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

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Message-ID: <CAPXgP11+j+fDexHHmAZbBBidtrydrpWeh3DGWOhkuoybNj9skA@mail.gmail.com>
Date:	Thu, 5 Jul 2012 13:47:26 +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 Thu, Jul 5, 2012 at 12:20 PM, Michael Neuling <mikey@...ling.org> wrote:

> I can only make 2) happen on SMP.  It's when the second CPU is coming up
> and it's printing something.  The first CPU isn't printing anything at
> this stage (there is no garbled console here) so I don't think it's a
> race.  I see it consistently in show_regs().  Every printk without a
> newline.  ie I get this:
> ---
> NIP: c000000000048164 LR: c000000000048160 CTR: 0000000000000000
> REGS: c00000007e59fb50 TRAP: 0700   Tainted: G        W     (3.5.0-rc5-mikey)
> MSR: 9000000000021032
> <
> SF
> ,HV
> ,ME
> ,IR
> ,DR
> ,RI
>>
>   CR: 28000042  XER: 22000000
> SOFTE: 0
> CFAR: c0000000007402f8
> TASK = c00000007e56bb40[0] 'swapper/1' THREAD: c00000007e59c000
>  CPU: 1
> ---
>
> It's consistent for printks without newlines in show_regs().  MSR
> through to XER should all be on the same line.

I see. Something to fix then, I'll have a look.

Does this happen only very early during bootup, or also later when the
box fully initialized?

The output of 'dmesg' later looks always correct, right?

Thanks,
Kay
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