linux-kernel - Re: [PATCH 26/50] powerpc: Add show_stack

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Message-ID: <85528fea-48e3-627b-d497-dc58ed408f87@arista.com>
Date:   Wed, 6 Nov 2019 16:01:16 +0000
From:   Dmitry Safonov <dima@...sta.com>
To:     Michael Ellerman <mpe@...erman.id.au>, 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>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 26/50] powerpc: Add show_stack_loglvl()

On 11/6/19 9:52 AM, Michael Ellerman wrote:
> Dmitry Safonov <dima@...sta.com> writes:
>> 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).
> 
> Yes, I've had bug reports where the stacktrace is missing, which is
> annoying. Thanks for trying to fix the problem.
> 
>> 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.
>>
>> Introduce show_stack_loglvl(), that eventually will substitute
>> show_stack().
>>
>> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>> Cc: Michael Ellerman <mpe@...erman.id.au>
>> Cc: Paul Mackerras <paulus@...ba.org>
>> Cc: linuxppc-dev@...ts.ozlabs.org
>> [1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
>> Signed-off-by: Dmitry Safonov <dima@...sta.com>
>> ---
>>  arch/powerpc/kernel/process.c | 18 +++++++++++++-----
>>  1 file changed, 13 insertions(+), 5 deletions(-)
> 
> This looks good to me.
> 
> Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)

Thanks for the review and time!

-- 
          Dmitry