Re: [PATCH 5/4] run-command: implement abort_async for pthreads
- From
Jeff King <peff@peff.net>
- Date
- Apr 1, 2011, 20:17 UTC
- Message-ID
- <20110401201714.GA16501@sigill.intra.peff.net>
- In-Reply-To
- <AANLkTi=ro88pwpA+Gfu5p2dB3ntn8PUcwvjHRh3iRy_H@mail.gmail.com>
On Fri, Apr 01, 2011 at 10:13:23PM +0200, Erik Faye-Lund wrote:
Show 17 quoted lines
> 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.
Show 5 quoted lines
> 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