linux-kernel - Re: [printk] fbc14616f4: BUG:kernel_reboot-without-warning_in_test

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Message-ID: <20170407152304.bkbceqmg3kxeqvur@hirez.programming.kicks-ass.net>
Date:   Fri, 7 Apr 2017 17:23:04 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Pavel Machek <pavel@....cz>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Jan Kara <jack@...e.cz>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Ye Xiaolong <xiaolong.ye@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Petr Mladek <pmladek@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, Len Brown <len.brown@...el.com>,
        linux-kernel@...r.kernel.org, lkp@...org
Subject: Re: [printk]  fbc14616f4:
 BUG:kernel_reboot-without-warning_in_test_stage

On Sat, Apr 08, 2017 at 12:13:06AM +0900, Sergey Senozhatsky wrote:
> On (04/07/17 14:44), Pavel Machek wrote:
> [..]
> > > [..]
> > > > I believe "spend at most 2 seconds in printk(), then print a warning
> > > > and offload" is a solution closer to what we had before.
> > > 
> > > a warning here can be very noisy.
> > 
> > Well, on normally-configured it should be ok. We don't commonly see
> > printk problems... If it is too noisy, perhaps we should increase from
> > 2 seconds, but I don't think it will be problem.
> 
> we are looking at different typical setups :) serial console being 45
> seconds behind logbuf does not surprise me anymore.

That does sound like you're doing something wrong and should look at
reducing printk() more than anything else.