linux-kernel - Re: [BUG] cdev_put() race condition

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Message-Id: <200812172039.03436.hverkuil@xs4all.nl>
Date:	Wed, 17 Dec 2008 20:39:03 +0100
From:	Hans Verkuil <hverkuil@...all.nl>
To:	video4linux-list@...hat.com
Cc:	Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org
Subject: Re: [BUG] cdev_put() race condition

On Wednesday 17 December 2008 20:30:32 Hans Verkuil wrote:
>
> This solves this particular problem. But this will certainly break v4l as
> it is right now, since the spin_lock means that the kref's release cannot
> do any sleeps, which is possible in v4l. If we want to allow that in
> cdev, then the spinlock has to be replaced by a mutex. But I have the
> strong feeling that that's not going to happen :-)

Note that if we ever allow drivers to hook in their own release callback, 
then we certainly should switch to a mutex in the cdev struct, rather than 
a global mutex. It obviously makes life more complicated for cdev, but much 
easier for drivers.

Regards,

 	Hans

-- 
Hans Verkuil - video4linux developer - sponsored by TANDBERG
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