| /* Copyright (C) 2003-2015 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library; if not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #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> |
| |
| |
| /* Unlock RWLOCK. */ |
| 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); |
| |
| 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; |
| 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); |
| return 0; |
| } |
| |
| weak_alias (__pthread_rwlock_unlock, pthread_rwlock_unlock) |
| hidden_def (__pthread_rwlock_unlock) |