Enqueuing a local timer after the tick has been stopped will result in the timer being ignored until the next random interrupt.
Perform sanity checks to report these situations. Reviewed-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com> Signed-off-by: Frederic Weisbecker <frede...@kernel.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Ingo Molnar <mi...@kernel.org> Cc: Paul E. McKenney <paul...@kernel.org> --- kernel/sched/core.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ca2bb629595f..24552911f92b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -674,6 +674,22 @@ int get_nohz_timer_target(void) return cpu; } +/* Make sure the timer won't be ignored in dynticks-idle case */ +static void wake_idle_assert_possible(void) +{ +#ifdef CONFIG_SCHED_DEBUG + /* + * Timers are re-evaluated after idle IRQs. In case of softirq, + * we assume IRQ tail. Ksoftirqd shouldn't reach here as the + * timer base wouldn't be idle. And inline softirq processing + * after a call to local_bh_enable() within idle loop sound too + * fun to be considered here. + */ + WARN_ONCE(in_task(), + "Late timer enqueue may be ignored\n"); +#endif +} + /* * When add_timer_on() enqueues a timer into the timer wheel of an * idle CPU then this timer might expire before the next timer event @@ -688,8 +704,10 @@ static void wake_up_idle_cpu(int cpu) { struct rq *rq = cpu_rq(cpu); - if (cpu == smp_processor_id()) + if (cpu == smp_processor_id()) { + wake_idle_assert_possible(); return; + } if (set_nr_and_not_polling(rq->idle)) smp_send_reschedule(cpu); -- 2.25.1