linux-kernel - Re: [PATCH v2] printk: make sure to print log on console.

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Message-ID: <20180619092629.55146df7@gandalf.local.home>
Date:   Tue, 19 Jun 2018 09:26:29 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Maninder Singh <maninder1.s@...sung.com>,
        sergey.senozhatsky@...il.com, linux-kernel@...r.kernel.org,
        a.sahrawat@...sung.com, pankaj.m@...sung.com, v.narang@...sung.com
Subject: Re: [PATCH v2] printk: make sure to print log on console.

On Tue, 19 Jun 2018 18:49:53 +0900
Sergey Senozhatsky <sergey.senozhatsky.work@...il.com> wrote:

> On (06/19/18 11:32), Petr Mladek wrote:
> > > -               if (suppress_message_printing(msg->level)) {
> > > +               if (!ignore_loglevel && (msg->flags & LOG_NOCONS)) {
> > > 
> > > 
> > > `ignore_loglevel' is a module param and can change any time via
> > > 	/sys/module/printk/parameters/ignore_loglevel
> > > we need to respect its value.  
> > 
> > I would prefer to keep the patch as is. I see it the following way.
> > 
> > Also console_loglevel can be changed anytime by /proc/sys/kernel/printk.
> > The patch basically moves the decision about the message visibility from
> > console_unlock() to vprintk_emit(). The logic is easier when all
> > aspects are handled in a single location and only once.  
> 
> But when I set /sys/module/printk/parameters/ignore_loglevel I naturally
> expect it to take an immediate action. Without waiting for the consoles
> to catch up and to discard N messages [if the consoles were behind the
> logbuf head].
>

It's not that critical to have that change take immediate effect. It's
not a common operation, and I doubt anyone (but perhaps you ;-) will
even notice any difference.

-- Steve