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Date: Mon, 2 Nov 2015 22:34:01 +0300
Message-ID: <CAPAsAGzpTM84NEESPt_jY0i-+W2SB37KtW1TXy93e8R2F7rEtw@mail.gmail.com>
Subject: Re: [lkp] [fs] df4c0e36f1: NMI watchdog: BUG: soft lockup - CPU#0
 stuck for 22s! [swapper/0:1]
From: Andrey Ryabinin <ryabinin.a.a@gmail.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: kernel test robot <ying.huang@linux.intel.com>, LKP <lkp@01.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Rientjes <rientjes@google.com>,
        Pekka Enberg <penberg@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
        Andi Kleen <andi@firstfloor.org>, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Christoph Lameter <cl@linux.com>, Sasha Levin <sasha.levin@oracle.com>,
        Konstantin Khlebnikov <koct9i@gmail.com>,
        Yuri Gribov <tetra2005@gmail.com>,
        Andrey Konovalov <adech.fo@gmail.com>,
        Konstantin Serebryany <kcc@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>
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2015-11-02 20:39 GMT+03:00 Dave Hansen <dave.hansen@intel.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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