PM / QoS: Fix workqueue deadlock when using pm_qos_update_request_timeout()
authorStephen Boyd <sboyd@codeaurora.org>
Tue, 13 Aug 2013 21:12:40 +0000 (14:12 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 20 Aug 2013 15:43:05 +0000 (08:43 -0700)
commit1dba303727f52ea062580b0a9b3f0c3b462769cf
tree9c0de1f3110b263a10868020f3bbd9583e3014ab
parent237e0153190c92a4deb80782973f60557a6b2cdb
PM / QoS: Fix workqueue deadlock when using pm_qos_update_request_timeout()

commit 40fea92ffb5fa0ef26d10ae0fe5688bc8e61c791 upstream.

pm_qos_update_request_timeout() updates a qos and then schedules
a delayed work item to bring the qos back down to the default
after the timeout. When the work item runs, pm_qos_work_fn() will
call pm_qos_update_request() and deadlock because it tries to
cancel itself via cancel_delayed_work_sync(). Future callers of
that qos will also hang waiting to cancel the work that is
canceling itself. Let's extract the little bit of code that does
the real work of pm_qos_update_request() and call it from the
work function so that we don't deadlock.

Before ed1ac6e (PM: don't use [delayed_]work_pending()) this didn't
happen because the work function wouldn't try to cancel itself.

[backport to 3.10 - gregkh]

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Reviewed-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernel/power/qos.c