kthread_should_stop
while (!kthread_should_stop()) {
kthread_should_stop() ||
if (kthread_should_stop())
while (!kthread_should_stop()) {
kthread_should_stop() || gvt->service_request);
if (kthread_should_stop())
while (!kthread_should_stop()) {
} while (!kthread_should_stop());
int kthread_should_stop(void);