This is part of work in progress getting locking back into shape on
powerpc. (If we ever were in shape, which is doubtful.) Using the
ia64 version means we have a needless sync at the start of
gomp_mutex_lock (courtesy of __sync_val_compare_and_swap) and a
needless isync at the end of gomp_mutex_unlock (slightly odd use
of __sync_lock_test_and_set to release a lock). It would be nice to
get rid of the __sync_val_compare_and_swap in config/linux/mutex.c
too.
* config/linux/powerpc/mutex.h: Rewrite.
Index: libgomp/config/linux/powerpc/mutex.h
===================================================================
--- libgomp/config/linux/powerpc/mutex.h (revision 181425)
+++ libgomp/config/linux/powerpc/mutex.h (working copy)
@@ -1,2 +1,75 @@
-/* On PowerPC __sync_lock_test_and_set isn't a full barrier. */
-#include "config/linux/ia64/mutex.h"
+/* Copyright (C) 2011 Free Software Foundation, Inc.
+ Contributed by Alan Modra <[email protected]>
+
+ This file is part of the GNU OpenMP Library (libgomp).
+
+ Libgomp is free software; you can redistribute it and/or modify it
+ under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3, or (at your option)
+ any later version.
+
+ Libgomp 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 General Public License for
+ more details.
+
+ Under Section 7 of GPL version 3, you are granted additional
+ permissions described in the GCC Runtime Library Exception, version
+ 3.1, as published by the Free Software Foundation.
+
+ You should have received a copy of the GNU General Public License and
+ a copy of the GCC Runtime Library Exception along with this program;
+ see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+ <http://www.gnu.org/licenses/>. */
+
+/* This is a Linux specific implementation of a mutex synchronization
+ mechanism for libgomp. This type is private to the library. This
+ implementation uses atomic instructions and the futex syscall. */
+
+#ifndef GOMP_MUTEX_H
+#define GOMP_MUTEX_H 1
+
+typedef int gomp_mutex_t;
+extern void gomp_mutex_lock_slow (gomp_mutex_t *mutex, int);
+extern void gomp_mutex_unlock_slow (gomp_mutex_t *mutex);
+
+#define GOMP_MUTEX_INIT_0 1
+
+enum memmodel
+{
+ MEMMODEL_RELAXED = 0,
+ MEMMODEL_CONSUME = 1,
+ MEMMODEL_ACQUIRE = 2,
+ MEMMODEL_RELEASE = 3,
+ MEMMODEL_ACQ_REL = 4,
+ MEMMODEL_SEQ_CST = 5,
+ MEMMODEL_LAST = 6
+};
+
+static inline void gomp_mutex_init (gomp_mutex_t *mutex)
+{
+ *mutex = 0;
+}
+
+static inline void gomp_mutex_destroy (gomp_mutex_t *mutex)
+{
+}
+
+static inline void gomp_mutex_lock (gomp_mutex_t *mutex)
+{
+ int oldval = 0;
+
+ __atomic_compare_exchange_4 (mutex, &oldval, 1, false,
+ MEMMODEL_ACQUIRE, MEMMODEL_RELAXED);
+ if (__builtin_expect (oldval != 0, 0))
+ gomp_mutex_lock_slow (mutex, oldval);
+}
+
+static inline void gomp_mutex_unlock (gomp_mutex_t *mutex)
+{
+ int oldval = __atomic_exchange_4 (mutex, 0, MEMMODEL_RELEASE);
+
+ if (__builtin_expect (oldval > 1, 0))
+ gomp_mutex_unlock_slow (mutex);
+}
+#endif /* GOMP_MUTEX_H */
--
Alan Modra
Australia Development Lab, IBM
