linux-kernel - [PATCH] power: opp: Fix rcu_dereference

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Date:	Tue, 14 Jun 2011 18:33:20 +0530
From:	Santosh Shilimkar <santosh.shilimkar@...com>
To:	<linux-pm@...ts.linux-foundation.org>
CC:	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Nishanth Menon <nm@...com>,
	Kevin Hilman <khilman@...prootsystems.com>
Subject: [PATCH] power: opp: Fix rcu_dereference_check() without protection!

With RCU debug options enabled, below warning is observed.

===================================================
[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
drivers/base/power/opp.c:151 invoked rcu_dereference_check() without protection!

other info that might help us debug this:

rcu_scheduler_active = 1, debug_locks = 1
no locks held by swapper/1.
...

---------------------------------------------------

Fix the same by protecting it with rcu_read lock.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...com>
Cc: Rafael J. Wysocki <rjw@...k.pl>
Cc: Nishanth Menon <nm@...com>
Cc: Kevin Hilman <khilman@...prootsystems.com>
---
 drivers/base/power/opp.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
index 56a6899..cbed5e1 100644
--- a/drivers/base/power/opp.c
+++ b/drivers/base/power/opp.c
@@ -148,7 +148,9 @@ unsigned long opp_get_voltage(struct opp *opp)
 	struct opp *tmp_opp;
 	unsigned long v = 0;
 
+	rcu_read_lock();
 	tmp_opp = rcu_dereference(opp);
+	rcu_read_unlock();
 	if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available)
 		pr_err("%s: Invalid parameters\n", __func__);
 	else
-- 
1.6.0.4

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