[PATCH] powerpc fix for gomp_mutex_unlock in libgomp

Janis Johnson janis187@us.ibm.com
Mon Dec 1 23:08:00 GMT 2008


When a write barrier was removed from the powerpc version of
sync_lock_test_and_set a couple of months ago some libgomp tests started
failing intermittently.  This patch copies Steve Ellcey's solution to
the same problem in IA64 by making a target-specific copy of
gomp_mutex_unlock that explicitly forces a write barrier.

Bootstrapped and regression tested on powerpc64-linux; OK for trunk?

2008-12-01  Janis Johnson  <janis187@us.ibm.com>

	PR libgomp/38270
	* config/linux/powerpc/mutex.h: New.

Index: libgomp/config/linux/powerpc/mutex.h
===================================================================
--- libgomp/config/linux/powerpc/mutex.h	(revision 0)
+++ libgomp/config/linux/powerpc/mutex.h	(revision 0)
@@ -0,0 +1,69 @@
+/* Copyright (C) 2005, 2008 Free Software Foundation, Inc.
+   Contributed by Richard Henderson <rth@redhat.com>.
+
+   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 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.
+
+   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 Lesser General Public License for
+   more details.
+
+   You should have received a copy of the GNU Lesser General Public License 
+   along with libgomp; see the file COPYING.LIB.  If not, write to the
+   Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+   MA 02110-1301, USA.  */
+
+/* As a special exception, if you link this library with other files, some
+   of which are compiled with GCC, to produce an executable, this library
+   does not by itself cause the resulting executable to be covered by the
+   GNU General Public License.  This exception does not however invalidate
+   any other reasons why the executable file might be covered by the GNU
+   General Public License.  */
+
+/* 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;
+
+#define GOMP_MUTEX_INIT_0 1
+
+static inline void gomp_mutex_init (gomp_mutex_t *mutex)
+{
+  *mutex = 0;
+}
+
+extern void gomp_mutex_lock_slow (gomp_mutex_t *mutex);
+static inline void gomp_mutex_lock (gomp_mutex_t *mutex)
+{
+  if (!__sync_bool_compare_and_swap (mutex, 0, 1))
+    gomp_mutex_lock_slow (mutex);
+}
+
+extern void gomp_mutex_unlock_slow (gomp_mutex_t *mutex);
+
+/* Like IA64, POWER needs a __sync_synchronize call before
+   __sync_lock_test_and_set because __sync_lock_test_and_set is
+   not a full memory fence.  */
+static inline void gomp_mutex_unlock (gomp_mutex_t *mutex)
+{
+  int val;
+  __sync_synchronize ();
+  val = __sync_lock_test_and_set (mutex, 0);
+  if (__builtin_expect (val > 1, 0))
+    gomp_mutex_unlock_slow (mutex);
+}
+
+static inline void gomp_mutex_destroy (gomp_mutex_t *mutex)
+{
+}
+
+#endif /* GOMP_MUTEX_H */




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