/* 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)