Re: [Xen-devel] [PATCH] pciback: deferred handling of pci configuration space accesses

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 24 Apr 2006, at 14:52, Ryan wrote:

>  Previously, the virtual configuration space handlers ran in
> the same context as the event channel interrupt handler (which was 
> often
> atomic if not always atomic). Now the interrupt handler schedules a
> callback function (a bottom half) in the system work queue (keventd)
> that will get called in process context at a slightly later time. This
> allows the handlers in the virtual configuration space to run in 
> process
> context and to call any core PCI function regardless of whether it will
> sleep or not.
This is okay in principle, but I found the op_in_progress counter 
rather confusing and I'm not sure why it's needed? If it's to prevent a 
double schedule_work() call on a single PCI request then I'm not sure 
that it's watertight. Does it need to be?
 -- Keir


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