linux-kernel - [PATCH 3/4] PM / devfreq: add locking documentation for recommended

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Date:	Fri, 18 Jan 2013 13:52:34 -0600
From:	Nishanth Menon <nm@...com>
To:	linux-pm <linux-pm@...r.kernel.org>
CC:	Rafael <rjw@...k.pl>, Kevin <khilman@...prootsystems.com>,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	lkml <linux-kernel@...r.kernel.org>,
	lo <linux-omap@...r.kernel.org>, Jack <jack@...ed.me.uk>,
	Alexander <holler@...oftware.de>, Nishanth Menon <nm@...com>
Subject: [PATCH 3/4] PM / devfreq: add locking documentation for recommended_opp

OPP pointers are protected by RCU locks, the pointer validity is
permissible only under the section of rcu_read_lock to rcu_read_unlock

Add documentation to the effect.

Signed-off-by: Nishanth Menon <nm@...com>
---
 drivers/devfreq/devfreq.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 53766f3..3b36797 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -994,6 +994,11 @@ module_exit(devfreq_exit);
  * @freq:	The frequency given to target function
  * @flags:	Flags handed from devfreq framework.
  *
+ * Locking: This function must be called under rcu_read_lock(). opp is a rcu
+ * protected pointer. The reason for the same is that the opp pointer which is
+ * returned will remain valid for use with opp_get_{voltage, freq} only while
+ * under the locked area. The pointer returned must be used prior to unlocking
+ * with rcu_read_unlock() to maintain the integrity of the pointer.
  */
 struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq,
 				    u32 flags)
-- 
1.7.9.5

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