/* *  linux/kernel/hrtimer.c * *  Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> *  Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar *  Copyright(C) 2006-2007  Timesys Corp., Thomas Gleixner * *  High-resolution kernel timers * *  In contrast to the low-resolution timeout API implemented in *  kernel/timer.c, hrtimers provide finer resolution and accuracy *  depending on system configuration and capabilities. * *  These timers are currently used for: *   - itimers *   - POSIX timers *   - nanosleep *   - precise in-kernel timing * *  Started by: Thomas Gleixner and Ingo Molnar * *  Credits: *	based on kernel/timer.c * *	Help, testing, suggestions, bugfixes, improvements were *	provided by: * *	George Anzinger, Andrew Morton, Steven Rostedt, Roman Zippel *	et. al. * *  For licencing details see kernel-base/COPYING */ #include <linux/cpu.h>#include <linux/module.h>#include <linux/percpu.h>#include <linux/hrtimer.h>#include <linux/notifier.h>#include <linux/syscalls.h>#include <linux/kallsyms.h>#include <linux/interrupt.h>#include <linux/tick.h>#include <linux/seq_file.h>#include <linux/err.h>#include <linux/debugobjects.h>#include <linux/sched.h>#include <linux/timer.h> #include <asm/uaccess.h> /** * ktime_get - get the monotonic time in ktime_t format * * returns the time in ktime_t format */ktime_t ktime_get(void){	struct timespec now; 	ktime_get_ts(&now); 	return timespec_to_ktime(now);}EXPORT_SYMBOL_GPL(ktime_get); /** * ktime_get_real - get the real (wall-) time in ktime_t format * * returns the time in ktime_t format */ktime_t ktime_get_real(void){	struct timespec now; 	getnstimeofday(&now); 	return timespec_to_ktime(now);} EXPORT_SYMBOL_GPL(ktime_get_real); /* * The timer bases: * * Note: If we want to add new timer bases, we have to skip the two * clock ids captured by the cpu-timers. We do this by holding empty * entries rather than doing math adjustment of the clock ids. * This ensures that we capture erroneous accesses to these clock ids * rather than moving them into the range of valid clock id's. */DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) ={ 	.clock_base =	{		{			.index = CLOCK_REALTIME,			.get_time = &ktime_get_real,			.resolution = KTIME_LOW_RES,		},		{			.index = CLOCK_MONOTONIC,			.get_time = &ktime_get,			.resolution = KTIME_LOW_RES,		},	}}; /** * ktime_get_ts - get the monotonic clock in timespec format * @ts:		pointer to timespec variable * * The function calculates the monotonic clock from the realtime * clock and the wall_to_monotonic offset and stores the result * in normalized timespec format in the variable pointed to by @ts. */void ktime_get_ts(struct timespec *ts){	struct timespec tomono;	unsigned long seq; 	do {		seq = read_seqbegin(&xtime_lock);		getnstimeofday(ts);		tomono = wall_to_monotonic; 	} while (read_seqretry(&xtime_lock, seq)); 	set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,				ts->tv_nsec + tomono.tv_nsec);}EXPORT_SYMBOL_GPL(ktime_get_ts); /* * Get the coarse grained time at the softirq based on xtime and * wall_to_monotonic. */static void hrtimer_get_softirq_time(struct hrtimer_cpu_base *base){	ktime_t xtim, tomono;	struct timespec xts, tom;	unsigned long seq; 	do {		seq = read_seqbegin(&xtime_lock);		xts = current_kernel_time();		tom = wall_to_monotonic;	} while (read_seqretry(&xtime_lock, seq)); 	xtim = timespec_to_ktime(xts);	tomono = timespec_to_ktime(tom);	base->clock_base[CLOCK_REALTIME].softirq_time = xtim;	base->clock_base[CLOCK_MONOTONIC].softirq_time =		ktime_add(xtim, tomono);} /* * Functions and macros which are different for UP/SMP systems are kept in a * single place */#ifdef CONFIG_SMP /* * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock * means that all timers which are tied to this base via timer->base are * locked, and the base itself is locked too. * * So __run_timers/migrate_timers can safely modify all timers which could * be found on the lists/queues. * * When the timer's base is locked, and the timer removed from list, it is * possible to set timer->base = NULL and drop the lock: the timer remains * locked. */staticstruct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,					     unsigned long *flags){	struct hrtimer_clock_base *base; 	for (;;) {		base = timer->base;		if (likely(base != NULL)) {			spin_lock_irqsave(&base->cpu_base->lock, *flags);			if (likely(base == timer->base))				return base;			/* The timer has migrated to another CPU: */			spin_unlock_irqrestore(&base->cpu_base->lock, *flags);		}		cpu_relax();	}} /* * Switch the timer base to the current CPU when possible. */static inline struct hrtimer_clock_base *switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,		    int pinned){	struct hrtimer_clock_base *new_base;	struct hrtimer_cpu_base *new_cpu_base;	int cpu, preferred_cpu = -1; 	cpu = smp_processor_id();#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)	if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu)) {		preferred_cpu = get_nohz_load_balancer();		if (preferred_cpu >= 0)			cpu = preferred_cpu;	}#endif again:	new_cpu_base = &per_cpu(hrtimer_bases, cpu);	new_base = &new_cpu_base->clock_base[base->index]; 	if (base != new_base) {		/*		 * We are trying to schedule the timer on the local CPU.		 * However we can't change timer's base while it is running,		 * so we keep it on the same CPU. No hassle vs. reprogramming		 * the event source in the high resolution case. The softirq		 * code will take care of this when the timer function has		 * completed. There is no conflict as we hold the lock until		 * the timer is enqueued.		 */		if (unlikely(hrtimer_callback_running(timer)))			return base; 		/* See the comment in lock_timer_base() */		timer->base = NULL;		spin_unlock(&base->cpu_base->lock);		spin_lock(&new_base->cpu_base->lock); 		/* Optimized away for NOHZ=n SMP=n */		if (cpu == preferred_cpu) {			/* Calculate clock monotonic expiry time */#ifdef CONFIG_HIGH_RES_TIMERS			ktime_t expires = ktime_sub(hrtimer_get_expires(timer),							new_base->offset);#else			ktime_t expires = hrtimer_get_expires(timer);#endif 			/*			 * Get the next event on target cpu from the			 * clock events layer.			 * This covers the highres=off nohz=on case as well.			 */			ktime_t next = clockevents_get_next_event(cpu); 			ktime_t delta = ktime_sub(expires, next); 			/*			 * We do not migrate the timer when it is expiring			 * before the next event on the target cpu because			 * we cannot reprogram the target cpu hardware and			 * we would cause it to fire late.			 */			if (delta.tv64 < 0) {				cpu = smp_processor_id();				spin_unlock(&new_base->cpu_base->lock);				spin_lock(&base->cpu_base->lock);				timer->base = base;				goto again;			}		}		timer->base = new_base;	}	return new_base;} #else /* CONFIG_SMP */ static inline struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags){	struct hrtimer_clock_base *base = timer->base; 	spin_lock_irqsave(&base->cpu_base->lock, *flags); 	return base;} # define switch_hrtimer_base(t, b, p)	(b) #endif	/* !CONFIG_SMP */ /* * Functions for the union type storage format of ktime_t which are * too large for inlining: */#if BITS_PER_LONG < 64# ifndef CONFIG_KTIME_SCALAR/** * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable * @kt:		addend * @nsec:	the scalar nsec value to add * * Returns the sum of kt and nsec in ktime_t format */ktime_t ktime_add_ns(const ktime_t kt, u64 nsec){	ktime_t tmp; 	if (likely(nsec < NSEC_PER_SEC)) {		tmp.tv64 = nsec;	} else {		unsigned long rem = do_div(nsec, NSEC_PER_SEC); 		tmp = ktime_set((long)nsec, rem);	} 	return ktime_add(kt, tmp);} EXPORT_SYMBOL_GPL(ktime_add_ns); /** * ktime_sub_ns - Subtract a scalar nanoseconds value from a ktime_t variable * @kt:		minuend * @nsec:	the scalar nsec value to subtract * * Returns the subtraction of @nsec from @kt in ktime_t format */ktime_t ktime_sub_ns(const ktime_t kt, u64 nsec){	ktime_t tmp; 	if (likely(nsec < NSEC_PER_SEC)) {		tmp.tv64 = nsec;	} else {		unsigned long rem = do_div(nsec, NSEC_PER_SEC); 		tmp = ktime_set((long)nsec, rem);	} 	return ktime_sub(kt, tmp);} EXPORT_SYMBOL_GPL(ktime_sub_ns);# endif /* !CONFIG_KTIME_SCALAR */ /* * Divide a ktime value by a nanosecond value */u64 ktime_divns(const ktime_t kt, s64 div){	u64 dclc;	int sft = 0; 	dclc = ktime_to_ns(kt);	/* Make sure the divisor is less than 2^32: */	while (div >> 32) {		sft++;		div >>= 1;	}	dclc >>= sft;	do_div(dclc, (unsigned long) div); 	return dclc;}#endif /* BITS_PER_LONG >= 64 */ /* * Add two ktime values and do a safety check for overflow: */ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs){	ktime_t res = ktime_add(lhs, rhs); 	/*	 * We use KTIME_SEC_MAX here, the maximum timeout which we can	 * return to user space in a timespec:	 */	if (res.tv64 < 0 || res.tv64 < lhs.tv64 || res.tv64 < rhs.tv64)		res = ktime_set(KTIME_SEC_MAX, 0); 	return res;} EXPORT_SYMBOL_GPL(ktime_add_safe); #ifdef CONFIG_DEBUG_OBJECTS_TIMERS static struct debug_obj_descr hrtimer_debug_descr; /* * fixup_init is called when: * - an active object is initialized */static int hrtimer_fixup_init(void *addr, enum debug_obj_state state){	struct hrtimer *timer = addr; 	switch (state) {	case ODEBUG_STATE_ACTIVE:		hrtimer_cancel(timer);		debug_object_init(timer, &hrtimer_debug_descr);		return 1;	default:		return 0;	}} /* * fixup_activate is called when: * - an active object is activated * - an unknown object is activated (might be a statically initialized object) */static int hrtimer_fixup_activate(void *addr, enum debug_obj_state state){	switch (state) { 	case ODEBUG_STATE_NOTAVAILABLE:		WARN_ON_ONCE(1);		return 0; 	case ODEBUG_STATE_ACTIVE:		WARN_ON(1); 	default:		return 0;	}} /* * fixup_free is called when: * - an active object is freed */static int hrtimer_fixup_free(void *addr, enum debug_obj_state state){	struct hrtimer *timer = addr; 	switch (state) {	case ODEBUG_STATE_ACTIVE:		hrtimer_cancel(timer);		debug_object_free(timer, &hrtimer_debug_descr);		return 1;	default:		return 0;	}} static struct debug_obj_descr hrtimer_debug_descr = {	.name		= "hrtimer",	.fixup_init	= hrtimer_fixup_init,	.fixup_activate	= hrtimer_fixup_activate,	.fixup_free	= hrtimer_fixup_free,}; static inline void debug_hrtimer_init(struct hrtimer *timer){	debug_object_init(timer, &hrtimer_debug_descr);} static inline void debug_hrtimer_activate(struct hrtimer *timer){	debug_object_activate(timer, &hrtimer_debug_descr);} static inline void debug_hrtimer_deactivate(struct hrtimer *timer){	debug_object_deactivate(timer, &hrtimer_debug_descr);} static inline void debug_hrtimer_free(struct hrtimer *timer){	debug_object_free(timer, &hrtimer_debug_descr);} static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,			   enum hrtimer_mode mode); void hrtimer_init_on_stack(struct hrtimer *timer, clockid_t clock_id,			   enum hrtimer_mode mode){	debug_object_init_on_stack(timer, &hrtimer_debug_descr);	__hrtimer_init(timer, clock_id, mode);} void destroy_hrtimer_on_stack(struct hrtimer *timer){	debug_object_free(timer, &hrtimer_debug_descr);} #elsestatic inline void debug_hrtimer_init(struct hrtimer *timer) { }static inline void debug_hrtimer_activate(struct hrtimer *timer) { }static inline void debug_hrtimer_deactivate(struct hrtimer *timer) { }#endif /* High resolution timer related functions */#ifdef CONFIG_HIGH_RES_TIMERS /* * High resolution timer enabled ? */static int hrtimer_hres_enabled __read_mostly  = 1;

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