fix cpu consume at idle

lib/u_async.c

@@ -867,20 +867,19 @@ void uasync_poll(struct UASYNC* ua, int timeout_tb) {
         req_timeout.tv_usec = (timeout_tb % 10000) * 100;
     }
     
-    // Use minimum of requested and next timer if both finite
-    struct timeval poll_timeout;
-    if (timeout_tb < 0) {
-        // Infinite requested - use next timer if any
-        poll_timeout = next_timeout;
-    } else {
-        // Finite requested - min of requested and next
-        if (next_timeout.tv_sec < req_timeout.tv_sec ||
-            (next_timeout.tv_sec == req_timeout.tv_sec && next_timeout.tv_usec < req_timeout.tv_usec)) {
-            poll_timeout = next_timeout;
-        } else {
-            poll_timeout = req_timeout;
-        }
-    }
+    struct timeval poll_timeout;
+    if (timeout_tb < 0) {
+        poll_timeout = next_timeout;
+    } else {
+        if (next_timeout.tv_sec < req_timeout.tv_sec ||
+            (next_timeout.tv_sec == req_timeout.tv_sec && next_timeout.tv_usec < req_timeout.tv_usec)) {
+            poll_timeout = next_timeout;
+        } else {
+            poll_timeout = req_timeout;
+        }
+    }
+    if (poll_timeout.tv_sec == 0 && poll_timeout.tv_usec == 0 && timeout_tb > 0) poll_timeout = req_timeout;
+
     
     int timeout_ms;
     if (timeout_tb < 0 && (next_timeout.tv_sec > 0 || next_timeout.tv_usec > 0)) {