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Commit 963e5d3b authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt
Browse files

powerpc: Make decrementer interrupt robust against offlined CPUs 



With some implementations, it is possible that a timer interrupt
occurs every few seconds on an offline CPU. In this case, just
re-arm the decrementer and return immediately

Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent ecb78ab6

arch/powerpc/kernel/time.c

+11 −4
Original line number Original line Diff line number Diff line
@@ -577,14 +577,21 @@ void timer_interrupt(struct pt_regs * regs) 
	struct clock_event_device *evt = &decrementer->event;

	struct clock_event_device *evt = &decrementer->event;

	u64 now;

	u64 now;





	/* Ensure a positive value is written to the decrementer, or else

	 * some CPUs will continue to take decrementer exceptions.

	 */

	set_dec(DECREMENTER_MAX);



	/* Some implementations of hotplug will get timer interrupts while

	 * offline, just ignore these

	 */

	if (!cpu_online(smp_processor_id()))

		return;



	trace_timer_interrupt_entry(regs);

	trace_timer_interrupt_entry(regs);





	__get_cpu_var(irq_stat).timer_irqs++;

	__get_cpu_var(irq_stat).timer_irqs++;





	/* Ensure a positive value is written to the decrementer, or else

	 * some CPUs will continuue to take decrementer exceptions */

	set_dec(DECREMENTER_MAX);



#if defined(CONFIG_PPC32) && defined(CONFIG_PMAC)

#if defined(CONFIG_PPC32) && defined(CONFIG_PMAC)

	if (atomic_read(&ppc_n_lost_interrupts) != 0)

	if (atomic_read(&ppc_n_lost_interrupts) != 0)

		do_IRQ(regs);

		do_IRQ(regs);