owstTaskTerminator.cpp

 156 if (exit_termination(tasks, terminator)) {
 157 MonitorLockerEx locker(_blocker, Mutex::_no_safepoint_check_flag);
 158 if (tasks >= _offered_termination - 1) {
 159 locker.notify_all();
 160 } else {
 161 for (; tasks > 1; tasks--) {
 162 locker.notify();
 163 }
 164 }
 165 _spin_master = NULL;
 166 return false;
 167 } else if (_offered_termination == _n_threads) {
 168 return true;
 169 }
 170 }

Line 167, it checks termination without _blocker lock( _offer_termination is a shared variable).