8634 epoll fails to wake on certain edge-triggered conditions
8635 epoll should not emit POLLNVAL
8636 recursive epoll should emit EPOLLRDNORM
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Toomas Soome <tsoome@me.com>
Reviewed by: Igor Kozhukhov <igor@dilos.org>

@@ -20,10 +20,11 @@
  */
 
 /*
  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
+ * Copyright 2017 Joyent, Inc.
  */
 
 
 /*
  * evtchn.c

@@ -448,25 +449,25 @@
         struct evtsoftdata *ep;
         minor_t minor = getminor(dev);
         short mask = 0;
 
         ep = EVTCHNDRV_INST2SOFTS(EVTCHNDRV_MINOR2INST(minor));
-        *phpp = (struct pollhead *)NULL;
 
         if (ev & POLLOUT)
                 mask |= POLLOUT;
         if (ep->ring_overflow)
                 mask |= POLLERR;
         if (ev & (POLLIN | POLLRDNORM)) {
                 mutex_enter(&ep->evtchn_lock);
-                if (ep->ring_cons != ep->ring_prod)
+                if (ep->ring_cons != ep->ring_prod) {
                         mask |= (POLLIN | POLLRDNORM) & ev;
-                else
-                        if (mask == 0 && !anyyet)
-                                *phpp = &ep->evtchn_pollhead;
+                }
                 mutex_exit(&ep->evtchn_lock);
         }
+        if ((mask == 0 && !anyyet) || (ev & POLLET)) {
+                *phpp = &ep->evtchn_pollhead;
+        }
         *revp = mask;
         return (0);
 }