killing thread ?

[Paul Rubin]

"Martin v. Löwis" <martin at v.loewis.de> writes:
> Python does not implement a thread switching code; these are
> operating system threads.
> 
> If you are thinking that the interpreter loop could look whether it
> shall terminate: this works only if the thread is not in a blocking
> system call.

How does this sound:

The interpreter loop can check whether there's a kill pending for
any other threads (that's just looking at a flag that will be false
almost all the time).  

If there's a kill pending, the interpreter sends a signal to
the target thread.  That should unblock any blocked i/o.
A global signal handler then raises an exception in the
target thread which gets handled the usual way.

That does leave the target thread able to catch the exception
and keep looping.  Even still, it improves on the present situation.

I can imagine some ways to hair up the exception mechanism to stop
that from happening, but that starts to mess with exception semantics
rather deeply.