git hangs on pthread_join

4 messages, 3 authors, 2016-06-15 · open the first message on its own page

git hangs on pthread_join

From: Ian Kumlien <hidden>
Date: 2016-06-15 22:57:25

Hi,

I'm running a rather special configuration, basically i have a gerrit
server pushing
git data over openvpn connections (company regulations n' stuff)...

git 1.8.2.1 is started by xinetd
...
        port            = 9418
        socket_type     = stream
        wait            = no
        user            = gerrit2
        server          = /usr/bin/git
        server_args     =  daemon --inetd --syslog --export-all
--enable=receive-pack --init-timeout=3 --timeout=180 --base-path=<path>
...
        nice            = 10
        per_source      = UNLIMITED
        instances       = UNLIMITED
        flags           = KEEPALIVE NODELAY
---

Keepalive and nodelay has been added post fact, the same goes for the
timeouts.

I have found "git receive-pack"s that has been running for days/weeks
without terminating....

Attaching gdb and doing a trace results in:
#0  0x0000003261207b35 in pthread_join () from /lib64/libpthread.so.0
#1  0x00000000004ce58b in finish_async ()
#2  0x000000000045744b in cmd_receive_pack ()
#3  0x0000000000404851 in handle_internal_command ()
#4  0x0000000000404c9d in main ()
(sorry don't have any debug data for the binary packages apparenlty (rpms
was
built from the official source))

(RHEL 5 machine with glibc 2.5-65.el5_7.1)

Anyone that has any clues about what could be going wrong?

Re: git hangs on pthread_join

From: Martin Fick <hidden>
Date: 2016-06-15 22:57:25

On Thursday, May 23, 2013 07:01:43 am you wrote:
I'm running a rather special configuration, basically i
have a gerrit server pushing
... 
I have found "git receive-pack"s that has been running
for days/weeks without terminating....
... 
Anyone that has any clues about what could be going
wrong? --

Have you narrowed down whether this is a git client problem, 
or a server problem (gerrit in your case).  Is this a 
repeatable issue.  Try the same operation against a clone of 
the repo using just git.  Check on the server side for .noz 
files in you repo (a jgit thing),

-Martin

Re: git hangs on pthread_join

From: Jeff King <hidden>
Date: 2016-06-15 22:57:28

On Thu, May 23, 2013 at 03:01:43PM +0200, Ian Kumlien wrote:
git 1.8.2.1 is started by xinetd
[...]
I have found "git receive-pack"s that has been running for days/weeks
without terminating....

Attaching gdb and doing a trace results in:
#0  0x0000003261207b35 in pthread_join () from /lib64/libpthread.so.0
#1  0x00000000004ce58b in finish_async ()
#2  0x000000000045744b in cmd_receive_pack ()
#3  0x0000000000404851 in handle_internal_command ()
#4  0x0000000000404c9d in main ()
I recently fixed a deadlock that could happen in receive-pack when
clients hung up before sending a valid pack header. The fix is commit
49ecfa1, and it's in git v1.8.2.2.

The stack trace for the deadlock fixed by 49ecfa1 would have
unpack_with_sideband between #1 and #2 above, but it is entirely
possible that it is simply inlined in your build of git, depending on
the -O level of your build (it is a static function that is only called
from one place). So it seems likely that it is the culprit.

-Peff

Re: git hangs on pthread_join

From: Ian Kumlien <hidden>
Date: 2016-06-15 22:57:29

On Tue, May 28, 2013 at 01:51:09PM -0400, Jeff King wrote:
On Thu, May 23, 2013 at 03:01:43PM +0200, Ian Kumlien wrote:
quoted
git 1.8.2.1 is started by xinetd
[...]
I have found "git receive-pack"s that has been running for days/weeks
without terminating....

Attaching gdb and doing a trace results in:
#0  0x0000003261207b35 in pthread_join () from /lib64/libpthread.so.0
#1  0x00000000004ce58b in finish_async ()
#2  0x000000000045744b in cmd_receive_pack ()
#3  0x0000000000404851 in handle_internal_command ()
#4  0x0000000000404c9d in main ()
I recently fixed a deadlock that could happen in receive-pack when
clients hung up before sending a valid pack header. The fix is commit
49ecfa1, and it's in git v1.8.2.2.
With dodgy connections this could easily happen =)

Really nice catch!
The stack trace for the deadlock fixed by 49ecfa1 would have
unpack_with_sideband between #1 and #2 above, but it is entirely
possible that it is simply inlined in your build of git, depending on
the -O level of your build (it is a static function that is only called
from one place). So it seems likely that it is the culprit.
Yeah, since it's a RHEL 5 machine i don't even get a debug rpm package
=P

I will upgrade all machines and keep monitoring, thanks!
-Peff
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