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)
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tue, 13 Aug 2013 22:42:05 +0000 (00:42 +0200)
commit40fea92ffb5fa0ef26d10ae0fe5688bc8e61c791
treedc3d38be74a14dc868a6ee9d420451afd435f6f1
parentd4e4ab86bcba5a72779c43dc1459f71fea3d89c8
PM / QoS: Fix workqueue deadlock when using pm_qos_update_request_timeout()

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.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Reviewed-by: Tejun Heo <tj@kernel.org>
Cc: 3.9+ <stable@vger.kernel.org> # 3.9+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
kernel/power/qos.c