From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ey0-f170.google.com (mail-ey0-f170.google.com [209.85.215.170]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 3C2592C0201 for ; Thu, 5 Jul 2012 22:50:35 +1000 (EST) Received: by eaal12 with SMTP id l12so3620787eaa.15 for ; Thu, 05 Jul 2012 05:50:32 -0700 (PDT) Message-ID: <1341492628.834.3.camel@mop> Subject: Re: [PATCH v3] printk: Have printk() never buffer its data From: Kay Sievers To: Michael Neuling Date: Thu, 05 Jul 2012 14:50:28 +0200 In-Reply-To: References: <1340651142.7037.2.camel@gandalf.stny.rr.com> <20120625150722.8cd4f45d.akpm@linux-foundation.org> <20120625235531.GB3652@kroah.com> <20120626002307.GA4389@kroah.com> <1340726856.977.6.camel@mop> <22482.1341471787@neuling.org> <16043.1341483625@neuling.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: Greg Kroah-Hartman , LKML , Steven Rostedt , "Paul E. McKenney" , linuxppc-dev@ozlabs.org, Joe Perches , Andrew Morton , Wu Fengguang , Linus Torvalds , Ingo Molnar List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2012-07-05 at 13:47 +0200, Kay Sievers wrote: > On Thu, Jul 5, 2012 at 12:20 PM, Michael Neuling 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? If it's an early printk issue like it looks like, where stuff got printed before we had any console registered, this might fix the issue you are seeing. Could you possibly try this patch? Thanks, Kay --- a/kernel/printk.c +++ b/kernel/printk.c @@ -1957,6 +1951,12 @@ skip: */ console_idx = log_next(console_idx); console_seq++; + /* + * We will get here again when we register a new + * CON_PRINTBUFFER console. Clear the flag so we + * will properly dump everything later. + */ + msg->flags &= ~LOG_NOCONS; goto skip; }