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From: Hans Verkuil <hverkuil@xs4all.nl>
To: video4linux-list@redhat.com
Cc: Greg KH <greg@kroah.com>, linux-kernel@vger.kernel.org
Subject: Re: [BUG] cdev_put() race condition
Date: Wed, 17 Dec 2008 20:39:03 +0100	[thread overview]
Message-ID: <200812172039.03436.hverkuil@xs4all.nl> (raw)
In-Reply-To: <200812172030.32535.hverkuil@xs4all.nl>

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

WARNING: multiple messages have this Message-ID (diff)
From: Hans Verkuil <hverkuil@xs4all.nl>
To: video4linux-list@redhat.com
Cc: Greg KH <greg@kroah.com>, linux-kernel@vger.kernel.org
Subject: Re: [BUG] cdev_put() race condition
Date: Wed, 17 Dec 2008 20:39:03 +0100	[thread overview]
Message-ID: <200812172039.03436.hverkuil@xs4all.nl> (raw)
In-Reply-To: <200812172030.32535.hverkuil@xs4all.nl>

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

--
video4linux-list mailing list
Unsubscribe mailto:video4linux-list-request@redhat.com?subject=unsubscribe
https://www.redhat.com/mailman/listinfo/video4linux-list

  parent reply	other threads:[~2008-12-17 19:39 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-12-08 20:56 [BUG] cdev_put() race condition Hans Verkuil
2008-12-08 20:56 ` Hans Verkuil
2008-12-16 10:06 ` Hans Verkuil
2008-12-16 10:06   ` Hans Verkuil
2008-12-16 20:22 ` Greg KH
2008-12-16 21:00   ` Hans Verkuil
2008-12-16 21:00     ` Hans Verkuil
2008-12-16 21:21     ` Greg KH
2008-12-16 23:23       ` Hans Verkuil
2008-12-16 23:23         ` Hans Verkuil
2008-12-16 23:30         ` Greg KH
2008-12-17 13:37           ` Hans Verkuil
2008-12-17 13:37             ` Hans Verkuil
2008-12-17 14:52             ` Boaz Harrosh
2008-12-17 15:07               ` Hans Verkuil
2008-12-17 15:07                 ` Hans Verkuil
2008-12-17 16:09                 ` Boaz Harrosh
2008-12-17 17:33                   ` Hans Verkuil
2008-12-17 17:33                     ` Hans Verkuil
2008-12-17 18:08                     ` Al Viro
2008-12-18  8:12                       ` Boaz Harrosh
2008-12-18  8:25                     ` Boaz Harrosh
2008-12-17 18:16             ` Greg KH
2008-12-17 19:27               ` Laurent Pinchart
2008-12-17 19:27                 ` Laurent Pinchart
2008-12-17 19:35                 ` Greg KH
2008-12-17 19:30               ` Hans Verkuil
2008-12-17 19:30                 ` Hans Verkuil
2008-12-17 19:38                 ` Greg KH
2008-12-17 19:39                 ` Hans Verkuil [this message]
2008-12-17 19:39                   ` Hans Verkuil
2008-12-17 19:53                   ` Greg KH
2008-12-17 20:18                     ` Hans Verkuil
2008-12-17 20:18                       ` Hans Verkuil
2008-12-17 20:52                       ` Greg KH

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