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

From: Kay Sievers <kay@vrfy.org>
To: Michael Neuling <mikey@neuling.org>
Cc: linuxppc-dev@ozlabs.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
	Wu Fengguang <fengguang.wu@intel.com>,
	Joe Perches <joe@perches.com>,
	"Paul E. McKenney" <paulmck@us.ibm.com>
Subject: Re: [PATCH v3] printk: Have printk() never buffer its data
Date: Thu, 5 Jul 2012 13:47:26 +0200	[thread overview]
Message-ID: <CAPXgP11+j+fDexHHmAZbBBidtrydrpWeh3DGWOhkuoybNj9skA@mail.gmail.com> (raw)
In-Reply-To: <16043.1341483625@neuling.org>

On Thu, Jul 5, 2012 at 12:20 PM, Michael Neuling <mikey@neuling.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