PM / QoS: Create device constraints objects on notifier registration (23e0fc5a) · Commits · 戴 / test

The current behavior of dev_pm_qos_add_notifier() makes device PM QoS notifiers less than useful. Namely, it silently returns success when called before any PM QoS constraints are added for the device, so the caller will assume that the notifier has been registered, but when someone actually adds some nontrivial constraints for the device eventually, the previous callers of dev_pm_qos_add_notifier() will not know about that and their notifier routines will not be executed (contrary to their expectations). To address this problem make dev_pm_qos_add_notifier() create the constraints object for the device if it is not present when the routine is called. Signed-off-by:

Rafael J. Wysocki <rjw@sisk.pl> Acked-by : markgross <markgross@thegnar.org>

drivers/base/power/qos.c

+12 −7

Original line number	Diff line number	Diff line
		@@ -352,21 +352,26 @@ EXPORT_SYMBOL_GPL(dev_pm_qos_remove_request);
		*
		* Will register the notifier into a notification chain that gets called
		* upon changes to the target value for the device.
		*
		* If the device's constraints object doesn't exist when this routine is called,
		* it will be created (or error code will be returned if that fails).
		*/
		int dev_pm_qos_add_notifier(struct device dev, struct notifier_block notifier)
		{
		int retval = 0;
		int ret = 0;

		mutex_lock(&dev_pm_qos_mtx);

		/* Silently return if the constraints object is not present. */
		if (dev->power.constraints)
		retval = blocking_notifier_chain_register(
		dev->power.constraints->notifiers,
		notifier);
		if (!dev->power.constraints)
		ret = dev->power.power_state.event != PM_EVENT_INVALID ?
		dev_pm_qos_constraints_allocate(dev) : -ENODEV;

		if (!ret)
		ret = blocking_notifier_chain_register(
		dev->power.constraints->notifiers, notifier);

		mutex_unlock(&dev_pm_qos_mtx);
		return retval;
		return ret;
		}
		EXPORT_SYMBOL_GPL(dev_pm_qos_add_notifier);

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