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Code Issues Releases Wiki Activity

locking/mutex: Use try_cmpxchg()

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For simpler and better code.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Waiman Long <longman@redhat.com>
Reviewed-by: Yanfei Xu <yanfei.xu@windriver.com>
Link: https://lore.kernel.org/r/20210630154114.834438545@infradead.org
This commit is contained in:
Peter Zijlstra 2021-06-30 17:35:17 +02:00
parent 0e8a89d49d
commit ab4e4d9f79
1 changed files with 6 additions and 21 deletions
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27
kernel/locking/mutex.c
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@ -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);