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>
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