xen: add resend_irq_on_evtchn() definition into events.c

Define resend_irq_on_evtchn() which ia64/xen uses.
Although it isn't used by current x86/xen code, it's arch generic
so that put it into common code.
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/xen/events.c

@@ -586,6 +586,22 @@ static void set_affinity_irq(unsigned irq, cpumask_t dest)
 	rebind_irq_to_cpu(irq, tcpu);
 }
 
+int resend_irq_on_evtchn(unsigned int irq)
+{
+	int masked, evtchn = evtchn_from_irq(irq);
+	struct shared_info *s = HYPERVISOR_shared_info;
+
+	if (!VALID_EVTCHN(evtchn))
+		return 1;
+
+	masked = sync_test_and_set_bit(evtchn, s->evtchn_mask);
+	sync_set_bit(evtchn, s->evtchn_pending);
+	if (!masked)
+		unmask_evtchn(evtchn);
+
+	return 1;
+}
+
 static void enable_dynirq(unsigned int irq)
 {
 	int evtchn = evtchn_from_irq(irq);

include/xen/events.h

@@ -31,6 +31,7 @@ int bind_ipi_to_irqhandler(enum ipi_vector ipi,
 void unbind_from_irqhandler(unsigned int irq, void *dev_id);
 
 void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector);
+int resend_irq_on_evtchn(unsigned int irq);
 
 static inline void notify_remote_via_evtchn(int port)
 {