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From: "SZEDER Gábor" <szeder.dev@gmail•com>
To: Johannes Schindelin <Johannes.Schindelin@gmx•de>
Cc: "Randall S. Becker" <rsbecker@nexbridge•com>,
	'Junio C Hamano' <gitster@pobox•com>,
	git@vger•kernel.org, 'Max Kirillov' <max@max630•net>
Subject: Re: [ANNOUNCE] Git v2.21.0-rc1 (NonStop Results)
Date: Fri, 15 Feb 2019 14:02:13 +0100	[thread overview]
Message-ID: <20190215130213.GK1622@szeder.dev> (raw)
In-Reply-To: <nycvar.QRO.7.76.6.1902142234070.45@tvgsbejvaqbjf.bet>

On Thu, Feb 14, 2019 at 10:36:42PM +0100, Johannes Schindelin wrote:
> On Thu, 14 Feb 2019, Randall S. Becker wrote:
> 
> > t5562 still hangs (blocking) - this breaks our CI pipeline since the
> > test hangs and we have no explanation of whether the hang is in git or
> > the tests.
> 
> I have "good" news: it now also hangs on Ubuntu 16.04 in Azure Pipelines'
> Linux agents.

I haven't yet seen that hang in the wild and couldn't reproduce it on
purpose, but there is definitely something fishy with t5562 even on
Linux and even without that perl generate_zero_bytes helper.

  $ git checkout cc95bc2025^
  Previous HEAD position was cc95bc2025 t5562: replace /dev/zero with a pipe from generate_zero_bytes
  HEAD is now at 24b451e77c t5318: replace use of /dev/zero with generate_zero_bytes
  $ make
  <snip>
  $ cd t
  # take note of the shell's PID
  $ echo $$
  15522
  $ ./t5562-http-backend-content-length.sh --stress |tee LOG
  OK    3.0
  OK    1.0
  OK    6.0
  OK    0.0
  <snap>

And then in another terminal run this:

  $ pstree -a -p 15522

or, to make it easier noticable what changed and what stayed the same:

  $ watch -d pstree -a -p 15522

The output will sooner or later will look like this:

  bash,15522
    └─t5562-http-back,21082 ./t5562-http-backend-content-length.sh --stress
        ├─t5562-http-back,21089 ./t5562-http-backend-content-length.sh --stress
        │   └─sh,24906 ./t5562-http-backend-content-length.sh --stress
        ├─t5562-http-back,21090 ./t5562-http-backend-content-length.sh --stress
        │   └─sh,26660 ./t5562-http-backend-content-length.sh --stress
        ├─t5562-http-back,21092 ./t5562-http-backend-content-length.sh --stress
        │   └─sh,4202 ./t5562-http-backend-content-length.sh --stress
        │       └─sh,5696 ./t5562-http-backend-content-length.sh --stress
        │           └─perl,5697 /home/szeder/src/git/t/t5562/invoke-with-content-length.pl push_body.gz.trunc git http-backend
        │               └─(git,5722)
        ├─t5562-http-back,21093 ./t5562-http-backend-content-length.sh --stress
        │   └─sh,25572 ./t5562-http-backend-content-length.sh --stress
  <snip>

It won't show most of the processes run in the tests, because they are
just too fast and short-lived.  However, occasionally it does show a
stuck git process, which is shown as <defunct> in regular 'ps aux'
output:

  szeder   5722  0.0  0.0      0     0 pts/16   Z+   13:36   0:00 [git] <defunct>

Note that this is not a "proper" hang, in the sense that this process
is not stuck forever, but only for about 1 minute, after which it
disappears, and the test continues and eventually finishes with
success.  I've looked into the logs of a couple of such stuck jobs,
and it seems that it varies in which test that git process happened to
get stuck.


 

  parent reply	other threads:[~2019-02-15 13:02 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-14 15:04 [ANNOUNCE] Git v2.21.0-rc1 (NonStop Results) Randall S. Becker
2019-02-14 19:56 ` Junio C Hamano
2019-02-14 21:36 ` Johannes Schindelin
2019-02-14 22:25   ` Randall S. Becker
2019-02-15 13:02   ` SZEDER Gábor [this message]
2019-02-15 13:49     ` Randall S. Becker
2019-02-15 20:37     ` Max Kirillov
2019-02-15 21:13       ` Randall S. Becker
2019-02-16  8:26         ` Max Kirillov
2019-02-18 20:50     ` [PATCH] t5562: chunked sleep to avoid lost SIGCHILD Max Kirillov
2019-02-18 20:54       ` Randall S. Becker
2019-02-18 20:59         ` Max Kirillov
2019-02-19 18:38       ` Junio C Hamano

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