[Bug 664115] Re: parted calls 'udevadm settle' after every change causing it to hang for 180s if no udevd with matching magic key is running.

[Launchpad Bug Tracker]

** Branch linked: lp:ubuntu/lucid/parted

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Title:
  parted calls 'udevadm settle' after every change causing it to hang
  for 180s if no udevd with matching magic key is running.

Status in OEM Priority Project:
  In Progress
Status in “parted” package in Ubuntu:
  Fix Released
Status in “parted” source package in Lucid:
  In Progress
Status in “parted” source package in Maverick:
  Fix Released

Bug description:
  parted can take a very long time when run within a chroot.

  The issue here is an interface mismatch between udevd and udevadm.

  'udevadm settle' works by sending a netlink message to the udevd
  process. However, the magic key (UDEV_MONITOR_MAGIC) udevd uses to
  communicate w/ udevadm changed between lucid and maverick (presumably
  due to a non-backwards-compatible interface change). So, if you are
  running a maverick system and try to run lucid's udevadm in a chroot,
  there will be no compatible udevd to respond. The long delay is due to
  a hardcoded timeout default in udevadm - it will wait up to 180s for
  udevd to signal settle completion.

  Development branch: Fixed in parted 2.3-4ubuntu2 by not calling
  'udevadm settle' if we're chrooted.

  TEST CASE: I verified this by debootstrapping both a lucid and a
  maverick chroot on a maverick host. In a pristine host config:

     chroot /chroot/lucid udevadm settle    -> hang
     chroot /chroot/maverick udevadm settle -> no hang

  If I modify the host's udev to listen to lucid's UDEV_MONITOR_MAGIC
  define, I get the inverse results.

  So how does live-helper trigger this? parted has an ubuntu-specific
  patch that calls 'udevadm settle' after manipulating partitions to
  avoid races with other applications that might be triggered by
  partition changes.

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