Fix: ACCESS_ONCE() removed in kernel 4.15

[lttng-modules.git] / wrapper / compiler.h

diff --git a/wrapper/compiler.h b/wrapper/compiler.h
index 0c016327da5dd27a7e5f06cbffe8379269aa5870..e4533d4955c9cb03f4ed702c44bd66b8953d4f5c 100644 (file)
--- a/wrapper/compiler.h
+++ b/wrapper/compiler.h
@@ -39,4 +39,17 @@
 # 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 */