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[3.8.y.z,extended,stable] Patch "[media] media: dmxdev: remove dvb_ringbuffer_flush() on writer side" has been added to staging queue

Message ID 1374015234-26848-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa July 16, 2013, 10:53 p.m. UTC
This is a note to let you know that I have just added a patch titled

    [media] media: dmxdev: remove dvb_ringbuffer_flush() on writer side

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.5.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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From 5d14cf8bea8b702004c650d1c836e0c546f3177e Mon Sep 17 00:00:00 2001
From: Soeren Moch <smoch@web.de>
Date: Wed, 5 Jun 2013 21:26:23 -0300
Subject: [media] media: dmxdev: remove dvb_ringbuffer_flush() on writer side

commit 414abbd2cd4c2618895f02ed3a76ec6647281436 upstream.

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 <smoch@web.de>
Reviewed-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/media/dvb-core/dmxdev.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

--
1.8.1.2
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Patch

diff --git a/drivers/media/dvb-core/dmxdev.c b/drivers/media/dvb-core/dmxdev.c
index d81dbb2..f847c9e 100644
--- a/drivers/media/dvb-core/dmxdev.c
+++ b/drivers/media/dvb-core/dmxdev.c
@@ -377,10 +377,8 @@  static int dvb_dmxdev_section_callback(const u8 *buffer1, size_t buffer1_len,
 		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 u8 *buffer1, size_t buffer1_len,
 	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;