[S390] console_unblank woes.

The software watchdog calls machine_restart from a timer function.
The s390 machine_restart calls console_unblank to flush the console
output. This is needed for panic to get the panic message printed.
If console_unblank is called in interrupt a BUG is triggered in
acquire_console_sem. That makes the software watchdog panic instead
of restarting the machine. To get around this problem the call to
console_unblank is made conditionally on !in_interrupt() ||
oops_in_progress.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/setup.c

@@ -289,19 +289,34 @@ void (*_machine_power_off)(void) = do_machine_power_off_nonsmp;
 
 void machine_restart(char *command)
 {
-	console_unblank();
+	if (!in_interrupt() || oops_in_progress)
+		/*
+		 * Only unblank the console if we are called in enabled
+		 * context or a bust_spinlocks cleared the way for us.
+		 */
+		console_unblank();
 	_machine_restart(command);
 }
 
 void machine_halt(void)
 {
-	console_unblank();
+	if (!in_interrupt() || oops_in_progress)
+		/*
+		 * Only unblank the console if we are called in enabled
+		 * context or a bust_spinlocks cleared the way for us.
+		 */
+		console_unblank();
 	_machine_halt();
 }
 
 void machine_power_off(void)
 {
-	console_unblank();
+	if (!in_interrupt() || oops_in_progress)
+		/*
+		 * Only unblank the console if we are called in enabled
+		 * context or a bust_spinlocks cleared the way for us.
+		 */
+		console_unblank();
 	_machine_power_off();
 }