poll needs to set POLLNVAL if file descriptor is bad

ChangeLog

@@ -4777,3 +4777,5 @@
 	* net/net_poll.c: When readahead data is availalbe, the network poll
 	  logic should set POLLIN (or POLLRDNORM), not POLLOUT.  Max Holtzberg
 	  (2013-5-23)
+	* fs/fs_poll.c:  Actually, it should not ignore invlid descriptors, it
+	  should set the POLLNVAL event and return immediately (2013-5-23).

fs/fs_poll.c

@@ -162,18 +162,31 @@ static inline int poll_setup(FAR struct pollfd *fds, nfds_t nfds, sem_t *sem)
   /* Process each descriptor in the list */
 
   for (i = 0; i < nfds; i++)
-    {
-      /* Ignore negative descriptors */
-
-      if (fds[i].fd >= 0)
     {
       /* Setup the poll descriptor */
 
       fds[i].sem     = sem;
-          fds[i].revents = 0;
       fds[i].priv    = NULL;
 
-          /* Set up the poll */
+      /* Check for invalid descriptors */
+
+      if (fds[i].fd < 0)
+        {
+          /* Set POLLNVAL to indicate the invalid fd member */
+
+          fds[i].revents = POLLNVAL;
+
+          /* And increment the semaphore so that poll will return
+           * immediately (but with a successful return value).
+           */
+
+          sem_post(sem);
+        }
+      else
+        {
+          /* Set up the poll on this valid file descriptor */
+
+          fds[i].revents = 0;
 
           ret = poll_fdsetup(fds[i].fd, &fds[i], true);
           if (ret < 0)
@@ -219,6 +232,7 @@ static inline int poll_teardown(FAR struct pollfd *fds, nfds_t nfds, int *count)
             {
               ret = status;
             }
+        }
 
       /* Check if any events were posted */
 
@@ -231,7 +245,6 @@ static inline int poll_teardown(FAR struct pollfd *fds, nfds_t nfds, int *count)
 
       fds[i].sem = NULL;
     }
-    }
 
   return ret;
 }