Hi Kim,
On Sun, 15 Apr 2018, Kim Gybels wrote:
> On (13/04/18 14:36), Johannes Schindelin wrote:
> > > The poll provided in compat/poll.c is not interrupted by receiving
> > > SIGCHLD. Use a timeout for cleaning up dead children in a timely
> > > manner.
> >
> > Maybe say "When using this poll emulation, use a timeout ..."?
>
> I will rewrite the commit message when I reroll the patch. Calling the
> poll "uninterruptible" might be wrong as well, although the poll
> doesn't return with EINTR when a child process terminates, it might
> still be interruptible in other ways. On a related note, the handler
> for SIGCHLD is simply not called in Git-for-Windows' daemon.
Right. There is no signal infrastructure on Windows that is an exact
equivalent of what Junio desires.
> > > @@ -1161,8 +1162,13 @@ static int service_loop(struct socketlist *socklist)
> > > int i;
> > >
> > > check_dead_children();
> > > -
> > > - if (poll(pfd, socklist->nr, -1) < 0) {
> > > +#ifdef NO_POLL
> > > + poll_timeout = live_children ? 100 : -1;
> > > +#endif
> > > + int ret = poll(pfd, socklist->nr, poll_timeout);
> > > + if (ret == 0) {
> > > + continue;
> > > + } else if (ret < 0) {
> >
> > I would find it a bit easier on the eyes if this did not use curlies, and
> > dropped the unnecessary `else` (`continue` will take care of that):
> >
> > if (!ret)
> > continue;
> > if (ret < 0)
> > [...]
>
> Funny, that's how I would normally write it, if I wasn't so focused on
> trying to follow the coding quidelines. While I'm at it, I will also
> fix that sneaky double space after the if.
:-)
> Is it ok to add the timeout for all platforms using the poll
> emulation, since I only tested for Windows?
>From my reading of the patch, it changes only one thing, and only in the
case that the developer asked to build with NO_POLL (which means that the
platform does not have a native poll()): instead of waiting indefinitely,
the poll() call is interrupted in regular intervals to give
reap_dead_children() a chance to clean up.
And that's all it does.
So it is a simply heartbeat for platforms that require it, and that
heartbeat would not even hurt any platform that would *not* require it.
In short: from my point of view, it is fine to add the timeout for all
NO_POLL platforms, even if it was only tested on Windows.
Of course, we *do* know that there is one other user of NO_POLL: the
NonStop platform.
Randall, would you mind testing these two patches on NonStop?
Thanks,
Johannes
