[S390] prevent softirqs if delay is called disabled

The new delay implementation uses the clock comparator and an external
interrupt even if it is called disabled for interrupts. To do this
all external interrupt source except clock comparator are switched of
before enabling external interrupts. The external interrupt at the
end of the delay period may not execute softirqs or we can end up in a
dead-lock.

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

arch/s390/lib/delay.c

@@ -15,6 +15,7 @@
 #include <linux/delay.h>
 #include <linux/timex.h>
 #include <linux/irqflags.h>
+#include <linux/interrupt.h>
 
 void __delay(unsigned long loops)
 {
@@ -35,7 +36,11 @@ void __udelay(unsigned long usecs)
 {
 	u64 end, time, jiffy_timer = 0;
 	unsigned long flags, cr0, mask, dummy;
+	int irq_context;
 
+	irq_context = in_interrupt();
+	if (!irq_context)
+		local_bh_disable();
 	local_irq_save(flags);
 	if (raw_irqs_disabled_flags(flags)) {
 		jiffy_timer = S390_lowcore.jiffy_timer;
@@ -62,6 +67,8 @@ void __udelay(unsigned long usecs)
 		__ctl_load(cr0, 0, 0);
 		S390_lowcore.jiffy_timer = jiffy_timer;
 	}
+	if (!irq_context)
+		_local_bh_enable();
 	set_clock_comparator(S390_lowcore.jiffy_timer);
 	local_irq_restore(flags);
 }