linux-kernel - Re: [PATCH V6] panic: Move panic

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Date:   Tue, 22 Feb 2022 11:06:44 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Cc:     linux-kernel@...r.kernel.org, bhe@...hat.com, pmladek@...e.com,
        akpm@...ux-foundation.org, anton@...msg.org, ccross@...roid.com,
        dyoung@...hat.com, feng.tang@...el.com, john.ogness@...utronix.de,
        keescook@...omium.org, kernel@...ccoli.net,
        kexec@...ts.infradead.org, rostedt@...dmis.org,
        senozhatsky@...omium.org, tony.luck@...el.com, vgoyal@...hat.com
Subject: Re: [PATCH V6] panic: Move panic_print before kmsg dumpers

On (22/02/14 11:13), Guilherme G. Piccoli wrote:
> 
> The additional messages from panic_print could overwrite the oldest
> messages when the buffer is full. The only reasonable solution is to
> use a large enough log buffer, hence we added an advice into the kernel
> parameters documentation about that.

By additional panic_print messages you mean that panic_print_sys_info()
will print everything (except PANIC_PRINT_ALL_PRINTK_MSG) twice?

Do we really need to dump everything twice? show_mem(), show_state(),
ftrace_dump(DUMP_ALL). That's quite a bit of extra data.

Can instead this be something like (?):

@@ -286,6 +289,8 @@ void panic(const char *fmt, ...)
 	 */
 	atomic_notifier_call_chain(&panic_notifier_list, 0, buf);


+	panic_print_sys_info(panic_print & ~PANIC_PRINT_ALL_PRINTK_MSG);


 	kmsg_dump(KMSG_DUMP_PANIC);
  
 	/*
@@ -316,7 +321,7 @@ void panic(const char *fmt, ...)
 	debug_locks_off();
 	console_flush_on_panic(CONSOLE_FLUSH_PENDING);


+	panic_print_sys_info(PANIC_PRINT_ALL_PRINTK_MSG);


 	if (!panic_blink)
 		panic_blink = no_blink;