V4L/DVB (5818): CinergyT2: fix flush_workqueue() vs work->func() deadlock
authorOleg Nesterov <oleg@tv-sign.ru>
Mon, 2 Jul 2007 15:26:20 +0000 (12:26 -0300)
committerMauro Carvalho Chehab <mchehab@infradead.org>
Tue, 3 Jul 2007 18:11:19 +0000 (15:11 -0300)
commit1e4597e8f0049dccedb0e011934007309fa2aeab
tree74e8413d6bd1c5202fb3767ce18ae22fae235a25
parentf057131fb6eb2c45f6023e3da41ccd6e4e71aee9
V4L/DVB (5818): CinergyT2: fix flush_workqueue() vs work->func() deadlock

Spotted and tested by Thomas Sattler <tsattler@gmx.de>.

cinergyT2.c does cancel_delayed_work() + flush_scheduled_work() while
holding cinergyt2->sem. This leads to deadlock because work->func()
needs the same mutex to complete. Another bug is that this code in fact
can't reliably stop the re-arming delayed_work.

Convert this code to use cancel_rearming_delayed_work() and move it
out of ->sem. Another mutex, ->wq_sem, was added to protect against the
concurrent open/resume.

This patch is a horrible hack to fix the lockup which happens in practice.
As Dmitry Torokhov pointed out this driver has other problems and needs
further changes.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
drivers/media/dvb/cinergyT2/cinergyT2.c