Events: fixed balancing between workers with EPOLLEXCLUSIVE. Linux with EPOLLEXCLUSIVE usually notifies only the process which was first to add the listening socket to the epoll instance. As a result most of the connections are handled by the first worker process (ticket #2285). To fix this, we re-add the socket periodically, so other workers will get a chance to accept connections.

--- a/src/event/ngx_event.h
+++ b/src/event/ngx_event.h
@@ -462,6 +462,7 @@ extern ngx_uint_t             ngx_accept
 extern ngx_uint_t             ngx_accept_mutex_held;
 extern ngx_msec_t             ngx_accept_mutex_delay;
 extern ngx_int_t              ngx_accept_disabled;
+extern ngx_uint_t             ngx_use_exclusive_accept;
 
 
 #if (NGX_STAT_STUB)