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
index c911c6b9564daa8f7b4e66f0c045d3acbc6d16db..f6fa432d2dfde74f9930e0d2a450e6322fa2b0d3 100644 (file)
@@ -507,7 +507,6 @@ pg_atomic_compare_exchange_u64(volatile pg_atomic_uint64 *ptr,
{
#ifndef PG_HAVE_ATOMIC_U64_SIMULATION
AssertPointerAlignment(ptr, 8);
- AssertPointerAlignment(expected, 8);
#endif
return pg_atomic_compare_exchange_u64_impl(ptr, expected, newval);
}
@@ -576,7 +575,7 @@ pg_atomic_sub_fetch_u64(volatile pg_atomic_uint64 *ptr, int64 sub_)
* Full barrier semantics (even when value is unchanged).
*/
static inline uint64
-pg_atomic_monotonic_advance_u64(volatile pg_atomic_uint64 *ptr, uint64 target_)
+pg_atomic_monotonic_advance_u64(volatile pg_atomic_uint64 *ptr, uint64 target)
{
uint64 currval;
@@ -585,23 +584,19 @@ pg_atomic_monotonic_advance_u64(volatile pg_atomic_uint64 *ptr, uint64 target_)
#endif
currval = pg_atomic_read_u64_impl(ptr);
- if (currval >= target_)
+ if (currval >= target)
{
pg_memory_barrier();
return currval;
}
-#ifndef PG_HAVE_ATOMIC_U64_SIMULATION
- AssertPointerAlignment(&currval, 8);
-#endif
-
- while (currval < target_)
+ while (currval < target)
{
- if (pg_atomic_compare_exchange_u64_impl(ptr, &currval, target_))
- break;
+ if (pg_atomic_compare_exchange_u64(ptr, &currval, target))
+ return target;
}
- return Max(target_, currval);
+ return currval;
}
#undef INSIDE_ATOMICS_H
index 94ba2597fb7f1dd2faaa3e96fd77021ff2261d39..edaab7c8957fc626cd8fb9103187fd5244816191 100644 (file)
@@ -173,6 +173,8 @@ pg_atomic_compare_exchange_u64_impl(volatile pg_atomic_uint64 *ptr,
uint32 condition_register;
bool ret;
+ AssertPointerAlignment(expected, 8);
+
/* Like u32, but s/lwarx/ldarx/; s/stwcx/stdcx/; s/cmpw/cmpd/ */
#ifdef HAVE_I_CONSTRAINT__BUILTIN_CONSTANT_P
if (__builtin_constant_p(*expected) &&
index 3efa79dc3df3a67569843dfd1798556a4be3d93e..2a8eca30fcf9d0e58a0b225336d0efa5f1890450 100644 (file)
@@ -207,6 +207,8 @@ pg_atomic_compare_exchange_u64_impl(volatile pg_atomic_uint64 *ptr,
{
char ret;
+ AssertPointerAlignment(expected, 8);
+
/*
* Perform cmpxchg and use the zero flag which it implicitly sets when
* equal to measure the success.
index 9d91370fa8cde316840248d1aefd5844d86acacb..872d2f02af4a2c37ac901f3b95e2fca4292ed597 100644 (file)
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;
index e060c0868a963ec2c8c0db97ff63949b33f909fc..840a45e7788c7484a91e7304f7b5dbdd0ce0fd7f 100644 (file)
@@ -102,6 +102,7 @@ pg_atomic_compare_exchange_u64_impl(volatile pg_atomic_uint64 *ptr,
bool ret;
uint64 current;
+ AssertPointerAlignment(expected, 8);
current = atomic_cas_64(&ptr->value, *expected, newval);
ret = current == *expected;
*expected = current;