If a worker thread dies the Pitboss will set a bit corresponding to the dead worker thread ID (/number) in iPendingPeerCleanups in the TWorkerThreadRegister instance for each other worker and send them a TWorkerCleanupDeadPeerMsg . The worker threads will respond by sending TWorkerMsg::ECleanupDeadPeerResp back when they have cleaned up anything related to the dead worker and the PitBoss will reset the bit in their TWorkerThreadRegister instance. HandleWorkerCleanupCompletionByPeer()