From: Srivatsa Vaddagiri <vatsa@in.ibm.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@osdl.org>,
Bjorn Helgaas <bjorn.helgaas@hp.com>,
linux-kernel@vger.kernel.org, Myron Stowe <myron.stowe@hp.com>,
Jens Axboe <axboe@kernel.dk>, Dipankar <dipankar@in.ibm.com>,
Gautham shenoy <ego@in.ibm.com>
Subject: Re: workqueue deadlock
Date: Mon, 11 Dec 2006 10:28:31 +0530 [thread overview]
Message-ID: <20061211045830.GB5339@in.ibm.com> (raw)
In-Reply-To: <20061210082616.GB14057@elte.hu>
On Sun, Dec 10, 2006 at 09:26:16AM +0100, Ingo Molnar wrote:
> something like the pseudocode further below - when applied to a data
> structure it has semantics and scalability close to that of
> preempt_disable(), but it is still preemptible and the lock is specific.
Ingo,
The psuedo-code you have provided can still fail to avoid
the deadlock reported by Bjorn Helgaas earlier in this thread:
http://lkml.org/lkml/2006/12/6/352
Thread1->flush_workqueue->mutex_lock(cpu4's hotplug_lock)
Thread2(keventd)->run_workqueue->som_work_fn-> ..
flush_workqueue->mutex_lock(cpu4's hotplug_lock)
Both deadlock with each other.
All this mess could easily be avoided if we implement a reference-count
based cpu_hotplug_lock(), as suggested by Arjan and Linus before and
implemented by Gautham here:
http://lkml.org/lkml/2006/10/26/65
--
Regards,
vatsa
prev parent reply other threads:[~2006-12-11 5:00 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-07 0:26 workqueue deadlock Bjorn Helgaas
2006-12-07 6:17 ` Srivatsa Vaddagiri
2006-12-07 6:45 ` Srivatsa Vaddagiri
2006-12-07 18:51 ` Andrew Morton
2006-12-07 19:37 ` Andrew Morton
2006-12-08 2:53 ` Srivatsa Vaddagiri
2006-12-08 4:54 ` Andrew Morton
2006-12-08 7:58 ` Srivatsa Vaddagiri
2006-12-09 10:26 ` Ingo Molnar
2006-12-09 19:47 ` Andrew Morton
2006-12-10 8:26 ` Ingo Molnar
2006-12-10 8:43 ` Andrew Morton
2006-12-10 11:49 ` Ingo Molnar
2006-12-10 12:16 ` Andrew Morton
2006-12-10 12:19 ` Ingo Molnar
2006-12-10 12:34 ` Andrew Morton
2006-12-11 6:09 ` Ingo Molnar
2006-12-10 14:18 ` Rafael J. Wysocki
2006-12-11 6:52 ` Dipankar Sarma
2006-12-11 16:34 ` Rafael J. Wysocki
2006-12-11 5:45 ` Srivatsa Vaddagiri
2006-12-11 6:03 ` Andrew Morton
2006-12-11 4:58 ` Srivatsa Vaddagiri [this message]
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