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locking/barriers: Use '__unqual_scalar_typeof' for load-acquire macros

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Passing volatile-qualified pointers to the asm-generic implementations of
the load-acquire macros results in a re-load from the stack due to the
temporary result variable inheriting the volatile semantics thanks to the
use of 'typeof()'.

Define these temporary variables using 'unqual_scalar_typeof' to drop
the volatile qualifier in the case that they are scalar types.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Will Deacon 2019-12-19 16:22:56 +00:00
parent dee081bf8f
commit 549887271a
1 changed files with 8 additions and 8 deletions
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16
include/asm-generic/barrier.h
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@ -128,10 +128,10 @@ do { \
#ifndef __smp_load_acquire
#define __smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
__unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
__smp_mb(); \
___p1; \
(typeof(*p))___p1; \
})
#endif
@ -183,10 +183,10 @@ do { \
#ifndef smp_load_acquire
#define smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
__unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
barrier(); \
___p1; \
(typeof(*p))___p1; \
})
#endif
@ -229,14 +229,14 @@ do { \
#ifndef smp_cond_load_relaxed
#define smp_cond_load_relaxed(ptr, cond_expr) ({ \
typeof(ptr) __PTR = (ptr); \
typeof(*ptr) VAL; \
__unqual_scalar_typeof(*ptr) VAL; \
for (;;) { \
VAL = READ_ONCE(*__PTR); \
if (cond_expr) \
break; \
cpu_relax(); \
} \
VAL; \
(typeof(*ptr))VAL; \
})
#endif
@ -250,10 +250,10 @@ do { \
*/
#ifndef smp_cond_load_acquire
#define smp_cond_load_acquire(ptr, cond_expr) ({ \
typeof(*ptr) _val; \
__unqual_scalar_typeof(*ptr) _val; \
_val = smp_cond_load_relaxed(ptr, cond_expr); \
smp_acquire__after_ctrl_dep(); \
_val; \
(typeof(*ptr))_val; \
})
#endif