linux-kernel - [PATCH 1/8] x86, apic.c: Disable irq0 if CPU enables ARAT for local apic timer

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Date:	Wed,  5 Oct 2011 09:39:12 -0700
From:	"Fenghua Yu" <fenghua.yu@...el.com>
To:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H Peter Anvin" <hpa@...or.com>,
	"Zwane Mwaikambo" <zwane@....linux.org.uk>,
	"Tony Luck" <tony.luck@...el.com>,
	"Asit K Mallick" <asit.k.mallick@...el.com>,
	"Suresh B Siddha" <suresh.b.siddha@...el.com>,
	"Len Brown" <lenb@...nel.org>
Cc:	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"Fenghua Yu" <fenghua.yu@...el.com>
Subject: [PATCH 1/8] x86, apic.c: Disable irq0 if CPU enables ARAT for local apic timer

From: Fenghua Yu <fenghua.yu@...el.com>

irq0 won't generate any interrupt after local apic timers is enabled and ARAT
is enabled. Disable irq0 in this case. Thus irq0 won't block BSP offline.

Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
---
 arch/x86/kernel/apic/apic.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 52fa563..8813acf 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -506,6 +506,7 @@ static DEFINE_PER_CPU(struct clock_event_device, lapic_events);
 static void __cpuinit setup_APIC_timer(void)
 {
 	struct clock_event_device *levt = &__get_cpu_var(lapic_events);
+	int cpu = smp_processor_id();
 
 	if (this_cpu_has(X86_FEATURE_ARAT)) {
 		lapic_clockevent.features &= ~CLOCK_EVT_FEAT_C3STOP;
@@ -517,6 +518,10 @@ static void __cpuinit setup_APIC_timer(void)
 	levt->cpumask = cpumask_of(smp_processor_id());
 
 	clockevents_register_device(levt);
+
+	/* irq0 won't be used any more if CPU supports ARAT feature. */
+	if (cpu == 0 && this_cpu_has(X86_FEATURE_ARAT))
+		disable_irq(0);
 }
 
 /*
-- 
1.6.0.3

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