uasync: fix stall detection — record timestamp after poll wait, not before

lib/u_async.c

@@ -985,11 +985,10 @@ void uasync_poll(struct UASYNC* ua, int timeout_tb) {
     if (!ua->sockets || !ua->timeout_heap) return;
 
     uint64_t now_us_poll_entry = get_time_us();
-    if (ua->last_poll_entry_us && now_us_poll_entry - ua->last_poll_entry_us > 10000) {
-        DEBUG_WARN(DEBUG_CATEGORY_UASYNC, "Event loop stall: %lluus since last poll entry",
-                   (unsigned long long)(now_us_poll_entry - ua->last_poll_entry_us));
+    if (ua->last_poll_exit_us && now_us_poll_entry - ua->last_poll_exit_us > 10000) {
+        DEBUG_WARN(DEBUG_CATEGORY_UASYNC, "Event loop stall: %lluus since end of last poll processing",
+                   (unsigned long long)(now_us_poll_entry - ua->last_poll_exit_us));
     }
-    ua->last_poll_entry_us = now_us_poll_entry;
 
     DEBUG_DEBUG(DEBUG_CATEGORY_UASYNC, "poll(%d sockets, %zu timers, timeout=%d.%dms)",
                 ua->sockets->count, ua->timeout_heap->size, timeout_tb >= 0 ? timeout_tb / 10000 : -1,
@@ -1040,6 +1039,7 @@ void uasync_poll(struct UASYNC* ua, int timeout_tb) {
             timeout_ms = (poll_timeout.tv_sec * 1000) + (poll_timeout.tv_usec / 1000);
         } else {
             // Nothing to do - return immediately
+            ua->last_poll_exit_us = get_time_us();
             return;
         }
     }
@@ -1051,6 +1051,7 @@ void uasync_poll(struct UASYNC* ua, int timeout_tb) {
         int max_events = 64;
         
         int ret = epoll_wait(ua->epoll_fd, events, max_events, timeout_ms);
+        ua->last_poll_exit_us = get_time_us();
         if (ret < 0) {
             if (errno == EINTR) {
                 return;
@@ -1086,6 +1087,7 @@ void uasync_poll(struct UASYNC* ua, int timeout_tb) {
             nanosleep(&ts, NULL);
 #endif
         }
+        ua->last_poll_exit_us = get_time_us();
         process_timeouts(ua);
         return;
     }
@@ -1129,6 +1131,7 @@ void uasync_poll(struct UASYNC* ua, int timeout_tb) {
     tv.tv_usec = (timeout_ms % 1000) * 1000;
     
     int ret = select((int)max_fd + 1, &read_fds, &write_fds, &except_fds, &tv);
+    ua->last_poll_exit_us = get_time_us();
     
     if (ret < 0) {
         int err = WSAGetLastError();
@@ -1203,6 +1206,7 @@ void uasync_poll(struct UASYNC* ua, int timeout_tb) {
     }
     
     int ret = poll(ua->poll_fds, ua->poll_fds_count, timeout_ms);
+    ua->last_poll_exit_us = get_time_us();
     if (ret < 0) {
         if (errno == EINTR) {
             return;
@@ -1327,7 +1331,7 @@ struct UASYNC* uasync_create(void) {
     ua->posted_tasks_head = NULL;
     ua->immediate_queue_head = NULL;
     ua->immediate_queue_tail = NULL;
-    ua->last_poll_entry_us = 0;
+    ua->last_poll_exit_us = 0;
 
     DEBUG_DEBUG(DEBUG_CATEGORY_ETCP, "Creating SA...");
     ua->sockets = socket_array_create(16);

lib/u_async.h

@@ -75,7 +75,7 @@ struct UASYNC {
     pthread_mutex_t posted_lock;
 #endif
     volatile sig_atomic_t stop;
-    uint64_t last_poll_entry_us;
+    uint64_t last_poll_exit_us;
 };
 
 // Type definitions