From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeff King <peff@peff.net>
Subject: Re: [PATCH 5/4] run-command: implement abort_async for pthreads
Date: Fri, 1 Apr 2011 16:17:14 -0400
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Cc: Johannes Sixt <j6t@kdbg.org>, git@vger.kernel.org
To: Erik Faye-Lund <kusmabite@gmail.com>
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On Fri, Apr 01, 2011 at 10:13:23PM +0200, Erik Faye-Lund wrote:

> On Fri, Apr 1, 2011 at 10:05 PM, Jeff King <peff@peff.net> wrote:
> > On Fri, Apr 01, 2011 at 09:57:14PM +0200, Erik Faye-Lund wrote:
> >
> >> > But this does not help the case at hand in any way. How would you interrupt a
> >> > thread that is blocked in ReadFile()? The point of pthread_cancel() is that
> >> > it interrupts blocked system calls
> >>
> >> There is no mention of such a guarantee in POSIX (section 2.9.5 Thread
> >> Cancellation), so relying on that is undefined behavior.
> >
> > Eh? My pthreads(7) says that read() is required to be a cancellation
> > point acrroding to POSIX. I didn't dig up the actual reference in the
> > standard, though.
> 
> I don't understand where the implementor would get that from after
> reading through it, but if there's something I've missed we can fix it
> by replacing my pthread_cancel with this, no?

Out of curiosity, which POSIX are you reading? My page references
POSIX.1-2001, but technically pthreads were originally defined in
POSIX.1c-1995.

> static inline int pthread_cancel(pthread_t thread)
> {
> 	SetEvent(thread.cancel_event);
> 	CancelSynchronousIo(thread.handle);
> }

There are a ton of cancellation points, not just I/O (e.g., sleep).
However, interrupting a read would probably be sufficient for git's
purposes.

-Peff