diff options
Diffstat (limited to 'nptl/pthread_rwlock_trywrlock.c')
| -rw-r--r-- | nptl/pthread_rwlock_trywrlock.c | 61 |
1 files changed, 0 insertions, 61 deletions
diff --git a/nptl/pthread_rwlock_trywrlock.c b/nptl/pthread_rwlock_trywrlock.c deleted file mode 100644 index 0d9ccaf79c..0000000000 --- a/nptl/pthread_rwlock_trywrlock.c +++ /dev/null @@ -1,61 +0,0 @@ -/* Copyright (C) 2002-2017 Free Software Foundation, Inc. - This file is part of the GNU C Library. - Contributed by Ulrich Drepper <drepper@redhat.com>, 2002. - - 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 "pthreadP.h" -#include <atomic.h> - -/* See pthread_rwlock_common.c for an overview. */ -int -__pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock) -{ - /* When in a trywrlock, we can acquire the write lock if it is in states - #1 (idle and read phase) and #5 (idle and write phase), and also in #6 - (readers waiting, write phase) if we prefer writers. - If we observe any other state, we are allowed to fail and do not need to - "synchronize memory" as specified by POSIX (hence relaxed MO is - sufficient for the first load and the CAS failure path). - We face a similar issue as in tryrdlock in that we need to both avoid - live-locks / starvation and must not fail spuriously (see there for - further comments) -- and thus must loop until we get a definitive - observation or state change. */ - unsigned int r = atomic_load_relaxed (&rwlock->__data.__readers); - bool prefer_writer = - (rwlock->__data.__flags != PTHREAD_RWLOCK_PREFER_READER_NP); - while (((r & PTHREAD_RWLOCK_WRLOCKED) == 0) - && (((r >> PTHREAD_RWLOCK_READER_SHIFT) == 0) - || (prefer_writer && ((r & PTHREAD_RWLOCK_WRPHASE) != 0)))) - { - /* Try to transition to states #7 or #8 (i.e., acquire the lock). */ - if (atomic_compare_exchange_weak_acquire ( - &rwlock->__data.__readers, &r, - r | PTHREAD_RWLOCK_WRPHASE | PTHREAD_RWLOCK_WRLOCKED)) - { - atomic_store_relaxed (&rwlock->__data.__writers_futex, 1); - atomic_store_relaxed (&rwlock->__data.__wrphase_futex, 1); - atomic_store_relaxed (&rwlock->__data.__cur_writer, - THREAD_GETMEM (THREAD_SELF, tid)); - return 0; - } - /* TODO Back-off. */ - /* See above. */ - } - return EBUSY; -} - -strong_alias (__pthread_rwlock_trywrlock, pthread_rwlock_trywrlock) |