linux-kernel - Re: Yet more softlockups.

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Date:	Fri, 05 Jul 2013 09:41:13 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Dave Jones <davej@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Seiji Aguchi <seiji.aguchi@....com>
Subject: Re: Yet more softlockups.

On 07/05/2013 09:02 AM, Thomas Gleixner wrote:
> On Fri, 5 Jul 2013, Dave Jones wrote:
>> On Fri, Jul 05, 2013 at 05:15:07PM +0200, Thomas Gleixner wrote:
>>   > On Fri, 5 Jul 2013, Dave Jones wrote:
>>   >
>>   > > BUG: soft lockup - CPU#3 stuck for 23s! [trinity-child1:14565]
>>   > > perf samples too long (2519 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
>>   > > INFO: NMI handler (perf_event_nmi_handler) took too long to run: 238147.002 msecs
>>   >
>>   > So we see a softlockup of 23 seconds and the perf_event_nmi_handler
>>   > claims it did run 23.8 seconds.
>>   >
>>   > Are there more instances of NMI handler messages ?
>>
>> [ 2552.006181] perf samples too long (2511 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
>> [ 2552.008680] INFO: NMI handler (perf_event_nmi_handler) took too long to run: 500392.002 msecs
>
> Yuck. Spending 50 seconds in NMI context surely explains a softlockup :)
>

Hmmm... this makes me wonder if the interrupt tracepoint stuff is at 
fault here, as it changes the IDT handling for NMI context.

	-hpa

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