linux-kernel - Re: [PATCHv3 42/50] xtensa: Add loglvl to show

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Date:   Mon, 11 May 2020 22:45:34 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Dmitry Safonov <dima@...sta.com>,
        Andrew Morton <akpm@...ux-foundation.org>
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>,
        Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        linux-xtensa@...ux-xtensa.org
Subject: Re: [PATCHv3 42/50] xtensa: Add loglvl to show_trace()

Hi,

On Sat, Apr 18, 2020 at 09:19:36PM +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).
> 
> 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 show_trace() as a preparation for introducing
> show_stack_loglvl().
> 
> Cc: Chris Zankel <chris@...kel.net>
> Cc: Max Filippov <jcmvbkbc@...il.com>
> Cc: linux-xtensa@...ux-xtensa.org
> [1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
> Signed-off-by: Dmitry Safonov <dima@...sta.com>
> ---
>  arch/xtensa/kernel/traps.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
> index 0976e27b8d5d..c397a02457bc 100644
> --- a/arch/xtensa/kernel/traps.c
> +++ b/arch/xtensa/kernel/traps.c
> -void show_trace(struct task_struct *task, unsigned long *sp)
> +static void show_trace(struct task_struct *task, unsigned long *sp,
> +		       const char *loglvl)
>  {
>  	if (!sp)
>  		sp = stack_pointer(task);
>  
> -	pr_info("Call Trace:\n");
> -	walk_stackframe(sp, show_trace_cb, NULL);
> +	printk("%sCall Trace:\n", loglvl);
> +	walk_stackframe(sp, show_trace_cb, (void *)loglvl);
>  }
>  
>  #define STACK_DUMP_ENTRY_SIZE 4
> @@ -511,7 +515,7 @@ void show_stack(struct task_struct *task, unsigned long *sp)
>  	print_hex_dump(KERN_INFO, " ", DUMP_PREFIX_NONE,
>  		       STACK_DUMP_LINE_SIZE, STACK_DUMP_ENTRY_SIZE,
>  		       sp, len, false);
> -	show_trace(task, sp);
> +	show_trace(task, stack, KERN_INFO);

it should have been

	show_trace(task, sp, KERN_INFO);

Andrew, can you fold the following patch as a fixup please:


diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index f9217b6b45c8..efc3a29cde80 100644
--- a/arch/xtensa/kernel/traps.c
+++ b/arch/xtensa/kernel/traps.c
@@ -515,7 +515,7 @@ void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl)
 	print_hex_dump(loglvl, " ", DUMP_PREFIX_NONE,
 		       STACK_DUMP_LINE_SIZE, STACK_DUMP_ENTRY_SIZE,
 		       sp, len, false);
-	show_trace(task, stack, loglvl);
+	show_trace(task, sp, loglvl);
 }
 
 DEFINE_SPINLOCK(die_lock);
-- 
2.26.1


-- 
2.26.1


>  }
>  
>  DEFINE_SPINLOCK(die_lock);
> -- 
> 2.26.0
> 

-- 
Sincerely yours,
Mike.