From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Yang, Sheng" <sheng.yang@intel.com>
Subject: Re: device-assignment deadlock
Date: Tue, 12 May 2009 17:05:52 +0800
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To: Alex Williamson <alex.williamson@hp.com>
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[I was kicked off from the mailing list by periodic unknown reason last 
Friday... Sorry]

> 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,

This part again...

I think simply move kvm_deassign_irq() out of critical region is OK, and I 
also add the lock which seems missing in deassign_guest_irq(). Would post a 
patch soon.

-- 
regards
Yang, Sheng