linux-kernel - [PATCH] rt_mutex: correctly initialize lockdep in rt_mutex_init_proxy

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Date:   Sat, 10 Jun 2017 02:48:04 +0000
From:   "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
To:     "peterz@...radead.org" <peterz@...radead.org>
Cc:     "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] rt_mutex: correctly initialize lockdep in
 rt_mutex_init_proxy_locked

lockdep can't deal with NULL name or key, and doesn't do anything
with the lock when that happens.

Make rt_mutex_init_proxy_locked pass a name and a key for the lock.

Fixes: f5694788ad8d ("rt_mutex: Add lockdep annotations")
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 kernel/locking/rtmutex.c        |  6 ++++--
 kernel/locking/rtmutex_common.h | 12 ++++++++++--
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 43123533e9b1..f540961cec30 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1679,10 +1679,12 @@ EXPORT_SYMBOL_GPL(__rt_mutex_init);
  * possible at this point because the pi_state which contains the rtmutex
  * is not yet visible to other tasks.
  */
-void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
+void __rt_mutex_init_proxy_locked(struct rt_mutex *lock,
+				const char *name,
+				struct lock_class_key *key,
 				struct task_struct *proxy_owner)
 {
-	__rt_mutex_init(lock, NULL, NULL);
+	__rt_mutex_init(lock, name, key);
 	debug_rt_mutex_proxy_lock(lock, proxy_owner);
 	rt_mutex_set_owner(lock, proxy_owner);
 }
diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h
index 72ad45a9a794..110dc1ed1e89 100644
--- a/kernel/locking/rtmutex_common.h
+++ b/kernel/locking/rtmutex_common.h
@@ -100,8 +100,16 @@ enum rtmutex_chainwalk {
  * PI-futex support (proxy locking functions, etc.):
  */
 extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
-extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
-				       struct task_struct *proxy_owner);
+extern void __rt_mutex_init_proxy_locked(struct rt_mutex *lock,
+					 const char *name,
+					 struct lock_class_key *key,
+					 struct task_struct *proxy_owner);
+#define rt_mutex_init_proxy_locked(lock, proxy_owner) \
+do { \
+	static struct lock_class_key __key; \
+	__rt_mutex_init_proxy_locked(lock, #lock, &__key, proxy_owner); \
+} while (0)
+
 extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
 				  struct task_struct *proxy_owner);
 extern void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter);
-- 
2.11.0