linux-kernel - Re: [PATCH v2] panic: Add options to print system info when panic happens

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Date:   Tue, 27 Nov 2018 13:23:18 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Feng Tang <feng.tang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <john.stultz@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2] panic: Add options to print system info when panic
 happens

On Tue, 27 Nov 2018 15:15:20 +0800
Feng Tang <feng.tang@...el.com> wrote:

> Kernel panic issues are always painful to debug, partially
> because it's not easy to get enough information of the
> context when panic happens.
> 
> And we have ramoops and kdump for that, while this commit
> tries to provide a easier way to show the system info by adding
> a cmdline parameter, referring some idea from sysrq handler.
> 
> Signed-off-by: Feng Tang <feng.tang@...el.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: John Stultz <john.stultz@...aro.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> ---
> Changelog:
>  v2:
>     - change text "dump/DUMP" to "print/PRINT" which
>       is more accurate, suggested by Andrew Morton 
>     - add code to print ftrace buffer 
> 
>  Documentation/admin-guide/kernel-parameters.txt |  8 +++++++
>  kernel/panic.c                                  | 28 +++++++++++++++++++++++++
>  2 files changed, 36 insertions(+)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 19f4423..80c819a 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -3081,6 +3081,14 @@
>  			timeout < 0: reboot immediately
>  			Format: <timeout>
>  
> +	panic_print=	Bitmask for printing system info when panic happens.
> +			User can chose combination of the following bits:
> +			bit 0: print all tasks info
> +			bit 1: print system memory info
> +			bit 2: print timer info
> +			bit 3: print locks info if CONFIG_LOCKDEP is on

> +			bit 4: print ftrace buffer

Note, "ftrace_dump_on_oops" accomplishes the same thing.

Should this be a sysctl setting as well?

-- Steve

> +
>  	panic_on_warn	panic() instead of WARN().  Useful to cause kdump
>  			on a WARN().
>  
> diff --git a/kernel/panic.c b/kernel/panic.c
> index f6d549a..fb6ccd1 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -45,6 +45,13 @@ int panic_on_warn __read_mostly;
>  int panic_timeout = CONFIG_PANIC_TIMEOUT;
>  EXPORT_SYMBOL_GPL(panic_timeout);
>  
> +#define PANIC_PRINT_TASK_INFO		0x00000001
> +#define PANIC_PRINT_MEM_INFO		0x00000002
> +#define PANIC_PRINT_TIMER_INFO		0x00000004
> +#define PANIC_PRINT_LOCK_INFO		0x00000008
> +#define PANIC_PRINT_FTRACE_INFO		0x00000010
> +static unsigned long panic_print;
> +
>  ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
>  
>  EXPORT_SYMBOL(panic_notifier_list);
> @@ -124,6 +131,24 @@ void nmi_panic(struct pt_regs *regs, const char *msg)
>  }
>  EXPORT_SYMBOL(nmi_panic);
>  
> +static void panic_print_sys_info(void)
> +{
> +	if (panic_print & PANIC_PRINT_TASK_INFO)
> +		show_state();
> +
> +	if (panic_print & PANIC_PRINT_MEM_INFO)
> +		show_mem(0, NULL);
> +
> +	if (panic_print & PANIC_PRINT_TIMER_INFO)
> +		sysrq_timer_list_show();
> +
> +	if (panic_print & PANIC_PRINT_LOCK_INFO)
> +		debug_show_all_locks();
> +
> +	if (panic_print & PANIC_PRINT_FTRACE_INFO)
> +		ftrace_dump(DUMP_ALL);
> +}
> +
>  /**
>   *	panic - halt the system
>   *	@fmt: The text string to print
> @@ -250,6 +275,8 @@ void panic(const char *fmt, ...)
>  	debug_locks_off();
>  	console_flush_on_panic();
>  
> +	panic_print_sys_info();
> +
>  	if (!panic_blink)
>  		panic_blink = no_blink;
>  
> @@ -654,6 +681,7 @@ void refcount_error_report(struct pt_regs *regs, const char *err)
>  #endif
>  
>  core_param(panic, panic_timeout, int, 0644);
> +core_param(panic_print, panic_print, ulong, 0644);
>  core_param(pause_on_oops, pause_on_oops, int, 0644);
>  core_param(panic_on_warn, panic_on_warn, int, 0644);
>  core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);