linux-kernel - Re: Linux 2.6.28-rc8

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Date:	Fri, 12 Dec 2008 09:24:56 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Frans Pop <elendil@...net.nl>, Eric Anholt <eric@...olt.net>,
	nix.or.die@...glemail.com, linux-kernel@...r.kernel.org,
	rjw@...k.pl, Arjan van de Ven <arjan@...radead.org>,
	Yinghai Lu <yinghai@...nel.org>
Subject: Re: Linux 2.6.28-rc8


* Pekka Enberg <penberg@...helsinki.fi> wrote:

> Hi Ingo,
> 
> On Thu, Dec 11, 2008 at 10:36 PM, Ingo Molnar <mingo@...e.hu> wrote:
> > ok. In this case i'd suggest we should just remove the warning. People do
> > get scared by needless kernel stack dumps - no matter whether it's marked
> > informational or not.
> >
> > So how about the patch below, queued up in tip/x86/debug? Arjan, what do
> > you think?
> 
> How come we don't put it under CONFIG_X86_DEBUG or something and hide 
> somewhere in the "Kernel debugging" menu?

okay - how about the following then instead - we still keep the warning, 
but do various things to make it appear less scary.

	Ingo

----------------->
>From 8808500f26a61757cb414da76b271bbd09d5958c Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@...e.hu>
Date: Fri, 12 Dec 2008 09:20:12 +0100
Subject: [PATCH] x86: soften multi-BAR mapping sanity check warning message

Impact: make debug warning less scary

The ioremap() time multi-BAR map warning has been causing false
positives:

  http://lkml.org/lkml/2008/12/10/432
  http://lkml.org/lkml/2008/12/11/136

So make it less scary by making it once-per-boot, by making it KERN_INFO
and by adding this text:

  "Info: mapping multiple BARs. Your kernel is fine."

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 arch/x86/mm/ioremap.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index d4c4307..bd85d42 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -223,7 +223,8 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
 	 * Check if the request spans more than any BAR in the iomem resource
 	 * tree.
 	 */
-	WARN_ON(iomem_map_sanity_check(phys_addr, size));
+	WARN_ONCE(iomem_map_sanity_check(phys_addr, size),
+		  KERN_INFO "Info: mapping multiple BARs. Your kernel is fine.");
 
 	/*
 	 * Don't allow anybody to remap normal RAM that we're using..

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