linux-kernel - Re: [PATCH] block: avoid infinite loop in get_task_io

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Date:	Thu, 31 May 2012 12:47:53 +0200
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>, Alan Cox <alan@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] block: avoid infinite loop in get_task_io_context()

On 05/31/2012 12:38 PM, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> On Wed, 2012-05-30 at 22:35 +0200, Eric Dumazet wrote:
>> On Wed, 2012-05-30 at 21:08 +0200, Eric Dumazet wrote:
>>> On Wed, 2012-05-30 at 20:55 +0200, Jens Axboe wrote:
>>>> On 05/30/2012 08:33 PM, Eric Dumazet wrote:
>>>>> On Wed, 2012-05-30 at 14:54 +0200, Jens Axboe wrote:
>>>>>> Hi Linus,
>>>>>>
>>>>>> On top of the for-3.5/core pull request, here are the driver related
>>>>>> changes for 3.5. It contains:
>>>>>
>>>>> Hi Jens
>>>>>
>>>>> Not sure if this is related, but latest Linus tree cannot boot anymore
>>>>> here...
>>>>>
>>>>> BUG: soft lockup - CPU#3 stuck for 22s ! [mountall.1603]
>>>>
>>>> Hrmpf, can you attach your .config?
>>>>
>>>
>>> I can do a bisection pretty fast I think
>>
>> Not sure if bisection was good, but result is :
> 
> Bisection gave nothing, because its an old bug ?
> 
> Following patch cures it.
> 
> [PATCH] block: avoid infinite loop in get_task_io_context()
> 
> Calling get_task_io_context() on a exiting task which isn't %current can
> loop forever. This triggers at boot time on my dev machine.
> 
> BUG: soft lockup - CPU#3 stuck for 22s ! [mountall.1603]

Eric, do you have a task trace to go with this lockup, where task !=
current?

In any case, it is a legit bug fix. I have applied it.

-- 
Jens Axboe

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