From 09f71dbeb287e367beea56d9ac8a3d356ef5e02a Mon Sep 17 00:00:00 2001 From: Karl Mehltretter Date: Thu, 23 Jul 2026 06:10:55 +0200 Subject: m68k: Fix backtraces for non-running tasks When no stack pointer is supplied, show_stack() starts at thread.esp0. This is the saved userspace register frame, not where a task was switched out. For kernel threads it points to the zeroed frame created by copy_thread(), so sched_show_task() prints no useful backtrace. Use thread.ksp for non-current tasks. It is saved by switch_to() and is already used by __get_wchan(). For current, start at the current stack frame, as is already done when no task is supplied. Tested on qemu-system-m68k -M virt using SysRq-t. All task dumps contained resolved frames. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Karl Mehltretter Reviewed-by: Geert Uytterhoeven Tested-by: Geert Uytterhoeven Link: https://patch.msgid.link/20260723041055.47289-1-kmehltretter@gmail.com Signed-off-by: Geert Uytterhoeven --- arch/m68k/kernel/traps.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/m68k/kernel/traps.c b/arch/m68k/kernel/traps.c index d2f25e8895e5..60759ba3cbd4 100644 --- a/arch/m68k/kernel/traps.c +++ b/arch/m68k/kernel/traps.c @@ -936,8 +936,8 @@ void show_stack(struct task_struct *task, unsigned long *stack, int i; if (!stack) { - if (task) - stack = (unsigned long *)task->thread.esp0; + if (task && task != current) + stack = (unsigned long *)task->thread.ksp; else stack = (unsigned long *)&stack; } -- cgit v1.2.3