[Python-Dev] Interrupt thread.join() with Ctrl-C / KeyboardInterrupt on Windows

Nathaniel Smith njs at pobox.com
Tue Aug 8 18:12:02 EDT 2017

On Tue, Aug 8, 2017 at 2:29 PM, Steve Dower <steve.dower at python.org> wrote:
> On 08Aug2017 1151, Nathaniel Smith wrote:
>> It looks like Thread.join ultimately ends up blocking in
>> Python/thread_nt.h:EnterNonRecursiveMutex, which has a maze of #ifdefs
>> behind it -- I think there are 3 different implementation you might
>> end up with, depending on how CPython was built? Two of them seem to
>> ultimately block in WaitForSingleObject, which would be easy to adapt
>> to handle control-C. Unfortunately I think the implementation that
>> actually gets used on modern systems is the one that blocks in
>> SleepConditionVariableSRW, and I don't see any easy way for a
>> control-C to interrupt that. But maybe I'm missing something -- I'm
>> not a Windows expert.
> I'd have to dig back through the recent attempts at changing this, but I
> believe the SleepConditionVariableSRW path is unused for all versions of
> Windows.
> A couple of people (including myself) attempted to enable that code path,
> but it has some subtle issues that were causing test failures, so we
> abandoned all the attempts. Though ISTR that someone put in more effort than
> most of us, but I don't think we've merged it (and if we have, it'd only be
> in 3.7 at this stage).

Ah, you're right -- the comments say it's used on Windows 7 and later,
but the code disagrees. Silly me for trusting the comments :-). So it
looks like it would actually be fairly straightforward to add
control-C interruption support.


Nathaniel J. Smith -- https://vorpus.org

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