Messages in this thread Patch in this message | | | Date | Wed, 30 Jun 2021 17:35:17 +0200 | From | Peter Zijlstra <> | Subject | [RFC][PATCH 1/4] locking/mutex: Use try_cmpxchg() |
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For simpler and better code.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- kernel/locking/mutex.c | 27 ++++++--------------------- 1 file changed, 6 insertions(+), 21 deletions(-)
--- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -100,7 +100,7 @@ static inline struct task_struct *__mute 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 *__mute */ 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_unlo { 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 @@ -226,7 +220,7 @@ static void __mutex_handoff(struct mutex 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); @@ -238,11 +232,8 @@ static void __mutex_handoff(struct mutex 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; } } @@ -1237,8 +1228,6 @@ static noinline void __sched __mutex_unl */ 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); @@ -1247,16 +1236,12 @@ static noinline void __sched __mutex_unl 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);
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