[PATCH 2/5] evtchn: don't pointlessly use get_domain()

[Jan Beulich <jbeulich@xxxxxxxx>]

For short-lived references rcu_lock_domain() is the better (slightly
cheaper) alternative.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -642,7 +642,7 @@ int evtchn_close(struct domain *d1, int
              */
             write_unlock(&chn1->lock);
             write_unlock(&chn2->lock);
-            put_domain(d2);
+            rcu_unlock_domain(d2);
             chn2 = NULL;
         }
 
@@ -677,7 +677,7 @@ int evtchn_close(struct domain *d1, int
              */
             write_unlock(&chn1->lock);
             write_unlock(&chn2->lock);
-            put_domain(d2);
+            rcu_unlock_domain(d2);
             chn2 = NULL;
         }
 
@@ -725,9 +725,8 @@ int evtchn_close(struct domain *d1, int
 
         if ( !chn2 )
         {
-            /* If we unlock chn1 then we could lose d2. Must get a reference. 
*/
-            if ( unlikely(!get_domain(d2)) )
-                BUG();
+            /* If we unlock chn1 then we could lose d2. */
+            rcu_lock_domain(d2);
 
             chn2 = _evtchn_from_port(d2, chn1->u.interdomain.remote_port);
             BUG_ON(!chn2);
@@ -778,7 +777,7 @@ int evtchn_close(struct domain *d1, int
          */
         write_unlock(&chn1->lock);
         write_unlock(&chn2->lock);
-        put_domain(d2);
+        rcu_unlock_domain(d2);
     }
 
     write_unlock(&d1->event_lock);