From 76a0b73e8102c5bfb5cb791e34992472f5d1d33e Mon Sep 17 00:00:00 2001 From: Torvald Riegel Date: Tue, 14 Jun 2016 15:12:00 +0200 Subject: Remove atomic_compare_and_exchange_bool_rel. atomic_compare_and_exchange_bool_rel and catomic_compare_and_exchange_bool_rel are removed and replaced with the new C11-like atomic_compare_exchange_weak_release. The concurrent code in nscd/cache.c has not been reviewed yet, so this patch does not add detailed comments. * nscd/cache.c (cache_add): Use new C11-like atomic operation instead of atomic_compare_and_exchange_bool_rel. * nptl/pthread_mutex_unlock.c (__pthread_mutex_unlock_full): Likewise. * include/atomic.h (atomic_compare_and_exchange_bool_rel, catomic_compare_and_exchange_bool_rel): Remove. * sysdeps/aarch64/atomic-machine.h (atomic_compare_and_exchange_bool_rel): Likewise. * sysdeps/alpha/atomic-machine.h (atomic_compare_and_exchange_bool_rel): Likewise. * sysdeps/arm/atomic-machine.h (atomic_compare_and_exchange_bool_rel): Likewise. * sysdeps/mips/atomic-machine.h (atomic_compare_and_exchange_bool_rel): Likewise. * sysdeps/tile/atomic-machine.h (atomic_compare_and_exchange_bool_rel): Likewise. --- nptl/pthread_mutex_unlock.c | 34 ++++++++++++++++++++++------------ 1 file changed, 22 insertions(+), 12 deletions(-) (limited to 'nptl/pthread_mutex_unlock.c') diff --git a/nptl/pthread_mutex_unlock.c b/nptl/pthread_mutex_unlock.c index 334ce38342..82aaa95d7b 100644 --- a/nptl/pthread_mutex_unlock.c +++ b/nptl/pthread_mutex_unlock.c @@ -237,15 +237,24 @@ __pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr) int private = (robust ? PTHREAD_ROBUST_MUTEX_PSHARED (mutex) : PTHREAD_MUTEX_PSHARED (mutex)); - if ((mutex->__data.__lock & FUTEX_WAITERS) != 0 - || atomic_compare_and_exchange_bool_rel (&mutex->__data.__lock, 0, - THREAD_GETMEM (THREAD_SELF, - tid))) + /* Unlock the mutex using a CAS unless there are futex waiters or our + TID is not the value of __lock anymore, in which case we let the + kernel take care of the situation. Use release MO in the CAS to + synchronize with acquire MO in lock acquisitions. */ + int l = atomic_load_relaxed (&mutex->__data.__lock); + do { - INTERNAL_SYSCALL_DECL (__err); - INTERNAL_SYSCALL (futex, __err, 2, &mutex->__data.__lock, - __lll_private_flag (FUTEX_UNLOCK_PI, private)); + if (((l & FUTEX_WAITERS) != 0) + || (l != THREAD_GETMEM (THREAD_SELF, tid))) + { + INTERNAL_SYSCALL_DECL (__err); + INTERNAL_SYSCALL (futex, __err, 2, &mutex->__data.__lock, + __lll_private_flag (FUTEX_UNLOCK_PI, private)); + break; + } } + while (!atomic_compare_exchange_weak_release (&mutex->__data.__lock, + &l, 0)); THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); break; @@ -278,15 +287,16 @@ __pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr) /* One less user. */ --mutex->__data.__nusers; - /* Unlock. */ - int newval, oldval; + /* Unlock. Use release MO in the CAS to synchronize with acquire MO in + lock acquisitions. */ + int newval; + int oldval = atomic_load_relaxed (&mutex->__data.__lock); do { - oldval = mutex->__data.__lock; newval = oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK; } - while (atomic_compare_and_exchange_bool_rel (&mutex->__data.__lock, - newval, oldval)); + while (!atomic_compare_exchange_weak_release (&mutex->__data.__lock, + &oldval, newval)); if ((oldval & ~PTHREAD_MUTEX_PRIO_CEILING_MASK) > 1) lll_futex_wake (&mutex->__data.__lock, 1, -- cgit v1.2.3