Subject: Re: utime/stime decreasing on thread exit
From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>,
       Spencer Candland <spencer@bluehost.com>, linux-kernel@vger.kernel.org,
       Ingo Molnar <mingo@elte.hu>
In-Reply-To: <20091109172020.GA7751@redhat.com>
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	 <20091109172020.GA7751@redhat.com>
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Date: Mon, 09 Nov 2009 18:31:43 +0100
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On Mon, 2009-11-09 at 18:20 +0100, Oleg Nesterov wrote:

> > I just checked .22 and there we seem to hold p->sighand->siglock over
> > the full task iteration.
> 
> Yes. Then thread_group_cputime() was changed so that it didn't itearate
> over sub-threads, then this callsite was move outside of ->siglock, now
> it does while_each_thread() again.
> 
> > So we might as well revert back to that if
> > people really mind counting things twice :-)
> 
> Stanislaw has already sent the patch, but I don't know what happened
> with this patch:
> 
> 	[PATCH 1/2] posix-cpu-timers: avoid do_sys_times() races with __exit_signal()
> 	http://marc.info/?l=linux-kernel&m=124505545131145

That patch has the siglock in the function calling
thread_group_cputime(), the 22 code had it near the loop proper, which
to me seems a more sensible thing, since there could be more callers,
no?

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