X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=wrapper%2Fcompiler.h;h=b9f8c51861e7c20da983777eafde536a3f185312;hb=57ccbfa6a8a79c7b84394c2097efaf7935607aa5;hp=1496f33e3807821fd19ac72e76e7bf35aacacd1f;hpb=52563d02a9234215b62c5f519aa1b5d8589ccd0a;p=lttng-modules.git

diff --git a/wrapper/compiler.h b/wrapper/compiler.h
index 1496f33e..b9f8c518 100644
--- a/wrapper/compiler.h
+++ b/wrapper/compiler.h
@@ -9,6 +9,7 @@
 #define _LTTNG_WRAPPER_COMPILER_H
 
 #include <linux/compiler.h>
+#include <linux/version.h>
 
 /*
  * Don't allow compiling with buggy compiler.
@@ -39,4 +40,21 @@
 # define WRITE_ONCE(x, val)	({ ACCESS_ONCE(x) = val; })
 #endif
 
+/*
+ * In v4.15 a smp read barrier was added to READ_ONCE to replace
+ * lockless_dereference(), replicate this behavior on prior kernels
+ * and remove calls to smp_read_barrier_depends which was dropped
+ * in v5.9.
+ */
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,15,0))
+#define LTTNG_READ_ONCE(x)	READ_ONCE(x)
+#else
+#define LTTNG_READ_ONCE(x)			\
+({						\
+	typeof(x) __val = READ_ONCE(x);		\
+	smp_read_barrier_depends();		\
+	__val;					\
+})
+#endif
+
 #endif /* _LTTNG_WRAPPER_COMPILER_H */