The meat and potatoes of READ_ONCE() is defined by the __READ_ONCE()
macro, which uses a volatile casts in an attempt to avoid tearing of
byte, halfword, word and double-word accesses. Allow this to be
overridden by the architecture code in the case that things like memory
barriers are also required.
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
---
include/asm-generic/rwonce.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/include/asm-generic/rwonce.h b/include/asm-generic/rwonce.h
index 92cc2f223cb3..f9dfa88fc04d 100644
--- a/include/asm-generic/rwonce.h
+++ b/include/asm-generic/rwonce.h
@@ -33,7 +33,9 @@
* atomicity or dependency ordering guarantees. Note that this may result
* in tears!
*/
+#ifndef __READ_ONCE
#define __READ_ONCE(x) (*(const volatile __unqual_scalar_typeof(x) *)&(x))
+#endif
#define __READ_ONCE_SCALAR(x) \
({ \
--
2.27.0.212.ge8ba1cc988-goog
