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Re: [PATCH v4] sched: fix incorrect wait time and wait count statistics

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [PATCH v4] sched: fix incorrect wait time and wait count statistics
Date 2015-11-09 11:40 +0100
Message-ID <qsS1I-5cB-15@gated-at.bofh.it> (permalink)
References <qooYi-54u-21@gated-at.bofh.it> <qoqQq-6jx-1@gated-at.bofh.it> <qrPID-5cI-25@gated-at.bofh.it> <qs1JL-4zz-1@gated-at.bofh.it>
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On Fri, Nov 06, 2015 at 06:41:43PM -0800, Joonwoo Park wrote:
> On Fri, Nov 06, 2015 at 02:57:49PM +0100, Peter Zijlstra wrote:
> > On Tue, Oct 27, 2015 at 09:46:53PM -0700, Joonwoo Park wrote:
> > > @@ -1272,6 +1272,15 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
> > >  	WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
> > >  			!p->on_rq);
> > >  
> > > +	/*
> > > +	 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
> > > +	 * because schedstat_wait_{start,end} rebase migrating task's wait_start
> > > +	 * time relying on p->on_rq.
> > > +	 */
> > > +	WARN_ON_ONCE(p->state == TASK_RUNNING &&
> > > +		     p->sched_class == &fair_sched_class &&
> > > +		     (p->on_rq && !task_on_rq_migrating(p)));
> > > +
> > 
> > Why do we have to test p->on_rq? Would not ->state == RUNNING imply
> > that?
> > 
> 
> sched_fork() sets p->state = RUNNING before changing task cpu.
> Please let me know if you got better idea.

Ah, indeed. OK.
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Re: [PATCH v4] sched: fix incorrect wait time and wait count  statistics Peter Zijlstra <peterz@infradead.org> - 2015-11-06 15:00 +0100
  Re: [PATCH v4] sched: fix incorrect wait time and wait count  statistics Joonwoo Park <joonwoop@codeaurora.org> - 2015-11-07 03:50 +0100
    Re: [PATCH v4] sched: fix incorrect wait time and wait count  statistics Peter Zijlstra <peterz@infradead.org> - 2015-11-09 11:40 +0100
      Re: [PATCH v5] sched: fix incorrect wait time and wait count  statistics Joonwoo Park <joonwoop@codeaurora.org> - 2015-11-13 04:40 +0100

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