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Remove bogus assertion in pg_atomic_monotonic_advance_u64

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This code wanted to ensure that the 'exchange' variable passed to
pg_atomic_compare_exchange_u64 has correct alignment, but apparently
platforms don't actually require anything that doesn't come naturally.

While messing with pg_atomic_monotonic_advance_u64: instead of using
Max() to determine the value to return, just use
pg_atomic_compare_exchange_u64()'s return value to decide; also, use
pg_atomic_compare_exchange_u64 instead of the _impl version; also remove
the unnecessary underscore at the end of variable name "target".

Backpatch to 17, where this code was introduced by commit bf3ff7bf83bc.

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/36796438-a718-cf9b-2071-b2c1b947c1b5@gmail.com
This commit is contained in:
Alvaro Herrera
2024-07-04 13:25:31 +02:00
parent ab0ae64320
commit 768f0c3e21
5 changed files with 14 additions and 11 deletions
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3
src/include/port/atomics/generic-gcc.h
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@@ -240,6 +240,7 @@ static inline bool
pg_atomic_compare_exchange_u64_impl(volatile pg_atomic_uint64 *ptr,
uint64 *expected, uint64 newval)
{
AssertPointerAlignment(expected, 8);
return __atomic_compare_exchange_n(&ptr->value, expected, newval, false,
__ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
}
@@ -253,6 +254,8 @@ pg_atomic_compare_exchange_u64_impl(volatile pg_atomic_uint64 *ptr,
{
bool ret;
uint64 current;
AssertPointerAlignment(expected, 8);
current = __sync_val_compare_and_swap(&ptr->value, *expected, newval);
ret = current == *expected;
*expected = current;