Re: [Xen-devel] [PATCH] xen/manage: Always freeze/thaw processes when suspend/resuming

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 18/08/14 10:41, Ross Lagerwall wrote:
> Always freeze processes when suspending and thaw processes when resuming
> to prevent a race noticeable with HVM guests.
> 
> This prevents a deadlock where the khubd kthread (which is designed to
> be freezable) acquires a usb device lock and then tries to allocate
> memory which requires the disk which hasn't been resumed yet.
> Meanwhile, the xenwatch thread deadlocks waiting for the usb device
> lock.
> 
> Freezing processes fixes this because the khubd thread is only thawed
> after the xenwatch thread finishes resuming all the devices.

I think this is the safest fix for this issue but I'm a bit concerned
about how much extra time the freeze_processes() call will add to the
suspend.

Can you measure how long it takes for a typical VM?

David


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