linux-kernel - Re: [PATCH] x86-64: Disable local APIC timer use on AMD systems with C1E

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Date:	Tue, 25 Sep 2007 22:55:04 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...l.org>,
	Linus Torvalds <torvalds@...l.org>, Andi Kleen <ak@...e.de>,
	Chuck Ebbert <cebbert@...hat.com>,
	Dave Jones <davej@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Len Brown <lenb@...nel.org>,
	"Langsdorf, Mark" <mark.langsdorf@....com>
Subject: Re: [PATCH] x86-64: Disable local APIC timer use on AMD systems with C1E

On Tuesday, 25 September 2007 21:37, Thomas Gleixner wrote:
> commit 3556ddfa9284a86a59a9b78fe5894430f6ab4eef titled
> 
>  [PATCH] x86-64: Disable local APIC timer use on AMD systems with C1E
> 
> solves a problem with AMD dual core laptops e.g. HP nx6325 (Turion 64
> X2) with C1E enabled:
> 
> When both cores go into idle at the same time, then the system switches
> into C1E state, which is basically the same as C3. This stops the local
> apic timer.
> 
> This was debugged right after the dyntick merge on i386 and despite the
> patch title it fixes only the 32 bit path.
> 
> x86_64 is still missing this fix. It seems that mainline is not really
> affected by this issue, as the PIT is running and keeps jiffies
> incrementing, but that's just waiting for trouble. 
> 
> -mm suffers from this problem due to the x86_64 high resolution timer
> patches.
> 
> This is a quick and dirty port of the i386 code to x86_64. 
> 
> I spent quite a time with Rafael to debug the -mm / hrt wreckage until
> someone pointed us to this. I really had forgotten that we debugged this
> half a year ago already. 
> 
> Sigh, is it just me or is there something yelling arch/x86 into my ear?
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

I have reworked the patch a bit so that it applies on top of 2.6.23-rc8-mm1
and compiles (my version is attached).

With this patch applied, the kernel boots correctly on the nx6325.

Greetings,
Rafael

View attachment "x86-64-disable-local-APIC-timer-use-on-AMD-systems-with-C1E.patch" of type "text/x-diff" (2644 bytes)