https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99537
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-10 branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:ad9ae82ed1c33e1803f33bb367b0b4c9ee2e3e63 commit r10-9594-gad9ae82ed1c33e1803f33bb367b0b4c9ee2e3e63 Author: Jonathan Wakely <jwak...@redhat.com> Date: Thu Mar 11 16:44:57 2021 +0000 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. (cherry picked from commit 15825b17cf3fbf28181c51fe94a2898f448f915c)
