Mutex in shared memory when one user crashes?

Question

Suppose that a process is creating a mutex in shared memory and locking it and dumps core while the mutex is locked.

Now in another process how do I detect that mute

Answer 1

I left this WRONG post undeleted only if someone will have the same idea and will find this discussion of use!

---

You can use this approach. 1) Lock the POSIX shared mutex 2) Save the process-id in the shared memory. 3) Unlock the shared mutex 4) On correct exit clean the process-id

If the process coredumps the next process will find that in the shared memory there is a process-id saved on step #2. If there is no process with this process-id in the OS then no one owns the shared mutex. So it's just necessary to replace the process-id.

Update in order to answer the comment:

Scenario 1: 1. P1 starts 2. P1 creates/opens a named mutex if it doesn't exists 3. P1 timed_locks the named mutex and successfuly does it (waits for 10 secs if necessary); 4. P1 coredumps 5. P2 starts after the coredump 6. P2 creates/opens a named mutex, it exists, it's OK 7. P2 timed_locks the named mutex and fails to lock (waits for 10 secs if necessary); 8. P2 remove the named mutex 9. P2 recreates a named mutex & lock it