[PATCH v8 3/3] xen/events: do some cleanups in evtchn_fifo_set_pending()

[Juergen Gross <jgross@xxxxxxxx>]

evtchn_fifo_set_pending() can be simplified a little bit.

Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V8:
- new patch
---
 xen/common/event_fifo.c | 34 +++++++++++++++-------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/xen/common/event_fifo.c b/xen/common/event_fifo.c
index 443593c3b3..77609539b1 100644
--- a/xen/common/event_fifo.c
+++ b/xen/common/event_fifo.c
@@ -175,6 +175,18 @@ static void evtchn_fifo_set_pending(struct vcpu *v, struct 
evtchn *evtchn)
         return;
     }
 
+    /*
+     * 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);
+        return;
+    }
+
     /*
      * Lock all queues related to the event channel (in case of a queue change
      * this might be two).
@@ -233,25 +245,8 @@ static void evtchn_fifo_set_pending(struct vcpu *v, struct 
evtchn *evtchn)
      * 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);
         }
@@ -294,7 +291,6 @@ static void evtchn_fifo_set_pending(struct vcpu *v, struct 
evtchn *evtchn)
         q->tail = port;
     }
 
- unlock:
     if ( q != old_q )
         spin_unlock(&old_q->lock);
     spin_unlock_irqrestore(&q->lock, flags);
-- 
2.26.2