diff options
Diffstat (limited to 'kernel/sched/clock.c')
| -rw-r--r-- | kernel/sched/clock.c | 78 |
1 files changed, 47 insertions, 31 deletions
diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index c3ae1446461..6bd6a6731b2 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -26,9 +26,10 @@ * at 0 on boot (but people really shouldn't rely on that). * * cpu_clock(i) -- can be used from any context, including NMI. - * sched_clock_cpu(i) -- must be used with local IRQs disabled (implied by NMI) * local_clock() -- is cpu_clock() on the current cpu. * + * sched_clock_cpu(i) + * * How: * * The implementation either uses sched_clock() when @@ -50,15 +51,6 @@ * Furthermore, explicit sleep and wakeup hooks allow us to account for time * that is otherwise invisible (TSC gets stopped). * - * - * Notes: - * - * The !IRQ-safetly of sched_clock() and sched_clock_cpu() comes from things - * like cpufreq interrupts that can change the base clock (TSC) multiplier - * and cause funny jumps in time -- although the filtering provided by - * sched_clock_cpu() should mitigate serious artifacts we cannot rely on it - * in general since for !CONFIG_HAVE_UNSTABLE_SCHED_CLOCK we fully rely on - * sched_clock(). */ #include <linux/spinlock.h> #include <linux/hardirq.h> @@ -66,6 +58,8 @@ #include <linux/percpu.h> #include <linux/ktime.h> #include <linux/sched.h> +#include <linux/static_key.h> +#include <linux/workqueue.h> /* * Scheduler clock - returns current time in nanosec units. @@ -82,7 +76,37 @@ EXPORT_SYMBOL_GPL(sched_clock); __read_mostly int sched_clock_running; #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK -__read_mostly int sched_clock_stable; +static struct static_key __sched_clock_stable = STATIC_KEY_INIT; + +int sched_clock_stable(void) +{ + if (static_key_false(&__sched_clock_stable)) + return false; + return true; +} + +void set_sched_clock_stable(void) +{ + if (!sched_clock_stable()) + static_key_slow_dec(&__sched_clock_stable); +} + +static void __clear_sched_clock_stable(struct work_struct *work) +{ + /* XXX worry about clock continuity */ + if (sched_clock_stable()) + static_key_slow_inc(&__sched_clock_stable); +} + +static DECLARE_WORK(sched_clock_work, __clear_sched_clock_stable); + +void clear_sched_clock_stable(void) +{ + if (keventd_up()) + schedule_work(&sched_clock_work); + else + __clear_sched_clock_stable(&sched_clock_work); +} struct sched_clock_data { u64 tick_raw; @@ -242,20 +266,20 @@ u64 sched_clock_cpu(int cpu) struct sched_clock_data *scd; u64 clock; - WARN_ON_ONCE(!irqs_disabled()); - - if (sched_clock_stable) + if (sched_clock_stable()) return sched_clock(); if (unlikely(!sched_clock_running)) return 0ull; + preempt_disable(); scd = cpu_sdc(cpu); if (cpu != smp_processor_id()) clock = sched_clock_remote(scd); else clock = sched_clock_local(scd); + preempt_enable(); return clock; } @@ -265,7 +289,7 @@ void sched_clock_tick(void) struct sched_clock_data *scd; u64 now, now_gtod; - if (sched_clock_stable) + if (sched_clock_stable()) return; if (unlikely(!sched_clock_running)) @@ -316,14 +340,10 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event); */ u64 cpu_clock(int cpu) { - u64 clock; - unsigned long flags; - - local_irq_save(flags); - clock = sched_clock_cpu(cpu); - local_irq_restore(flags); + if (static_key_false(&__sched_clock_stable)) + return sched_clock_cpu(cpu); - return clock; + return sched_clock(); } /* @@ -335,14 +355,10 @@ u64 cpu_clock(int cpu) */ u64 local_clock(void) { - u64 clock; - unsigned long flags; + if (static_key_false(&__sched_clock_stable)) + return sched_clock_cpu(raw_smp_processor_id()); - local_irq_save(flags); - clock = sched_clock_cpu(smp_processor_id()); - local_irq_restore(flags); - - return clock; + return sched_clock(); } #else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ @@ -362,12 +378,12 @@ u64 sched_clock_cpu(int cpu) u64 cpu_clock(int cpu) { - return sched_clock_cpu(cpu); + return sched_clock(); } u64 local_clock(void) { - return sched_clock_cpu(0); + return sched_clock(); } #endif /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ |