1 files changed, 22 insertions, 25 deletions

diff --git a/kernel/mutex.c b/kernel/mutex.c
index ff05f4bd86e..6d647aedffe 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -209,11 +209,13 @@ int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
  */
 static inline int mutex_can_spin_on_owner(struct mutex *lock)
 {
+	struct task_struct *owner;
 	int retval = 1;
 
 	rcu_read_lock();
-	if (lock->owner)
-		retval = lock->owner->on_cpu;
+	owner = ACCESS_ONCE(lock->owner);
+	if (owner)
+		retval = owner->on_cpu;
 	rcu_read_unlock();
 	/*
 	 * if lock->owner is not set, the mutex owner may have just acquired
@@ -461,7 +463,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 			 * performed the optimistic spinning cannot be done.
 			 */
 			if (ACCESS_ONCE(ww->ctx))
-				break;
+				goto slowpath;
 		}
 
 		/*
@@ -472,7 +474,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 		owner = ACCESS_ONCE(lock->owner);
 		if (owner && !mutex_spin_on_owner(lock, owner)) {
 			mspin_unlock(MLOCK(lock), &node);
-			break;
+			goto slowpath;
 		}
 
 		if ((atomic_read(&lock->count) == 1) &&
@@ -499,7 +501,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 		 * the owner complete.
 		 */
 		if (!owner && (need_resched() || rt_task(task)))
-			break;
+			goto slowpath;
 
 		/*
 		 * The cpu_relax() call is a compiler barrier which forces
@@ -513,6 +515,10 @@ slowpath:
 #endif
 	spin_lock_mutex(&lock->wait_lock, flags);
 
+	/* once more, can we acquire the lock? */
+	if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, 0) == 1))
+		goto skip_wait;
+
 	debug_mutex_lock_common(lock, &waiter);
 	debug_mutex_add_waiter(lock, &waiter, task_thread_info(task));
 
@@ -520,9 +526,6 @@ slowpath:
 	list_add_tail(&waiter.list, &lock->wait_list);
 	waiter.task = task;
 
-	if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, -1) == 1))
-		goto done;
-
 	lock_contended(&lock->dep_map, ip);
 
 	for (;;) {
@@ -536,7 +539,7 @@ slowpath:
 		 * other waiters:
 		 */
 		if (MUTEX_SHOW_NO_WAITER(lock) &&
-		   (atomic_xchg(&lock->count, -1) == 1))
+		    (atomic_xchg(&lock->count, -1) == 1))
 			break;
 
 		/*
@@ -561,24 +564,25 @@ slowpath:
 		schedule_preempt_disabled();
 		spin_lock_mutex(&lock->wait_lock, flags);
 	}
+	mutex_remove_waiter(lock, &waiter, current_thread_info());
+	/* set it to 0 if there are no waiters left: */
+	if (likely(list_empty(&lock->wait_list)))
+		atomic_set(&lock->count, 0);
+	debug_mutex_free_waiter(&waiter);
 
-done:
+skip_wait:
+	/* got the lock - cleanup and rejoice! */
 	lock_acquired(&lock->dep_map, ip);
-	/* got the lock - rejoice! */
-	mutex_remove_waiter(lock, &waiter, current_thread_info());
 	mutex_set_owner(lock);
 
 	if (!__builtin_constant_p(ww_ctx == NULL)) {
-		struct ww_mutex *ww = container_of(lock,
-						      struct ww_mutex,
-						      base);
+		struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
 		struct mutex_waiter *cur;
 
 		/*
 		 * This branch gets optimized out for the common case,
 		 * and is only important for ww_mutex_lock.
 		 */
-
 		ww_mutex_lock_acquired(ww, ww_ctx);
 		ww->ctx = ww_ctx;
 
@@ -592,15 +596,8 @@ done:
 		}
 	}
 
-	/* set it to 0 if there are no waiters left: */
-	if (likely(list_empty(&lock->wait_list)))
-		atomic_set(&lock->count, 0);
-
 	spin_unlock_mutex(&lock->wait_lock, flags);
-
-	debug_mutex_free_waiter(&waiter);
 	preempt_enable();
-
 	return 0;
 
 err:
@@ -686,7 +683,7 @@ __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 	might_sleep();
 	ret =  __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
 				   0, &ctx->dep_map, _RET_IP_, ctx);
-	if (!ret && ctx->acquired > 0)
+	if (!ret && ctx->acquired > 1)
 		return ww_mutex_deadlock_injection(lock, ctx);
 
 	return ret;
@@ -702,7 +699,7 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 	ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
 				  0, &ctx->dep_map, _RET_IP_, ctx);
 
-	if (!ret && ctx->acquired > 0)
+	if (!ret && ctx->acquired > 1)
 		return ww_mutex_deadlock_injection(lock, ctx);
 
 	return ret;