From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mout.web.de ([212.227.15.3]:62266 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750735Ab3DNJDu (ORCPT ); Sun, 14 Apr 2013 05:03:50 -0400 Message-ID: <516A70EE.5010303@web.de> Date: Sun, 14 Apr 2013 11:03:42 +0200 From: Soeren Moch MIME-Version: 1.0 To: mchehab@redhat.com CC: linux-media@vger.kernel.org Subject: [PATCH] media: dmxdev: remove dvb_ringbuffer_flush() on writer side References: <5150F926.8070505@web.de> In-Reply-To: <5150F926.8070505@web.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: In dvb_ringbuffer lock-less synchronizationof reader and writer threads is done with separateread and write pointers. Sincedvb_ringbuffer_flush() modifies the read pointer, this function must not be called from the writer thread. This patch removes the dvb_ringbuffer_flush() calls in the dmxdev ringbuffer write functions, this fixes Oopses "Unable to handle kernel paging request" I could observe for the call chaindvb_demux_read ->dvb_dmxdev_buffer_read -> dvb_ringbuffer_read_user -> __copy_to_user (the reader side of the ringbuffer). The flush calls at the write side are not necessary anyway since ringbuffer_flush is also called in dvb_dmxdev_buffer_read() when an error condition is set in the ringbuffer. This patch should also be applied to stable kernels. Signed-off-by: Soeren Moch CC: --- a/drivers/media/dvb-core/dmxdev.c 2013-04-05 21:21:15.000000000 +0200 +++ b/drivers/media/dvb-core/dmxdev.c 2013-04-14 09:01:58.000000000 +0200 @@ -377,10 +377,8 @@ static int dvb_dmxdev_section_callback(c ret = dvb_dmxdev_buffer_write(&dmxdevfilter->buffer, buffer2, buffer2_len); } - if (ret < 0) { - dvb_ringbuffer_flush(&dmxdevfilter->buffer); + if (ret < 0) dmxdevfilter->buffer.error = ret; - } if (dmxdevfilter->params.sec.flags & DMX_ONESHOT) dmxdevfilter->state = DMXDEV_STATE_DONE; spin_unlock(&dmxdevfilter->dev->lock); @@ -416,10 +414,8 @@ static int dvb_dmxdev_ts_callback(const ret = dvb_dmxdev_buffer_write(buffer, buffer1, buffer1_len); if (ret == buffer1_len) ret = dvb_dmxdev_buffer_write(buffer, buffer2, buffer2_len); - if (ret < 0) { - dvb_ringbuffer_flush(buffer); + if (ret < 0) buffer->error = ret; - } spin_unlock(&dmxdevfilter->dev->lock); wake_up(&buffer->queue); return 0;