linux-kernel - Re: [PATCH 32/35] clockevents: Fix cpu down race for hrtimer based broadcasting

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Message-ID: <20150219095343.GF5029@twins.programming.kicks-ass.net>
Date:	Thu, 19 Feb 2015 10:53:43 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org, rjw@...ysocki.net,
	tglx@...utronix.de
Subject: Re: [PATCH 32/35] clockevents: Fix cpu down race for hrtimer based
 broadcasting

On Thu, Feb 19, 2015 at 12:31:53PM +0530, Preeti U Murthy wrote:
> On 02/18/2015 06:36 PM, Peter Zijlstra wrote:
> > On Wed, Feb 18, 2015 at 08:40:52AM +0530, Preeti U Murthy wrote:
> >>
> >> Look at the changelog, 
> > 
> > Heh, yah, clearly I tl;dr'd that. Indeed.
> > 
> >> it explains why tick_takeover must be called
> >> *before* __cpu_die(). 
> > 
> > Since you reported this, can you test if things work if you move that
> > function call to before __cpu_die() ?
> 
> Yes it does. I had tested and posted out a patch to fix the issue
> here:https://lkml.org/lkml/2015/1/30/821. I see now that tglx proposes
> to get rid of "taking over" tick duties going forward, rather "handing
> over" tick duties would be better. So the patch in the above link would
> not be acceptable. But minus the taking over of the do_timer, the cpu
> doing the hotplug takes over broadcast duty before __cpu_die() in this
> patch. This design works.

Great, /me amends patch.
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