Merge branches 'for-3.10/appleir', 'for-3.10/hid-debug', 'for-3.10/hid-driver-transpo...

[firefly-linux-kernel-4.4.55.git] / drivers / xen / events.c

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index d17aa41a9041428fbff17a890b2af18b64422ef4..aa85881d17b23f7ff6425be0140b6aed0c63c942 100644 (file)
--- a/drivers/xen/events.c
+++ b/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