linux-kernel - Re: [tip:timers/urgent] tick: Cleanup NOHZ per cpu data on cpu down

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Date:	Tue, 14 May 2013 09:48:12 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	mingo@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org,
	bitbucket@...ine.de,
	tip-bot for Thomas Gleixner <tipbot@...or.com>,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:timers/urgent] tick: Cleanup NOHZ per cpu data on cpu down



On 05/13/2013 03:10 PM, Thomas Gleixner wrote:
> On Mon, 13 May 2013, Prarit Bhargava wrote:
>> Thomas, while this does fix up the NULL pointer issue, I think you've introduced
>> a new bug in the schedule timer code.
> 
> I don't think that I introduced a new bug. I'm quite sure that change
> unearthed another issue which was papered over by the stale data.
> 
> That memset is putting the data structure into the same state as we
> have on boot. From tick-sched perspective cpu onlining is not
> different between boot and an offline/online cycle
> 
>> While doing up and downs on the same CPU, I now occasionally see long delays in
>> the up and down...
> 
>> [   81.744565] smpboot: Booting Node 1 Processor 19 APIC 0x28
>> [   82.848591] smpboot: CPU 19 is now offline
>>
>> Long delay in bringing CPU "up"
>>
>> [   89.826533] smpboot: Booting Node 1 Processor 19 APIC 0x28
>> [   84.905358] smpboot: CPU 19 is now offline
>> [   87.565274] smpboot: Booting Node 1 Processor 19 APIC 0x28
> 
> Errm, the timestamps are random. -ENOTUSEFUL
>  

I'm always saying my computer is full of lies ;)

Here's the bottom line.  The patch included in this thread plus the patch you
pointed me to here

http://marc.info/?l=linux-kernel&m=136847403809031&w=2

seem to resolve the cpu up/down + thermal interrupt issues that I've been seeing.

So thank you :)

Tested-by: Prarit Bhargava <prarit@...hat.com>

P.
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