From: Li Zefan <lizefan@huawei.com>
To: Tejun Heo <tj@kernel.org>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
LKML <linux-kernel@vger.kernel.org>,
Cgroups <cgroups@vger.kernel.org>
Subject: Re: [PATCH] cgroup: make cgrp->event_list_lock irqsafe
Date: Wed, 6 Mar 2013 15:00:52 +0800 [thread overview]
Message-ID: <5136E9A4.7000201@huawei.com> (raw)
In-Reply-To: <20130306062224.GJ1227@htj.dyndns.org>
On 2013/3/6 14:22, Tejun Heo wrote:
> Hello, Li.
>
> On Wed, Mar 06, 2013 at 11:28:01AM +0800, Li Zefan wrote:
>> cgroup_event_wake() is called with hardirq-safe wqh->lock held, so
>> the nested cgrp->event_list_lock should also be hardirq-safe.
>>
>> Fortunately I don't think the deadlock can happen in real life.
>>
>> Lockdep never complained, maybe because it never found wqh->lock was
>> held in irq context?
>
> Why should wqh->lock be hard-irq-safe? Is it actually grabbed from
> irq context?
becase cgroup_event_wake() is a callback to a wait queue, and it's wake_up()
that acquires wqh->lock with irq disabled.
> Locks which are grabbed with irq disabled aren't
> necessarily irq context locks as that doesn't lead to deadlocks. They
> need to be actually grabbed from irq context.
>
> Thanks.
>
next prev parent reply other threads:[~2013-03-06 7:01 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-06 3:28 [PATCH] cgroup: make cgrp->event_list_lock irqsafe Li Zefan
2013-03-06 6:22 ` Tejun Heo
2013-03-06 7:00 ` Li Zefan [this message]
2013-03-06 7:02 ` Tejun Heo
2013-03-06 7:15 ` Li Zefan
2013-03-06 7:21 ` Tejun Heo
2013-03-06 7:23 ` Tejun Heo
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