// Could be release if wildcard(8) is acquire
if ( (success = m_tail.compare_exchange_strong(
tail_was_me,NULL,wildcard(7))) ) { // acq_rel
// Could be release if wildcard(8) is acquire
if ( (success = m_tail.compare_exchange_strong(
tail_was_me,NULL,wildcard(7))) ) { // acq_rel