hello,
When a hub interrupt urb completes hub_irq() checks whether the waitqueue is
active (if the hub
thread is sleeping). If it isn't sleeping, the hub never gets scheduled for event
processing.
It causes a problem with the uml hcd. When a hub is detected, during it's
configuration, just after
the interrupt urb has been submitted, the hcd code completes the interrupt urb to
indicate that
there are more devices attached. Because the hub thread is still configuring the
device, it is not
sleeping and the event is missed.
I see no reason why this cannot happen with a real hcd, for example when
plugging in a device in a
hub while the system is polling another hub.
The only reason I see for this is that the list spinlock is held during the entire
usb_hub_events()
call and that would cause hub_irq() to block.
The locking on the eventlist could be made finer (releasing the spinlock as soon as
the event has
been dequeued) and done irqsave. The check to see if the waitqueue is active in
hub_irq() can be
removed.
Is this correct and/or desirable?
thank you,
J.
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