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[Brian Elliott <bdelliott@xxxxxxxxx>]

Public bug reported:

The instance locking introduced in
cc5388bbe81aba635fb757e202d860aeed98f3e8 keeps the power state sane
between stop and the periodic task power sync.  However, locking on
an instance in the periodic task thread can potentially lock
that thread for a long time.

Example:
1) User boots an instance.  The instance gets locked by uuid.
2) Driver spawn begins and the image starts downloading from glance.
3) During spawn, periodic tasks run.  Sync power states tries to grab
the same instance lock by uuid.
4) Periodic task thread hangs until the driver spawn completes in
another greenthread.

This scenario results in nova-compute appearing unresponsive for
a long time.

** Affects: nova
     Importance: Undecided
     Assignee: Brian Elliott (belliott)
         Status: In Progress

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https://bugs.launchpad.net/bugs/1363231

Title:
  Periodic thread lockup

Status in OpenStack Compute (Nova):
  In Progress

Bug description:
  The instance locking introduced in
  cc5388bbe81aba635fb757e202d860aeed98f3e8 keeps the power state sane
  between stop and the periodic task power sync.  However, locking on
  an instance in the periodic task thread can potentially lock
  that thread for a long time.

  Example:
  1) User boots an instance.  The instance gets locked by uuid.
  2) Driver spawn begins and the image starts downloading from glance.
  3) During spawn, periodic tasks run.  Sync power states tries to grab
  the same instance lock by uuid.
  4) Periodic task thread hangs until the driver spawn completes in
  another greenthread.

  This scenario results in nova-compute appearing unresponsive for
  a long time.

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