diff options
Diffstat (limited to 'nptl/pthread_rwlock_unlock.c')
-rw-r--r-- | nptl/pthread_rwlock_unlock.c | 53 |
1 files changed, 11 insertions, 42 deletions
diff --git a/nptl/pthread_rwlock_unlock.c b/nptl/pthread_rwlock_unlock.c index 320837d5af..ef46e88263 100644 --- a/nptl/pthread_rwlock_unlock.c +++ b/nptl/pthread_rwlock_unlock.c @@ -18,60 +18,29 @@ #include <errno.h> #include <sysdep.h> -#include <lowlevellock.h> #include <futex-internal.h> #include <pthread.h> #include <pthreadP.h> #include <stap-probe.h> -#include <elide.h> +#include "pthread_rwlock_common.c" -/* Unlock RWLOCK. */ +/* See pthread_rwlock_common.c for an overview. */ int __pthread_rwlock_unlock (pthread_rwlock_t *rwlock) { - int futex_shared = - rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED; - LIBC_PROBE (rwlock_unlock, 1, rwlock); - /* Trying to elide an unlocked lock may crash the process. This - is expected and is compatible with POSIX.1-2008: "results are - undefined if the read-write lock rwlock is not held by the - calling thread". */ - if (ELIDE_UNLOCK (rwlock->__data.__writer == 0 - && rwlock->__data.__nr_readers == 0)) - return 0; - - lll_lock (rwlock->__data.__lock, rwlock->__data.__shared); - if (rwlock->__data.__writer) - rwlock->__data.__writer = 0; + /* We distinguish between having acquired a read vs. a write lock by looking + at the writer TID. If it's equal to our TID, we must be the writer + because nobody else can have stored this value. Also, if we are a + reader, we will read from the wrunlock store with value 0 by the most + recent writer because that writer happens-before us. */ + if (atomic_load_relaxed (&rwlock->__data.__cur_writer) + == THREAD_GETMEM (THREAD_SELF, tid)) + __pthread_rwlock_wrunlock (rwlock); else - --rwlock->__data.__nr_readers; - /* If there are still readers present, we do not yet need to wake writers - nor are responsible to wake any readers. */ - if (rwlock->__data.__nr_readers == 0) - { - /* Note that if there is a blocked writer, we effectively make it - responsible for waking any readers because we don't wake readers in - this case. */ - if (rwlock->__data.__nr_writers_queued) - { - ++rwlock->__data.__writer_wakeup; - lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); - futex_wake (&rwlock->__data.__writer_wakeup, 1, futex_shared); - return 0; - } - else if (rwlock->__data.__nr_readers_queued) - { - ++rwlock->__data.__readers_wakeup; - lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); - futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX, - futex_shared); - return 0; - } - } - lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); + __pthread_rwlock_rdunlock (rwlock); return 0; } |