From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Kim Gybels <kgybels@infogroep.be>
Cc: "Randall S. Becker" <rsbecker@nexbridge.com>,
git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
Jeff King <peff@peff.net>
Subject: Re: [PATCH 1/2] daemon: use timeout for uninterruptible poll
Date: Wed, 18 Apr 2018 23:16:03 +0200 (DST) [thread overview]
Message-ID: <nycvar.QRO.7.76.6.1804182307450.4241@ZVAVAG-6OXH6DA.rhebcr.pbec.zvpebfbsg.pbz> (raw)
In-Reply-To: <20180415170859.GA30197@infogroep.be>
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
next prev parent reply other threads:[~2018-04-18 21:16 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-12 21:07 [PATCH 0/2] Fix early EOF with GfW daemon Kim Gybels
2018-04-12 21:07 ` [PATCH 1/2] daemon: use timeout for uninterruptible poll Kim Gybels
2018-04-13 12:36 ` Johannes Schindelin
2018-04-15 17:08 ` Kim Gybels
2018-04-18 21:16 ` Johannes Schindelin [this message]
2018-04-15 21:54 ` Junio C Hamano
2018-04-15 22:16 ` Junio C Hamano
2018-04-18 21:07 ` Johannes Schindelin
2018-04-18 21:51 ` Junio C Hamano
2018-04-19 21:33 ` Kim Gybels
2018-04-19 23:18 ` Junio C Hamano
2018-04-12 21:07 ` [PATCH 2/2] daemon: graceful shutdown of client connection Kim Gybels
2018-04-13 13:03 ` Johannes Schindelin
2018-04-15 20:21 ` Kim Gybels
2018-04-18 21:48 ` Johannes Schindelin
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