linux-kernel - [PATCH -mm 0/4] cputimers/proc: do_task_stat: don't walk through the thread list under ->siglock

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Date:	Mon, 29 Mar 2010 20:12:04 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Americo Wang <xiyou.wangcong@...il.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>,
	linux-kernel@...r.kernel.org
Subject: [PATCH -mm 0/4] cputimers/proc: do_task_stat: don't walk through
	the thread list under ->siglock

On 03/29, Oleg Nesterov wrote:
>
> Yes sure. I dislike the do_task_stat() case because we always do this,
> even if this info is not needed, say, for /bin/ps.

Note also that nobody else in /fs/proc needs ->siglock. Except
do_io_accounting(), but in this case the user-space explicitly asks for
this info.

OK, This is V2. Still RFC, although I think 1/4 makes sense in any case.

Please comment. Again, I am more or less sure these changes are "correct",
but I don't know what /bin/top can think ;)

I don't really like the fact thread_group_times() takes cputimer.lock,
but imho lock_task_sighand() in do_task_stat() is much worse.

Oleg.

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