lightningd: log when we have to defer hook registration.

diff --git a/lightningd/plugin.c b/lightningd/plugin.c
index 9ce2fc44..17e4a192 100644
--- a/lightningd/plugin.c
+++ b/lightningd/plugin.c
@@ -124,7 +124,8 @@ static bool plugins_all_in_state(const struct plugins *plugins,
 }
 
 /* Once they've all replied with their manifests, we can order them. */
-static void check_plugins_manifests(struct plugins *plugins)
+static void check_plugins_manifests(struct plugins *plugins,
+				    struct logger *log)
 {
 	struct plugin *plugin;
 	struct plugin **depfail;
@@ -133,7 +134,7 @@ static void check_plugins_manifests(struct plugins *plugins)
 		return;
 
 	/* Now things are settled, try to order hooks. */
-	depfail = plugin_hooks_make_ordered(tmpctx);
+	depfail = plugin_hooks_make_ordered(tmpctx, log);
 	for (size_t i = 0; i < tal_count(depfail); i++) {
 		/* Only complain and free plugins! */
 		if (depfail[i]->plugin_state != NEEDS_INIT)
@@ -284,7 +285,7 @@ static void destroy_plugin(struct plugin *p)
 
 	/* If this was last one manifests were waiting for, handle deps */
 	if (p->plugin_state == AWAITING_GETMANIFEST_RESPONSE)
-		check_plugins_manifests(p->plugins);
+		check_plugins_manifests(p->plugins, p->plugins->ld->log);
 
 	/* Daemon shutdown overrules plugin's importance; aborts init checks */
 	if (p->plugins->ld->state == LD_STATE_SHUTDOWN) {
@@ -1843,7 +1844,7 @@ static void plugin_manifest_cb(const char *buffer,
 		plugin_kill(plugin, LOG_INFORM,
 			    "Not a dynamic plugin");
 	else
-		check_plugins_manifests(plugin->plugins);
+		check_plugins_manifests(plugin->plugins, plugin->log);
 }
 
 /* If this is a valid plugin return full path name, otherwise NULL */
diff --git a/lightningd/plugin_hook.c b/lightningd/plugin_hook.c
index 34d21075..b80040ea 100644
--- a/lightningd/plugin_hook.c
+++ b/lightningd/plugin_hook.c
@@ -132,8 +132,8 @@ static void hook_done(struct lightningd *ld,
 	/* If we're the last one out, we can update hooks */
 	if (--hook->num_users == 0) {
 		if (hook->new_hooks) {
-			log_debug(ld->log, "Updating hooks for %s now usage is done.",
-				  hook->name);
+			log_unusual(ld->log, "Updating hooks for %s now usage is done.",
+				    hook->name);
 			/* Free this later (after final_cb) if not already done */
 			tal_steal(tmpctx, hook->hooks);
 			hook->hooks = hook->new_hooks;
@@ -472,6 +472,7 @@ static struct hook_node *get_best_candidate(struct hook_node *graph)
 }
 
 static struct plugin **plugin_hook_make_ordered(const tal_t *ctx,
+						struct logger *log,
 						struct plugin_hook *hook)
 {
 	struct hook_node *graph, *n;
@@ -551,7 +552,10 @@ static struct plugin **plugin_hook_make_ordered(const tal_t *ctx,
 		tal_free(hook->hooks);
 		hook->hooks = hook->new_hooks;
 		hook->new_hooks = NULL;
-	}
+	} else
+		/* If this ever live locks, we will see this in the log! */
+		log_unusual(log, "Deferring registration of hook %s until it's not in use.",
+			    hook->name);
 	return NULL;
 }
 
@@ -565,14 +569,15 @@ static void append_plugin_once(struct plugin ***ret, struct plugin *p)
 	tal_arr_expand(ret, p);
 }
 
-struct plugin **plugin_hooks_make_ordered(const tal_t *ctx)
+struct plugin **plugin_hooks_make_ordered(const tal_t *ctx,
+					  struct logger *log)
 {
 	size_t num_hooks;
 	struct plugin_hook **hooks = get_hooks(&num_hooks);
 	struct plugin **ret = tal_arr(ctx, struct plugin *, 0);
 
 	for (size_t i=0; i<num_hooks; i++) {
-		struct plugin **these = plugin_hook_make_ordered(ctx, hooks[i]);
+		struct plugin **these = plugin_hook_make_ordered(ctx, log, hooks[i]);
 		for (size_t j = 0; j < tal_count(these); j++)
 			append_plugin_once(&ret, these[j]);
 	}
diff --git a/lightningd/plugin_hook.h b/lightningd/plugin_hook.h
index 51ddaf43..b1f108a3 100644
--- a/lightningd/plugin_hook.h
+++ b/lightningd/plugin_hook.h
@@ -128,6 +128,7 @@ void plugin_hook_add_deps(struct plugin_hook *hook,
 			  const jsmntok_t *after);
 
 /* Returns array of plugins which cannot be ordered (empty on success) */
-struct plugin **plugin_hooks_make_ordered(const tal_t *ctx);
+struct plugin **plugin_hooks_make_ordered(const tal_t *ctx,
+					  struct logger *log);
 
 #endif /* LIGHTNING_LIGHTNINGD_PLUGIN_HOOK_H */
diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index e2df084a..a036ecc2 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -2639,7 +2639,8 @@ def test_hook_in_use(node_factory):
             l2.rpc.plugin_stop(plugin=dep_b)
 
     # We should have deferred hook update at least once!
-    l2.daemon.wait_for_log("Updating hooks for htlc_accepted now usage is done.")
+    l2.daemon.wait_for_log("UNUSUAL plugin-dep_b.py: Deferring registration of hook htlc_accepted until it's not in use.")
+    l2.daemon.wait_for_log("UNUSUAL lightningd: Updating hooks for htlc_accepted now usage is done.")
 
 
 def test_htlc_accepted_hook_fwdto(node_factory):