RE: [PATCH 0/1] Fix hang in t5562, introduced in v2.21.0-rc1

> To: Randall S. Becker <rsbecker@nexbridge.com>
> Cc: 'Johannes Schindelin via GitGitGadget' <gitgitgadget@gmail.com>;
> git@vger.kernel.org; 'Max Kirillov' <max@max630.net>
> Subject: Re: [PATCH 0/1] Fix hang in t5562, introduced in v2.21.0-rc1
> 
> "Randall S. Becker" <rsbecker@nexbridge.com> writes:
> 
> > Unfortunately, subtest 13 still hangs on NonStop, even with this
> > patch, so our Pipeline still hangs. I'm glad it's better on Azure, but
> > I don't think this actually addresses the root cause of the hang.
> 
> Sigh.
> 
> > possible this is not the test that is failing, but actually the
> > git-http-backend? The code is not in a loop, if that helps. It is not
> > consuming any significant cycles. I don't know that part of the code
> > at all, sadly. The code is here:
> >
> > * in the operating system from here up *
> >   cleanup_children + 0x5D0 (UCr)
> >   cleanup_children_on_exit + 0x70 (UCr)
> >   git_atexit_dispatch + 0x200 (UCr)
> >   __process_atexit_functions + 0xA0 (DLL zcredll)
> >   CRE_TERMINATOR_ + 0xB50 (DLL zcredll)
> >   exit + 0x2A0 (DLL zcrtldll)
> >   die_webcgi + 0x240 (UCr)
> >   die_errno + 0x360 (UCr)
> >   write_or_die + 0x1C0 (UCr)
> >   end_headers + 0x1A0 (UCr)
> >   die_webcgi + 0x220 (UCr)
> >   die + 0x320 (UCr)
> >   inflate_request + 0x520 (UCr)
> >   run_service + 0xC20 (UCr)
> >   service_rpc + 0x530 (UCr)
> >   cmd_main + 0xD00 (UCr)
> >   main + 0x190 (UCr)
> >
> > Best guess is that a signal (SIGCHLD?) is possibly getting eaten or
> > neglected somewhere between the test, perl, and git-http-backend.
> 
> So we are trying to die(), which actually happens in die_webcgi(), and

> to write some message _but_ notice an error inside
> write_or_dir() and try to exit because we do not want to recurse forever
> trying to die, giving a message to say how/why we died, and die because
> failing to give that message, forever.
> 
> But in our attempt to exit(), we try to "cleanup children" and that is