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Subject[PATCH 05/18] asm/rwonce: Remove smp_read_barrier_depends() invocation
Date
Alpha overrides __READ_ONCE() directly, so there's no need to use
smp_read_barrier_depends() in the core code. This also means that
__READ_ONCE() can be relied upon to provide dependency ordering.

Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
---
include/asm-generic/rwonce.h | 19 ++++---------------
1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/include/asm-generic/rwonce.h b/include/asm-generic/rwonce.h
index f9dfa88fc04d..cc810f1f18ca 100644
--- a/include/asm-generic/rwonce.h
+++ b/include/asm-generic/rwonce.h
@@ -30,24 +30,16 @@

/*
* Use __READ_ONCE() instead of READ_ONCE() if you do not require any
- * atomicity or dependency ordering guarantees. Note that this may result
- * in tears!
+ * atomicity. 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) \
-({ \
- __unqual_scalar_typeof(x) __x = __READ_ONCE(x); \
- smp_read_barrier_depends(); \
- (typeof(x))__x; \
-})
-
#define READ_ONCE(x) \
({ \
compiletime_assert_rwonce_type(x); \
- __READ_ONCE_SCALAR(x); \
+ __READ_ONCE(x); \
})

#define __WRITE_ONCE(x, val) \
@@ -74,12 +66,9 @@ unsigned long __read_once_word_nocheck(const void *addr)
*/
#define READ_ONCE_NOCHECK(x) \
({ \
- unsigned long __x; \
- compiletime_assert(sizeof(x) == sizeof(__x), \
+ compiletime_assert(sizeof(x) == sizeof(unsigned long), \
"Unsupported access size for READ_ONCE_NOCHECK()."); \
- __x = __read_once_word_nocheck(&(x)); \
- smp_read_barrier_depends(); \
- (typeof(x))__x; \
+ (typeof(x))__read_once_word_nocheck(&(x)); \
})

static __no_kasan_or_inline
--
2.27.0.212.ge8ba1cc988-goog
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