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.
   */
  
  
  #include <sys/errno.h>
  #include <sys/types.h>
*** 654,671 ****
          if (state == NULL) {
                  return (EBADF);
          }
  
          if (((events & (POLLIN | POLLRDNORM)) == 0) && !anyyet) {
-                 *reventsp = 0;
                  return (EINVAL);
          }
  
          /*
           * if we pushed requests on the user ring since the last poll, wakeup
           * the user app
           */
          usring = &state->bt_user_ring;
          if (usring->ur_prod_polled != usring->ur_ring.req_prod_pvt) {
  
                  /*
                   * XXX - is this faster here or xpvtap_user_request_push??
--- 655,672 ----
          if (state == NULL) {
                  return (EBADF);
          }
  
          if (((events & (POLLIN | POLLRDNORM)) == 0) && !anyyet) {
                  return (EINVAL);
          }
  
          /*
           * if we pushed requests on the user ring since the last poll, wakeup
           * the user app
           */
+         *reventsp = 0;
          usring = &state->bt_user_ring;
          if (usring->ur_prod_polled != usring->ur_ring.req_prod_pvt) {
  
                  /*
                   * XXX - is this faster here or xpvtap_user_request_push??
*** 675,692 ****
                   */
                  RING_PUSH_REQUESTS(&usring->ur_ring);
  
                  usring->ur_prod_polled = usring->ur_ring.sring->req_prod;
                  *reventsp =  POLLIN | POLLRDNORM;
  
!         /* no new requests */
!         } else {
!                 *reventsp = 0;
!                 if (!anyyet) {
                          *phpp = &state->bt_pollhead;
                  }
-         }
  
          return (0);
  }
  
  
--- 676,690 ----
                   */
                  RING_PUSH_REQUESTS(&usring->ur_ring);
  
                  usring->ur_prod_polled = usring->ur_ring.sring->req_prod;
                  *reventsp =  POLLIN | POLLRDNORM;
+         }
  
!         if ((*reventsp == 0 && !anyyet) || (events & POLLET)) {
                  *phpp = &state->bt_pollhead;
          }
  
          return (0);
  }