diff options
Diffstat (limited to 'nptl/pthread_mutex_trylock.c')
| -rw-r--r-- | nptl/pthread_mutex_trylock.c | 57 |
1 files changed, 53 insertions, 4 deletions
diff --git a/nptl/pthread_mutex_trylock.c b/nptl/pthread_mutex_trylock.c index ec7da61c73..d478eca21b 100644 --- a/nptl/pthread_mutex_trylock.c +++ b/nptl/pthread_mutex_trylock.c @@ -92,6 +92,9 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex) case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP: THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, &mutex->__data.__list.__next); + /* We need to set op_pending before starting the operation. Also + see comments at ENQUEUE_MUTEX. */ + __asm ("" ::: "memory"); oldval = mutex->__data.__lock; do @@ -117,7 +120,12 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex) /* But it is inconsistent unless marked otherwise. */ mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT; + /* We must not enqueue the mutex before we have acquired it. + Also see comments at ENQUEUE_MUTEX. */ + __asm ("" ::: "memory"); ENQUEUE_MUTEX (mutex); + /* We need to clear op_pending after we enqueue the mutex. */ + __asm ("" ::: "memory"); THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); /* Note that we deliberately exist here. If we fall @@ -133,6 +141,8 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex) int kind = PTHREAD_MUTEX_TYPE (mutex); if (kind == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP) { + /* We do not need to ensure ordering wrt another memory + access. Also see comments at ENQUEUE_MUTEX. */ THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); return EDEADLK; @@ -140,6 +150,8 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex) if (kind == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP) { + /* We do not need to ensure ordering wrt another memory + access. */ THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); @@ -158,6 +170,9 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex) id, 0); if (oldval != 0 && (oldval & FUTEX_OWNER_DIED) == 0) { + /* We haven't acquired the lock as it is already acquired by + another owner. We do not need to ensure ordering wrt another + memory access. */ THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); return EBUSY; @@ -171,13 +186,20 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex) if (oldval == id) lll_unlock (mutex->__data.__lock, PTHREAD_ROBUST_MUTEX_PSHARED (mutex)); + /* FIXME This violates the mutex destruction requirements. See + __pthread_mutex_unlock_full. */ THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); return ENOTRECOVERABLE; } } while ((oldval & FUTEX_OWNER_DIED) != 0); + /* We must not enqueue the mutex before we have acquired it. + Also see comments at ENQUEUE_MUTEX. */ + __asm ("" ::: "memory"); ENQUEUE_MUTEX (mutex); + /* We need to clear op_pending after we enqueue the mutex. */ + __asm ("" ::: "memory"); THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); mutex->__data.__owner = id; @@ -203,10 +225,15 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex) int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP; if (robust) - /* Note: robust PI futexes are signaled by setting bit 0. */ - THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, - (void *) (((uintptr_t) &mutex->__data.__list.__next) - | 1)); + { + /* Note: robust PI futexes are signaled by setting bit 0. */ + THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, + (void *) (((uintptr_t) &mutex->__data.__list.__next) + | 1)); + /* We need to set op_pending before starting the operation. Also + see comments at ENQUEUE_MUTEX. */ + __asm ("" ::: "memory"); + } oldval = mutex->__data.__lock; @@ -215,12 +242,16 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex) { if (kind == PTHREAD_MUTEX_ERRORCHECK_NP) { + /* We do not need to ensure ordering wrt another memory + access. */ THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); return EDEADLK; } if (kind == PTHREAD_MUTEX_RECURSIVE_NP) { + /* We do not need to ensure ordering wrt another memory + access. */ THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); /* Just bump the counter. */ @@ -242,6 +273,9 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex) { if ((oldval & FUTEX_OWNER_DIED) == 0) { + /* We haven't acquired the lock as it is already acquired by + another owner. We do not need to ensure ordering wrt another + memory access. */ THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); return EBUSY; @@ -262,6 +296,9 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex) if (INTERNAL_SYSCALL_ERROR_P (e, __err) && INTERNAL_SYSCALL_ERRNO (e, __err) == EWOULDBLOCK) { + /* The kernel has not yet finished the mutex owner death. + We do not need to ensure ordering wrt another memory + access. */ THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); return EBUSY; @@ -279,7 +316,12 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex) /* But it is inconsistent unless marked otherwise. */ mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT; + /* We must not enqueue the mutex before we have acquired it. + Also see comments at ENQUEUE_MUTEX. */ + __asm ("" ::: "memory"); ENQUEUE_MUTEX (mutex); + /* We need to clear op_pending after we enqueue the mutex. */ + __asm ("" ::: "memory"); THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); /* Note that we deliberately exit here. If we fall @@ -302,13 +344,20 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex) PTHREAD_ROBUST_MUTEX_PSHARED (mutex)), 0, 0); + /* To the kernel, this will be visible after the kernel has + acquired the mutex in the syscall. */ THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); return ENOTRECOVERABLE; } if (robust) { + /* We must not enqueue the mutex before we have acquired it. + Also see comments at ENQUEUE_MUTEX. */ + __asm ("" ::: "memory"); ENQUEUE_MUTEX_PI (mutex); + /* We need to clear op_pending after we enqueue the mutex. */ + __asm ("" ::: "memory"); THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); } |