linux-kernel - [patch] Re: nohz and strange sleep latencies

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Message-ID: <20071125202557.GB7739@elf.ucw.cz>
Date:	Sun, 25 Nov 2007 21:25:57 +0100
From:	Pavel Machek <pavel@....cz>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ingo Molnar <mingo@...e.hu>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: [patch] Re: nohz and strange sleep latencies

Hi!

Okay, so the problem seems to be we are using unreliable lapic
timer... which is stopped in C3 (and in C2 on broken machines).

I do not see any mechanism to disable lapic; there seems to be some
mechanism to work around stopped lapic timer is used (in
acpi/processor_idle.c) but it does not seem to work. So what about
this?

							Pavel
Signed-off-by: Pavel Machek <pavel@...e.cz>

diff --git a/arch/x86/kernel/apic_32.c b/arch/x86/kernel/apic_32.c
index 08b07c1..b9bf79c 100644
--- a/arch/x86/kernel/apic_32.c
+++ b/arch/x86/kernel/apic_32.c
@@ -63,8 +63,8 @@ static int enable_local_apic __initdata 
 static int local_apic_timer_verify_ok;
 /* Disable local APIC timer from the kernel commandline or via dmi quirk
    or using CPU MSR check */
-int local_apic_timer_disabled;
-/* Local APIC timer works in C2 */
+int local_apic_timer_disabled = 1;
+/* Local APIC timer works in C2: used in processor_idle.c  */
 int local_apic_timer_c2_ok;
 EXPORT_SYMBOL_GPL(local_apic_timer_c2_ok);
 

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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