers/proc: do_task_stat()->task_times() can
	race with getrusage()

do_task_stat()->task_times() can race with getrusage(), they both can
try to update task->prev_Xtime at the same time.

Remove this bit of d180c5bc "sched: Introduce task_times() to replace
task_{u,s}time()".

See also the next patch.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---

 fs/proc/array.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- 34-rc1/fs/proc/array.c~PROC_4_DTS_TASK_TIMES_IS_RACY	2010-03-24 19:53:23.000000000 +0100
+++ 34-rc1/fs/proc/array.c	2010-03-24 19:57:37.000000000 +0100
@@ -449,7 +449,8 @@ static int do_task_stat(struct seq_file 
 	if (!whole) {
 		min_flt = task->min_flt;
 		maj_flt = task->maj_flt;
-		task_times(task, &utime, &stime);
+		utime = task->utime;
+		stime = task->stime;
 		gtime = task->gtime;
 	}
 

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