linux-kernel - Re: [RFC PATCH 0/3] Fix quiet console in pre-panic scenarios

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Message-ID: <20200316143517.651abbeb@gandalf.local.home>
Date:   Mon, 16 Mar 2020 14:35:17 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Eugeniu Rosca <roscaeugeniu@...il.com>
Cc:     linux-kernel@...r.kernel.org, Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Jisheng Zhang <Jisheng.Zhang@...aptics.com>,
        Valdis Kletnieks <valdis.kletnieks@...edu>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Andrew Gabbasov <andrew_gabbasov@...tor.com>,
        Dirk Behme <dirk.behme@...bosch.com>,
        Eugeniu Rosca <erosca@...adit-jv.com>
Subject: Re: [RFC PATCH 0/3] Fix quiet console in pre-panic scenarios

On Sun, 15 Mar 2020 18:09:00 +0100
Eugeniu Rosca <roscaeugeniu@...il.com> wrote:

> Dear community,
> 
> The motivation behind this seris is to save days/weeks, if not months,
> of debugging efforts for users who:
> 
>  * experience an issue like softlockup/hardlockup/hung task/oom, whose
>    reproduction is not clear and whose occurrence rate is very low
>  * are constrained to use a low loglevel value (1,2,3) in production
>  * mostly rely on console logs to debug the issue post-mortem
>    (e.g. saved to persistent storage via e.g. pstore)
> 
> As pointed out in the last patch from this series, under the above
> circumstances, users might simply lack any relevant logs during
> post-mortem analysis.
> 
> Why this series is marked as RFC is because:
>  * There are several possible approaches to turn console verbosity on
>    and off. Current series employs the 'ignore_loglevel' functionality,
>    but an alternative way is to use the 'console_loglevel' variable. The
>    latter is more intrusive, hence the former has been chosen as v1.
>  * Manipulating 'ignore_loglevel' might be seen as an abuse, especially
>    because it breaks the expectation of users who assume the system to
>    be dead silent after passing loglevel=0 on kernel command line.
> 
> Thank you for your comments!

I don't see any issues with this patch set. What do others think?

Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

[ Note, I only acked, and did not give a deep review of it ]

-- Steve

> 
> Eugeniu Rosca (3):
>   printk: convert ignore_loglevel to atomic_t
>   printk: add console_verbose_{start,end}
>   watchdog: Turn console verbosity on when reporting softlockup
> 
>  include/linux/printk.h | 10 ++++++++++
>  kernel/printk/printk.c | 30 ++++++++++++++++++++++++++----
>  kernel/watchdog.c      |  4 ++++
>  3 files changed, 40 insertions(+), 4 deletions(-)
>