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media: dmxdev: remove dvb_ringbuffer_flush() on writer side

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commit 414abbd2cd 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>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Jianguo Wu <wujianguo@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Soeren Moch 2013-06-05 21:26:23 -03:00 committed by Greg Kroah-Hartman
parent 915b4b0510
commit 9ef2f22482
1 changed files with 2 additions and 6 deletions
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8
drivers/media/dvb/dvb-core/dmxdev.c
View file

@ -379,10 +379,8 @@ 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);
@ -418,10 +416,8 @@ 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;