diff options
Diffstat (limited to 'kernel/sched/clock.c')
| -rw-r--r-- | kernel/sched/clock.c | 174 |
1 files changed, 106 insertions, 68 deletions
diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index ca0f8fc945c6..f5e6dd6a6b3a 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -1,5 +1,6 @@ +// SPDX-License-Identifier: GPL-2.0-only /* - * sched_clock for unstable cpu clocks + * sched_clock() for unstable CPU clocks * * Copyright (C) 2008 Red Hat, Inc., Peter Zijlstra * @@ -11,7 +12,7 @@ * Guillaume Chazarain <guichaz@gmail.com> * * - * What: + * What this file implements: * * cpu_clock(i) provides a fast (execution time) high resolution * clock with bounded drift between CPUs. The value of cpu_clock(i) @@ -26,11 +27,11 @@ * at 0 on boot (but people really shouldn't rely on that). * * cpu_clock(i) -- can be used from any context, including NMI. - * local_clock() -- is cpu_clock() on the current cpu. + * local_clock() -- is cpu_clock() on the current CPU. * * sched_clock_cpu(i) * - * How: + * How it is implemented: * * The implementation either uses sched_clock() when * !CONFIG_HAVE_UNSTABLE_SCHED_CLOCK, which means in that case the @@ -40,7 +41,7 @@ * Otherwise it tries to create a semi stable clock from a mixture of other * clocks, including: * - * - GTOD (clock monotomic) + * - GTOD (clock monotonic) * - sched_clock() * - explicit idle events * @@ -52,38 +53,23 @@ * that is otherwise invisible (TSC gets stopped). * */ -#include <linux/spinlock.h> -#include <linux/hardirq.h> -#include <linux/export.h> -#include <linux/percpu.h> -#include <linux/ktime.h> -#include <linux/sched.h> -#include <linux/nmi.h> + #include <linux/sched/clock.h> -#include <linux/static_key.h> -#include <linux/workqueue.h> -#include <linux/compiler.h> -#include <linux/tick.h> -#include <linux/init.h> +#include "sched.h" /* * Scheduler clock - returns current time in nanosec units. * This is default implementation. * Architectures and sub-architectures can override this. */ -unsigned long long __weak sched_clock(void) +notrace unsigned long long __weak sched_clock(void) { return (unsigned long long)(jiffies - INITIAL_JIFFIES) * (NSEC_PER_SEC / HZ); } EXPORT_SYMBOL_GPL(sched_clock); -__read_mostly int sched_clock_running; - -void sched_clock_init(void) -{ - sched_clock_running = 1; -} +static DEFINE_STATIC_KEY_FALSE(sched_clock_running); #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK /* @@ -110,28 +96,28 @@ struct sched_clock_data { static DEFINE_PER_CPU_SHARED_ALIGNED(struct sched_clock_data, sched_clock_data); -static inline struct sched_clock_data *this_scd(void) +static __always_inline struct sched_clock_data *this_scd(void) { return this_cpu_ptr(&sched_clock_data); } -static inline struct sched_clock_data *cpu_sdc(int cpu) +notrace static inline struct sched_clock_data *cpu_sdc(int cpu) { return &per_cpu(sched_clock_data, cpu); } -int sched_clock_stable(void) +notrace int sched_clock_stable(void) { return static_branch_likely(&__sched_clock_stable); } -static void __scd_stamp(struct sched_clock_data *scd) +notrace static void __scd_stamp(struct sched_clock_data *scd) { scd->tick_gtod = ktime_get_ns(); scd->tick_raw = sched_clock(); } -static void __set_sched_clock_stable(void) +notrace static void __set_sched_clock_stable(void) { struct sched_clock_data *scd; @@ -166,7 +152,7 @@ static void __set_sched_clock_stable(void) * The only way to fully avoid random clock jumps is to boot with: * "tsc=unstable". */ -static void __sched_clock_work(struct work_struct *work) +notrace static void __sched_clock_work(struct work_struct *work) { struct sched_clock_data *scd; int cpu; @@ -192,7 +178,7 @@ static void __sched_clock_work(struct work_struct *work) static DECLARE_WORK(sched_clock_work, __sched_clock_work); -static void __clear_sched_clock_stable(void) +notrace static void __clear_sched_clock_stable(void) { if (!sched_clock_stable()) return; @@ -201,23 +187,46 @@ static void __clear_sched_clock_stable(void) schedule_work(&sched_clock_work); } -void clear_sched_clock_stable(void) +notrace void clear_sched_clock_stable(void) { __sched_clock_stable_early = 0; smp_mb(); /* matches sched_clock_init_late() */ - if (sched_clock_running == 2) + if (static_key_count(&sched_clock_running.key) == 2) __clear_sched_clock_stable(); } +notrace static void __sched_clock_gtod_offset(void) +{ + struct sched_clock_data *scd = this_scd(); + + __scd_stamp(scd); + __gtod_offset = (scd->tick_raw + __sched_clock_offset) - scd->tick_gtod; +} + +void __init sched_clock_init(void) +{ + /* + * Set __gtod_offset such that once we mark sched_clock_running, + * sched_clock_tick() continues where sched_clock() left off. + * + * Even if TSC is buggered, we're still UP at this point so it + * can't really be out of sync. + */ + local_irq_disable(); + __sched_clock_gtod_offset(); + local_irq_enable(); + + static_branch_inc(&sched_clock_running); +} /* * We run this as late_initcall() such that it runs after all built-in drivers, * notably: acpi_processor and intel_idle, which can mark the TSC as unstable. */ static int __init sched_clock_init_late(void) { - sched_clock_running = 2; + static_branch_inc(&sched_clock_running); /* * Ensure that it is impossible to not do a static_key update. * @@ -238,12 +247,12 @@ late_initcall(sched_clock_init_late); * min, max except they take wrapping into account */ -static inline u64 wrap_min(u64 x, u64 y) +static __always_inline u64 wrap_min(u64 x, u64 y) { return (s64)(x - y) < 0 ? x : y; } -static inline u64 wrap_max(u64 x, u64 y) +static __always_inline u64 wrap_max(u64 x, u64 y) { return (s64)(x - y) > 0 ? x : y; } @@ -254,13 +263,13 @@ static inline u64 wrap_max(u64 x, u64 y) * - filter out backward motion * - use the GTOD tick value to create a window to filter crazy TSC values */ -static u64 sched_clock_local(struct sched_clock_data *scd) +static __always_inline u64 sched_clock_local(struct sched_clock_data *scd) { u64 now, clock, old_clock, min_clock, max_clock, gtod; s64 delta; again: - now = sched_clock(); + now = sched_clock_noinstr(); delta = now - scd->tick_raw; if (unlikely(delta < 0)) delta = 0; @@ -281,13 +290,38 @@ again: clock = wrap_max(clock, min_clock); clock = wrap_min(clock, max_clock); - if (cmpxchg64(&scd->clock, old_clock, clock) != old_clock) + if (!raw_try_cmpxchg64(&scd->clock, &old_clock, clock)) goto again; return clock; } -static u64 sched_clock_remote(struct sched_clock_data *scd) +noinstr u64 local_clock_noinstr(void) +{ + u64 clock; + + if (static_branch_likely(&__sched_clock_stable)) + return sched_clock_noinstr() + __sched_clock_offset; + + if (!static_branch_likely(&sched_clock_running)) + return sched_clock_noinstr(); + + clock = sched_clock_local(this_scd()); + + return clock; +} + +u64 local_clock(void) +{ + u64 now; + preempt_disable_notrace(); + now = local_clock_noinstr(); + preempt_enable_notrace(); + return now; +} +EXPORT_SYMBOL_GPL(local_clock); + +static notrace u64 sched_clock_remote(struct sched_clock_data *scd) { struct sched_clock_data *my_scd = this_scd(); u64 this_clock, remote_clock; @@ -302,21 +336,21 @@ again: * cmpxchg64 below only protects one readout. * * We must reread via sched_clock_local() in the retry case on - * 32bit as an NMI could use sched_clock_local() via the + * 32-bit kernels as an NMI could use sched_clock_local() via the * tracer and hit between the readout of - * the low32bit and the high 32bit portion. + * the low 32-bit and the high 32-bit portion. */ this_clock = sched_clock_local(my_scd); /* - * We must enforce atomic readout on 32bit, otherwise the - * update on the remote cpu can hit inbetween the readout of - * the low32bit and the high 32bit portion. + * We must enforce atomic readout on 32-bit, otherwise the + * update on the remote CPU can hit in between the readout of + * the low 32-bit and the high 32-bit portion. */ remote_clock = cmpxchg64(&scd->clock, 0, 0); #else /* - * On 64bit the read of [my]scd->clock is atomic versus the - * update, so we can avoid the above 32bit dance. + * On 64-bit kernels the read of [my]scd->clock is atomic versus the + * update, so we can avoid the above 32-bit dance. */ sched_clock_local(my_scd); again: @@ -343,7 +377,7 @@ again: val = remote_clock; } - if (cmpxchg64(ptr, old_val, val) != old_val) + if (!try_cmpxchg64(ptr, &old_val, val)) goto again; return val; @@ -354,7 +388,7 @@ again: * * See cpu_clock(). */ -u64 sched_clock_cpu(int cpu) +notrace u64 sched_clock_cpu(int cpu) { struct sched_clock_data *scd; u64 clock; @@ -362,8 +396,8 @@ u64 sched_clock_cpu(int cpu) if (sched_clock_stable()) return sched_clock() + __sched_clock_offset; - if (unlikely(!sched_clock_running)) - return 0ull; + if (!static_branch_likely(&sched_clock_running)) + return sched_clock(); preempt_disable_notrace(); scd = cpu_sdc(cpu); @@ -378,27 +412,25 @@ u64 sched_clock_cpu(int cpu) } EXPORT_SYMBOL_GPL(sched_clock_cpu); -void sched_clock_tick(void) +notrace void sched_clock_tick(void) { struct sched_clock_data *scd; if (sched_clock_stable()) return; - if (unlikely(!sched_clock_running)) + if (!static_branch_likely(&sched_clock_running)) return; - WARN_ON_ONCE(!irqs_disabled()); + lockdep_assert_irqs_disabled(); scd = this_scd(); __scd_stamp(scd); sched_clock_local(scd); } -void sched_clock_tick_stable(void) +notrace void sched_clock_tick_stable(void) { - u64 gtod, clock; - if (!sched_clock_stable()) return; @@ -410,16 +442,14 @@ void sched_clock_tick_stable(void) * TSC to be unstable, any computation will be computing crap. */ local_irq_disable(); - gtod = ktime_get_ns(); - clock = sched_clock(); - __gtod_offset = (clock + __sched_clock_offset) - gtod; + __sched_clock_gtod_offset(); local_irq_enable(); } /* - * We are going deep-idle (irqs are disabled): + * We are going deep-idle (IRQs are disabled): */ -void sched_clock_idle_sleep_event(void) +notrace void sched_clock_idle_sleep_event(void) { sched_clock_cpu(smp_processor_id()); } @@ -428,7 +458,7 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event); /* * We just idled; resync with ktime. */ -void sched_clock_idle_wakeup_event(void) +notrace void sched_clock_idle_wakeup_event(void) { unsigned long flags; @@ -444,17 +474,25 @@ void sched_clock_idle_wakeup_event(void) } EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event); -#else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ +#else /* !CONFIG_HAVE_UNSTABLE_SCHED_CLOCK: */ + +void __init sched_clock_init(void) +{ + static_branch_inc(&sched_clock_running); + local_irq_disable(); + generic_sched_clock_init(); + local_irq_enable(); +} -u64 sched_clock_cpu(int cpu) +notrace u64 sched_clock_cpu(int cpu) { - if (unlikely(!sched_clock_running)) + if (!static_branch_likely(&sched_clock_running)) return 0; return sched_clock(); } -#endif /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ +#endif /* !CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ /* * Running clock - returns the time that has elapsed while a guest has been @@ -464,7 +502,7 @@ u64 sched_clock_cpu(int cpu) * On bare metal this function should return the same as local_clock. * Architectures and sub-architectures can override this. */ -u64 __weak running_clock(void) +notrace u64 __weak running_clock(void) { return local_clock(); } |