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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: peterz@infradead.org
Cc: kosaki.motohiro@gmail.com, oleg@redhat.com,
	y-goto@jp.fujitsu.com, mingo@elte.hu,
	kamezawa.hiroyu@jp.fujitsu.com, linux-kernel@vger.kernel.org
Subject: Re: [BUG] TASK_DEAD task is able to be woken up in special condition
Date: Tue, 24 Jan 2012 13:01:12 -0500	[thread overview]
Message-ID: <4F1EF1E8.4090909@jp.fujitsu.com> (raw)
In-Reply-To: <1327400618.2614.13.camel@laptop>

On 1/24/2012 5:23 AM, Peter Zijlstra wrote:
> On Wed, 2011-12-28 at 16:07 -0500, KOSAKI Motohiro wrote:
>> I looked at scheduler code today briefly. now I'm afraid following code 
>> have similar race.
>>
>>
>>          if (task_contributes_to_load(p))
>>                  rq->nr_uninterruptible--;
>>
>>
>>
>> Can't following schenario be happen?
>>
>>
>> CPU0                    CPU1
>> --------------------------------------------------------
>> deactivate_task()
>>                         task->state = TASK_UNINTERRUPTIBLE;
>> activate_task()
>>    rq->nr_uninterruptible--;
>>
>>                         schedule()
>>                           deactivate_task()
>>                             rq->nr_uninterruptible++;
>>
>> Totally, nr_uninterruptible wasn't incremented.
>>
>>
>> I'm still not sure. I need to read more sched code. 
> 
> You shouldn't ever set another tasks ->state. 

I'm sorry. I haven't catch your point. I think following step is
valid kernel code. Do you disagree?

>>                         task->state = TASK_UNINTERRUPTIBLE;
>>                         schedule()


  reply	other threads:[~2012-01-24 18:01 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-12-22  0:42 [BUG] TASK_DEAD task is able to be woken up in special condition Yasunori Goto
2011-12-22  2:14 ` KOSAKI Motohiro
2011-12-22  8:22   ` Yasunori Goto
2011-12-22 20:02     ` KOSAKI Motohiro
2011-12-23  9:49 ` Peter Zijlstra
2011-12-23 15:41   ` Oleg Nesterov
2011-12-26  8:23     ` Yasunori Goto
2011-12-26 17:11       ` Oleg Nesterov
2011-12-27  6:48         ` Yasunori Goto
2012-01-06 10:22           ` Yasunori Goto
2012-01-06 11:01             ` Peter Zijlstra
2012-01-06 12:01               ` Yasunori Goto
2012-01-06 12:43                 ` Peter Zijlstra
2012-01-06 14:12                   ` Oleg Nesterov
2012-01-06 14:19                     ` Oleg Nesterov
2012-01-07  1:31                     ` Yasunori Goto
2012-01-16 11:51                       ` Yasunori Goto
2012-01-16 13:38                         ` Peter Zijlstra
2012-01-17  8:40                           ` Yasunori Goto
2012-01-17  9:06                             ` Ingo Molnar
2012-01-17 15:12                               ` Oleg Nesterov
2012-01-18  9:42                                 ` Ingo Molnar
2012-01-18 14:20                                   ` Oleg Nesterov
2012-01-24 10:19                                     ` Peter Zijlstra
2012-01-24 10:55                                       ` Peter Zijlstra
2012-01-24 17:25                                         ` KOSAKI Motohiro
2012-01-25 15:45                                         ` Oleg Nesterov
2012-01-25 16:51                                           ` Peter Zijlstra
2012-01-25 17:43                                             ` Oleg Nesterov
2012-01-26 15:32                                               ` Peter Zijlstra
2012-01-26 16:26                                                 ` Oleg Nesterov
2012-01-27  8:59                                                   ` Peter Zijlstra
2012-01-24 10:11                                   ` Peter Zijlstra
2012-01-26  9:39                                     ` Ingo Molnar
2012-01-28 12:03                             ` [tip:sched/core] sched: Fix ancient race in do_exit() tip-bot for Yasunori Goto
2012-01-28 21:12                               ` Linus Torvalds
2012-01-29 16:07                                 ` Oleg Nesterov
2012-01-29 17:44                                   ` Linus Torvalds
2012-01-29 18:28                                     ` Linus Torvalds
2012-01-29 18:59                                     ` Oleg Nesterov
2012-01-30 16:27                                       ` Linus Torvalds
2012-01-06 13:48             ` [BUG] TASK_DEAD task is able to be woken up in special condition Oleg Nesterov
2011-12-28 21:07         ` KOSAKI Motohiro
2012-01-24 10:23           ` Peter Zijlstra
2012-01-24 18:01             ` KOSAKI Motohiro [this message]
2012-01-25  6:15               ` Mike Galbraith
2012-01-26 21:24                 ` KOSAKI Motohiro
2012-01-25 10:10           ` Peter Zijlstra
2012-01-26 20:25             ` [tip:sched/urgent] sched: Fix rq->nr_uninterruptible update race tip-bot for Peter Zijlstra
2012-01-27  5:20               ` Rakib Mullick
2012-01-27  8:19                 ` Peter Zijlstra
2012-01-27 14:11                   ` Rakib Mullick
2012-01-26 21:21             ` [BUG] TASK_DEAD task is able to be woken up in special condition KOSAKI Motohiro
2012-01-27  8:21               ` Peter Zijlstra
2011-12-26  6:52   ` Yasunori Goto

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