From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from smtp.gentoo.org ([140.211.166.183]:48745 "EHLO smtp.gentoo.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S968086AbcA0U50 (ORCPT ); Wed, 27 Jan 2016 15:57:26 -0500 Subject: Re: [PATCH for v4.5] vb2: fix nasty vb2_thread regression To: Hans Verkuil , linux-media References: <56A8B34A.7010606@xs4all.nl> Cc: Junghak Sung From: Matthias Schwarzott Message-ID: <56A92F1C.9080005@gentoo.org> Date: Wed, 27 Jan 2016 21:57:00 +0100 MIME-Version: 1.0 In-Reply-To: <56A8B34A.7010606@xs4all.nl> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: Am 27.01.2016 um 13:08 schrieb Hans Verkuil: > The vb2_thread implementation was made generic and was moved from > videobuf2-v4l2.c to videobuf2-core.c in commit af3bac1a. Unfortunately > that clearly was never tested since it broke read() causing NULL address > references. > > The root cause was confused handling of vb2_buffer vs v4l2_buffer (the pb > pointer in various core functions). > > The v4l2_buffer no longer exists after moving the code into the core and > it is no longer needed. However, the vb2_thread code passed a pointer to > a vb2_buffer to the core functions were a v4l2_buffer pointer was expected > and vb2_thread expected that the vb2_buffer fields would be filled in > correctly. > > This is obviously wrong since v4l2_buffer != vb2_buffer. Note that the > pb pointer is a void pointer, so no type-checking took place. > > This patch fixes this problem: > > 1) allow pb to be NULL for vb2_core_(d)qbuf. The vb2_thread code will use > a NULL pointer here since they don't care about v4l2_buffer anyway. > 2) let vb2_core_dqbuf pass back the index of the received buffer. This is > all vb2_thread needs: this index is the index into the q->bufs array > and vb2_thread just gets the vb2_buffer from there. > 3) the fileio->b pointer (that originally contained a v4l2_buffer) is > removed altogether since it is no longer needed. > > Tested with vivid and the cobalt driver. > > Signed-off-by: Hans Verkuil > Tested-by: Hans Verkuil > Reported-by: Matthias Schwarzott Hi Hans! Thank you for this patch. I gave this patch a try on the latest sources from git://linuxtv.org/media_tree.git Compiled for kernel 4.2.8 with media_build. Now it no longer oopses. It tunes fine (according to femon), but I still do not get a picture/dvbtraffic reports nothing. Regards Matthias