linux-kernel - Re: [PATCH 27/35] sched/idle: Use explicit broadcast oneshot control function

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Message-ID: <20150221111904.GF23367@worktop.ger.corp.intel.com>
Date:	Sat, 21 Feb 2015 12:19:04 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Nicolas Pitre <nico@...aro.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org, rjw@...ysocki.net,
	tglx@...utronix.de
Subject: Re: [PATCH 27/35] sched/idle: Use explicit broadcast oneshot control
 function

On Fri, Feb 20, 2015 at 07:56:17PM -0500, Nicolas Pitre wrote:
> On Mon, 16 Feb 2015, Peter Zijlstra wrote:
> 
> > From: Thomas Gleixner <tglx@...utronix.de>
> > 
> > Replace the clockevents_notify() call with an explicit function call.
> > 
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> 
> This patch makes my test system hang solid after letting it sit idle for 
> 5 to 15 minutes.  Reverting it and this issue goes away.
> 
> The explicit function call is not an equivalent replacement. In 
> clockevents_notify() the clockevents_lock is held across the call to 
> tick_broadcast_enter() or tick_broadcast_exit(). This patch drops the 
> locking.

Yeah, the Changelog introducing the explicit call states as much. I'll
have to go figure out why that matters here.
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