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

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Message-ID: <20181218151455.GE665@tigerII.localdomain>
Date:   Wed, 19 Dec 2018 00:14:55 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        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 (12/18/18 16:03), Borislav Petkov wrote:
> On Tue, Dec 18, 2018 at 11:55:58PM +0900, Sergey Senozhatsky wrote:
> > Good question. Theoretically, there can be some interesting stuff.
> > Examples: https://bugzilla.redhat.com/show_bug.cgi?id=1515373#c6
> > or        https://github.com/systemd/systemd/issues/5433
> 
> Just like that last page says, people should use the printk.devkmsg=
> option when they wanna see all messages. Normally, we do add cmdline
> options to the kernel cmdline when debugging, like
> 
> debug ignore_loglevel log_buf_len=16M ...

Right, but unlike log_buf_len, devkmsg is a bit close to a "binary" knob:
either all messages or none; it's not like we can say "printk.devkmsg=100
messages per 5 * HZ max".

	-ss