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From: Tejun Heo <tj@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: tglx@linutronix.de, mingo@elte.hu, avi@redhat.com, efault@gmx.de,
	rusty@rustcorp.com.au, linux-kernel@vger.kernel.org,
	Gautham R Shenoy <ego@in.ibm.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 4/7] sched: implement force_cpus_allowed()
Date: Tue, 08 Dec 2009 17:41:20 +0900	[thread overview]
Message-ID: <4B1E1130.9050108@kernel.org> (raw)
In-Reply-To: <4B1CE1E8.2070803@kernel.org>

Hello,

On 12/07/2009 08:07 PM, Tejun Heo wrote:
> On 12/07/2009 07:54 PM, Peter Zijlstra wrote:
>> So we seem to do cleanup_workqueue_thread() from CPU_POST_DEAD, but at
>> that time any thread that might still be around will most certainly not
>> be running on the offlined cpu anymore.
>>
>> If you really want to ensure you remain on the cpu, you have to complete
>> from CPU_DOWN_PREPARE.
>>
>> We're not running things from offline CPUs.
> 
> Oh, no, we're not doing that.  We can't do that.  What we're doing is
> to continue to process works which were queued on the now offline cpu
> unless it has been flushed/cancled from one of the cpu down
> notifications and the reason why we need to be able to fork after
> active is clear is to guarantee those flush/cancels don't deadlock.

Does my explanation justify the patch?

Thanks.

-- 
tejun

  reply	other threads:[~2009-12-08  8:41 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-12-02  3:56 [PATCHSET tip/sched/core] sched: concurrency managed workqueue related sched patches Tejun Heo
2009-12-02  3:56 ` [PATCH 1/7] sched: revert 498657a478c60be092208422fefa9c7b248729c2 Tejun Heo
2009-12-02 10:42   ` [tip:sched/core] sched: Revert 498657a478c60be092208422fefa9c7b248729c2 tip-bot for Tejun Heo
2009-12-02  3:56 ` [PATCH 2/7] sched: rename preempt_notifiers to sched_notifiers and refactor implementation Tejun Heo
2009-12-02  3:56 ` [PATCH 3/7] sched: refactor try_to_wake_up() Tejun Heo
2009-12-02  9:05   ` Mike Galbraith
2009-12-02  9:51     ` Tejun Heo
2009-12-02 10:10       ` Mike Galbraith
2009-12-02 10:14         ` Tejun Heo
2009-12-02 11:01           ` Peter Zijlstra
2009-12-03  6:11   ` [PATCH UDPATED " Tejun Heo
2009-12-02  3:56 ` [PATCH 4/7] sched: implement force_cpus_allowed() Tejun Heo
2009-12-04 10:40   ` Peter Zijlstra
2009-12-04 10:43     ` Peter Zijlstra
2009-12-07  4:34       ` Tejun Heo
2009-12-07  8:35         ` Peter Zijlstra
2009-12-07 10:34           ` Tejun Heo
2009-12-07 10:54             ` Peter Zijlstra
2009-12-07 11:07               ` Tejun Heo
2009-12-08  8:41                 ` Tejun Heo [this message]
2009-12-08  9:02                   ` Peter Zijlstra
2009-12-08  9:12                     ` Tejun Heo
2009-12-08 10:34                       ` Peter Zijlstra
2009-12-08 10:38                         ` Peter Zijlstra
2009-12-08 11:26                           ` Tejun Heo
2009-12-08 11:24                         ` Tejun Heo
2009-12-08 11:48                           ` Peter Zijlstra
2009-12-08 11:56                             ` Tejun Heo
2009-12-08 12:10                               ` Peter Zijlstra
2009-12-08 12:23                                 ` Tejun Heo
2009-12-08 13:35                                   ` Peter Zijlstra
2009-12-09  5:25                                     ` Tejun Heo
2009-12-09  7:41                                       ` Peter Zijlstra
2009-12-09  8:03                                         ` Tejun Heo
2009-12-02  3:56 ` [PATCH 5/7] sched: make sched_notifiers unconditional Tejun Heo
2009-12-02  3:56 ` [PATCH 6/7] sched: add wakeup/sleep sched_notifiers and allow NULL notifier ops Tejun Heo
2009-12-02  3:56 ` [PATCH 7/7] sched: implement try_to_wake_up_local() Tejun Heo
2009-12-03  6:13   ` [PATCH UPDATED " Tejun Heo
2009-12-04 10:47     ` Peter Zijlstra
2009-12-07  3:31       ` Tejun Heo
2009-12-04 10:44   ` [PATCH " Peter Zijlstra
2009-12-07  3:26     ` Tejun Heo
2009-12-07  8:50       ` Peter Zijlstra
2009-12-07  8:56         ` Peter Zijlstra
2009-12-07 10:27           ` Tejun Heo
2009-12-08  8:53             ` Peter Zijlstra
2009-12-08  9:16               ` Tejun Heo

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