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Commit dde8437d authored by Vincent Guittot's avatar Vincent Guittot Committed by Rafael J. Wysocki
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PM / OPP: RCU reclaim 



synchronize_rcu() blocks the caller of opp_enable/disbale
for a complete grace period. This blocking duration prevents
any intensive use of the functions. Replace synchronize_rcu()
by call_rcu() which will call our function for freeing the old
opp element.

The duration of opp_enable() and opp_disable() will be no more
dependant of the grace period.

Signed-off-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 77b67063

drivers/base/power/opp.c

+14 −5
Original line number Diff line number Diff line
@@ -65,6 +65,7 @@ struct opp { 
	unsigned long u_volt;



	struct device_opp *dev_opp;

	struct rcu_head head;

};



/**
@@ -441,6 +442,17 @@ int opp_add(struct device *dev, unsigned long freq, unsigned long u_volt) 
	return 0;

}



/**

 * opp_free_rcu() - helper to clear the struct opp when grace period has

 * elapsed without blocking the the caller of opp_set_availability

 */

static void opp_free_rcu(struct rcu_head *head)

{

	struct opp *opp = container_of(head, struct opp, head);



	kfree(opp);

}



/**

 * opp_set_availability() - helper to set the availability of an opp

 * @dev:		device for which we do this operation
@@ -512,7 +524,7 @@ static int opp_set_availability(struct device *dev, unsigned long freq, 


	list_replace_rcu(&opp->node, &new_opp->node);

	mutex_unlock(&dev_opp_list_lock);

	synchronize_rcu();

	call_rcu(&opp->head, opp_free_rcu);



	/* Notify the change of the OPP availability */

	if (availability_req)
@@ -522,13 +534,10 @@ static int opp_set_availability(struct device *dev, unsigned long freq, 
		srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_DISABLE,

					 new_opp);



	/* clean up old opp */

	new_opp = opp;

	goto out;

	return 0;



unlock:

	mutex_unlock(&dev_opp_list_lock);

out:

	kfree(new_opp);

	return r;

}