plugins: simplify shutdown loop, simply close the db

The only thing that needs ld->wallet after this is destroy_invoices_waiter (off jsonrpc)
Could not find any other destructors (destroy_*) that need wallet or db access after this.
Any db access would now segfault.

lightningd/lightningd.c

@@ -1197,7 +1197,7 @@ int main(int argc, char *argv[])
 	remove_sigchild_handler(sigchld_conn);
 	shutdown_subdaemons(ld);
 
-	/* Tell plugins we're shutting down, closes the db for write access. */
+	/* Tell plugins we're shutting down, closes the db. */
 	shutdown_plugins(ld);
 
 	/* Cleanup JSON RPC separately: destructors assume some list_head * in ld */

lightningd/plugin.c

@@ -2088,18 +2088,13 @@ void plugins_set_builtin_plugins_dir(struct plugins *plugins,
 				NULL, NULL);
 }
 
-static void plugin_shutdown_timeout(struct lightningd *ld)
-{
-	io_break(plugin_shutdown_timeout);
-}
-
 void shutdown_plugins(struct lightningd *ld)
 {
 	struct plugin *p, *next;
 
-	/* Don't complain about important plugins vanishing and
-	 * crash any attempt to write to db. */
+	/* Don't complain about important plugins vanishing; close the db. */
 	ld->plugins->shutdown = true;
+	ld->wallet->db = tal_free(ld->wallet->db);
 
 	/* Tell them all to shutdown; if they care. */
 	list_for_each_safe(&ld->plugins->plugins, p, next, list) {
@@ -2110,20 +2105,17 @@ void shutdown_plugins(struct lightningd *ld)
 
 	/* If anyone was interested in shutdown, give them time. */
 	if (!list_empty(&ld->plugins->plugins)) {
-		struct timers *orig_timers, *timer;
+		struct timers *timer;
+		struct timer *expired;
 
 		/* 30 seconds should do it, use a clean timers struct */
-		orig_timers = ld->timers;
 		timer = tal(NULL, struct timers);
 		timers_init(timer, time_mono());
-		new_reltimer(timer, timer, time_from_sec(30),
-				  plugin_shutdown_timeout, ld);
+		new_reltimer(timer, timer, time_from_sec(30), NULL, NULL);
+
+		void *ret = io_loop(timer, &expired);
+		assert(ret == NULL || ret == destroy_plugin);
 
-		ld->timers = timer;
-		void *ret = io_loop_with_timers(ld);
-		assert(ret == plugin_shutdown_timeout || ret == destroy_plugin);
-		ld->timers = orig_timers;
-		tal_free(timer);
 
 		/* Report and free remaining plugins. */
 		while (!list_empty(&ld->plugins->plugins)) {

lightningd/plugin_hook.c

@@ -338,7 +338,6 @@ void plugin_hook_db_sync(struct db *db)
 	size_t i;
 	size_t num_hooks;
 
-	db_check_plugins_not_shutdown(db);
 	const char **changes = db_changes(db);
 	num_hooks = tal_count(hook->hooks);
 	if (num_hooks == 0)

wallet/db.c

@@ -1276,7 +1276,6 @@ struct db *db_setup(const tal_t *ctx, struct lightningd *ld,
 	struct db *db = db_open(ctx, ld->wallet_dsn);
 	bool migrated;
 	db->log = new_log(db, ld->log_book, NULL, "database");
-	db->plugins_shutdown = &ld->plugins->shutdown;
 
 	db_begin_transaction(db);
 
@@ -2351,11 +2350,6 @@ void db_changes_add(struct db_stmt *stmt, const char * expanded)
 	tal_arr_expand(&db->changes, tal_strdup(db->changes, expanded));
 }
 
-void db_check_plugins_not_shutdown(struct db *db)
-{
-	assert(!*db->plugins_shutdown);
-}
-
 const char **db_changes(struct db *db)
 {
 	return db->changes;

wallet/db.h

@@ -249,9 +249,6 @@ struct db_stmt *db_prepare_v2_(const char *location, struct db *db,
 #define db_prepare_v2(db,query)						\
 	db_prepare_v2_(__FILE__ ":" stringify(__LINE__), db, query)
 
-/* Check that plugins are not shutting down when calling db_write hook */
-void db_check_plugins_not_shutdown(struct db *db);
-
 /**
  * Access pending changes that have been added to the current transaction.
  */

wallet/db_common.h

@@ -34,9 +34,6 @@ struct db {
 	 * Used to bump the data_version in the DB.*/
 	bool dirty;
 
-	/* Only needed to check shutdown state of plugins */
-	const bool *plugins_shutdown;
-
 	/* The current DB version we expect to update if changes are
 	 * committed. */
 	u32 data_version;