tty/hvc/hvc_console: Fix wakeup of HVC thread on hvc_kick()

Some backends call hvc_kick() to wakeup the HVC thread from its
slumber upon incoming characters. This however doesn't work
properly because it uses msleep_interruptible() which is mostly
immune to wake_up_process(). It will basically go back to sleep
until the timeout is expired (only signals can really wake it).

Replace it with a simple shedule_timeout_interruptible() instead,
which may wakeup earlier every now and then but we really don't
care in this case.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/hvc/hvc_console.c

@@ -760,10 +760,17 @@ static int khvcd(void *unused)
 			if (poll_mask == 0)
 				schedule();
 			else {
+				unsigned long j_timeout;
+
 				if (timeout < MAX_TIMEOUT)
 					timeout += (timeout >> 6) + 1;
 
-				msleep_interruptible(timeout);
+				/*
+				 * We don't use msleep_interruptible otherwise
+				 * "kick" will fail to wake us up
+				 */
+				j_timeout = msecs_to_jiffies(timeout) + 1;
+				schedule_timeout_interruptible(j_timeout);
 			}
 		}
 		__set_current_state(TASK_RUNNING);