Commit ab4e4d9f authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

locking/mutex: Use try_cmpxchg() 



For simpler and better code.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarWaiman Long <longman@redhat.com>
Reviewed-by: default avatarYanfei Xu <yanfei.xu@windriver.com>
Link: https://lore.kernel.org/r/20210630154114.834438545@infradead.org
parent 0e8a89d4

kernel/locking/mutex.c

+6 −21
Original line number Diff line number Diff line
@@ -100,7 +100,7 @@ static inline struct task_struct *__mutex_trylock_or_owner(struct mutex *lock) 


	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) {
@@ -124,11 +124,8 @@ static inline struct task_struct *__mutex_trylock_or_owner(struct mutex *lock) 
		 */

		flags &= ~MUTEX_FLAG_HANDOFF;



		old = atomic_long_cmpxchg_acquire(&lock->owner, owner, curr | flags);

		if (old == owner)

		if (atomic_long_try_cmpxchg_acquire(&lock->owner, &owner, curr | flags))

			return NULL;



		owner = old;

	}



	return __owner_task(owner);
@@ -168,10 +165,7 @@ 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
@@ -216,7 +210,7 @@ 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);
@@ -228,11 +222,8 @@ static void __mutex_handoff(struct mutex *lock, struct task_struct *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;

	}

}
@@ -1229,8 +1220,6 @@ 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);
@@ -1239,16 +1228,12 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne 
		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);