static int os_host_main_loop_wait(int64_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 (!timeout && (spin_counter > MAX_MAIN_LOOP_SPIN)) { static bool notified; if (!notified && !qtest_driver()) { fprintf(stderr, "main-loop: WARNING: I/O thread spun for %d iterations\n", MAX_MAIN_LOOP_SPIN); notified = true; } timeout = SCALE_MS; } if (timeout) { spin_counter = 0; qemu_mutex_unlock_iothread(); } else { spin_counter++; } ret = qemu_poll_ns((GPollFD *)gpollfds->data, gpollfds->len, timeout); if (timeout) { qemu_mutex_lock_iothread(); } glib_pollfds_poll(); return ret; }