From 28e7356f8f1767aafe4bec80430cb15ebabc97b7 Mon Sep 17 00:00:00 2001 From: Mike Galbraith Date: Sat, 11 Apr 2015 15:15:59 +0200 Subject: [PATCH] rt, nohz_full: fix nohz_full for PREEMPT_RT_FULL A task being ticked and trying to shut the tick down will fail due to having just awakened ksoftirqd, subtract it from nr_running. Signed-off-by: Mike Galbraith Signed-off-by: Sebastian Andrzej Siewior --- kernel/sched/core.c | 17 ++++++++++++++++- kernel/time/tick-sched.c | 5 +++++ 2 files changed, 21 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 43da2422df47..96f5efaeebea 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -742,14 +742,29 @@ static inline bool got_nohz_idle_kick(void) #endif /* CONFIG_NO_HZ_COMMON */ #ifdef CONFIG_NO_HZ_FULL + +static int ksoftirqd_running(void) +{ + struct task_struct *softirqd; + + if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL)) + return 0; + softirqd = this_cpu_ksoftirqd(); + if (softirqd && softirqd->on_rq) + return 1; + return 0; +} + bool sched_can_stop_tick(void) { /* * More than one running task need preemption. * nr_running update is assumed to be visible * after IPI is sent from wakers. + * + * NOTE, RT: if ksoftirqd is awake, subtract it. */ - if (this_rq()->nr_running > 1) + if (this_rq()->nr_running - ksoftirqd_running() > 1) return false; return true; diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 59eaf1b274f2..dfcd6f27e621 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -227,7 +227,12 @@ void __tick_nohz_full_check(void) static void nohz_full_kick_work_func(struct irq_work *work) { + unsigned long flags; + + /* ksoftirqd processes sirqs with interrupts enabled */ + local_irq_save(flags); __tick_nohz_full_check(); + local_irq_restore(flags); } static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = { -- 2.39.2