[PATCH] s390: fix preempt_count of idle thread with cpu hotplug

Set preempt_count of idle_thread to zero before switching off cpu. Otherwise
the preempt_count will be wrong if the cpu is switched on again since the
thread will be reused.

Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/s390/kernel/process.c

···
 	__ctl_set_bit(8, 15);
 
 #ifdef CONFIG_HOTPLUG_CPU
-	if (cpu_is_offline(cpu))
+	if (cpu_is_offline(cpu)) {
+		preempt_enable_no_resched();
 		cpu_die();
+	}
 #endif
 
 	local_mcck_disable();