xen/events: do some cleanups in evtchn_fifo_set_pending()

evtchn_fifo_set_pending() can be simplified a little bit. Especially
testing for the fifo control block to exist can be moved out of the
main if clause of the function enabling to avoid testing the LINKED bit
twice.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/common/event_fifo.c b/xen/common/event_fifo.c
index a6cca4798dbb618454b79f89702044778772d2dc..d508d572198b7b1584b29b65a0f2c84082297039 100644 (file)
--- a/xen/common/event_fifo.c
+++ b/xen/common/event_fifo.c
@@ -229,29 +229,24 @@ static void evtchn_fifo_set_pending(struct vcpu *v, struct evtchn *evtchn)
         goto done;
     }
 
+    /*
+     * Control block not mapped.  The guest must not unmask an
+     * event until the control block is initialized, so we can
+     * just drop the event.
+     */
+    if ( unlikely(!v->evtchn_fifo->control_block) )
+    {
+        printk(XENLOG_G_WARNING
+               "%pv has no FIFO event channel control block\n", v);
+        goto unlock;
+    }
+
     /*
      * Link the event if it unmasked and not already linked.
      */
     if ( !guest_test_bit(d, EVTCHN_FIFO_MASKED, word) &&
-         !guest_test_bit(d, EVTCHN_FIFO_LINKED, word) )
+         !guest_test_and_set_bit(d, EVTCHN_FIFO_LINKED, word) )
     {
-        event_word_t *tail_word;
-
-        /*
-         * Control block not mapped.  The guest must not unmask an
-         * event until the control block is initialized, so we can
-         * just drop the event.
-         */
-        if ( unlikely(!v->evtchn_fifo->control_block) )
-        {
-            printk(XENLOG_G_WARNING
-                   "%pv has no FIFO event channel control block\n", v);
-            goto unlock;
-        }
-
-        if ( guest_test_and_set_bit(d, EVTCHN_FIFO_LINKED, word) )
-            goto unlock;
-
         /*
          * If this event was a tail, the old queue is now empty and
          * its tail must be invalidated to prevent adding an event to
@@ -286,6 +281,8 @@ static void evtchn_fifo_set_pending(struct vcpu *v, struct evtchn *evtchn)
         linked = false;
         if ( q->tail )
         {
+            event_word_t *tail_word;
+
             tail_word = evtchn_fifo_word_from_port(d, q->tail);
             linked = evtchn_fifo_set_link(d, tail_word, port);
         }