linux-kernel - Re: [PATCH 02/10 v2] posix-timers: Remove dead process posix cpu timers caching

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Message-ID: <52A77188.50200@jp.fujitsu.com>
Date:	Tue, 10 Dec 2013 14:54:48 -0500
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	fweisbec@...il.com
CC:	kosaki.motohiro@...fujitsu.com, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, mingo@...nel.org, peterz@...radead.org,
	oleg@...hat.com, akpm@...ux-foundation.org
Subject: Re: [PATCH 02/10 v2] posix-timers: Remove dead process posix cpu
 timers caching

(12/9/2013 12:58 PM), Frederic Weisbecker wrote:
> Now that we removed dead thread posix cpu timers caching,
> lets remove the dead process wide version. This caching
> is similar to the per thread version but it should be even
> more rare:
> 
> * If the process id dead, we are not reading its timers
> status from a thread belonging to its group since they
> are all dead. So this caching only concern remote process
> timers reads. Now posix cpu timers using itimers or timer_settime()
> can't do remote process timers anyway so it's not even clear if there
> is actually a user for this caching.
> 
> * Unlike per thread timers caching, this only applies to
> zombies targets. Buried targets' process wide timers return
> 0 values. But then again, timer_gettime() can't read remote
> process timers, so if the process is dead, there can't be
> any reader left anyway.
> 
> Then again this caching seem to complicate the code for
> corner cases that are probably not worth it. So lets get
> rid of it.
> 
> Also remove the sample snapshot on dying process timer
> that is now useless, as suggested by Kosaki.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: Kosaki Motohiro <kosaki.motohiro@...fujitsu.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>

Looks good to me.

Acked-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>



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