linux-kernel - Re: [PATCH v3] printk: Have printk() never buffer its data

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Message-ID: <CAPXgP12_F_H2XPpo2wFmb-u3jBdV__=h67R-LVYbqHuLh7tqLg@mail.gmail.com>
Date:	Fri, 6 Jul 2012 02:56:19 +0200
From:	Kay Sievers <kay@...y.org>
To:	Michael Neuling <mikey@...ling.org>
Cc:	linuxppc-dev@...abs.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Joe Perches <joe@...ches.com>,
	"Paul E. McKenney" <paulmck@...ibm.com>
Subject: Re: [PATCH v3] printk: Have printk() never buffer its data

On Fri, Jul 6, 2012 at 2:41 AM, Michael Neuling <mikey@...ling.org> wrote:

>> > Does this happen only very early during bootup, or also later when the
>> > box fully initialized?
>
> I'm seeing during boot but not later (xmon (ppc kernel debugger) doesn't
> see it if I do 'echo x > /proc/sysrq-trigger') .  I wouldn't say
> it's "very early boot".  It's a secondary CPU coming up and the primary
> is waiting for it.  We've already configured the console when this
> happens.

Sounds like an early boot console.

>> > The output of 'dmesg' later looks always correct, right?
>
> No, dmesg also has the extra new lines: eg
>
> <4>NIP: c00000000004e234 LR: c00000000004e230 CTR: 0000000000000000
> <4>REGS: c00000007c3b7b50 TRAP: 0700   Tainted: G        W     (3.5.0-rc4-mikey)
> <4>MSR: 9000000000021032
> <4><
> <4>SF
> <4>,HV
> <4>,ME
> <4>,IR
> <4>,DR
> <4>,RI
> <4>>
> <4>  CR: 28000042  XER: 22000000

Can you please paste the output of /dev/kmsg of this section? So we
can see the timestamps and what really went into the record buffer.

>> Could you possibly try this patch?
>
> Sorry, doesn't help.  It also reprints the entire boot log to the
> console once the console get inited.

Which is the normal behaviour to do that, right? We should not have
touched any of that logic.

Thanks,
Kay
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