linux-kernel - Re: [patch] sched: add the other missing clock update to migrate

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Message-Id: <1258909123.6043.19.camel@marge.simson.net>
Date:	Sun, 22 Nov 2009 17:58:43 +0100
From:	Mike Galbraith <efault@....de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch] sched: add the other missing clock update to
 migrate_task()

On Sun, 2009-11-22 at 14:16 +0100, Peter Zijlstra wrote:

> We should make double_rq_lock() and double_lock_balance() behave
> equivalent wrt update_rq_clock().
> 
> Current, depending on CONFIG_PREEMPT, double_lock_balance() already
> updates both rq clocks.

Hm, right.  Better plan.  We can save an update in the wakeup path for
the tasks racing for the wakeup case too.  If the call is really a
lock/unlock go away, we don't need to bother.  Shave a ns or so.

	-Mike

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