linux-kernel - Re: [PATCH] fix granularity of task

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Date:	Thu, 12 Nov 2009 16:40:50 +0100
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Spencer Candland <spencer@...ehost.com>
Cc:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Américo Wang <xiyou.wangcong@...il.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH] fix granularity of task_u/stime(), v2

On Thu, Nov 12, 2009 at 04:00:38PM +0100, Peter Zijlstra wrote:
> On Thu, 2009-11-12 at 15:49 +0100, Stanislaw Gruszka wrote:
> >  I can not reproduce
> > the bug with below patch:
> > 
> > diff --git a/kernel/exit.c b/kernel/exit.c
> > index f7864ac..b85e384 100644
> > --- a/kernel/exit.c
> > +++ b/kernel/exit.c
> > @@ -110,8 +110,8 @@ static void __exit_signal(struct task_struct *tsk)
> >  		 * We won't ever get here for the group leader, since it
> >  		 * will have been the last reference on the signal_struct.
> >  		 */
> > -		sig->utime = cputime_add(sig->utime, task_utime(tsk));
> > -		sig->stime = cputime_add(sig->stime, task_stime(tsk));
> > +		sig->utime = cputime_add(sig->utime, tsk->utime); //task_utime(tsk));
> > +		sig->stime = cputime_add(sig->stime, tsk->stime); //task_stime(tsk));
> >  		sig->gtime = cputime_add(sig->gtime, task_gtime(tsk));
> >  		sig->min_flt += tsk->min_flt;
> >  		sig->maj_flt += tsk->maj_flt;
> 
> Yes, this is the thing I suggested and makes sense.

Ok, I'm going to post this.

Spencer,

seems you have more test cases for utime decreasing issues,
could you send links to me ? Somehow I could not find them 
by my own. Particularly test case used in development this commit
is interested:

  commit 49048622eae698e5c4ae61f7e71200f265ccc529
  Author: Balbir Singh <balbir@...ux.vnet.ibm.com>
  Date:   Fri Sep 5 18:12:23 2008 +0200
    sched: fix process time monotonicity

Stanislaw
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