On February 14, 2019 22:48, Max Kirillov wrote: > To: Randall S. Becker <rsbecker@xxxxxxxxxxxxx> > Cc: 'Max Kirillov' <max@xxxxxxxxxx>; 'Johannes Schindelin via GitGitGadget' > <gitgitgadget@xxxxxxxxx>; git@xxxxxxxxxxxxxxx; 'Junio C Hamano' > <gitster@xxxxxxxxx> > Subject: Re: [PATCH 0/1] Fix hang in t5562, introduced in v2.21.0-rc1 (stack > traces inside) > > On Thu, Feb 14, 2019 at 06:33:56PM -0500, Randall S. Becker wrote: > > Here is the full set of traces (from subtest 6, which just hung). > > There are no I/O errors reported on any pipe or file descriptor. There > > is one git process waiting for a read to occur but no one is doing any > > writing. Most processes are sitting in waitpid, except for the > > initiating git, which is waiting on a read that never receives data, so > everyone is asleep and hung. > > The git process sitting in read is reading from a PIPE, not a file. > > > > There are no other processes involved in the test that I can see. > > > > Perl (waiting for output to be read): > > waitpid + 0x130 (SLr) > > $n_EnterPriv + 0x280 (Milli) > > Perl_wait4pid + 0x130 (UCr) > > Perl_my_pclose + 0x4C0 (UCr) > > Perl_io_close + 0x180 (UCr) > > Perl_do_close + 0x620 (UCr) > > Perl_pp_close + 0xA70 (UCr) > > Perl_runops_standard + 0xF0 (UCr) > > S_run_body + 0x870 (UCr) > > perl_run + 0x2D0 (UCr) > > main + 0x3D0 (UCr) > > > > git-http-backend: > > waitpid + 0x320 (SLr) > > $n_EnterPriv + 0x280 (Milli) > > 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) > > > > git (one of them): > > read64_ + 0x140 (SLr) > > $n_EnterPriv + 0x280 (Milli) > > xread + 0x130 (UCr) > > read_in_full + 0x130 (UCr) > > get_packet_data + 0x4B0 (UCr) > > packet_read_with_status + 0x230 (UCr) > > packet_reader_read + 0x310 (UCr) > > receive_needs + 0x300 (UCr) > > upload_pack + 0x680 (UCr) > > cmd_upload_pack + 0x830 (UCr) > > run_builtin + 0x980 (UCr) > > handle_builtin + 0x570 (UCr) > > run_argv + 0x210 (UCr) > > cmd_main + 0x710 (UCr) > > main + 0x190 (UCr) > > > > bash: > > waitpid + 0x130 (SLr) > > $n_EnterPriv + 0x280 (Milli) > > waitchld + 0x1F0 (UCr) > > wait_for + 0xFD0 (UCr) > > execute_command_internal + 0x1990 (UCr) > > execute_command + 0xC0 (UCr) > > reader_loop + 0x4F0 (UCr) > > main + 0x1140 (UCr) > > > > git (the other one): > > waitpid + 0x130 (SLr) > > $n_EnterPriv + 0x280 (Milli) > > wait_or_whine + 0xE0 (UCr) > > finish_command + 0x100 (UCr) > > run_command + 0x1F0 (UCr) > > execv_dashed_external + 0x800 (UCr) > > run_argv + 0x250 (UCr) > > cmd_main + 0x710 (UCr) > > main + 0x190 (UCr) > > This list does not say which process whose child but it seems like #3 is child of > #2 and #2 waits for #3, but #3 does not exit. Which is strange because it > should have send SIGTERM to it. Could the git-upload-pack somehow be > masking SIGTERM? SIGTERM cannot be masked or easily caught on the platform, so I don't think that's it. waitpid fails if the supplied pid is invalid, so it's not that either. However, I am not certain SIGPIPE is raised if a waited read is posted on a different pipe.