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

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Message-ID: <56379FDE.6010603@intel.com>
Date:	Mon, 2 Nov 2015 09:39:42 -0800
From:	Dave Hansen <dave.hansen@...el.com>
To:	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	kernel test robot <ying.huang@...ux.intel.com>
Cc:	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>,
	Dmitry Chernenkov <dmitryc@...gle.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]

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.
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