libstdc++: Use acq_rel memory ordering [PR 99537]

As Lewis Baker wrote in the PR:

> The 'fetch_sub()' operation in _M_release_ownership() should be using
> memory_order::acq_rel instead of memory_order::release. The use of
> 'release' only is insufficient as it does not synchronise with any
> corresponding 'acquire' operation.

> With the current implementation, it's possible that a prior write to
> one of the _M_value or _M_head data-members by a thread releasing the
> second-to-last reference might not be visible to another thread that
> releases the last reference and frees the memory, resulting in
> potential write to freed memory.

This simply changes the memory order to acq_rel as suggested.

libstdc++-v3/ChangeLog:

	PR libstdc++/99537
	* include/std/stop_token (_Stop_state_t::_M_release_ownership):
	Use acq_rel memory ordering.

0 files changed, 0 insertions, 0 deletions