On February 18, 2019 15:41, Johannes Schindelin wrote: > To: Randall S. Becker <rsbecker@xxxxxxxxxxxxx> > Cc: 'Junio C Hamano' <gitster@xxxxxxxxx>; 'Johannes Schindelin via > GitGitGadget' <gitgitgadget@xxxxxxxxx>; git@xxxxxxxxxxxxxxx; 'Max Kirillov' > <max@xxxxxxxxxx> > Subject: RE: [PATCH 0/1] Fix hang in t5562, introduced in v2.21.0-rc1 > > Hi Randall, > > On Thu, 14 Feb 2019, Randall S. Becker wrote: > > > On February 14, 2019 17:39, Junio C Hamano wrote: > > > To: Randall S. Becker <rsbecker@xxxxxxxxxxxxx> > > > Cc: 'Johannes Schindelin via GitGitGadget' <gitgitgadget@xxxxxxxxx>; > > > git@xxxxxxxxxxxxxxx; 'Max Kirillov' <max@xxxxxxxxxx> > > > Subject: Re: [PATCH 0/1] Fix hang in t5562, introduced in > > > v2.21.0-rc1 > > > > > > "Randall S. Becker" <rsbecker@xxxxxxxxxxxxx> 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 > > then try > > > 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 > > what gets > > > stuck. > > > > > > One big difference before and after the /dev/zero change is that the > > process > > > is now on a downstream of the pipe. If we prepare a large file with > > > a > > finite > > > size full of NULs and replace /dev/null with it, instead of feeding > > > NULs > > from > > > the pipe, would it change the equation? > > > > Doubtful. The processes are still around, and are waiting on read but > > not actively reading (CPU time is not going up, so we're not reading > > an infinite stream). To me, this is a pipe situation where there is > > simply nothing waiting on the pipe (maybe a flush missing?). I'm > > grasping are straws without knowing the actual process architecture of the > test to debug it. > > So could you try with this patch? > > -- snipsnap -- > diff --git a/http-backend.c b/http-backend.c index d5cea0329a..7c1b4a2555 > 100644 > --- a/http-backend.c > +++ b/http-backend.c > @@ -427,6 +427,7 @@ static void inflate_request(const char *prog_name, > int out, int buffer_input, ss > > done: > git_inflate_end(&stream); > + close(0); > close(out); > free(full_request); > } Based on d62dad7a7d (v2.21.0-rc0) undoing all of the fixes, this change on its own makes no difference to the hang situation - it is still there as it was when originally reported. Using POSIX::_exit does not change the outcome of the test either on its own or in conjunction with this fix.
