---

yaml
---
r: 361872
b: refs/heads/master
c: c26377e
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: d3eb2c89e7ba996e8781b22a6e7d0a895ef55630
+refs/heads/master: c26377e62f4e6bfb4d99ef88526047209701a83f

trunk/drivers/xen/events.c

@@ -403,11 +403,23 @@ static void unmask_evtchn(int port)
 
 	if (unlikely((cpu != cpu_from_evtchn(port))))
 		do_hypercall = 1;
-	else
+	else {
+		/*
+		 * Need to clear the mask before checking pending to
+		 * avoid a race with an event becoming pending.
+		 *
+		 * EVTCHNOP_unmask will only trigger an upcall if the
+		 * mask bit was set, so if a hypercall is needed
+		 * remask the event.
+		 */
+		sync_clear_bit(port, BM(&s->evtchn_mask[0]));
 		evtchn_pending = sync_test_bit(port, BM(&s->evtchn_pending[0]));
 
-	if (unlikely(evtchn_pending && xen_hvm_domain()))
-		do_hypercall = 1;
+		if (unlikely(evtchn_pending && xen_hvm_domain())) {
+			sync_set_bit(port, BM(&s->evtchn_mask[0]));
+			do_hypercall = 1;
+		}
+	}
 
 	/* Slow path (hypercall) if this is a non-local port or if this is
 	 * an hvm domain and an event is pending (hvm domains don't have
@@ -418,8 +430,6 @@ static void unmask_evtchn(int port)
 	} else {
 		struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
 
-		sync_clear_bit(port, BM(&s->evtchn_mask[0]));
-
 		/*
 		 * The following is basically the equivalent of
 		 * 'hw_resend_irq'. Just like a real IO-APIC we 'lose