linux-kernel - Re: [PATCHv3 11/50] c6x: Add show_stack

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Date:   Sun, 26 Apr 2020 10:06:06 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Joe Perches <joe@...ches.com>, Dmitry Safonov <dima@...sta.com>,
        linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <0x7f454c46@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        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>,
        Aurelien Jacquiot <jacquiot.aurelien@...il.com>,
        Mark Salter <msalter@...hat.com>, linux-c6x-dev@...ux-c6x.org
Subject: Re: [PATCHv3 11/50] c6x: Add show_stack_loglvl()

On 2020/04/26 3:18, Joe Perches wrote:
> On Sat, 2020-04-18 at 21:19 +0100, Dmitry Safonov 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).
> []
>> diff --git a/arch/c6x/kernel/traps.c b/arch/c6x/kernel/traps.c
> []
>> @@ -344,12 +344,13 @@ asmlinkage int process_exception(struct pt_regs *regs)
>>  
>>  static int kstack_depth_to_print = 48;
>>  
>> -static void show_trace(unsigned long *stack, unsigned long *endstack)
>> +static void show_trace(unsigned long *stack, unsigned long *endstack,
>> +		       const char *loglvl)
>>  {
>>  	unsigned long addr;
>>  	int i;
>>
>> -	pr_debug("Call trace:");
>> +	printk("%sCall trace:", loglvl);
> 
> These are not equivalent transforms as pr_debug
> is compiled to nothing unless DEBUG is defined
> or CONFIG_DYNAMIC_DEBUG is enabled.

I guess this user is expecting pr_debug() as unconditional printk(KERN_DEBUG), for
show_trace() and show_stack() will become waste of code if pr_debug() prints nothing.
If this user wants pr_debug() to be conditional, #ifdef'ing these functions is the better.

> 
> Perhaps all the conversions should be checked
> for these "not the same" object code changes.
>