Re: [PATCH] input: tsc2005: fix locking issue

On Tue, Mar 22, 2011 at 04:59:02PM +0200, Aaro Koskinen wrote:

Hi,

On Mon, 21 Mar 2011, Dmitry Torokhov wrote:

quoted

On Mon, Mar 21, 2011 at 06:24:10PM +0200, Aaro Koskinen wrote:

quoted

Commit 0b950d3 (Input: tsc2005 - add open/close) introduced a
locking issue with the ESD watchdog: __tsc2005_disable() is calling
cancel_delayed_work_sync() with mutex held, and the work also needs the
same mutex.

Fix the problem by using cancel_delayed_work() on disable. If
the ESD work was running it will check if the device is closed
or suspended, and in that case it will do nothing and skip
re-arming. cancel_delayed_work_sync() is still needed when the module
is removed.

Hmm, indeed. However, instead of moving cancel_delayed_work_sync() to
remove maybe we should use mutex_trylock() in tsc2005_esd_work()?
If trylock fails that means that device is in the middle of open/close
transition. We should just reschedule the work and get out of there.

But I guess the reschedule should not happen if we are in the middle of
close/disable? And without the mutex we cannot know that.

It should be OK to reschedule even as we enabling/disabling because
cancel_delayed_work_sync() handles re-arming works so even if ESD work
is being executed at the time we closing the device it will be killed
off completely.

Thanks.

-- 
Dmitry