PM / QoS: Fix workqueue deadlock when using pm_qos_update_request_timeout() (40fea92f) · Commits · 戴 / test

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 (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

+13 −7

Original line number	Diff line number	Diff line
		@@ -296,6 +296,17 @@ int pm_qos_request_active(struct pm_qos_request *req)
		}
		EXPORT_SYMBOL_GPL(pm_qos_request_active);

		static void __pm_qos_update_request(struct pm_qos_request *req,
		s32 new_value)
		{
		trace_pm_qos_update_request(req->pm_qos_class, new_value);

		if (new_value != req->node.prio)
		pm_qos_update_target(
		pm_qos_array[req->pm_qos_class]->constraints,
		&req->node, PM_QOS_UPDATE_REQ, new_value);
		}

		/**
		* pm_qos_work_fn - the timeout handler of pm_qos_update_request_timeout
		* @work: work struct for the delayed work (timeout)
		@@ -308,7 +319,7 @@ static void pm_qos_work_fn(struct work_struct *work)
		struct pm_qos_request,
		work);

		pm_qos_update_request(req, PM_QOS_DEFAULT_VALUE);
		__pm_qos_update_request(req, PM_QOS_DEFAULT_VALUE);
		}

		/**
		@@ -364,12 +375,7 @@ void pm_qos_update_request(struct pm_qos_request *req,
		}

		cancel_delayed_work_sync(&req->work);

		trace_pm_qos_update_request(req->pm_qos_class, new_value);
		if (new_value != req->node.prio)
		pm_qos_update_target(
		pm_qos_array[req->pm_qos_class]->constraints,
		&req->node, PM_QOS_UPDATE_REQ, new_value);
		__pm_qos_update_request(req, new_value);
		}
		EXPORT_SYMBOL_GPL(pm_qos_update_request);

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