test: create isolated ev_loop for swim unit tests

The SWIM unit tests code with the fake events and time does lots
of forbidden things: it manually invokes pending watcher
callbacks; manages global time without a kernel; puts not
existing descriptors into the loop. These foul blows open the
gates to the full control over IO events, descriptors, virtual
time. Hundreds of virtual seconds pass in milliseconds in
reality, it makes SWIM unit tests fast despite complex logic.

All these actions does not affect the loop until yield. On yield
a scheduler fiber wakes up and

    1) infinitely generates EV_READ on not existing descriptors
       because a kernel considers them closed;

    2) manual pending callbacks invocation asserts, because it is
       not allowed for non-scheduler fibers.

To avoid these problems a new isolated loop is created, not
visible for the scheduler. Here the fake events library can rack
and ruin whatever it wants.

Needed for #4250

src/lib/swim/swim.c

@@ -519,7 +519,7 @@ swim_wait_ack(struct swim *swim, struct swim_member *member,
 			timeout *= 2;
 		member->ping_deadline = swim_time() + timeout;
 		wait_ack_heap_insert(&swim->wait_ack_heap, member);
-		swim_ev_timer_again(loop(), &swim->wait_ack_tick);
+		swim_ev_timer_again(swim_loop(), &swim->wait_ack_tick);
 	}
 }
 
@@ -802,7 +802,7 @@ swim_new_member(struct swim *swim, const struct sockaddr_in *addr,
 		return NULL;
 	}
 	if (mh_size(swim->members) > 1)
-		swim_ev_timer_again(loop(), &swim->round_tick);
+		swim_ev_timer_again(swim_loop(), &swim->round_tick);
 
 	/* Dissemination component. */
 	swim_on_member_update(swim, member);
@@ -1122,7 +1122,7 @@ swim_complete_step(struct swim_task *task,
 	 * It could be stopped by the step begin function, if the
 	 * sending was too long.
 	 */
-	swim_ev_timer_again(loop(), &swim->round_tick);
+	swim_ev_timer_again(swim_loop(), &swim->round_tick);
 	/*
 	 * It is possible that the original member was deleted
 	 * manually during the task execution.
@@ -1813,16 +1813,17 @@ swim_cfg(struct swim *swim, const char *uri, double heartbeat_rate,
 		addr = swim->self->addr;
 	}
 	struct ev_timer *t = &swim->round_tick;
+	struct ev_loop *l = swim_loop();
 	if (t->repeat != heartbeat_rate && heartbeat_rate > 0) {
 		swim_ev_timer_set(t, 0, heartbeat_rate);
 		if (swim_ev_is_active(t))
-			swim_ev_timer_again(loop(), t);
+			swim_ev_timer_again(l, t);
 	}
 	t = &swim->wait_ack_tick;
 	if (t->repeat != ack_timeout && ack_timeout > 0) {
 		swim_ev_timer_set(t, 0, ack_timeout);
 		if (swim_ev_is_active(t))
-			swim_ev_timer_again(loop(), t);
+			swim_ev_timer_again(l, t);
 	}
 
 	if (new_self != NULL) {
@@ -1953,9 +1954,10 @@ swim_size(const struct swim *swim)
 void
 swim_delete(struct swim *swim)
 {
+	struct ev_loop *l = swim_loop();
 	swim_scheduler_destroy(&swim->scheduler);
-	swim_ev_timer_stop(loop(), &swim->round_tick);
-	swim_ev_timer_stop(loop(), &swim->wait_ack_tick);
+	swim_ev_timer_stop(l, &swim->round_tick);
+	swim_ev_timer_stop(l, &swim->wait_ack_tick);
 	mh_int_t node;
 	mh_foreach(swim->members, node) {
 		struct swim_member *m =
@@ -2018,8 +2020,9 @@ void
 swim_quit(struct swim *swim)
 {
 	assert(swim_is_configured(swim));
-	swim_ev_timer_stop(loop(), &swim->round_tick);
-	swim_ev_timer_stop(loop(), &swim->wait_ack_tick);
+	struct ev_loop *l = swim_loop();
+	swim_ev_timer_stop(l, &swim->round_tick);
+	swim_ev_timer_stop(l, &swim->wait_ack_tick);
 	swim_scheduler_stop_input(&swim->scheduler);
 	/* Start the last round - quiting. */
 	swim_new_round(swim);

src/lib/swim/swim_ev.c

@@ -55,3 +55,9 @@ swim_ev_timer_stop(struct ev_loop *loop, struct ev_timer *watcher)
 {
 	ev_timer_stop(loop, watcher);
 }
+
+struct ev_loop *
+swim_loop(void)
+{
+	return loop();
+}

src/lib/swim/swim_ev.h

@@ -52,6 +52,24 @@ swim_ev_timer_again(struct ev_loop *loop, struct ev_timer *watcher);
 void
 swim_ev_timer_stop(struct ev_loop *loop, struct ev_timer *watcher);
 
+/**
+ * The unit tests code with the fake events and time does lots of
+ * forbidden things: it manually invokes pending watcher
+ * callbacks; manages global time without a kernel; puts not
+ * existing descriptors into the loop. All these actions does not
+ * affect the loop until yield. On yield a scheduler fiber wakes
+ * up and 1) infinitely generates EV_READ on not existing
+ * descriptors because considers them closed; 2) manual pending
+ * callbacks invocation asserts, because it is not allowed for
+ * non-scheduler fibers. To avoid these problems a new isolated
+ * loop is created, not visible for the scheduler. Here the fake
+ * events library can rack and ruin whatever it wants. This
+ * function is supposed to be an alias for 'loop()' in the
+ * Tarantool core, but be an isolated object in tests.
+ */
+struct ev_loop *
+swim_loop(void);
+
 #define swim_ev_is_active ev_is_active
 
 #define swim_ev_init ev_init

src/lib/swim/swim_io.c

@@ -148,7 +148,7 @@ swim_task_schedule(struct swim_task *task, struct swim_scheduler *scheduler)
 {
 	assert(! swim_task_is_scheduled(task));
 	rlist_add_tail_entry(&scheduler->queue_output, task, in_queue_output);
-	swim_ev_io_start(loop(), &scheduler->output);
+	swim_ev_io_start(swim_loop(), &scheduler->output);
 }
 
 void
@@ -289,16 +289,17 @@ int
 swim_scheduler_bind(struct swim_scheduler *scheduler,
 		    const struct sockaddr_in *addr)
 {
-	swim_ev_io_stop(loop(), &scheduler->input);
-	swim_ev_io_stop(loop(), &scheduler->output);
+	struct ev_loop *l = swim_loop();
+	swim_ev_io_stop(l, &scheduler->input);
+	swim_ev_io_stop(l, &scheduler->output);
 	struct swim_transport *t = &scheduler->transport;
 	int rc = swim_transport_bind(t, (const struct sockaddr *) addr,
 				     sizeof(*addr));
 	if (t->fd >= 0) {
 		swim_ev_io_set(&scheduler->output, t->fd, EV_WRITE);
 		swim_ev_io_set(&scheduler->input, t->fd, EV_READ);
-		swim_ev_io_start(loop(), &scheduler->input);
-		swim_ev_io_start(loop(), &scheduler->output);
+		swim_ev_io_start(l, &scheduler->input);
+		swim_ev_io_start(l, &scheduler->output);
 	}
 	return rc;
 }
@@ -306,7 +307,7 @@ swim_scheduler_bind(struct swim_scheduler *scheduler,
 void
 swim_scheduler_stop_input(struct swim_scheduler *scheduler)
 {
-	swim_ev_io_stop(loop(), &scheduler->input);
+	swim_ev_io_stop(swim_loop(), &scheduler->input);
 }
 
 void
@@ -323,7 +324,7 @@ swim_scheduler_destroy(struct swim_scheduler *scheduler)
 			t->cancel(t, scheduler, -1);
 	}
 	swim_transport_destroy(&scheduler->transport);
-	swim_ev_io_stop(loop(), &scheduler->output);
+	swim_ev_io_stop(swim_loop(), &scheduler->output);
 	swim_scheduler_stop_input(scheduler);
 }
 

test/unit/swim_test_ev.c

@@ -62,6 +62,19 @@ struct swim_event;
 typedef void (*swim_event_process_f)(struct swim_event *, struct ev_loop *);
 typedef void (*swim_event_delete_f)(struct swim_event *);
 
+/**
+ * An isolated event loop not visible to the fiber scheduler,
+ * where it is safe to use fake file descriptors, manually invoke
+ * callbacks etc.
+ */
+static struct ev_loop *test_loop;
+
+struct ev_loop *
+swim_loop(void)
+{
+	return test_loop;
+}
+
 /**
  * Base event. It is stored in the event heap and virtualizes
  * other events.
@@ -330,6 +343,8 @@ swim_test_ev_init(void)
 	events_hash = mh_i64ptr_new();
 	assert(events_hash != NULL);
 	event_heap_create(&event_heap);
+	test_loop = ev_loop_new(0);
+	assert(test_loop != NULL);
 }
 
 void
@@ -338,4 +353,5 @@ swim_test_ev_free(void)
 	swim_test_ev_reset();
 	event_heap_destroy(&event_heap);
 	mh_i64ptr_delete(events_hash);
+	ev_loop_destroy(test_loop);
 }

test/unit/swim_test_utils.c

@@ -607,7 +607,7 @@ swim_wait_timeout(double timeout, struct swim_cluster *cluster,
 {
 	swim_ev_set_brk(timeout);
 	double deadline = swim_time() + timeout;
-	struct ev_loop *loop = loop();
+	struct ev_loop *loop = swim_loop();
 	/*
 	 * There can be pending out of bound IO events, affecting
 	 * the result. For example, 'quit' messages, which are