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PM / OPP: RCU reclaim

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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: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Vincent Guittot 2012-10-23 01:21:49 +02:00 committed by Rafael J. Wysocki
parent 77b67063bb
commit dde8437d06
1 changed files with 14 additions and 5 deletions
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19
drivers/base/power/opp.c
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@ -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;
}