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 <b...@kernel.crashing.org>
---
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index afb1b56..b3dab20 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -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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