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[Brad Figg <brad.figg@xxxxxxxxxxxxx>]

This bug is missing log files that will aid in diagnosing the problem.
>From a terminal window please run:

apport-collect 1359514

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable
to run this command, please add a comment stating that fact and change
the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the
Ubuntu Kernel Team.

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

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https://bugs.launchpad.net/bugs/1359514

Title:
  pci-xgene-msi: fixed deadlock in irq_set_affinity

Status in “linux” package in Ubuntu:
  Incomplete

Bug description:
  Issue:  CPU affinity is changed while irqbalance is running.
      
      + Problem explanation:
      
        - Old code
      
          + Call xgene_msi_cascade function (CPU x)
      
          + raw_spin_lock(&desc->lock);  (CPU x)
      
          + Goto generic_handle_irq (CPU x)
      
          + The CPU x doesn't have a chance to exit the xgene_msi_cascade function to unlock desc->lock before Linux scheduce and call xgene_msi_set_affinity (irqbalance is caller) in the same CPU x
      
          + In irq_set_affinity, call raw_spin_lock_irqsave(&desc->lock, flags) which cause deadlock to CPU x because it disables preempt
      
        - New code
      
          + Use chained_irq_enter and exit as the standard way to cascade interrupt functions.

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