loop: Improvements for thread-safety

- Implement `loop_schedule` method for queueing events from other threads
- Make `loop_poll_events` `recursive` static variable a field of the Loop
  structure

src/nvim/event/defs.h

@@ -4,7 +4,7 @@
 #include <assert.h>
 #include <stdarg.h>
 
-#define EVENT_HANDLER_MAX_ARGC 4
+#define EVENT_HANDLER_MAX_ARGC 6
 
 typedef void (*argv_callback)(void **argv);
 typedef struct message {
@@ -12,6 +12,7 @@ typedef struct message {
   argv_callback handler;
   void *argv[EVENT_HANDLER_MAX_ARGC];
 } Event;
+typedef void(*event_scheduler)(Event event, void *data);
 
 #define VA_EVENT_INIT(event, p, h, a)                   \
   do {                                                  \

src/nvim/event/loop.c

@@ -10,20 +10,19 @@
 # include "event/loop.c.generated.h"
 #endif
 
-typedef struct idle_event {
-  uv_idle_t idle;
-  Event event;
-} IdleEvent;
-
 
 void loop_init(Loop *loop, void *data)
 {
   uv_loop_init(&loop->uv);
+  loop->recursive = 0;
   loop->uv.data = loop;
   loop->children = kl_init(WatcherPtr);
   loop->children_stop_requests = 0;
   loop->events = queue_new_parent(loop_on_put, loop);
   loop->fast_events = queue_new_child(loop->events);
+  loop->thread_events = queue_new_parent(NULL, NULL);
+  uv_mutex_init(&loop->mutex);
+  uv_async_init(&loop->uv, &loop->async, async_cb);
   uv_signal_init(&loop->uv, &loop->children_watcher);
   uv_timer_init(&loop->uv, &loop->children_kill_timer);
   uv_timer_init(&loop->uv, &loop->poll_timer);
@@ -31,9 +30,7 @@ void loop_init(Loop *loop, void *data)
 
 void loop_poll_events(Loop *loop, int ms)
 {
-  static int recursive = 0;
+  if (loop->recursive++) {
-
-  if (recursive++) {
     abort();  // Should not re-enter uv_run
   }
 
@@ -55,10 +52,19 @@ void loop_poll_events(Loop *loop, int ms)
     uv_timer_stop(&loop->poll_timer);
   }
 
-  recursive--;  // Can re-enter uv_run now
+  loop->recursive--;  // Can re-enter uv_run now
   queue_process_events(loop->fast_events);
 }
 
+// Schedule an event from another thread
+void loop_schedule(Loop *loop, Event event)
+{
+  uv_mutex_lock(&loop->mutex);
+  queue_put_event(loop->thread_events, event);
+  uv_async_send(&loop->async);
+  uv_mutex_unlock(&loop->mutex);
+}
+
 void loop_on_put(Queue *queue, void *data)
 {
   Loop *loop = data;
@@ -72,14 +78,32 @@ void loop_on_put(Queue *queue, void *data)
 
 void loop_close(Loop *loop)
 {
+  uv_mutex_destroy(&loop->mutex);
   uv_close((uv_handle_t *)&loop->children_watcher, NULL);
   uv_close((uv_handle_t *)&loop->children_kill_timer, NULL);
   uv_close((uv_handle_t *)&loop->poll_timer, NULL);
+  uv_close((uv_handle_t *)&loop->async, NULL);
   do {
     uv_run(&loop->uv, UV_RUN_DEFAULT);
   } while (uv_loop_close(&loop->uv));
+  queue_free(loop->events);
+  queue_free(loop->fast_events);
+  queue_free(loop->thread_events);
+  kl_destroy(WatcherPtr, loop->children);
+}
+
+static void async_cb(uv_async_t *handle)
+{
+  Loop *l = handle->loop->data;
+  uv_mutex_lock(&l->mutex);
+  while (!queue_empty(l->thread_events)) {
+    Event ev = queue_get(l->thread_events);
+    queue_put_event(l->fast_events, ev);
+  }
+  uv_mutex_unlock(&l->mutex);
 }
 
 static void timer_cb(uv_timer_t *handle)
 {
 }
+

src/nvim/event/loop.h

@@ -16,11 +16,14 @@ KLIST_INIT(WatcherPtr, WatcherPtr, _noop)
 
 typedef struct loop {
   uv_loop_t uv;
-  Queue *events, *fast_events;
+  Queue *events, *fast_events, *thread_events;
   klist_t(WatcherPtr) *children;
   uv_signal_t children_watcher;
   uv_timer_t children_kill_timer, poll_timer;
   size_t children_stop_requests;
+  uv_async_t async;
+  uv_mutex_t mutex;
+  int recursive;
 } Loop;
 
 #define CREATE_EVENT(queue, handler, argc, ...)                  \