[PATCH 2/4] locking/ww_mutex: Fix acquire/release imbalance in ww_acquire_init()/ww_acquire_fini()

From: Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
	Boqun Feng <boqun.feng@gmail.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Davidlohr Bueso <dave@stgolabs.net>
Cc: linux-kernel@vger.kernel.org, Juri Lelli <juri.lelli@redhat.com>,
	Waiman Long <longman@redhat.com>
Subject: [PATCH 2/4] locking/ww_mutex: Fix acquire/release imbalance in ww_acquire_init()/ww_acquire_fini()
Date: Tue, 16 Mar 2021 11:31:17 -0400	[thread overview]
Message-ID: <20210316153119.13802-3-longman@redhat.com> (raw)
In-Reply-To: <20210316153119.13802-1-longman@redhat.com>

In ww_acquire_init(), mutex_acquire() is gated by CONFIG_DEBUG_LOCK_ALLOC.
The dep_map in the ww_acquire_ctx structure is also gated by the
same config. However mutex_release() in ww_acquire_fini() is gated by
CONFIG_DEBUG_MUTEXES. It is possible to set CONFIG_DEBUG_MUTEXES without
setting CONFIG_DEBUG_LOCK_ALLOC though it is an unlikely configuration.
That may cause a compilation error as dep_map isn't defined in this
case. Fix this potential problem by enclosing mutex_release() inside
CONFIG_DEBUG_LOCK_ALLOC.

Signed-off-by: Waiman Long <longman@redhat.com>
---
 include/linux/ww_mutex.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h
index 850424e5d030..6ecf2a0220db 100644
--- a/include/linux/ww_mutex.h
+++ b/include/linux/ww_mutex.h
@@ -173,9 +173,10 @@ static inline void ww_acquire_done(struct ww_acquire_ctx *ctx)
  */
 static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx)
 {
-#ifdef CONFIG_DEBUG_MUTEXES
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
 	mutex_release(&ctx->dep_map, _THIS_IP_);
-
+#endif
+#ifdef CONFIG_DEBUG_MUTEXES
 	DEBUG_LOCKS_WARN_ON(ctx->acquired);
 	if (!IS_ENABLED(CONFIG_PROVE_LOCKING))
 		/*
-- 
2.18.1

