Messages in this thread Patch in this message | | | Date | Sat, 18 Sep 2010 11:57:26 -0700 | From | Greg KH <> | Subject | [002/123] xen: handle events as edge-triggered |
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From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
commit dffe2e1e1a1ddb566a76266136c312801c66dcf7 upstream.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/xen/events.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/xen/events.c +++ b/drivers/xen/events.c @@ -362,7 +362,7 @@ int bind_evtchn_to_irq(unsigned int evtc 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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