Fix: rcu: Fix data-race due to atomic_t copy-by-value (5.5.6, 5.4.22)

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

diff --git a/wrapper/compiler.h b/wrapper/compiler.h
index bd69fad3ce952e8da48c4a804bbb05d89056f4aa..e4533d4955c9cb03f4ed702c44bd66b8953d4f5c 100644 (file)
--- a/wrapper/compiler.h
+++ b/wrapper/compiler.h
@@ -27,13 +27,29 @@
  * Don't allow compiling with buggy compiler.
  */
 
+#ifdef GCC_VERSION
+
 /*
  * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58854
  */
-#ifdef __ARMEL__
-# if GCC_VERSION >= 40800 && GCC_VERSION <= 40802
-#  error Your gcc version produces clobbered frame accesses
+# ifdef __ARMEL__
+#  if GCC_VERSION >= 40800 && GCC_VERSION <= 40802
+#   error Your gcc version produces clobbered frame accesses
+#  endif
 # 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 */