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

From: Peter Zijlstra
Date: Sat Feb 21 2015 - 06:19:19 EST


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@xxxxxxxxxxxxx>
> >
> > Replace the clockevents_notify() call with an explicit function call.
> >
> > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>
> 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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