TLDR: you are currently relying on unspecified behaviour of signal(2); use sigaction (carefully) instead. Firstly, SIGCHLD is strange. From the manual page for sigaction; POSIX.1-1990 disallowed setting the action for SIGCHLD to SIG_IGN. POSIX.1-2001 allows this possibility, so that ignoring SIGCHLD can be used to prevent the creation of zombies (see wait(2)). Nevertheless, the historical … Read more
Zombie processes and zombie objects are totally unrelated. Zombie processes are when a parent starts a child process and the child process ends, but the parent doesn’t pick up the child’s exit code. The process object has to stay around until this happens – it consumes no resources and is dead, but it still exists … Read more
You have killed the process, but a dead process doesn’t disappear from the process table until its parent process performs a task called “reaping” (essentially calling wait(3) for that process to read its exit status). Dead processes that haven’t been reaped are called “zombie processes.” The parent process id you see for 31756 is process … Read more
You can use atexit for this, and register any clean up tasks to be run when your program exits. atexit.register(func[, *args[, **kargs]]) In your cleanup process, you can also implement your own wait, and kill it when a your desired timeout occurs. >>> import atexit >>> import sys >>> import time >>> >>> >>> >>> … Read more
When a child exits, some process must wait on it to get its exit code. That exit code is stored in the process table until this happens. The act of reading that exit code is called “reaping” the child. Between the time a child exits and is reaped, it is called a zombie. (The whole … Read more
A zombie is already dead, so you cannot kill it. To clean up a zombie, it must be waited on by its parent, so killing the parent should work to eliminate the zombie. (After the parent dies, the zombie will be inherited by pid 1, which will wait on it and clear its entry in … Read more
Is there a clearer definition of a “zombie thread” than what I’ve explained here? Seems like a pretty good explanation to me – a thread that has terminated (and can therefore no longer release any resources), but whose resources (e.g. handles) are still around and (potentially) causing problems. Can zombie threads occur on .NET? (Why/Why … Read more