Commit dffe2e1e authored Aug 20, 2010 by Jeremy Fitzhardinge

xen: handle events as edge-triggered



Xen events are logically edge triggered, as Xen only calls the event
upcall when an event is newly set, but not continuously as it remains set.
As a result, use handle_edge_irq rather than handle_level_irq.

This has the important side-effect of fixing a long-standing bug of
events getting lost if:
 - an event's interrupt handler is running
 - the event is migrated to a different vcpu
 - the event is re-triggered

The most noticable symptom of these lost events is occasional lockups
of blkfront.

Many thanks to Tom Kopec and Daniel Stodden in tracking this down.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Tom Kopec <tek@acm.org>
Cc: Daniel Stodden <daniel.stodden@citrix.com>
Cc: Stable Kernel <stable@kernel.org>

parent aaca4964

drivers/xen/events.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -378,7 +378,7 @@ int bind_evtchn_to_irq(unsigned int evtchn)
		irq = find_unbound_irq();

		set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
		handle_level_irq, "event");
		handle_edge_irq, "event");

		evtchn_to_irq[evtchn] = irq;
		irq_info[irq] = mk_evtchn_info(evtchn);

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