[RESEND] power: opp: rcu reclaim

Message ID 1348580573-21877-1-git-send-email-vincent.guittot@linaro.org
State Accepted
Commit dde8437d06560366d8988c92b5774039ec703864
Headers show

Commit Message

Vincent Guittot Sept. 25, 2012, 1:42 p.m.
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>
---
 drivers/base/power/opp.c |   19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

Patch

diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
index ac993ea..49e4626 100644
--- a/drivers/base/power/opp.c
+++ b/drivers/base/power/opp.c
@@ -64,6 +64,7 @@  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)
 }
 
 /**
+ * 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
  * @freq:		OPP frequency to modify availability
@@ -511,7 +523,7 @@  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)
@@ -521,13 +533,10 @@  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;
 }