s390/unwind: unify task is current checks

Avoid mixture of task == NULL and task == current meaning the same
thing and simply always initialize task with current in unwind_start.
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/include/asm/stacktrace.h

@@ -38,7 +38,7 @@ static inline unsigned long get_stack_pointer(struct task_struct *task,
 {
 	if (regs)
 		return (unsigned long) kernel_stack_pointer(regs);
-	if (!task || task == current)
+	if (task == current)
 		return current_stack_pointer();
 	return (unsigned long) task->thread.ksp;
 }

arch/s390/include/asm/unwind.h

@@ -61,7 +61,8 @@ static inline void unwind_start(struct unwind_state *state,
 				struct pt_regs *regs,
 				unsigned long sp)
 {
-	sp = sp ? : get_stack_pointer(task, regs);
+	task = task ?: current;
+	sp = sp ?: get_stack_pointer(task, regs);
 	__unwind_start(state, task, regs, sp);
 }
 

arch/s390/kernel/dumpstack.c

@@ -93,8 +93,6 @@ int get_stack_info(unsigned long sp, struct task_struct *task,
 	if (!sp)
 		goto unknown;
 
-	task = task ? : current;
-
 	/* Check per-task stack */
 	if (in_task_stack(sp, task, info))
 		goto recursion_check;
@@ -128,8 +126,6 @@ void show_stack(struct task_struct *task, unsigned long *stack)
 	struct unwind_state state;
 
 	printk("Call Trace:\n");
-	if (!task)
-		task = current;
 	unwind_for_each_frame(&state, task, NULL, (unsigned long) stack)
 		printk(state.reliable ? " [<%016lx>] %pSR \n" :
 					"([<%016lx>] %pSR)\n",