Question

If I have an app that is creating threads which do their work and then exit, and one or more threads get themselves into a deadlock (possibly through no fault of my own!), is there a way of programmatically forcing one of the threads to advance past the WaitForSingleObject it might be stuck at, and thus resolving the deadlock?

I don’t necessarily want to terminate the thread, I just want to have it move on (and thus allow the threads to exit “gracefully”.

(yes, I know this sounds like a duplicate of my earlier question Delphi 2006 – What's the best way to gracefully kill a thread and still have the OnTerminate handler fire?, but the situation is slightly different – what I’m asking here is whether it is possible to make a WaitForSingleObject (Handle, INFINTE) behave like a WaitForSingleObject (Handle, ItCantPossiblyBeWorkingProperlyAfterThisLong)).

Please be gentle with me.

* MORE INFO *

The problem is not necessarily in code I have the source to. The actual situation is a serial COM port library (AsyncFree) that is thread based. When the port is USB-based, the library seems to have a deadlock between two of the threads it creates on closing the port. I’ve already discussed this at length in this forum. I did recode one of the WaitForSingleObject calls to not be infinite, and that cured that deadlock, but then another one appeared later in the thread shutdown sequence, this time in the Delphi TThread.Destroy routine.

So my rationale for this is simple: when my threads deadlock, I fix the code if I can. If I can’t, or one appears that I don’t know about, I just want the thread to finish. I doesn’t have to be pretty. I can’t afford to have my app choke.

Answer 1

You can make a handle used in WaitForSingleObject invalid by closing it (from some other thread). In this case WaitForSingleObject should return WAIT_FAILED and your thread will be ‘moved on’