Activate fd events in a pseudorandom order on older backends.

New backends like poll and kqueue and so on add fds to the queue in
the order that they are triggered.  But the select backend currently
activates low-numbered fds first, whereas the poll and win32 backends
currently favor whatever fds have been on for the longest.  This is no
good for fairness.

svn:r1318

1 files changed, 8 insertions, 4 deletions

diff --git a/poll.c b/poll.c
index 222b849e..08e148cb 100644
--- a/poll.c
+++ b/poll.c
@@ -117,7 +117,7 @@ poll_check_ok(struct pollop *pop)
 static int
 poll_dispatch(struct event_base *base, struct timeval *tv)
 {
-	int res, i, msec = -1, nfds;
+	int res, i, j, msec = -1, nfds;
 	struct pollop *pop = base->evbase;
 
 	poll_check_ok(pop);
@@ -142,11 +142,15 @@ poll_dispatch(struct event_base *base, struct timeval *tv)
 
 	event_debug(("%s: poll reports %d", __func__, res));
 
-	if (res == 0)
+	if (res == 0 || nfds == 0)
 		return (0);
 
-	for (i = 0; i < nfds; i++) {
-		int what = pop->event_set[i].revents;
+	i = random() % nfds;
+	for (j = 0; j < nfds; j++) {
+		int what;
+		if (++i == nfds)
+			i = 0;
+		what = pop->event_set[i].revents;
 		if (!what)
 			continue;