From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mout.web.de ([212.227.17.12]:58436 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751500Ab3ELIQo (ORCPT ); Sun, 12 May 2013 04:16:44 -0400 Message-ID: <518F4FEB.70908@web.de> Date: Sun, 12 May 2013 10:16:43 +0200 From: Soeren Moch MIME-Version: 1.0 To: Sakari Ailus CC: mchehab@redhat.com, linux-media@vger.kernel.org Subject: Re: [PATCH] media: dmxdev: remove dvb_ringbuffer_flush() on writer side References: <5150F926.8070505@web.de> <516A70EE.5010303@web.de> <20130510193955.GI1075@valkosipuli.retiisi.org.uk> In-Reply-To: <20130510193955.GI1075@valkosipuli.retiisi.org.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 10.05.2013 21:39, Sakari Ailus wrote: > Hi Soeren, > > Thanks for the patch! > > On Sun, Apr 14, 2013 at 11:03:42AM +0200, Soeren Moch wrote: >> In dvb_ringbuffer lock-less synchronizationof reader and writer threads is done >> with separateread and write pointers. Since dvb_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 chain dvb_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: > While the change the patch does itself appears sound to me, I need to ask > you to resend the patch using git send-email (it won't apply as-is). I can > do that this time, too; let me know what works for you. Please convert this patch to git format, thank you! > > Reviewed-by: Sakari Ailus And thanks for your rewiew, too. Soeren > >> --- 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; >>