linux-kernel - Re: [PATCHv3 31/50] sh: Add loglvl to printk

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Date:   Mon, 20 Apr 2020 15:52:37 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Dmitry Safonov <dima@...sta.com>
Cc:     linux-kernel@...r.kernel.org,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>, Jiri Slaby <jslaby@...e.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Rich Felker <dalias@...c.org>, linux-sh@...r.kernel.org
Subject: Re: [PATCHv3 31/50] sh: Add loglvl to printk_address()

On Sat, 18 Apr 2020 21:19:25 +0100 Dmitry Safonov <dima@...sta.com> wrote:

> Currently, the log-level of show_stack() depends on a platform
> realization. It creates situations where the headers are printed with
> lower log level or higher than the stacktrace (depending on
> a platform or user).
> 
> Furthermore, it forces the logic decision from user to an architecture
> side. In result, some users as sysrq/kdb/etc are doing tricks with
> temporary rising console_loglevel while printing their messages.
> And in result it not only may print unwanted messages from other CPUs,
> but also omit printing at all in the unlucky case where the printk()
> was deferred.
> 
> Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
> an easier approach than introducing more printk buffers.
> Also, it will consolidate printings with headers.
> 
> Add log level argument to printk_address() as a preparation to introduce
> show_stack_loglvl().
> 
> As a good side-effect show_fault_oops() now prints the address with
> KERN_EMREG as the rest of output, making sure there won't be situation
> where "PC: " is printed without actual address.
> 
> --- a/arch/sh/include/asm/kdebug.h
> +++ b/arch/sh/include/asm/kdebug.h
> @@ -12,7 +12,8 @@ enum die_val {
>  };
>  
>  /* arch/sh/kernel/dumpstack.c */
> -extern void printk_address(unsigned long address, int reliable);
> +extern void printk_address(unsigned long address, int reliable,
> +			   const char *loglvl);
>  extern void dump_mem(const char *str, const char *loglvl,
>  		     unsigned long bottom, unsigned long top);
>  
> ...
>
> --- a/arch/sh/mm/fault.c
> +++ b/arch/sh/mm/fault.c
> @@ -196,7 +196,7 @@ show_fault_oops(struct pt_regs *regs, unsigned long address)
>  
>  	printk(KERN_CONT " at %08lx\n", address);
>  	printk(KERN_ALERT "PC:");
> -	printk_address(regs->pc, 1);
> +	printk_address(regs->pc, 1, KERN_ALERT);
>  

It would be more intuitive to do

	printk_address(KERN_ALERT, regs->pc, 1);

because the loglevel always comes first.

I guess it doesn't matter much, as sh seems to be rather dead.