linux-kernel - Re: [RFC][PATCH] printk: increase devkmsg write() ratelimit

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Message-ID: <20181218172109.GK15430@hirez.programming.kicks-ass.net>
Date:   Tue, 18 Dec 2018 18:21:09 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Borislav Petkov <bp@...en8.de>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] printk: increase devkmsg write() ratelimit

On Wed, Dec 19, 2018 at 01:52:17AM +0900, Sergey Senozhatsky wrote:
> On (12/18/18 16:24), Borislav Petkov wrote:
> > On Wed, Dec 19, 2018 at 12:14:55AM +0900, Sergey Senozhatsky wrote:
> > > Right, but unlike log_buf_len, devkmsg is a bit close to a "binary" knob:
> > > either all messages or none;
> > 
> > ... which is perfectly fine for a debugging session.
> 
> But devkmsg ratelimits systemd errors, so one does not even know that
> "some debugging is required". For instance from my x86 box:
> 
>  Unmounting /home...
>  [..]
>  home.mount: Mount process exited, code=exited status=32
>  Failed unmounting /home.
> 
> I don't want to debug systemd, I want to know that something didn't
> work out. 10 messages max and 5 seconds interval looks a bit too strict.

Again, complain to system-doofus for printing so much crap to somewhere
it should not print to begin with.