[Bug 1215911] Re: wait-for-root fails to wait for plain /dev/sdaX partitions.

[Marc Deslauriers]

ACK on the debdiffs, they look good.

I've uploaded them for processing by the SRU team, with a slight change
to the quantal versioning.

Thanks!

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Title:
  wait-for-root fails to wait for plain /dev/sdaX partitions.

Status in “initramfs-tools” package in Ubuntu:
  Fix Released
Status in “initramfs-tools” source package in Precise:
  In Progress
Status in “initramfs-tools” source package in Quantal:
  In Progress
Status in “initramfs-tools” source package in Raring:
  In Progress

Bug description:
  SRU Justification:
  [Impact] 
    * Boot failures can occur with the wait-for-root utility in P/Q/R due to a race condition.
    * Because of this issue unattended reboots and boots can randomly fail.
    * The original bug was submitted against Precise LTS.

  [Test Case]
   * Reboot machine and look for "ALERT! /dev/sda1 does not exist. Dropping to a shell!". Entering exit from prompt should boot system normally.
   * We expect that continuous reboots should allow for the machine to boot normally without this alert.

  [Regression Potential] 
   * This patch has already been uploaded into Saucy, and tested.

  --

  Moving the discussion from http://www.spinics.net/lists/hotplug/msg05769.html
  to launchpad, for I think that this bug needs to be handled in initramfs-tools
  package rather than in udev package.

  ----------

  I'm experiencing random boot failures with wait-for-root utility in Ubuntu
  12.04 ( ubuntu-12.04-server-amd64.iso ) on a HP ProLiant DL360p Gen8 server.

  For example, wait-for-root waited for only 0.13 seconds before giving
  up at

    FSTYPE=$(wait-for-root "${ROOT}" ${ROOTDELAY:-30})

  line in scripts/local in the initramfs, and  immediately enters into

    panic "ALERT!  ${ROOT} does not exist.  Dropping to a shell!"

  line.

  This is a race condition and manually entering "exit" from the panic prompt
  boots the system normally. This is a critical bug for this environment because
  it will randomly fail to perform unattended reboot (e.g. automatic reboot after
  saving kdump).

  ----------

  I examined main() in wait-for-root using debug fprintf() and it turned out that
  udev_monitor_receive_device() is sometimes immediately returning NULL (although
  wait-for-root is using blocking socket).

  I examined udev_monitor_receive_device() in libudev.so.0 using debug fprintf()
  and it turned out that recvmsg() in udev_monitor_receive_device() (which is in
  libudev-monitor.c in udev package) is returning ENOBUFS error before recvmsg()
  returns information of the root partition.

  The wait-for-root utility in initramfs-tools package is not expecting recvmsg()
  to return ENOBUFS error. But since ENOBUFS is an inevitable error, I think that
  wait-for-root (i.e. the caller of udev_monitor_receive_device()) should handle
  this error.

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