linux-kernel - Re: [PATCH] posixtimers: Fix posix clock monotonicity v2

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Message-Id: <1237373887.5069.203.camel@laptop>
Date:	Wed, 18 Mar 2009 11:58:07 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org, stable@...nel.org,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] posixtimers: Fix posix clock monotonicity v2

On Wed, 2009-03-18 at 19:41 +0900, Hidetoshi Seto wrote:
> Impact: Regression fix (against clock_gettime() backwarding bug)
> 
> This patch re-introduces a couple of function, task_sched_runtime
> and thread_group_sched_runtime, which was once removed at the
> time of 2.6.28-rc1.
> 
> These functions protect the sampling of thread/process clock with
> rq lock.  This rq lock is required not to update rq->clock durling
> the sampling.
> i.e.
>   The clock_gettime() may return
>    ((accounted runtime before update) + (delta after update))
>   that is less than what it should be.
> 
> v1 -> v2:
> 	- Revises comments for functions and patch description.
> 	- Add note about accuracy of thread group's runtime.
> 
> Signed-off-by: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: stable@...nel.org	[2.6.28.x]

Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>

Thanks Hidetoshi-san.

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