/* * sched_clock for unstable cpu clocks * *  Copyright (C) 2008 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> * *  Updates and enhancements: *    Copyright (C) 2008 Red Hat, Inc. Steven Rostedt <srostedt@redhat.com> * * Based on code by: *   Ingo Molnar <mingo@redhat.com> *   Guillaume Chazarain <guichaz@gmail.com> * * Create a semi stable clock from a mixture of other events, including: *  - gtod *  - sched_clock() *  - explicit idle events * * We use gtod as base and the unstable clock deltas. The deltas are filtered, * making it monotonic and keeping it within an expected window. * * Furthermore, explicit sleep and wakeup hooks allow us to account for time * that is otherwise invisible (TSC gets stopped). * * The clock: sched_clock_cpu() is monotonic per cpu, and should be somewhat * consistent between cpus (never more than 2 jiffies difference). */#include <linux/spinlock.h>#include <linux/hardirq.h>#include <linux/module.h>#include <linux/percpu.h>#include <linux/ktime.h>#include <linux/sched.h> /* * Scheduler clock - returns current time in nanosec units. * This is default implementation. * Architectures and sub-architectures can override this. */unsigned long long __attribute__((weak)) sched_clock(void){	return (unsigned long long)(jiffies - INITIAL_JIFFIES)					* (NSEC_PER_SEC / HZ);} static __read_mostly int sched_clock_running; #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK__read_mostly int sched_clock_stable; struct sched_clock_data {	u64			tick_raw;	u64			tick_gtod;	u64			clock;}; static DEFINE_PER_CPU_SHARED_ALIGNED(struct sched_clock_data, sched_clock_data); static inline struct sched_clock_data *this_scd(void){	return &__get_cpu_var(sched_clock_data);} static inline struct sched_clock_data *cpu_sdc(int cpu){	return &per_cpu(sched_clock_data, cpu);} void sched_clock_init(void){	u64 ktime_now = ktime_to_ns(ktime_get());	int cpu; 	for_each_possible_cpu(cpu) {		struct sched_clock_data *scd = cpu_sdc(cpu); 		scd->tick_raw = 0;		scd->tick_gtod = ktime_now;		scd->clock = ktime_now;	} 	sched_clock_running = 1;} /* * min, max except they take wrapping into account */ static inline u64 wrap_min(u64 x, u64 y){	return (s64)(x - y) < 0 ? x : y;} static inline u64 wrap_max(u64 x, u64 y){	return (s64)(x - y) > 0 ? x : y;} /* * update the percpu scd from the raw @now value * *  - 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){	u64 now, clock, old_clock, min_clock, max_clock;	s64 delta; again:	now = sched_clock();	delta = now - scd->tick_raw;	if (unlikely(delta < 0))		delta = 0; 	old_clock = scd->clock; 	/*	 * scd->clock = clamp(scd->tick_gtod + delta,	 *		      max(scd->tick_gtod, scd->clock),	 *		      scd->tick_gtod + TICK_NSEC);	 */ 	clock = scd->tick_gtod + delta;	min_clock = wrap_max(scd->tick_gtod, old_clock);	max_clock = wrap_max(old_clock, scd->tick_gtod + TICK_NSEC); 	clock = wrap_max(clock, min_clock);	clock = wrap_min(clock, max_clock); 	if (cmpxchg64(&scd->clock, old_clock, clock) != old_clock)		goto again; 	return clock;} static u64 sched_clock_remote(struct sched_clock_data *scd){	struct sched_clock_data *my_scd = this_scd();	u64 this_clock, remote_clock;	u64 *ptr, old_val, val; 	sched_clock_local(my_scd);again:	this_clock = my_scd->clock;	remote_clock = scd->clock; 	/*	 * Use the opportunity that we have both locks	 * taken to couple the two clocks: we take the	 * larger time as the latest time for both	 * runqueues. (this creates monotonic movement)	 */	if (likely((s64)(remote_clock - this_clock) < 0)) {		ptr = &scd->clock;		old_val = remote_clock;		val = this_clock;	} else {		/*		 * Should be rare, but possible:		 */		ptr = &my_scd->clock;		old_val = this_clock;		val = remote_clock;	} 	if (cmpxchg64(ptr, old_val, val) != old_val)		goto again; 	return val;} u64 sched_clock_cpu(int cpu){	struct sched_clock_data *scd;	u64 clock; 	WARN_ON_ONCE(!irqs_disabled()); 	if (sched_clock_stable)		return sched_clock(); 	if (unlikely(!sched_clock_running))		return 0ull; 	scd = cpu_sdc(cpu); 	if (cpu != smp_processor_id())		clock = sched_clock_remote(scd);	else		clock = sched_clock_local(scd); 	return clock;} void sched_clock_tick(void){	struct sched_clock_data *scd;	u64 now, now_gtod; 	if (sched_clock_stable)		return; 	if (unlikely(!sched_clock_running))		return; 	WARN_ON_ONCE(!irqs_disabled()); 	scd = this_scd();	now_gtod = ktime_to_ns(ktime_get());	now = sched_clock(); 	scd->tick_raw = now;	scd->tick_gtod = now_gtod;	sched_clock_local(scd);} /* * We are going deep-idle (irqs are disabled): */void sched_clock_idle_sleep_event(void){	sched_clock_cpu(smp_processor_id());}EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event); /* * We just idled delta nanoseconds (called with irqs disabled): */void sched_clock_idle_wakeup_event(u64 delta_ns){	if (timekeeping_suspended)		return; 	sched_clock_tick();	touch_softlockup_watchdog();}EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event); #else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ void sched_clock_init(void){	sched_clock_running = 1;} u64 sched_clock_cpu(int cpu){	if (unlikely(!sched_clock_running))		return 0; 	return sched_clock();} #endif /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ unsigned long long cpu_clock(int cpu){	unsigned long long clock;	unsigned long flags; 	local_irq_save(flags);	clock = sched_clock_cpu(cpu);	local_irq_restore(flags); 	return clock;}EXPORT_SYMBOL_GPL(cpu_clock);