compiler.h: Avoid nested statement expression in data_race()

It appears that compilers have trouble with nested statement
expressions. Therefore, remove one level of statement expression nesting
from the data_race() macro. This will help avoiding potential problems
in the future as its usage increases.

Reported-by: Borislav Petkov <[email protected]>
Reported-by: Nathan Chancellor <[email protected]>
Signed-off-by: Marco Elver <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Will Deacon <[email protected]>
Tested-by: Nick Desaulniers <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]

Author: melver

include/linux/compiler.h

@@ -264,12 +264,12 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
  */
 #define data_race(expr)							\
 ({									\
-	__kcsan_disable_current();					\
-	({								\
-		__unqual_scalar_typeof(({ expr; })) __v = ({ expr; });	\
-		__kcsan_enable_current();				\
-		__v;							\
+	__unqual_scalar_typeof(({ expr; })) __v = ({			\
+		__kcsan_disable_current();				\
+		expr;							\
 	});								\
+	__kcsan_enable_current();					\
+	__v;								\
 })
 
 /*