From 33df9c538a18c515b696fa1e40d87ad9dbee8578 Mon Sep 17 00:00:00 2001
From: Volker Lendecke <vl@samba.org>
Date: Thu, 22 Jun 2017 08:34:34 +0200
Subject: [PATCH] messaging: Keep an array of event contexts registered

This is done with an explicit reference-counting and without talloc
destructors. The code is isolated enough for now that explicit refcount
management seems simpler. This might change in the future, but for
now keep it simple.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
---
 source3/lib/messages.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)

diff --git a/source3/lib/messages.c b/source3/lib/messages.c
index 02aa16c30c2..61005abf317 100644
--- a/source3/lib/messages.c
+++ b/source3/lib/messages.c
@@ -68,11 +68,18 @@ struct messaging_callback {
 	void *private_data;
 };
 
+struct messaging_registered_ev {
+	struct tevent_context *ev;
+	size_t refcount;
+};
+
 struct messaging_context {
 	struct server_id id;
 	struct tevent_context *event_ctx;
 	struct messaging_callback *callbacks;
 
+	struct messaging_registered_ev *event_contexts;
+
 	struct tevent_req **new_waiters;
 	size_t num_new_waiters;
 
@@ -160,6 +167,76 @@ struct messaging_rec *messaging_rec_create(
 	return result;
 }
 
+static bool messaging_register_event_context(struct messaging_context *ctx,
+					     struct tevent_context *ev)
+{
+	size_t i, num_event_contexts;
+	struct messaging_registered_ev *free_reg = NULL;
+	struct messaging_registered_ev *tmp;
+
+	num_event_contexts = talloc_array_length(ctx->event_contexts);
+
+	for (i=0; i<num_event_contexts; i++) {
+		struct messaging_registered_ev *reg = &ctx->event_contexts[i];
+
+		if (reg->ev == ev) {
+			reg->refcount += 1;
+			return true;
+		}
+		if (reg->refcount == 0) {
+			if (reg->ev != NULL) {
+				abort();
+			}
+			free_reg = reg;
+		}
+	}
+
+	if (free_reg == NULL) {
+		tmp = talloc_realloc(ctx, ctx->event_contexts,
+				     struct messaging_registered_ev,
+				     num_event_contexts+1);
+		if (tmp == NULL) {
+			return false;
+		}
+		ctx->event_contexts = tmp;
+
+		free_reg = &ctx->event_contexts[num_event_contexts];
+	}
+
+	*free_reg = (struct messaging_registered_ev) { .ev = ev, .refcount = 1 };
+
+	return true;
+}
+
+static bool messaging_deregister_event_context(struct messaging_context *ctx,
+					       struct tevent_context *ev)
+{
+	size_t i, num_event_contexts;
+
+	num_event_contexts = talloc_array_length(ctx->event_contexts);
+
+	for (i=0; i<num_event_contexts; i++) {
+		struct messaging_registered_ev *reg = &ctx->event_contexts[i];
+
+		if (reg->ev == ev) {
+			if (reg->refcount == 0) {
+				return false;
+			}
+			reg->refcount -= 1;
+
+			if (reg->refcount == 0) {
+				/*
+				 * Not strictly necessary, just
+				 * paranoia
+				 */
+				reg->ev = NULL;
+			}
+			return true;
+		}
+	}
+	return false;
+}
+
 static void messaging_recv_cb(struct tevent_context *ev,
 			      const uint8_t *msg, size_t msg_len,
 			      int *fds, size_t num_fds,
@@ -295,6 +372,12 @@ static NTSTATUS messaging_init_internal(TALLOC_CTX *mem_ctx,
 
 	ctx->event_ctx = ev;
 
+	ok = messaging_register_event_context(ctx, ev);
+	if (!ok) {
+		status = NT_STATUS_NO_MEMORY;
+		goto done;
+	}
+
 	sec_init();
 
 	ctx->msg_dgm_ref = messaging_dgm_ref(ctx,
@@ -716,6 +799,7 @@ struct tevent_req *messaging_filtered_read_send(
 	struct tevent_req *req;
 	struct messaging_filtered_read_state *state;
 	size_t new_waiters_len;
+	bool ok;
 
 	req = tevent_req_create(mem_ctx, &state,
 				struct messaging_filtered_read_state);
@@ -763,6 +847,12 @@ struct tevent_req *messaging_filtered_read_send(
 	msg_ctx->num_new_waiters += 1;
 	tevent_req_set_cleanup_fn(req, messaging_filtered_read_cleanup);
 
+	ok = messaging_register_event_context(msg_ctx, ev);
+	if (!ok) {
+		tevent_req_oom(req);
+		return tevent_req_post(req, ev);
+	}
+
 	return req;
 }
 
@@ -773,11 +863,17 @@ static void messaging_filtered_read_cleanup(struct tevent_req *req,
 		req, struct messaging_filtered_read_state);
 	struct messaging_context *msg_ctx = state->msg_ctx;
 	size_t i;
+	bool ok;
 
 	tevent_req_set_cleanup_fn(req, NULL);
 
 	TALLOC_FREE(state->fde);
 
+	ok = messaging_deregister_event_context(msg_ctx, state->ev);
+	if (!ok) {
+		abort();
+	}
+
 	/*
 	 * Just set the [new_]waiters entry to NULL, be careful not to mess
 	 * with the other "waiters" array contents. We are often called from
-- 
2.11.4.GIT