[Bug 802626] Re: vgchange may deadlock in initramfs when VG present that's not used for rootfs

[Serge Hallyn]

@Wessel, could you describe the deadlock you are talking about?

The hang I see is not a really a deadlock - it can't happen at random,
but only if udev is killed before it can acknowledge the DM_COOKIE.
Preventing udev's exit from blocking on the vgchange completing also
addressed that one.  But perhaps there is another potential deadlock,
which could happen even with a simple 'pvcreate' long after exiting
initramfs?

The comments in libdevmapper.h certainly seem to imply that it is better
to pass flags along in a DM_COOKIE, although 55-dm.rules appears to
handle the case of no cookie.  Can you explain if there is any real
downside to using --noudevsync?

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https://bugs.launchpad.net/bugs/802626

Title:
  vgchange may deadlock in initramfs when VG present that's not used for
  rootfs

Status in “lvm2” package in Ubuntu:
  Triaged
Status in “udev” package in Ubuntu:
  Confirmed
Status in “lvm2” source package in Oneiric:
  Triaged
Status in “udev” source package in Oneiric:
  Confirmed

Bug description:
  The system is now unable to boot.
  I had to boot on previous kernel 3.0.0.
  Symptoms are boot freezes. When debugging, issuing a vgscan works ok.
  doing the vgchange -a y just hangs. I need to reboot the system afterwards.

  ProblemType: Bug
  DistroRelease: Ubuntu 11.10
  Package: lvm2 2.02.66-4ubuntu2
  ProcVersionSignature: Ubuntu 3.0-0.1-generic 3.0.0-rc2
  Uname: Linux 3.0-0-generic x86_64
  Architecture: amd64
  Date: Mon Jun 27 18:15:46 2011
  ProcEnviron:
   LANGUAGE=fr_FR:en
   PATH=(custom, user)
   LANG=fr_FR.utf8
   LC_MESSAGES=fr_FR.UTF-8
   SHELL=/bin/bash
  SourcePackage: lvm2
  UpgradeStatus: No upgrade log present (probably fresh install)

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