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

From: Aaro Koskinen
Date: Tue Mar 22 2011 - 11:01:48 EST


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

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