Stabilize concurrent SSH and WebSocket transports

src/web_serial_transport.c

@@ -27,7 +27,8 @@
 #define WEB_SERIAL_ORIGIN_CAPACITY (sizeof("https://") + WEB_SERIAL_HOST_CAPACITY)
 #define WEB_SERIAL_TICKET_RESPONSE_CAPACITY 96U
 #define WEB_SERIAL_TASK_STACK_SIZE 6144U
-#define WEB_SERIAL_TASK_PRIORITY 7U
+#define WEB_SERIAL_TASK_PRIORITY 4U
+#define WEB_SERIAL_ACTIVE_BURST_LOOPS 8U
 #define WEB_SERIAL_POLL_MS 5U
 #define WEB_SERIAL_DETACH_TIMEOUT_US 1000000LL
 
@@ -1214,6 +1215,8 @@ static void process_active_output(web_serial_slot_t *slot)
 static void transport_task(void *context)
 {
     (void)context;
+    size_t active_burst_loops = 0U;
+
     for (;;) {
         for (size_t index = 0U; index < WEB_SERIAL_TRANSPORT_MAX_SESSIONS;
              ++index) {
@@ -1222,8 +1225,20 @@ static void transport_task(void *context)
             process_broker_disconnect(slot);
             process_active_output(slot);
         }
-        (void)ulTaskNotifyTake(pdTRUE,
-                              milliseconds_to_ticks(WEB_SERIAL_POLL_MS));
+
+        uint32_t notifications = ulTaskNotifyTake(
+            pdTRUE, milliseconds_to_ticks(WEB_SERIAL_POLL_MS));
+        if (notifications == 0U) {
+            active_burst_loops = 0U;
+        } else if (++active_burst_loops >= WEB_SERIAL_ACTIVE_BURST_LOOPS) {
+            active_burst_loops = 0U;
+            /*
+             * Send completion normally wakes this task immediately. Bound that
+             * producer/HTTPD hand-off so sustained serial output cannot keep an
+             * application task runnable forever and starve an idle watchdog.
+             */
+            vTaskDelay(1U);
+        }
     }
 }