1 files changed, 25 insertions, 0 deletions
diff --git a/main-loop.c b/main-loop.c
index eb80ff369f..f46aece8b8 100644
--- a/main-loop.c
+++ b/main-loop.c
@@ -188,14 +188,39 @@ static void glib_pollfds_poll(void)
     }
 }
 
+#define MAX_MAIN_LOOP_SPIN (1000)
+
 static int os_host_main_loop_wait(uint32_t timeout)
 {
     int ret;
+    static int spin_counter;
 
     glib_pollfds_fill(&timeout);
 
+    /* If the I/O thread is very busy or we are incorrectly busy waiting in
+     * the I/O thread, this can lead to starvation of the BQL such that the
+     * VCPU threads never run.  To make sure we can detect the later case,
+     * print a message to the screen.  If we run into this condition, create
+     * a fake timeout in order to give the VCPU threads a chance to run.
+     */
+    if (spin_counter > MAX_MAIN_LOOP_SPIN) {
+        static bool notified;
+
+        if (!notified) {
+            fprintf(stderr,
+                    "main-loop: WARNING: I/O thread spun for %d iterations\n",
+                    MAX_MAIN_LOOP_SPIN);
+            notified = true;
+        }
+
+        timeout = 1;
+    }
+
     if (timeout > 0) {
+        spin_counter = 0;
         qemu_mutex_unlock_iothread();
+    } else {
+        spin_counter++;
     }
 
     ret = g_poll((GPollFD *)gpollfds->data, gpollfds->len, timeout);