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Strengthen memory order for atomic<T>::wait/notify 

This matches the memory order in libc++.

libstdc++-v3/ChangeLog:
	* include/bits/atomic_wait.h: Change memory order from
	Acquire/Release with relaxed loads to SeqCst+Release for
	accesses to the waiter's count.
This commit is contained in:
Thomas Rodgers 2022-01-31 13:39:44 -08:00
parent 3ad29854f0
commit 07a971b28c
1 changed files with 6 additions and 6 deletions
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12
libstdc++-v3/include/bits/atomic_wait.h
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@ -209,18 +209,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
void
_M_enter_wait() noexcept
{ __atomic_fetch_add(&_M_wait, 1, __ATOMIC_ACQ_REL); }
{ __atomic_fetch_add(&_M_wait, 1, __ATOMIC_SEQ_CST); }
void
_M_leave_wait() noexcept
{ __atomic_fetch_sub(&_M_wait, 1, __ATOMIC_ACQ_REL); }
{ __atomic_fetch_sub(&_M_wait, 1, __ATOMIC_RELEASE); }
bool
_M_waiting() const noexcept
{
__platform_wait_t __res;
__atomic_load(&_M_wait, &__res, __ATOMIC_ACQUIRE);
return __res > 0;
__atomic_load(&_M_wait, &__res, __ATOMIC_SEQ_CST);
return __res != 0;
}
void
@ -258,7 +258,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__platform_wait(__addr, __old);
#else
__platform_wait_t __val;
__atomic_load(__addr, &__val, __ATOMIC_RELAXED);
__atomic_load(__addr, &__val, __ATOMIC_SEQ_CST);
if (__val == __old)
{
lock_guard<mutex> __l(_M_mtx);
@ -309,7 +309,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
if (_M_laundered())
{
__atomic_fetch_add(_M_addr, 1, __ATOMIC_ACQ_REL);
__atomic_fetch_add(_M_addr, 1, __ATOMIC_SEQ_CST);
__all = true;
}
_M_w._M_notify(_M_addr, __all, __bare);