From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alex Williamson <alex.williamson@hp.com>
Subject: device-assignment deadlock
Date: Fri, 08 May 2009 16:21:42 -0600
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Cc: kvm <kvm@vger.kernel.org>
To: Sheng Yang <sheng@linux.intel.com>
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Hi Sheng,

I think I'm running into the following deadlock in the kvm kernel module
when trying to use device assignment:

CPU A                               CPU B
kvm_vm_ioctl_deassign_dev_irq()
  mutex_lock(&kvm->lock);           worker_thread()
  -> kvm_deassign_irq()               -> kvm_assigned_dev_interrupt_work_handler()
    -> deassign_host_irq()              mutex_lock(&kvm->lock);
      -> cancel_work_sync() [blocked]

I wonder if we need finer granularity locking to avoid this.
Suggestions?  Thanks,

Alex