[PATCH] stacktrace: Use PF_KTHREAD to check for kernel threads

[Thomas Gleixner]

!current->mm is not a reliable indicator for kernel threads as they might
temporarily use a user mm. Check for PF_KTHREAD instead.

Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -228,7 +228,7 @@ unsigned int stack_trace_save_user(unsig
        };
 
        /* Trace user stack if not a kernel thread */
-       if (!current->mm)
+       if (current->flags & PF_KTHREAD)
                return 0;
 
        arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));