linux-kernel - Re: task's thread_info print in kernel oops

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Date:	Sun, 13 Jul 2014 21:57:08 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Vaibhav Shinde <v.bhav.shinde@...il.com>
Cc:	tj@...nel.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: task's thread_info print in kernel oops

On 07/14, Vaibhav Shinde wrote:
>
> During the kernel oops i observed the below debug message which shows the
> address of task's thread_info struct
>
> task: ffff880468e61a80 ti: ffff88026bc86000 task.ti: ffff88026bc86000
>
> ti: <current_thread_info()>
> task.ti <task_thread_info(current)
>
> As per my understanding, both the function calls will return the address of
> thread_info() struct of the current task,
> so it would be always the same.
>
> If so, could we apply the below change ?
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c

I too do not know, but perhaps this can help to detect that PER_CPU(kernel_stack)
or task->stack was corrupted.

> index b4e8500..904aeef 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -2902,9 +2902,8 @@ void show_regs_print_info(const char *log_lvl)
>  {
>         dump_stack_print_info(log_lvl);
>
> -       printk("%stask: %p ti: %p task.ti: %p\n",
> -              log_lvl, current, current_thread_info(),
> -              task_thread_info(current));
> +       printk("%stask: %p ti: %p\n",
> +              log_lvl, current, current_thread_info());
>  }
>
>  #endif
>
>
>
> Thanks,
> Vaibhav

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