The nohz full functionality depends on IRQ work to trigger its own interrupts. As it's used to restart the tick, we can't rely on the tick fallback for irq work callbacks, ie: we can't use the tick to restart the tick itself as it may well be completely stopped.
Lets reject the full dynticks initialization if that arch support isn't available. As a side effect, this makes sure that nohz kick is never called from the tick. Some lockup have been reported due to the kick trying to cancel the tick hrtimer from the tick itself, which of course doesn't work. Cc: Catalin Iacob <[email protected]> Cc: Dave Jones <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Signed-off-by: Frederic Weisbecker <[email protected]> --- include/linux/irq_work.h | 1 + kernel/time/tick-sched.c | 14 ++++++++++++++ 2 files changed, 15 insertions(+) diff --git a/include/linux/irq_work.h b/include/linux/irq_work.h index 708c895..cffdf47 100644 --- a/include/linux/irq_work.h +++ b/include/linux/irq_work.h @@ -33,6 +33,7 @@ void init_irq_work(struct irq_work *work, void (*func)(struct irq_work *)) #define DEFINE_IRQ_WORK(name, _f) struct irq_work name = { .func = (_f), } bool irq_work_queue(struct irq_work *work); +int arch_irq_work_has_own_interrupt(void); #ifdef CONFIG_SMP bool irq_work_queue_on(struct irq_work *work, int cpu); diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index eb4af01..767a081 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -365,6 +365,20 @@ void __init tick_nohz_init(void) return; } + /* + * Full dynticks uses irq work to drive the tick rescheduling on safe + * locking contexts. But then we need irq work to raise its own + * interrupts to avoid circular dependency on the tick + */ + if (!arch_irq_work_has_own_interrupt()) { + pr_warning("NO_HZ: Can't run full dynticks because arch doesn't " + "support irq work self-IPIs\n"); + cpumask_clear(tick_nohz_full_mask); + cpumask_copy(housekeeping_mask, cpu_possible_mask); + tick_nohz_full_running = false; + return; + } + cpu = smp_processor_id(); if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) { -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
