fix data race and thrd_create ENOMEM

src/async/async.c

@@ -27,7 +27,8 @@ struct async_work {
 
 struct re_async {
 	thrd_t *thrd;
-	uint16_t nthrds;
+	uint16_t thrds_req;
+	uint16_t thrds_started;
 	RE_ATOMIC bool run;
 	cnd_t wait;
 	mtx_t mtx;
@@ -80,7 +81,7 @@ static void async_destructor(void *data)
 	cnd_broadcast(&async->wait);
 	mtx_unlock(&async->mtx);
 
-	for (int i = 0; i < async->nthrds; i++) {
+	for (int i = 0; i < async->thrds_started; i++) {
 		thrd_join(async->thrd[i], NULL);
 	}
 
@@ -111,11 +112,15 @@ static void worker_check(void *arg)
 static void queueh(int id, void *data, void *arg)
 {
 	struct async_work *work = data;
-	(void)arg;
+	struct re_async *async	= arg;
 	(void)id;
 
 	work->cb(work->err, work->arg);
+
+	mtx_lock(&async->mtx);
 	list_unlink(&work->le);
+	mtx_unlock(&async->mtx);
+
 	mem_deref(work);
 }
 
@@ -156,15 +161,19 @@ int re_async_alloc(struct re_async **asyncp, uint16_t nthrds)
 
 	mem_destructor(async, async_destructor);
 
-	async->nthrds = nthrds;
+	async->thrds_req = nthrds;
 	re_atomic_rlx_set(&async->run, true);
 
-	for (int i = 0; i < async->nthrds; i++) {
+	for (int i = 0; i < async->thrds_req; i++) {
 		err = thread_create_name(&async->thrd[i],
 					 "async worker thread", worker_thread,
 					 async);
-		if (err)
+		if (err) {
+			mem_deref(async);
 			return err;
+		}
+
+		async->thrds_started++;
 	}
 
 	tmr_start(&async->tmr, 10, worker_check, async);