Messages in this thread Patch in this message | | | Date | Sun, 17 Jan 2010 17:26:53 -0800 | From | "H. Peter Anvin" <> | Subject | RFC: deprecate CONFIG_X86_CPU_DEBUG and schedule it for rapid removal |
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CONFIG_X86_CPU_DEBUG really seems to be causing more problems than it ever solved. This is an RFC for immediately deprecating it, and schedule it for removal in the 2.6.34 cycle.
If this was a high value feature, it would be different -- but it's not even close.
Posting this as an RFC just on the offchance someone actually depends on this.
-hpa
-- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.
From 0a7c8171aa6d0aed1eda3902f675eb9a259d4cde Mon Sep 17 00:00:00 2001 From: H. Peter Anvin <hpa@zytor.com> Date: Sun, 17 Jan 2010 17:05:59 -0800 Subject: [PATCH] x86: Mark CONFIG_X86_CPU_DEBUG for rapid deprecation MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit
The CONFIG_X86_CPU_DEBUG feature provides for a filesystem view of some x86 CPU state in debugfs. However, all this information is already available to userspace via dedicated interfaces, and this could just as easily be done in pure userspace.
It wouldn't be a problem, per se, except that this code has caused boot failures in real-world scenarios when people have enabled it, see for example kernel bugzilla 15075.
This is a good example of why this kind of functionality has no business being in the kernel in the first place.
Mark this code deprecated and schedule it for rapid removal.
Reported-by: Ozan Çağlayan <ozan@pardus.org.tr> Signed-Off-By: H. Peter Anvin <hpa@zytor.com> LKML-Reference: <4B4F1DE7.307@pardus.org.tr> Cc: Jaswinder Singh Rajput <jaswinder@kernel.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> --- Documentation/feature-removal-schedule.txt | 9 +++++++++ arch/x86/Kconfig | 9 ++++++++- 2 files changed, 17 insertions(+), 1 deletions(-)
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt index 870d190..49aabf1 100644 --- a/Documentation/feature-removal-schedule.txt +++ b/Documentation/feature-removal-schedule.txt @@ -493,3 +493,12 @@ Why: These two features use non-standard interfaces. There are the Who: Corentin Chary <corentin.chary@gmail.com> ---------------------------- + +What: Support for x86 debug information via debugfs (CONFIG_X86_CPU_DEBUG) +When: 2.6.34 +Why: This feature does not introduce any functionality that is not + available through pure userspace. However, it has been known + to causeboot failures in some hardware configurations. + +Who: H. Peter Anvin <hpa@zytor.com> + diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 3b2a5ac..eb1751d 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -987,11 +987,18 @@ config X86_CPUID /dev/cpu/31/cpuid. config X86_CPU_DEBUG - tristate "/sys/kernel/debug/x86/cpu/* - CPU Debug support" + tristate "/sys/kernel/debug/x86/cpu/* - CPU Debug support (DEPRECATED)" ---help--- If you select this option, this will provide various x86 CPUs information through debugfs. + This feature is strongly deprecated. It has been known to cause + problems with some hardware configurations and does not + provide any functionality that is not available through pure + userspace means. It will be removed in the near future. + + It is strongly recommended that you select N here. + choice prompt "High Memory Support" default HIGHMEM4G if !X86_NUMAQ -- 1.6.2.5
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