1 files changed, 8 insertions, 1 deletions

diff --git a/ot_event.c b/ot_event.c
index 8f55817..61cc07b 100644
--- a/ot_event.c
+++ b/ot_event.c
@@ -40,6 +40,9 @@ static struct epoll_event *g_ready;
 static int                 g_ready_space;
 
 const char *event_mechanism(void) { return "epoll"; }
+/* The set lives in the kernel, and epoll_ctl during another thread's
+   epoll_wait is what it is for */
+int         event_can_share(void) { return 1; }
 
 int event_init(void) {
   g_ready       = NULL;
@@ -118,6 +121,8 @@ static struct kevent *g_ready;
 static int            g_ready_space;
 
 const char *event_mechanism(void) { return "kqueue"; }
+/* The set lives in the kernel, and kevent may be called from any thread */
+int         event_can_share(void) { return 1; }
 
 int event_init(void) {
   g_ready       = NULL;
@@ -171,7 +176,7 @@ static int event_change(int fd, int what, uint32_t generation, int deleting) {
   return 0;
 }
 
-int event_add(int fd, int what, uint32_t generation) { return event_change(fd, what, generation, 0); }
+int event_add(int fd, int what, uint32_t generation) { return what ? event_change(fd, what, generation, 0) : 0; }
 int event_modify(int fd, int what, uint32_t generation) { return event_change(fd, what, generation, 0); }
 int event_del(int fd) { return event_change(fd, 0, 0, 1); }
 
@@ -229,6 +234,8 @@ static int           *g_where;
 static int            g_count, g_space, g_where_space;
 
 const char *event_mechanism(void) { return "poll"; }
+/* The arrays below are ours and nothing guards them */
+int         event_can_share(void) { return 0; }
 
 int event_init(void) {
   g_pfds = NULL, g_generation = NULL, g_where = NULL;