genirq: Add untracked irq handler

This adds a software irq handler for controllers that multiplex
interrupts from multiple devices, but don't know which device generated
the interrupt. For these devices, the irq handler that demuxes must
check every action for every software irq using the same h/w irq in order
to find out which device generated the interrupt. This will inevitably
trigger spurious interrupt detection if we are noting the irq.

The new irq handler does not track the handling for spurious interrupt
detection. An irq that uses this also won't get stats tracked since it
didn't generate the interrupt, nor added to randomness since they are
not random.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Cc: Jon Derrick <jonathan.derrick@intel.com>
Link: http://lkml.kernel.org/r/1466200821-29159-1-git-send-email-keith.busch@intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 14 insertions, 4 deletions

diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index a15b5485b446..d3f24905852c 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -132,10 +132,10 @@ void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action)
 	wake_up_process(action->thread);
 }
 
-irqreturn_t handle_irq_event_percpu(struct irq_desc *desc)
+irqreturn_t __handle_irq_event_percpu(struct irq_desc *desc, unsigned int *flags)
 {
 	irqreturn_t retval = IRQ_NONE;
-	unsigned int flags = 0, irq = desc->irq_data.irq;
+	unsigned int irq = desc->irq_data.irq;
 	struct irqaction *action;
 
 	for_each_action_of_desc(desc, action) {
@@ -164,7 +164,7 @@ irqreturn_t handle_irq_event_percpu(struct irq_desc *desc)
 
 			/* Fall through to add to randomness */
 		case IRQ_HANDLED:
-			flags |= action->flags;
+			*flags |= action->flags;
 			break;
 
 		default:
@@ -174,7 +174,17 @@ irqreturn_t handle_irq_event_percpu(struct irq_desc *desc)
 		retval |= res;
 	}
 
-	add_interrupt_randomness(irq, flags);
+	return retval;
+}
+
+irqreturn_t handle_irq_event_percpu(struct irq_desc *desc)
+{
+	irqreturn_t retval;
+	unsigned int flags = 0;
+
+	retval = __handle_irq_event_percpu(desc, &flags);
+
+	add_interrupt_randomness(desc->irq_data.irq, flags);
 
 	if (!noirqdebug)
 		note_interrupt(desc, retval);