From: Michal Schmidt <mschmidt@redhat.com>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Srivatsa Vaddagiri <vatsa@in.ibm.com>,
stable@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] destroy_workqueue() can livelock
Date: Fri, 13 Jul 2007 19:03:18 +0200 [thread overview]
Message-ID: <4697B056.9080508@redhat.com> (raw)
In-Reply-To: <20070713131655.GA1033@tv-sign.ru>
Oleg Nesterov wrote:
> Pointed out by Michal Schmidt <mschmidt@redhat.com>.
>
> The bug was introduced in 2.6.22 by me.
>
> cleanup_workqueue_thread() does flush_cpu_workqueue(cwq) in a loop until
> ->worklist becomes empty. This is live-lockable, a re-niced caller can
> get CPU after wake_up() and insert a new barrier before the lower-priority
> cwq->thread has a chance to clear ->current_work.
>
> Change cleanup_workqueue_thread() to do flush_cpu_workqueue(cwq) only once.
> We can rely on the fact that run_workqueue() won't return until it flushes
> all works. So it is safe to call kthread_stop() after that, the "should stop"
> request won't be noticed until run_workqueue() returns.
>
> Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
I confirm the patch fixes the bug I was seeing.
Michal
prev parent reply other threads:[~2007-07-13 17:03 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-13 13:16 [PATCH] destroy_workqueue() can livelock Oleg Nesterov
2007-07-13 17:03 ` Michal Schmidt [this message]
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