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 <[e-mail]>
Signed-off-by: Jeremy Fitzhardinge <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>

drivers/xen/events.c

···
 	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

···
 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)
 {