linux-kernel - Re: [PATCH] print kdump kernel loaded status in stack dump

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Date:   Wed, 17 Jan 2018 09:57:34 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Dave Young <dyoung@...hat.com>
Cc:     sergey.senozhatsky@...il.com, rostedt@...dmis.org,
        linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        kexec@...ts.infradead.org
Subject: Re: [PATCH] print kdump kernel loaded status in stack dump

On Wed 2018-01-17 12:50:57, Dave Young wrote:
> It is useful to print kdump kernel loaded status in dump_stack() 
> especially when panic happens so that we can  differenciate 
> kdump kernel early hang and a normal panic in a bug report.
>
> Signed-off-by: Dave Young <dyoung@...hat.com>
> ---
>  kernel/printk/printk.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> --- linux-x86.orig/kernel/printk/printk.c
> +++ linux-x86/kernel/printk/printk.c
> @@ -48,6 +48,7 @@
>  #include <linux/sched/clock.h>
>  #include <linux/sched/debug.h>
>  #include <linux/sched/task_stack.h>
> +#include <linux/kexec.h>
>  
>  #include <linux/uaccess.h>
>  #include <asm/sections.h>
> @@ -3127,6 +3128,8 @@ void dump_stack_print_info(const char *l
>  	if (dump_stack_arch_desc_str[0] != '\0')
>  		printk("%sHardware name: %s\n",
>  		       log_lvl, dump_stack_arch_desc_str);
> +	if (kexec_crash_loaded())
> +		printk("%skdump kernel loaded\n", log_lvl);

IMHO, it would be better to do it like for the workqueues.
I mean to call printk_kexec_info(log_lv1, current) here
that would be impletemented in kexec sources.
Then it could be maintained by kexec people.

Anyway, I wonder if the info about kexec_crash_loaded() is
enough. I am not much familiar with kexec. AFAIK,
the image might be loaded long time before it
is acutally used.

Finally, the style of the other lines is:

    Name: details

I would suggest to print something like:

    Kexec: details

, where the details might be whether the image is loaded,
whether the loaded kernel is being executed, and
other kexec-related flags.

How does that sound?

>  	print_worker_info(log_lvl, current);
>  }

Best Regards,
Petr