Commit 414abbd2 authored Jun 05, 2013 by Soeren Moch Committed by Mauro Carvalho Chehab Jun 19, 2013

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

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>
CC: <stable@vger.kernel.org>
Reviewed-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

parent 6914d70e

drivers/media/dvb-core/dmxdev.c

+2 −6

Original line number	Diff line number	Diff line
		@@ -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;