diff options
Diffstat (limited to 'nptl/pthread_rwlock_wrlock.c')
| -rw-r--r-- | nptl/pthread_rwlock_wrlock.c | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/nptl/pthread_rwlock_wrlock.c b/nptl/pthread_rwlock_wrlock.c new file mode 100644 index 0000000000..822aeed79c --- /dev/null +++ b/nptl/pthread_rwlock_wrlock.c @@ -0,0 +1,87 @@ +/* Copyright (C) 2003 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, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <errno.h> +#include <sysdep.h> +#include <lowlevellock.h> +#include <pthread.h> +#include <pthreadP.h> + + +/* Acquire write lock for RWLOCK. */ +int +__pthread_rwlock_wrlock (rwlock) + pthread_rwlock_t *rwlock; +{ + int result = 0; + + /* Make sure we are along. */ + lll_mutex_lock (rwlock->__data.__lock); + + while (1) + { + /* Get the rwlock if there is no writer and no reader. */ + if (rwlock->__data.__writer == 0 && rwlock->__data.__nr_readers == 0) + { + /* Mark self as writer. */ + rwlock->__data.__writer = THREAD_GETMEM (THREAD_SELF, tid); + break; + } + + /* Make sure we are not holding the rwlock as a writer. This is + a deadlock situation we recognize and report. */ + if (__builtin_expect (rwlock->__data.__writer + == THREAD_GETMEM (THREAD_SELF, tid), 0)) + { + result = EDEADLK; + break; + } + + /* Remember that we are a writer. */ + if (++rwlock->__data.__nr_writers_queued == 0) + { + /* Overflow on number of queued writers. */ + --rwlock->__data.__nr_writers_queued; + result = EAGAIN; + break; + } + + int waitval = rwlock->__data.__writer_wakeup; + + /* Free the lock. */ + lll_mutex_unlock (rwlock->__data.__lock); + + /* Wait for the writer or reader(s) to finish. */ + lll_futex_wait (&rwlock->__data.__writer_wakeup, waitval); + + /* Get the lock. */ + lll_mutex_lock (rwlock->__data.__lock); + + /* To start over again, remove the thread from the writer list. */ + --rwlock->__data.__nr_writers_queued; + } + + /* We are done, free the lock. */ + lll_mutex_unlock (rwlock->__data.__lock); + + return result; +} + +weak_alias (__pthread_rwlock_wrlock, pthread_rwlock_wrlock) +strong_alias (__pthread_rwlock_wrlock, __pthread_rwlock_wrlock_internal) |