Commit 4e77ae3e authored Oct 12, 2007 by Thomas Gleixner Committed by Thomas Gleixner Oct 12, 2007

x86: Fix irq0 / local apic timer accounting



The clock events merge introduced a change to the nmi watchdog code to
handle the not longer increasing local apic timer count in the
broadcast mode. This is fine for UP, but on SMP it pampers over a
stuck CPU which is not handling the broadcast interrupt due to the
unconditional sum up of local apic timer count and irq0 count.

To cover all cases we need to keep track on which CPU irq0 is
handled. In theory this is CPU#0 due to the explicit disabling of irq
balancing for irq0, but there are systems which ignore this on the
hardware level. The per cpu irq0 accounting allows us to remove the
irq0 to CPU0 binding as well.

Add a per cpu counter for irq0 and evaluate this instead of the global
irq0 count in the nmi watchdog code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>

parent b8ce3359

arch/x86/kernel/nmi_64.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -329,7 +329,7 @@ int __kprobes nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
		touched = 1;
		}

		sum = read_pda(apic_timer_irqs);
		sum = read_pda(apic_timer_irqs) + read_pda(irq0_irqs);
		if (__get_cpu_var(nmi_touch)) {
		__get_cpu_var(nmi_touch) = 0;
		touched = 1;

arch/x86/kernel/time_64.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -194,6 +194,8 @@ static irqreturn_t timer_interrupt(int irq, void *dev_id)

		static irqreturn_t timer_event_interrupt(int irq, void *dev_id)
		{
		add_pda(irq0_irqs, 1);

		global_clock_event->event_handler(global_clock_event);

		return IRQ_HANDLED;

include/asm-x86/pda.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -29,6 +29,7 @@ struct x8664_pda {
		short isidle;
		struct mm_struct *active_mm;
		unsigned apic_timer_irqs;
		unsigned irq0_irqs;
		} ____cacheline_aligned_in_smp;

		extern struct x8664_pda *_cpu_pda[];

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