[patch V4 part 1 06/36] compiler: Simple READ/WRITE_ONCE() implementations

Thomas Gleixner
2020-05-05T14:23:38Z

READ/WRITE_ONCE_NOCHECK() is required for atomics in code which cannot be
instrumented like the x86 int3 text poke code. As READ/WRITE_ONCE() is
undergoing a rewrite, provide __{READ,WRITE}_ONCE_SCALAR().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/compiler.h | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -313,6 +313,14 @@ unsigned long read_word_at_a_time(const
__u.__val; \
})

+#define __READ_ONCE_SCALAR(x) \
+ (*(const volatile typeof(x) *)&(x))
+
+#define __WRITE_ONCE_SCALAR(x, val) \
+do { \
+ *(volatile typeof(x) *)&(x) = val; \
+} while (0)
+
/**
* data_race - mark an expression as containing intentional data races
*