linux-kernel - Re: 2.6.24-rc5 "videobuf_read_start" [drivers/media/video/videobuf-dvb.ko] undefined!

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Date:	Wed, 12 Dec 2007 23:19:44 +0100
From:	Jean Delvare <khali@...ux-fr.org>
To:	Mauro Carvalho Chehab <mchehab@...radead.org>
Cc:	Adrian Bunk <bunk@...nel.org>, Shane <gnome42@...il.com>,
	Brandon Philips <brandon@...p.org>,
	linux-kernel@...r.kernel.org,
	video4linux-list <video4linux-list@...hat.com>
Subject: Re: 2.6.24-rc5 "videobuf_read_start"
 [drivers/media/video/videobuf-dvb.ko] undefined!

Hi Mauro,

On Wed, 12 Dec 2007 12:21:56 -0200, Mauro Carvalho Chehab wrote:
> What happened is that changeset 19bc5133dae9562e8824ef101464061f9854c1d8
> fixed some bad locks. 
> 
> After this changeset, videobuf_read_stream() holds q->lock and calls
> videobuf_read_start(). To avoid waiting forever for the lock to be
> released, he removed the mutex from videobuf_read_start with this line
> [1]:
> 
> -       err = videobuf_mmap_setup(q, count, size, V4L2_MEMORY_USERPTR);
> +       err = __videobuf_mmap_setup(q, count, size, V4L2_MEMORY_USERPTR);
> 
> So, after the patch, videobuf_read_start() can't be safely called. So,
> just adding EXPORT_SYMBOL_GPL() breaks videobuf-dvb at runtime.
> 
> The proper solution is provided by this changeset:
> http://git.kernel.org/?p=linux/kernel/git/mchehab/v4l-dvb.git;a=commitdiff;h=19fb1457990b6b7e15586ec7331541a184233acc

There's a "static" missing in that patch: __videobuf_read_start is only
used internally.

-- 
Jean Delvare
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