[S390] lockdep: show held locks when showing a stackdump

Follow i386/x86_64:
lockdep can be used to print held locks when printing a
backtrace. This can be useful when debugging things like
'scheduling while atomic' asserts.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/traps.c

@@ -129,7 +129,7 @@ __show_trace(unsigned long sp, unsigned long low, unsigned long high)
 	}
 }
 
-void show_trace(struct task_struct *task, unsigned long * stack)
+void show_trace(struct task_struct *task, unsigned long *stack)
 {
 	register unsigned long __r15 asm ("15");
 	unsigned long sp;
@@ -151,6 +151,9 @@ void show_trace(struct task_struct *task, unsigned long * stack)
 		__show_trace(sp, S390_lowcore.thread_info,
 			     S390_lowcore.thread_info + THREAD_SIZE);
 	printk("\n");
+	if (!task)
+		task = current;
+	debug_show_held_locks(task);
 }
 
 void show_stack(struct task_struct *task, unsigned long *sp)