Unlcoking a mutex from crashed thread

[superbonzo]

We are not able to find out the crash cause yet.

so, I suppose that the thread is probably invoking undefined behavior somewhere ( otherwise, you should be able to easily find out where the error occurs ) ...

In short it doesn't matter much if one thread or task is crashed, we are more concerned [...]

are you sure ? being undefined behavior anything could happen, eg the crashing thread could have corrupted memory accessed by other threads ( including the data of any mutex release mechanism you come out with ) rendering your efforts moot. You have a bug, you should fix it.

FYI, as other said, many aspects of exception handling ( especially on UB conditions ) are hardware and implementation dependent, so, what OS should this run on ? ( if on Windows, note that there's a dedicated subforum for that ... )