[Bug 1527645] Re: grub-mkconfig hangs (due to acting on closed handle?)

[Steve Langasek]

wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 17818
pipe([3, 4]) = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7fe3556d7a10) = 17819
close(4) = 0
read(3,

This is the standard usage of pipe. pipe opens two connected file
descriptors, and returns these fds in the array that's the argument to
pipe.  The process then forks, the parent closes one, the child closes
the other, and they talk across this pipe.

Since you are only stracing the grub-mkconfig process, and not following
forks ('strace -ff'), this trace doesn't show us what's actually
hanging.

grub-mkconfig, btw, is a shell script, so it's probably better to debug
it using 'sh -x /usr/sbin/grub-mkconfig' instead.

** Package changed: grub (Ubuntu) => grub2 (Ubuntu)

** Changed in: grub2 (Ubuntu)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1527645

Title:
  grub-mkconfig hangs (due to acting on closed handle?)

Status in grub2 package in Ubuntu:
  Incomplete

Bug description:
  Calling "grub-mkconfig -o /boot/grub/grub.cfg" hangs.  I came across
  this when running "apt-get upgrade", during the kernel post install
  step, where it hangs on this line in the log:

      run-parts: executing /etc/kernel/postinst.d/zz-update-grub
  3.19.0-41-generic /boot/vmlinuz-3.19.0-41-generic

  I ran strace on calling grub-mkconfig.  I'll attach the output, but
  here's a summary of the output.  To my untrained eye, it looks like
  grub-mkconfig is calling pipe() and read() on a closed handle.

  vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
  ... snip ...
  read(3, "/dev/mapper/ubuntu--vg-root\n", 128) = 28
  read(3, "", 128)                        = 0
  --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=17818, si_status=0, si_utime=0, si_stime=0} ---
  rt_sigreturn()                          = 0
  close(3)                                = 0
  wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 17818
  pipe([3, 4])                            = 0
  clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7fe3556d7a10) = 17819
  close(4)                                = 0
  read(3, 
          ^
          |
  NOTE: THE PROCESS HANGS THERE

  NOTE: AFTER KILLING THE PROCESS, THE LINE CONTINUES THERE
          |
          v
  read(3, 0x7ffddd6b62e0, 128)            = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
  --- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=16554, si_uid=0} ---
  +++ killed by SIGTERM +++
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Here are the package versions on hand as determined by "apt-cache
  policy grub grub-pc grub-efi"

  vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
  grub:
    Installed: (none)
    Candidate: 0.97-29ubuntu66
    Version table:
       0.97-29ubuntu66 0
          500 http://us.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
  grub-pc:
    Installed: 2.02~beta2-9ubuntu1.6
    Candidate: 2.02~beta2-9ubuntu1.6
    Version table:
   *** 2.02~beta2-9ubuntu1.6 0
          500 http://us.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
          500 http://security.ubuntu.com/ubuntu/ trusty-security/main amd64 Packages
          100 /var/lib/dpkg/status
       2.02~beta2-9 0
          500 http://us.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
  grub-efi:
    Installed: (none)
    Candidate: 2.02~beta2-9ubuntu1.6
    Version table:
       2.02~beta2-9ubuntu1.6 0
          500 http://us.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
          500 http://security.ubuntu.com/ubuntu/ trusty-security/main amd64 Packages
       2.02~beta2-9 0
          500 http://us.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  This is similar to what happened to me in bug #1510563 about a month
  ago.

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