linux-kernel - [PATCH v2] drivers: soc: ti: knav_qmss_queue: Pass lockdep expression to RCU lists

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Date:   Fri, 17 Jan 2020 19:00:49 +0530
From:   Amol Grover <frextrite@...il.com>
To:     Santosh Shilimkar <ssantosh@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Joel Fernandes <joel@...lfernandes.org>,
        Madhuparna Bhowmik <madhuparnabhowmik04@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Amol Grover <frextrite@...il.com>
Subject: [PATCH v2] drivers: soc: ti: knav_qmss_queue: Pass lockdep expression to RCU lists

inst->handles is traversed using list_for_each_entry_rcu
outside an RCU read-side critical section but under the protection
of knav_dev_lock.

Hence, add corresponding lockdep expression to silence false-positive
lockdep warnings, and harden RCU lists.

Add macro for the corresponding lockdep expression.

Signed-off-by: Amol Grover <frextrite@...il.com>
---
v2:
- Remove rcu_read_lock_held() from lockdep expression since it is
  implicitly checked for.

 drivers/soc/ti/knav_qmss_queue.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/soc/ti/knav_qmss_queue.c b/drivers/soc/ti/knav_qmss_queue.c
index 1ccc9064e1eb..37f3db6c041c 100644
--- a/drivers/soc/ti/knav_qmss_queue.c
+++ b/drivers/soc/ti/knav_qmss_queue.c
@@ -25,6 +25,8 @@
 
 static struct knav_device *kdev;
 static DEFINE_MUTEX(knav_dev_lock);
+#define knav_dev_lock_held() \
+	lockdep_is_held(&knav_dev_lock)
 
 /* Queue manager register indices in DTS */
 #define KNAV_QUEUE_PEEK_REG_INDEX	0
@@ -52,8 +54,9 @@ static DEFINE_MUTEX(knav_dev_lock);
 #define knav_queue_idx_to_inst(kdev, idx)			\
 	(kdev->instances + (idx << kdev->inst_shift))
 
-#define for_each_handle_rcu(qh, inst)			\
-	list_for_each_entry_rcu(qh, &inst->handles, list)
+#define for_each_handle_rcu(qh, inst)				\
+	list_for_each_entry_rcu(qh, &inst->handles, list,	\
+				knav_dev_lock_held())
 
 #define for_each_instance(idx, inst, kdev)		\
 	for (idx = 0, inst = kdev->instances;		\
-- 
2.24.1