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asm/rwonce: Remove smp_read_barrier_depends() invocation 

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: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Will Deacon 2019-10-30 16:51:07 +00:00
parent d646285885
commit 3c9184109e
1 changed files with 4 additions and 15 deletions
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19
include/asm-generic/rwonce.h
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@ -40,24 +40,16 @@
/* /*
* Use __READ_ONCE() instead of READ_ONCE() if you do not require any * Use __READ_ONCE() instead of READ_ONCE() if you do not require any
* atomicity or dependency ordering guarantees. Note that this may result * atomicity. Note that this may result in tears!
* in tears!
*/ */
#ifndef __READ_ONCE #ifndef __READ_ONCE
#define __READ_ONCE(x) (*(const volatile __unqual_scalar_typeof(x) *)&(x)) #define __READ_ONCE(x) (*(const volatile __unqual_scalar_typeof(x) *)&(x))
#endif #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) \ #define READ_ONCE(x) \
({ \ ({ \
compiletime_assert_rwonce_type(x); \ compiletime_assert_rwonce_type(x); \
__READ_ONCE_SCALAR(x); \ __READ_ONCE(x); \
}) })
#define __WRITE_ONCE(x, val) \ #define __WRITE_ONCE(x, val) \
@ -84,12 +76,9 @@ unsigned long __read_once_word_nocheck(const void *addr)
*/ */
#define READ_ONCE_NOCHECK(x) \ #define READ_ONCE_NOCHECK(x) \
({ \ ({ \
unsigned long __x; \ compiletime_assert(sizeof(x) == sizeof(unsigned long), \
compiletime_assert(sizeof(x) == sizeof(__x), \
"Unsupported access size for READ_ONCE_NOCHECK()."); \ "Unsupported access size for READ_ONCE_NOCHECK()."); \
__x = __read_once_word_nocheck(&(x)); \ (typeof(x))__read_once_word_nocheck(&(x)); \
smp_read_barrier_depends(); \
(typeof(x))__x; \
}) })
static __no_kasan_or_inline static __no_kasan_or_inline