linux-kernel - Re: [PATCH] sched/cputime: fix clock_nanosleep/clock

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Date:	Wed, 12 Nov 2014 13:52:50 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stanislaw Gruszka <sgruszka@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Rik van Riel <riel@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] sched/cputime: fix clock_nanosleep/clock_gettime
 inconsistency

On Wed, Nov 12, 2014 at 01:27:53PM +0100, Stanislaw Gruszka wrote:
> On Wed, Nov 12, 2014 at 12:45:38PM +0100, Peter Zijlstra wrote:
> > On Wed, Nov 12, 2014 at 12:37:37PM +0100, Peter Zijlstra wrote:
> > 
> > > Which would make the sample run ahead, making the sleep short. So would
> > > something like the below not cure things?
> > 
> > Before anyone asks, yes I tried running that 'reproducer' it doesn't.
> 
> I'd be surprised if the patch would help. Issue here happen at start of
> cputimer. We set sum_sched_runtime value of cputimer using not yet
> accounted threads runtime and then add that runtime values again to
> running cputimer on tick, making it's sum_exec_runtime bigger than
> actual threads runtime.

Ah yes, reading is hard.
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