Re: [PATCH v0.9.1 3/6] sched/umcg: implement UMCG syscalls

+
+	if (timo) {
+		hrtimer_init_sleeper_on_stack(&timeout, tsk->umcg_clock,
+					      HRTIMER_MODE_ABS);
+		hrtimer_set_expires_range_ns(&timeout.timer, (s64)timo,
+					     tsk->timer_slack_ns);
+	}
+
+	for (;;) {
+		set_current_state(TASK_INTERRUPTIBLE);
+
+		ret = -EINTR;
+		if (signal_pending(current))
+			break;
+
+		/*
+		 * Faults can block and scribble our wait state.
+		 */
+		pagefault_disable();
+		if (get_user(state, &self->state)) {
+			pagefault_enable();
+
+			ret = -EFAULT;
+			if (page) {
+				unpin_user_page(page);
+				page = NULL;
+				break;
+			}
+
+			if (pin_user_pages_fast((unsigned long)self, 1, 0, &page) != 1) {
+				page = NULL;
+				break;
+			}
+
+			continue;
+		}
+
+		if (page) {
+			unpin_user_page(page);
+			page = NULL;
+		}
+		pagefault_enable();
+
+		state &= UMCG_TASK_MASK;
+		if (state != UMCG_TASK_RUNNABLE) {
+			ret = 0;
+			if (state == UMCG_TASK_RUNNING)
+				break;
+
+			ret = -EINVAL;
+			break;
+		}
+
+		if (timo)
+			hrtimer_sleeper_start_expires(&timeout, HRTIMER_MODE_ABS);
+
+		freezable_schedule();