X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=wrapper%2Fcompiler.h;h=1496f33e3807821fd19ac72e76e7bf35aacacd1f;hb=80bb26003945e96a8ade9c8788dab9b2e08cbc08;hp=0c016327da5dd27a7e5f06cbffe8379269aa5870;hpb=cf262f57baebeb3db47b4a44d0ab153b4d2abb2d;p=lttng-modules.git

diff --git a/wrapper/compiler.h b/wrapper/compiler.h
index 0c016327..1496f33e 100644
--- a/wrapper/compiler.h
+++ b/wrapper/compiler.h
@@ -1,26 +1,13 @@
-#ifndef _LTTNG_WRAPPER_COMPILER_H
-#define _LTTNG_WRAPPER_COMPILER_H
-
-/*
+/* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
+ *
  * wrapper/compiler.h
  *
  * Copyright (C) 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * This 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; only
- * version 2.1 of the License.
- *
- * This 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 this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#ifndef _LTTNG_WRAPPER_COMPILER_H
+#define _LTTNG_WRAPPER_COMPILER_H
+
 #include <linux/compiler.h>
 
 /*
@@ -39,4 +26,17 @@
 # endif
 #endif
 
+/*
+ * READ/WRITE_ONCE were introduced in kernel 3.19 and ACCESS_ONCE
+ * was removed in 4.15. Prefer READ/WRITE but fallback to ACCESS
+ * when they are not available.
+ */
+#ifndef READ_ONCE
+# define READ_ONCE(x)		ACCESS_ONCE(x)
+#endif
+
+#ifndef WRITE_ONCE
+# define WRITE_ONCE(x, val)	({ ACCESS_ONCE(x) = val; })
+#endif
+
 #endif /* _LTTNG_WRAPPER_COMPILER_H */