From: Vasily Gorbik <gor@linux.ibm.com>
Date: Fri, 22 Nov 2019 12:35:34 +0100
Subject: s390/unwind: unify task is current checks
Git-commit: 103b4cca60d2c8c51f1290cc984b7046ccb8b46d
Patch-mainline: v5.5-rc1
References: jsc#SLE-11178

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>
Acked-by: Miroslav Benes <mbenes@suse.cz>
---
 arch/s390/include/asm/stacktrace.h |    2 +-
 arch/s390/include/asm/unwind.h     |    3 ++-
 arch/s390/kernel/dumpstack.c       |    4 ----
 3 files changed, 3 insertions(+), 6 deletions(-)

--- a/arch/s390/include/asm/stacktrace.h
+++ b/arch/s390/include/asm/stacktrace.h
@@ -38,7 +38,7 @@ static inline unsigned long get_stack_po
 {
 	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;
 }
--- a/arch/s390/include/asm/unwind.h
+++ b/arch/s390/include/asm/unwind.h
@@ -61,7 +61,8 @@ static inline void unwind_start(struct u
 				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);
 }
 
--- a/arch/s390/kernel/dumpstack.c
+++ b/arch/s390/kernel/dumpstack.c
@@ -92,8 +92,6 @@ int get_stack_info(unsigned long sp, str
 	if (!sp)
 		goto unknown;
 
-	task = task ? : current;
-
 	/* Check per-task stack */
 	if (in_task_stack(sp, task, info))
 		goto recursion_check;
@@ -127,8 +125,6 @@ static void show_trace(struct task_struc
 	struct unwind_state state;
 
 	printk("Call Trace:\n");
-	if (!task)
-		task = current;
 	unwind_for_each_frame(&state, task, NULL, sp)
 		printk(state.reliable ? " [<%016lx>] %pSR \n" :
 					"([<%016lx>] %pSR)\n",