linux-kernel - Re: [lkp] [fs] df4c0e36f1: NMI watchdog: BUG: soft lockup

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Date:	Mon, 2 Nov 2015 22:34:01 +0300
From:	Andrey Ryabinin <ryabinin.a.a@...il.com>
To:	Dave Hansen <dave.hansen@...el.com>
Cc:	kernel test robot <ying.huang@...ux.intel.com>, LKP <lkp@...org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Christoph Lameter <cl@...ux.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Yuri Gribov <tetra2005@...il.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Konstantin Serebryany <kcc@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [lkp] [fs] df4c0e36f1: NMI watchdog: BUG: soft lockup - CPU#0
 stuck for 22s! [swapper/0:1]

2015-11-02 20:39 GMT+03:00 Dave Hansen <dave.hansen@...el.com>:
> On 11/02/2015 01:32 AM, Andrey Ryabinin wrote:
>> And the major factor here is number 2.
>>
>> In your dmesg:
>> [   67.891156] rbtree testing -> 570841 cycles
>> [   88.609636] augmented rbtree testing
>> [  116.546697] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s!
>> [swapper/0:1]
>>
>>
>> I've tried to reproduce this, and got this:
>> [    0.693574] rbtree testing -> 15513 cycles
>> 570841/15513 = 36x times faster.
>>
>> [    1.159450] augmented rbtree testing -> 23675 cycles
>> [    1.864996]
>> It took less than a second, meanwhile in your case it didn't finish in
>> 22 seconds.
>>
>> This makes me think that your host is overloaded and the problem is on
>> your side.
>
> It's probably just a matter of putting some cond_resched()s in the test
> code.

Yes, but is it worthwhile? It's very likely that lockup will just
trigger in another place.
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