tree 8b15c43911b272535286e227d5263010a52e2438
parent 858559a29258a30d9f4839286b4aca6ab8c5c8d6
author Alexey Khoroshilov <khoroshilov@ispras.ru> 1384032523 -0300
committer Mauro Carvalho Chehab <m.chehab@samsung.com> 1385734705 -0200

[media] dvb_demux: fix deadlock in dmx_section_feed_release_filter()

dmx_section_feed_release_filter() locks dvbdmx->mutex and
if the feed is still filtering, it calls feed->stop_filtering(feed).
stop_filtering() is implemented by dmx_section_feed_stop_filtering()
that first of all try to lock the same mutex: dvbdmx->mutex.
That leads to a deadlock.
It does not happen often in practice because all callers of
release_filter() stop filtering by themselves.
So the problem can happen in case of race condition only.
The patch releases dvbdmx->mutex before call to feed->stop_filtering(feed)
and reacquires the mutex after that.
Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>