s390/time: return with irqs disabled from psw_idle

Modify the psw_idle waiting logic in entry[64].S to return with
interrupts disabled. This avoids potential issues with udelay
and interrupt loops as interrupts are not reenabled after
clock comparator interrupts.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/entry.S

@@ -886,13 +886,13 @@ cleanup_idle:
 	stm	%r9,%r10,__LC_SYSTEM_TIMER
 	mvc	__LC_LAST_UPDATE_TIMER(8),__TIMER_IDLE_EXIT(%r2)
 	# prepare return psw
-	n	%r8,BASED(cleanup_idle_wait)	# clear wait state bit
+	n	%r8,BASED(cleanup_idle_wait)	# clear irq & wait state bits
 	l	%r9,24(%r11)			# return from psw_idle
 	br	%r14
 cleanup_idle_insn:
 	.long	psw_idle_lpsw + 0x80000000
 cleanup_idle_wait:
-	.long	0xfffdffff
+	.long	0xfcfdffff
 
 /*
  * Integer constants

arch/s390/kernel/entry64.S

@@ -929,7 +929,7 @@ cleanup_idle:
 	stg	%r9,__LC_SYSTEM_TIMER
 	mvc	__LC_LAST_UPDATE_TIMER(8),__TIMER_IDLE_EXIT(%r2)
 	# prepare return psw
-	nihh	%r8,0xfffd		# clear wait state bit
+	nihh	%r8,0xfcfd		# clear irq & wait state bits
 	lg	%r9,48(%r11)		# return from psw_idle
 	br	%r14
 cleanup_idle_insn:

arch/s390/kernel/process.c

@@ -71,6 +71,7 @@ void arch_cpu_idle(void)
 	}
 	/* Halt the cpu and keep track of cpu time accounting. */
 	vtime_stop_cpu();
+	local_irq_enable();
 }
 
 void arch_cpu_idle_exit(void)

arch/s390/kernel/time.c

@@ -92,7 +92,6 @@ void clock_comparator_work(void)
 	struct clock_event_device *cd;
 
 	S390_lowcore.clock_comparator = -1ULL;
-	set_clock_comparator(S390_lowcore.clock_comparator);
 	cd = &__get_cpu_var(comparators);
 	cd->event_handler(cd);
 }

arch/s390/lib/delay.c

@@ -44,7 +44,6 @@ static void __udelay_disabled(unsigned long long usecs)
 	do {
 		set_clock_comparator(end);
 		vtime_stop_cpu();
-		local_irq_disable();
 	} while (get_tod_clock() < end);
 	lockdep_on();
 	__ctl_load(cr0, 0, 0);
@@ -64,7 +63,6 @@ static void __udelay_enabled(unsigned long long usecs)
 			set_clock_comparator(end);
 		}
 		vtime_stop_cpu();
-		local_irq_disable();
 		if (clock_saved)
 			local_tick_enable(clock_saved);
 	} while (get_tod_clock() < end);