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Use release memory ordering when incrementing reference counter

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As the relaxed memory ordering doesn't ensure any memory
synchronization, it is possible that the increment will succeed even
in the case when it should not - there is a race between
atomic_fetch_sub(..., acq_rel) and atomic_fetch_add(..., relaxed).
Only the result is consistent, but the previous value for both calls
could be same when both calls are executed at the same time.
This commit is contained in:
Ondřej Surý
2024-09-09 16:03:53 +02:00
committed by Ondřej Surý
parent d7d1804f16
commit 88227ea665
1 changed files with 2 additions and 2 deletions
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4
lib/isc/include/isc/refcount.h
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@@ -70,7 +70,7 @@ typedef atomic_uint_fast32_t isc_refcount_t;
#define isc_refcount_increment0(target) \
({ \
uint_fast32_t __v; \
__v = atomic_fetch_add_relaxed(target, 1); \
__v = atomic_fetch_add_release(target, 1); \
INSIST(__v < UINT32_MAX); \
__v; \
})
@@ -83,7 +83,7 @@ typedef atomic_uint_fast32_t isc_refcount_t;
#define isc_refcount_increment(target) \
({ \
uint_fast32_t __v; \
__v = atomic_fetch_add_relaxed(target, 1); \
__v = atomic_fetch_add_release(target, 1); \
INSIST(__v > 0 && __v < UINT32_MAX); \
__v; \
})