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From: Alan Cox <alan@redhat.com>
To: Laurent Pinchart <laurent.pinchart@skynet.be>
Cc: video4linux-list@redhat.com, linux-uvc-devel@lists.berlios.de
Subject: Re: [Linux-uvc-devel] Thread safety of ioctls
Date: Tue, 24 Jun 2008 09:39:51 -0400	[thread overview]
Message-ID: <20080624133951.GA9910@devserv.devel.redhat.com> (raw)
In-Reply-To: <200806240033.41145.laurent.pinchart@skynet.be>

On Tue, Jun 24, 2008 at 12:33:40AM +0200, Laurent Pinchart wrote:
> Not really. The ioctl handler is protected by the big kernel lock, so ioctls 
> are currently not reentrant.

Not so - the BKL drops on sleeping so any ioctl that sleeps is re-entrant.
Any code using locks of its own should be dropping their lock before any long
sleeps.

> Most drivers are probably not designed with thread safety in mind, and I'm 
> pretty sure lots of race conditions still lie in the depth of V4L(2) drivers. 

>From looking at the BKL dropping work that would unfortunately seem to be
the case for some drivers

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  reply	other threads:[~2008-06-24 13:39 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-06-23 10:26 Thread safety of ioctls Gregor Jasny
2008-06-23 13:29 ` Alan Cox
2008-06-23 22:33 ` [Linux-uvc-devel] " Laurent Pinchart
2008-06-24 13:39   ` Alan Cox [this message]
2008-06-24 21:34     ` Laurent Pinchart
2008-06-24 22:23       ` Alan Cox
2008-06-24 21:36   ` Mauro Carvalho Chehab
2008-06-24 22:04     ` Laurent Pinchart
2008-06-26 19:48   ` Driver hangs at DQBUF ioctl Gregor Jasny
2008-06-30 15:39     ` [Linux-uvc-devel] " Laurent Pinchart

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