Make EPOLLET the default

The whole worker thread mechanism assumes EPOLLET and non-blocking
descriptors, so that should be the default.

TODO: In debug mode, check that the provided file descriptor indeed
      is non-blocking.

include/maxscale/poll_core.h

@@ -76,7 +76,9 @@ typedef struct mxs_poll_data
  *                 data->thread.id: Will be updated by `poll_add_fd_to_worker`.
  *
  * @attention If the descriptor should be added to all workers, then the worker
- * thread id will be 0.
+ *            thread id will be 0.
+ *
+ * @attention The provided file descriptor *must* be non-blocking.
  *
  * @return 0 on success, non-zero on failure.
  */

server/core/poll.cc

@@ -291,6 +291,8 @@ static int add_fd_to_worker(int wid, int fd, uint32_t events, MXS_POLL_DATA* dat
 {
     ss_dassert((wid >= 0) && (wid <= n_threads));
 
+    events |= EPOLLET;
+
     struct epoll_event ev;
 
     ev.events = events;
@@ -309,6 +311,8 @@ static int add_fd_to_worker(int wid, int fd, uint32_t events, MXS_POLL_DATA* dat
 
 static int add_fd_to_workers(int fd, uint32_t events, MXS_POLL_DATA* data)
 {
+    events |= EPOLLET;
+
     struct epoll_event ev;
 
     ev.events = events;