linux-kernel - Re: linux-next 20111025: warnings in rcu_idle_exit_common()/rcu_idle_enter

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Message-ID: <20111102151426.GN2287@linux.vnet.ibm.com>
Date:	Wed, 2 Nov 2011 08:14:26 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Wu Fengguang <fengguang.wu@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Carsten Emde <cbe@...dl.org>
Subject: Re: linux-next 20111025: warnings in
 rcu_idle_exit_common()/rcu_idle_enter_common()

On Wed, Nov 02, 2011 at 10:56:26AM -0400, Steven Rostedt wrote:
> On Wed, 2011-11-02 at 07:44 -0700, Paul E. McKenney wrote:
> 
> > rcu: Fix idle-task checks
> > 
> > RCU has traditionally relied on idle_cpu() to determine whether a given
> > CPU is running in the context of an idle task, but recent changes have
> > invalidated this approach.
> 
> Correct. idle_cpu() returns if the CPU is idle or not, not if the CPU is
> running the idle thread. If the CPU wakes up on the idle thread and
> there's tasks on the run queue, then idle_cpu() will return false, even
> though the task running is the idle thread. But the CPU itself is not
> technically idle.
> 
> Acked-by: Steven Rostedt <rostedt@...dmis.org>

Thank you, Steven!  I have added your Acked-by.

							Thanx, Paul

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