diff options
Diffstat (limited to 'kernel/time/tick-sched.c')
| -rw-r--r-- | kernel/time/tick-sched.c | 47 |
1 files changed, 45 insertions, 2 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 79c275f08b7d..57bb3fe5aaa3 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -112,7 +112,8 @@ static void tick_sched_do_timer(ktime_t now) * this duty, then the jiffies update is still serialized by * jiffies_lock. */ - if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) + if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE) + && !tick_nohz_extended_cpu(cpu)) tick_do_timer_cpu = cpu; #endif @@ -166,6 +167,25 @@ static int __init tick_nohz_extended_setup(char *str) } __setup("nohz_extended=", tick_nohz_extended_setup); +static int __cpuinit tick_nohz_cpu_down_callback(struct notifier_block *nfb, + unsigned long action, + void *hcpu) +{ + unsigned int cpu = (unsigned long)hcpu; + + switch (action & ~CPU_TASKS_FROZEN) { + case CPU_DOWN_PREPARE: + /* + * If we handle the timekeeping duty for full dynticks CPUs, + * we can't safely shutdown that CPU. + */ + if (have_nohz_extended_mask && tick_do_timer_cpu == cpu) + return -EINVAL; + break; + } + return NOTIFY_OK; +} + static int __init init_tick_nohz_extended(void) { cpumask_var_t online_nohz; @@ -174,6 +194,8 @@ static int __init init_tick_nohz_extended(void) if (!have_nohz_extended_mask) return 0; + cpu_notifier(tick_nohz_cpu_down_callback, 0); + if (!zalloc_cpumask_var(&online_nohz, GFP_KERNEL)) { pr_warning("NO_HZ: Not enough memory to check extended nohz mask\n"); return -ENOMEM; @@ -188,11 +210,17 @@ static int __init init_tick_nohz_extended(void) /* Ensure we keep a CPU outside the dynticks range for timekeeping */ cpumask_and(online_nohz, cpu_online_mask, nohz_extended_mask); if (cpumask_equal(online_nohz, cpu_online_mask)) { - cpu = cpumask_any(cpu_online_mask); pr_warning("NO_HZ: Must keep at least one online CPU " "out of nohz_extended range\n"); + /* + * We know the current CPU doesn't have its tick stopped. + * Let's use it for the timekeeping duty. + */ + preempt_disable(); + cpu = smp_processor_id(); pr_warning("NO_HZ: Clearing %d from nohz_extended range\n", cpu); cpumask_clear_cpu(cpu, nohz_extended_mask); + preempt_enable(); } put_online_cpus(); free_cpumask_var(online_nohz); @@ -551,6 +579,21 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) return false; } + if (have_nohz_extended_mask) { + /* + * Keep the tick alive to guarantee timekeeping progression + * if there are full dynticks CPUs around + */ + if (tick_do_timer_cpu == cpu) + return false; + /* + * Boot safety: make sure the timekeeping duty has been + * assigned before entering dyntick-idle mode, + */ + if (tick_do_timer_cpu == TICK_DO_TIMER_NONE) + return false; + } + return true; } |
