1 files changed, 53 insertions, 71 deletions

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index d2df5e68b503..21c9e5da1858 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -32,8 +32,10 @@
 
 #ifdef CONFIG_DEBUG_MUTEXES
 # include "mutex-debug.h"
+# define MUTEX_WARN_ON(cond) DEBUG_LOCKS_WARN_ON(cond)
 #else
 # include "mutex.h"
+# define MUTEX_WARN_ON(cond)
 #endif
 
 void
@@ -91,55 +93,56 @@ static inline unsigned long __owner_flags(unsigned long owner)
 	return owner & MUTEX_FLAGS;
 }
 
-/*
- * Trylock variant that returns the owning task on failure.
- */
-static inline struct task_struct *__mutex_trylock_or_owner(struct mutex *lock)
+static inline struct task_struct *__mutex_trylock_common(struct mutex *lock, bool handoff)
 {
 	unsigned long owner, curr = (unsigned long)current;
 
 	owner = atomic_long_read(&lock->owner);
 	for (;;) { /* must loop, can race against a flag */
-		unsigned long old, flags = __owner_flags(owner);
+		unsigned long flags = __owner_flags(owner);
 		unsigned long task = owner & ~MUTEX_FLAGS;
 
 		if (task) {
-			if (likely(task != curr))
-				break;
-
-			if (likely(!(flags & MUTEX_FLAG_PICKUP)))
+			if (flags & MUTEX_FLAG_PICKUP) {
+				if (task != curr)
+					break;
+				flags &= ~MUTEX_FLAG_PICKUP;
+			} else if (handoff) {
+				if (flags & MUTEX_FLAG_HANDOFF)
+					break;
+				flags |= MUTEX_FLAG_HANDOFF;
+			} else {
 				break;
-
-			flags &= ~MUTEX_FLAG_PICKUP;
+			}
 		} else {
-#ifdef CONFIG_DEBUG_MUTEXES
-			DEBUG_LOCKS_WARN_ON(flags & MUTEX_FLAG_PICKUP);
-#endif
+			MUTEX_WARN_ON(flags & (MUTEX_FLAG_HANDOFF | MUTEX_FLAG_PICKUP));
+			task = curr;
 		}
 
-		/*
-		 * We set the HANDOFF bit, we must make sure it doesn't live
-		 * past the point where we acquire it. This would be possible
-		 * if we (accidentally) set the bit on an unlocked mutex.
-		 */
-		flags &= ~MUTEX_FLAG_HANDOFF;
-
-		old = atomic_long_cmpxchg_acquire(&lock->owner, owner, curr | flags);
-		if (old == owner)
-			return NULL;
-
-		owner = old;
+		if (atomic_long_try_cmpxchg_acquire(&lock->owner, &owner, task | flags)) {
+			if (task == curr)
+				return NULL;
+			break;
+		}
 	}
 
 	return __owner_task(owner);
 }
 
 /*
+ * Trylock or set HANDOFF
+ */
+static inline bool __mutex_trylock_or_handoff(struct mutex *lock, bool handoff)
+{
+	return !__mutex_trylock_common(lock, handoff);
+}
+
+/*
  * Actual trylock that will work on any unlocked state.
  */
 static inline bool __mutex_trylock(struct mutex *lock)
 {
-	return !__mutex_trylock_or_owner(lock);
+	return !__mutex_trylock_common(lock, false);
 }
 
 #ifndef CONFIG_DEBUG_LOCK_ALLOC
@@ -168,10 +171,7 @@ static __always_inline bool __mutex_unlock_fast(struct mutex *lock)
 {
 	unsigned long curr = (unsigned long)current;
 
-	if (atomic_long_cmpxchg_release(&lock->owner, curr, 0UL) == curr)
-		return true;
-
-	return false;
+	return atomic_long_try_cmpxchg_release(&lock->owner, &curr, 0UL);
 }
 #endif
 
@@ -226,23 +226,18 @@ static void __mutex_handoff(struct mutex *lock, struct task_struct *task)
 	unsigned long owner = atomic_long_read(&lock->owner);
 
 	for (;;) {
-		unsigned long old, new;
+		unsigned long new;
 
-#ifdef CONFIG_DEBUG_MUTEXES
-		DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current);
-		DEBUG_LOCKS_WARN_ON(owner & MUTEX_FLAG_PICKUP);
-#endif
+		MUTEX_WARN_ON(__owner_task(owner) != current);
+		MUTEX_WARN_ON(owner & MUTEX_FLAG_PICKUP);
 
 		new = (owner & MUTEX_FLAG_WAITERS);
 		new |= (unsigned long)task;
 		if (task)
 			new |= MUTEX_FLAG_PICKUP;
 
-		old = atomic_long_cmpxchg_release(&lock->owner, owner, new);
-		if (old == owner)
+		if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, new))
 			break;
-
-		owner = old;
 	}
 }
 
@@ -498,6 +493,14 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
 
+/*
+ * Trylock variant that returns the owning task on failure.
+ */
+static inline struct task_struct *__mutex_trylock_or_owner(struct mutex *lock)
+{
+	return __mutex_trylock_common(lock, false);
+}
+
 static inline
 bool ww_mutex_spin_on_owner(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
 			    struct mutex_waiter *waiter)
@@ -759,9 +762,7 @@ void __sched ww_mutex_unlock(struct ww_mutex *lock)
 	 * into 'unlocked' state:
 	 */
 	if (lock->ctx) {
-#ifdef CONFIG_DEBUG_MUTEXES
-		DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired);
-#endif
+		MUTEX_WARN_ON(!lock->ctx->acquired);
 		if (lock->ctx->acquired > 0)
 			lock->ctx->acquired--;
 		lock->ctx = NULL;
@@ -928,7 +929,6 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 		    struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
 {
 	struct mutex_waiter waiter;
-	bool first = false;
 	struct ww_mutex *ww;
 	int ret;
 
@@ -937,9 +937,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 
 	might_sleep();
 
-#ifdef CONFIG_DEBUG_MUTEXES
-	DEBUG_LOCKS_WARN_ON(lock->magic != lock);
-#endif
+	MUTEX_WARN_ON(lock->magic != lock);
 
 	ww = container_of(lock, struct ww_mutex, base);
 	if (ww_ctx) {
@@ -1007,6 +1005,8 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 
 	set_current_state(state);
 	for (;;) {
+		bool first;
+
 		/*
 		 * Once we hold wait_lock, we're serialized against
 		 * mutex_unlock() handing the lock off to us, do a trylock
@@ -1035,15 +1035,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 		spin_unlock(&lock->wait_lock);
 		schedule_preempt_disabled();
 
-		/*
-		 * ww_mutex needs to always recheck its position since its waiter
-		 * list is not FIFO ordered.
-		 */
-		if (ww_ctx || !first) {
-			first = __mutex_waiter_is_first(lock, &waiter);
-			if (first)
-				__mutex_set_flag(lock, MUTEX_FLAG_HANDOFF);
-		}
+		first = __mutex_waiter_is_first(lock, &waiter);
 
 		set_current_state(state);
 		/*
@@ -1051,7 +1043,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 		 * state back to RUNNING and fall through the next schedule(),
 		 * or we must see its unlock and acquire.
 		 */
-		if (__mutex_trylock(lock) ||
+		if (__mutex_trylock_or_handoff(lock, first) ||
 		    (first && mutex_optimistic_spin(lock, ww_ctx, &waiter)))
 			break;
 
@@ -1237,26 +1229,18 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
 	 */
 	owner = atomic_long_read(&lock->owner);
 	for (;;) {
-		unsigned long old;
-
-#ifdef CONFIG_DEBUG_MUTEXES
-		DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current);
-		DEBUG_LOCKS_WARN_ON(owner & MUTEX_FLAG_PICKUP);
-#endif
+		MUTEX_WARN_ON(__owner_task(owner) != current);
+		MUTEX_WARN_ON(owner & MUTEX_FLAG_PICKUP);
 
 		if (owner & MUTEX_FLAG_HANDOFF)
 			break;
 
-		old = atomic_long_cmpxchg_release(&lock->owner, owner,
-						  __owner_flags(owner));
-		if (old == owner) {
+		if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, __owner_flags(owner))) {
 			if (owner & MUTEX_FLAG_WAITERS)
 				break;
 
 			return;
 		}
-
-		owner = old;
 	}
 
 	spin_lock(&lock->wait_lock);
@@ -1412,9 +1396,7 @@ int __sched mutex_trylock(struct mutex *lock)
 {
 	bool locked;
 
-#ifdef CONFIG_DEBUG_MUTEXES
-	DEBUG_LOCKS_WARN_ON(lock->magic != lock);
-#endif
+	MUTEX_WARN_ON(lock->magic != lock);
 
 	locked = __mutex_trylock(lock);
 	if (locked)