From: Junio C Hamano <gitster@pobox.com>
To: Kim Gybels <kgybels@infogroep.be>
Cc: git@vger.kernel.org,
Johannes Schindelin <johannes.schindelin@gmx.de>,
Jeff King <peff@peff.net>
Subject: Re: [PATCH 1/2] daemon: use timeout for uninterruptible poll
Date: Mon, 16 Apr 2018 07:16:41 +0900 [thread overview]
Message-ID: <xmqqvacsyv1y.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <xmqq36zw16gv.fsf@gitster-ct.c.googlers.com> (Junio C. Hamano's message of "Mon, 16 Apr 2018 06:54:08 +0900")
Junio C Hamano <gitster@pobox.com> writes:
> I think you identified the problem and diagnosed it correctly, but I
> find that the change proposed here introduces a severe layering
> violation. The code is still calling what is called poll(), which
> should not have such a broken semantics.
I only mentioned a piece of fact (i.e. "the code calls poll() after
the patch"), but I guess I should have made it clear what makes that
a bad thing. Future readers of the code in daemon.c are required to
be aware of the limitation of some poll() emulation; they cannot
"optimize" out and made the code unware of the (non-)existence of
remaining children, for example. When the callsite uses poll(),
those who know how poll() ought to work won't be. The reason why
the xpoll() I mentioned as a possible alternative would be better is
because they will learn why we do not use normal poll() there and
why we maintain and pass live_children (and those who cut and paste
without understanding the existing code _will_ copy the calling site
of xpoll(), which will automatically copy the need to maintain the
number of remaining children ;-).
next prev parent reply other threads:[~2018-04-15 22:16 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
2018-04-15 21:54 ` Junio C Hamano
2018-04-15 22:16 ` Junio C Hamano [this message]
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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