From: Johannes Sixt <j6t@kdbg.org>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 4/4] send-pack: abort sideband demuxer on pack-objects error
Date: Thu, 14 Apr 2011 21:36:25 +0200 [thread overview]
Message-ID: <201104142136.25778.j6t@kdbg.org> (raw)
In-Reply-To: <20110414135449.GD12410@sigill.intra.peff.net>
On Donnerstag, 14. April 2011, Jeff King wrote:
> Obviously it totally breaks the start_async abstraction if the called
> code needs to care whether it forked or not. But we can use that to our
> advantage, since it means start_async callers must assume the interface
> is very limited. So I think we can do something like:
>
> 1. Async code declares which file descriptors it cares about. This
> would automatically include the pipe we give to it, of course.
> So the declared ones for a sideband demuxer would be stderr, and
> some network fd for reading.
>
> 2. In the pthreads case, we do nothing. In the forked case, the child
> closes every descriptor except the "interesting" ones.
>
> And that solves this problem, and the general case that async-callers
> have no idea if they have just leaked pipe descriptors in the forked
> case.
Sounds like a plan. How do you close all file descriptors? Just iterate up to
getrlimit(RLIMIT_NOFILE)?
>
> I'm still slightly confused, though, because I never see that descriptor
> get closed in the threaded case. So I still don't understand why it
> _doesn't_ deadlock with pthreads.
In the threaded case, this fd is closed by start_command(), where it is passed
as po.out in pack_objects(). In the fork case this is too late because a
duplicate was already inherited to the sideband demuxer.
However, pack_objects() works differently in the stateless_rpc case: then it
does not close fd anywhere, and I think it should be possible to construct a
similar case that hangs even in the threaded case. And the fix could simply
look like this:
diff --git a/builtin/send-pack.c b/builtin/send-pack.c
index 5e772c7..c8f601f 100644
--- a/builtin/send-pack.c
+++ b/builtin/send-pack.c
@@ -101,6 +101,7 @@ static int pack_objects(int fd, struct ref *refs,
free(buf);
close(po.out);
po.out = -1;
+ close(fd);
}
if (finish_command(&po))
-- Hannes
next prev parent reply other threads:[~2011-04-14 19:36 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-31 18:42 [PATCH 0/4] fix hang in git push when pack-objects fails Jeff King
2011-03-31 18:43 ` [PATCH 1/4] teach wait_or_whine a "quiet" mode Jeff King
2011-03-31 20:56 ` Johannes Sixt
2011-04-01 1:35 ` Jeff King
2011-03-31 18:44 ` [PATCH 2/4] finish_async: be quiet when waiting for async process Jeff King
2011-03-31 18:44 ` [PATCH 3/4] run-command: allow aborting async code prematurely Jeff King
2011-04-01 9:36 ` Erik Faye-Lund
2011-04-01 13:59 ` Jeff King
2011-03-31 18:44 ` [PATCH 4/4] send-pack: abort sideband demuxer on pack-objects error Jeff King
2011-04-13 19:53 ` Johannes Sixt
2011-04-14 13:54 ` Jeff King
2011-04-14 19:36 ` Johannes Sixt [this message]
2011-04-14 20:21 ` Jeff King
2011-04-14 20:43 ` Johannes Sixt
2011-04-14 20:51 ` Jeff King
2011-04-14 21:05 ` Johannes Sixt
2011-04-14 21:21 ` Junio C Hamano
2011-04-24 20:42 ` [PATCH/RFC 1/2] send-pack --stateless-rpc: properly close the outgoing channel Johannes Sixt
2011-04-24 20:49 ` [PATCH 2/2] send-pack: avoid deadlock when pack-object dies early Johannes Sixt
2011-04-25 16:50 ` Jeff King
2011-04-25 17:41 ` Johannes Sixt
2011-04-25 17:51 ` Junio C Hamano
2011-04-25 21:04 ` [PATCH v2] " Johannes Sixt
2011-04-26 8:23 ` Jeff King
2011-04-25 16:40 ` [PATCH/RFC 1/2] send-pack --stateless-rpc: properly close the outgoing channel Jeff King
2011-03-31 18:45 ` [PATCH 5/4] run-command: implement abort_async for pthreads Jeff King
2011-04-01 9:41 ` Erik Faye-Lund
2011-04-01 10:15 ` Erik Faye-Lund
2011-04-01 17:27 ` Johannes Sixt
2011-04-01 17:38 ` Jeff King
2011-04-01 19:26 ` Erik Faye-Lund
2011-04-01 19:33 ` Erik Faye-Lund
2011-04-01 19:42 ` Johannes Sixt
2011-04-01 19:57 ` Erik Faye-Lund
2011-04-01 20:05 ` Jeff King
2011-04-01 20:13 ` Erik Faye-Lund
2011-04-01 20:17 ` Jeff King
2011-04-01 20:18 ` Jeff King
2011-04-01 20:34 ` Erik Faye-Lund
2011-04-01 20:36 ` Johannes Sixt
2011-04-01 20:41 ` Erik Faye-Lund
2011-04-01 20:18 ` Johannes Sixt
2011-04-01 20:31 ` Erik Faye-Lund
2011-04-01 21:16 ` Jeff King
2011-04-02 12:27 ` Erik Faye-Lund
2011-04-01 14:00 ` Jeff King
2011-03-31 20:45 ` [PATCH 0/4] fix hang in git push when pack-objects fails Johannes Sixt
2011-04-01 1:34 ` Jeff King
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