From d7c5760a122d09dc532bc0976becc0d4caddc61e Mon Sep 17 00:00:00 2001 From: Bruno Haible Date: Wed, 1 Jul 2020 22:49:05 +0200 Subject: [PATCH] pthread-spin: Optimize fallback for GCC versions >= 4.7. * lib/pthread-spin.c (pthread_spin_init, pthread_spin_lock, pthread_spin_trylock, pthread_spin_unlock): Use a lock word instead of a lock byte. --- ChangeLog | 7 +++++++ lib/pthread-spin.c | 18 +++++++++--------- 2 files changed, 16 insertions(+), 9 deletions(-) diff --git a/ChangeLog b/ChangeLog index b1d391b4ab..06044eef96 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,10 @@ +2020-07-01 Bruno Haible + + pthread-spin: Optimize fallback for GCC versions >= 4.7. + * lib/pthread-spin.c (pthread_spin_init, pthread_spin_lock, + pthread_spin_trylock, pthread_spin_unlock): Use a lock word instead of a + lock byte. + 2020-07-01 Bruno Haible pthread-spin: Add error checking. diff --git a/lib/pthread-spin.c b/lib/pthread-spin.c index 73eb9f31f6..1f73f130be 100644 --- a/lib/pthread-spin.c +++ b/lib/pthread-spin.c @@ -69,8 +69,8 @@ pthread_spin_destroy (pthread_spinlock_t *lock) require to link with -latomic. */ # if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7) -/* Use GCC built-ins (available in GCC >= 4.7) that operate on the first byte - of the lock. +/* Use GCC built-ins (available in GCC >= 4.7) that operate on the first 32-bit + word of the lock. Documentation: */ @@ -81,7 +81,7 @@ int pthread_spin_init (pthread_spinlock_t *lock, int shared_across_processes _GL_UNUSED) { - __atomic_store_n ((char *) lock, 0, __ATOMIC_SEQ_CST); + __atomic_store_n ((unsigned int *) lock, 0, __ATOMIC_SEQ_CST); return 0; } @@ -89,9 +89,9 @@ int pthread_spin_lock (pthread_spinlock_t *lock) { /* Wait until *lock becomes 0, then replace it with 1. */ - asyncsafe_spinlock_t zero; + unsigned int zero; while (!(zero = 0, - __atomic_compare_exchange_n ((char *) lock, &zero, 1, false, + __atomic_compare_exchange_n ((unsigned int *) lock, &zero, 1, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))) ; return 0; @@ -100,9 +100,9 @@ pthread_spin_lock (pthread_spinlock_t *lock) int pthread_spin_trylock (pthread_spinlock_t *lock) { - asyncsafe_spinlock_t zero; + unsigned int zero; if (!(zero = 0, - __atomic_compare_exchange_n ((char *) lock, &zero, 1, false, + __atomic_compare_exchange_n ((unsigned int *) lock, &zero, 1, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))) return EBUSY; return 0; @@ -112,8 +112,8 @@ int pthread_spin_unlock (pthread_spinlock_t *lock) { /* If *lock is 1, then replace it with 0. */ - asyncsafe_spinlock_t one = 1; - if (!__atomic_compare_exchange_n ((char *) lock, &one, 0, false, + unsigned int one = 1; + if (!__atomic_compare_exchange_n ((unsigned int *) lock, &one, 0, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) abort (); return 0; -- 2.39.5