[ 74/79] media: dmxdev: remove dvb_ringbuffer_flush() on writer side

From: Greg Kroah-Hartman
Date: Fri Jul 26 2013 - 17:28:56 EST

3.10-stable review patch. If anyone has any objections, please let me know.


From: Soeren Moch <smoch@xxxxxx>

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
This patch should also be applied to stable kernels.

Signed-off-by: Soeren Moch <smoch@xxxxxx>
Reviewed-by: Sakari Ailus <sakari.ailus@xxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/media/dvb-core/dmxdev.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

--- a/drivers/media/dvb-core/dmxdev.c
+++ b/drivers/media/dvb-core/dmxdev.c
@@ -377,10 +377,8 @@ static int dvb_dmxdev_section_callback(c
ret = dvb_dmxdev_buffer_write(&dmxdevfilter->buffer, buffer2,
- 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;
@@ -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;
- }
return 0;

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