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

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Date:	Thu, 19 Feb 2015 12:31:53 +0530
From:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
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 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.

Regards
Preeti U Murthy
> 
> I _think_ it should be fine, but what do I know ;-)
> 

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