Reachability of Safe State for Online Update of Concurrent Programs

Online update helps in reducing the maintenance downtime by applying a patch to a running process. To avoid the errors that can arise due to an online update, existing online update solutions interleave the update with process execution at specific states called safe states. This approach works well for sequential processes but for multi-threaded process it presents the challenge of reaching a safe state across all threads. It turns out that in concurrent processes, even if individual threads can reach a safe state in bounded time a process may take unbounded time to reach a safe state or may never reach it.