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>

*** 20,29 ****
--- 20,30 ----
   */
  
  /*
   * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
+  * Copyright 2017 Joyent, Inc.
   */
  
  
  /*
   * evtchn.c
*** 448,472 ****
          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)
                          mask |= (POLLIN | POLLRDNORM) & ev;
!                 else
!                         if (mask == 0 && !anyyet)
!                                 *phpp = &ep->evtchn_pollhead;
                  mutex_exit(&ep->evtchn_lock);
          }
          *revp = mask;
          return (0);
  }
  
  
--- 449,473 ----
          struct evtsoftdata *ep;
          minor_t minor = getminor(dev);
          short mask = 0;
  
          ep = EVTCHNDRV_INST2SOFTS(EVTCHNDRV_MINOR2INST(minor));
  
          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) {
                          mask |= (POLLIN | POLLRDNORM) & ev;
!                 }
                  mutex_exit(&ep->evtchn_lock);
          }
+         if ((mask == 0 && !anyyet) || (ev & POLLET)) {
+                 *phpp = &ep->evtchn_pollhead;
+         }
          *revp = mask;
          return (0);
  }