From: Dennis Kaarsemaker <dennis@kaarsemaker.net>
To: Jeff King <peff@peff.net>
Cc: Konstantin Ryabitsev <konstantin@linuxfoundation.org>,
git@vger.kernel.org
Subject: Re: [PATCH 0/2] fix http deadlock on giant ref negotiations
Date: Fri, 15 May 2015 09:41:20 +0200 [thread overview]
Message-ID: <1431675680.14042.39.camel@kaarsemaker.net> (raw)
In-Reply-To: <20150515062901.GA30768@peff.net>
On vr, 2015-05-15 at 02:29 -0400, Jeff King wrote:
> On Wed, May 13, 2015 at 08:47:24PM -0400, Jeff King wrote:
>
> > The fundamental problem is the deadlock on the server side, which is
> > producing bogus protocol output. And that's a mismatch between what
> > Apache expects (that the CGI will read all of the input request and then
> > generate an output request) and what the CGI wants to do (stream output
> > as it reads the input).
>
> At first I was irritated with Apache for this. But thinking on it more,
> it's really due to our shoe-horning of a full-duplex protocol into the
> half-duplex HTTP protocol. Even if we could convince Apache to work in a
> full-duplex way here, and even if our client is full-duplex (since
> otherwise we are just trading pipe buffers for TCP buffers), we still
> may face arbitrary HTTP proxies or other infrastructure in the middle.
>
> So here's a series to try to address the issue. The first patch is a
> fixed version of the die-recursion fixup I posted earlier. The second is
> the interesting one.
>
> [1/2]: http-backend: fix die recursion with custom handler
> [2/2]: http-backend: spool ref negotiation requests to buffer
>
> I have no clue how to write a test that would trigger this reliably
> without requiring a gigantic test fixture. However, I did confirm that
> it fixes the problem on the chromium case you provided (which otherwise
> deadlocks reliably for me).
This looks similar to the failure I posted about alst year in
http://thread.gmane.org/gmane.comp.version-control.git/258514
Though the issue is different, it has the same 'hanging git fetch'
symptom due to the deadlock between upload-pack and http-backend.
The patch I sent back then is suboptimal, as it can cause larger packs
than necessary (we still use it though, as the alternative is a
non-working git), but it does include a test you may be able to use to
verify your fix, if this is indeed the same issue.
--
Dennis Kaarsemaker
http://www.kaarsemaker.net
next prev parent reply other threads:[~2015-05-15 7:41 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-13 21:04 Clone hangs when done over http with --reference Konstantin Ryabitsev
2015-05-14 0:47 ` Jeff King
2015-05-14 1:02 ` [PATCH] http-backend: fix die recursion with custom handler Jeff King
2015-05-15 6:20 ` Jeff King
2015-05-14 17:08 ` Clone hangs when done over http with --reference Konstantin Ryabitsev
2015-05-14 19:52 ` Jeff King
2015-05-15 6:29 ` [PATCH 0/2] fix http deadlock on giant ref negotiations Jeff King
2015-05-15 6:29 ` [PATCH 1/2] http-backend: fix die recursion with custom handler Jeff King
2015-05-15 6:33 ` [PATCH 2/2] http-backend: spool ref negotiation requests to buffer Jeff King
2015-05-15 18:22 ` Junio C Hamano
2015-05-15 18:28 ` Konstantin Ryabitsev
2015-05-20 7:35 ` [PATCH v2 0/3] fix http deadlock on giant ref negotiations Jeff King
2015-05-20 7:36 ` [PATCH v2 1/3] http-backend: fix die recursion with custom handler Jeff King
2015-05-20 7:36 ` [PATCH v2 2/3] t5551: factor out tag creation Jeff King
2015-05-20 7:37 ` [PATCH v2 3/3] http-backend: spool ref negotiation requests to buffer Jeff King
2015-05-26 2:07 ` Konstantin Ryabitsev
2015-05-26 2:24 ` Jeff King
2015-05-26 3:43 ` Junio C Hamano
2015-05-15 19:16 ` [PATCH 2/2] " Jeff King
2015-05-15 7:41 ` Dennis Kaarsemaker [this message]
2015-05-15 8:38 ` [PATCH 0/2] fix http deadlock on giant ref negotiations Jeff King
2015-05-15 8:44 ` Dennis Kaarsemaker
2015-05-15 8:53 ` Jeff King
2015-05-15 9:11 ` Dennis Kaarsemaker
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