lguest: fix lguest wake on guest clock tick, or fd activity

The Launcher could be inside the Guest on another CPU; wake_up_process
will do nothing because it is "running".  kick_process will knock it
back into our kernel in this case, otherwise we'll miss it until the
next guest exit.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/lguest/interrupts_and_traps.c

@@ -511,9 +511,9 @@ static enum hrtimer_restart clockdev_fn(struct hrtimer *timer)
 
 	/* Remember the first interrupt is the timer interrupt. */
 	set_bit(0, cpu->irqs_pending);
-	/* If the Guest is actually stopped, we need to wake it up. */
-	if (cpu->halted)
-		wake_up_process(cpu->tsk);
+	/* Guest may be stopped or running on another CPU. */
+	if (!wake_up_process(cpu->tsk))
+		kick_process(cpu->tsk);
 	return HRTIMER_NORESTART;
 }
 

drivers/lguest/lguest_user.c

@@ -24,8 +24,8 @@ static int break_guest_out(struct lg_cpu *cpu, const unsigned long __user*input)
 
 	if (on) {
 		cpu->break_out = 1;
-		/* Pop it out of the Guest (may be running on different CPU) */
-		wake_up_process(cpu->tsk);
+		if (!wake_up_process(cpu->tsk))
+			kick_process(cpu->tsk);
 		/* Wait for them to reset it */
 		return wait_event_interruptible(cpu->break_wq, !cpu->break_out);
 	} else {