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

Antoine Pitrou solipsis at pitrou.net
Wed Aug 9 03:58:30 EDT 2017


On Tue, 8 Aug 2017 14:29:41 -0700
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).

For the record, there are issues open for this:

- locks not interruptible on Windows:
https://bugs.python.org/issue29971
- enable optimized locks on Windows:
https://bugs.python.org/issue29871

Having Lock.acquire() be interruptible would be really nice as it's the
basis for so many of our synchronization primitives (including
Thread.join(), I believe).

Regards

Antoine.




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