powerpc: Fix races with irq_work (0215f7d8) · Commits · 戴 / test

If we set irq_work on a processor and immediately afterward, before the irq work has a chance to be processed, we change the decrementer value, we can seriously delay the handling of that irq_work. Fix it by checking in a few places for pending irq work, first before changing the decrementer in decrementer_set_next_event() and after changing it in the same function and in timer_interrupt(). Signed-off-by:

Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/time.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -536,6 +536,9 @@ void timer_interrupt(struct pt_regs * regs)
		now = *next_tb - now;
		if (now <= DECREMENTER_MAX)
		set_dec((int)now);
		/* We may have raced with new irq work */
		if (test_irq_work_pending())
		set_dec(1);
		__get_cpu_var(irq_stat).timer_irqs_others++;
		}

		@@ -802,8 +805,16 @@ static void __init clocksource_init(void)
		static int decrementer_set_next_event(unsigned long evt,
		struct clock_event_device *dev)
		{
		/* Don't adjust the decrementer if some irq work is pending */
		if (test_irq_work_pending())
		return 0;
		__get_cpu_var(decrementers_next_tb) = get_tb_or_rtc() + evt;
		set_dec(evt);

		/* We may have raced with new irq work */
		if (test_irq_work_pending())
		set_dec(1);

		return 0;
		}

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