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powerpc: Fix races with irq_work

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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>
This commit is contained in:
Benjamin Herrenschmidt 2014-01-14 17:11:39 +11:00
parent 30c826358d
commit 0215f7d8c5
1 changed files with 11 additions and 0 deletions
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11
arch/powerpc/kernel/time.c
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@ -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;
}