messaging: Deliver messages only once

This survived an autobuild, so no subsystem strictly needs this anymore. In
particular the notify subsystem has been rewritten.

Why this patch? It removes some complexity from core code, and it reduces the
potential memory overconsumption: Right now I'm working on a g_lock_ping_pong
test. This test does a lot of messaging_filtered_read_send calls in a tight
loop on a nested event context. With the current code we let the
messaging_filtered_read code consume the message that arrives, but it also
posts it for consumption by the main event context attached to the messaging
context with its "classic" callback. This test never comes back to the main
event context, so it accumulates more and more self-posted messages. That's
just unnecessary, given that due to the successful autobuild nothing but the
read1 test makes use of the "multicasting" of messages.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Wed Jun 21 07:30:39 CEST 2017 on sn-devel-144

1 files changed, 10 insertions, 14 deletions

diff --git a/source3/lib/messages.c b/source3/lib/messages.c
index a38f40e3345..b0edb30ab14 100644
--- a/source3/lib/messages.c
+++ b/source3/lib/messages.c
@@ -1015,7 +1015,7 @@ static bool messaging_append_new_waiters(struct messaging_context *msg_ctx)
 	return true;
 }
 
-static void messaging_dispatch_classic(struct messaging_context *msg_ctx,
+static bool messaging_dispatch_classic(struct messaging_context *msg_ctx,
 				       struct messaging_rec *rec)
 {
 	struct messaging_callback *cb, *next;
@@ -1041,13 +1041,10 @@ static void messaging_dispatch_classic(struct messaging_context *msg_ctx,
 		cb->fn(msg_ctx, cb->private_data, rec->msg_type,
 		       rec->src, &rec->buf);
 
-		/*
-		 * we continue looking for matching messages after finding
-		 * one. This matters for subsystems like the internal notify
-		 * code which register more than one handler for the same
-		 * message type
-		 */
+		return true;
 	}
+
+	return false;
 }
 
 /*
@@ -1058,9 +1055,13 @@ static void messaging_dispatch_rec(struct messaging_context *msg_ctx,
 				   struct messaging_rec *rec)
 {
 	size_t i;
+	bool consumed;
 
 	if (ev == msg_ctx->event_ctx) {
-		messaging_dispatch_classic(msg_ctx, rec);
+		consumed = messaging_dispatch_classic(msg_ctx, rec);
+		if (consumed) {
+			return;
+		}
 	}
 
 	if (!messaging_append_new_waiters(msg_ctx)) {
@@ -1102,12 +1103,7 @@ static void messaging_dispatch_rec(struct messaging_context *msg_ctx,
 		if ((ev == state->ev) &&
 		    state->filter(rec, state->private_data)) {
 			messaging_filtered_read_done(req, rec);
-
-			/*
-			 * Only the first one gets the fd-array
-			 */
-			rec->num_fds = 0;
-			rec->fds = NULL;
+			return;
 		}
 
 		i += 1;