807 lines
18 KiB
C
807 lines
18 KiB
C
/*
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* linux/kernel/hrtimer.c
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*
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* Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
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* Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
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*
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* High-resolution kernel timers
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*
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* In contrast to the low-resolution timeout API implemented in
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* kernel/timer.c, hrtimers provide finer resolution and accuracy
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* depending on system configuration and capabilities.
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*
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* These timers are currently used for:
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* - itimers
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* - POSIX timers
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* - nanosleep
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* - precise in-kernel timing
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*
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* Started by: Thomas Gleixner and Ingo Molnar
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*
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* Credits:
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* based on kernel/timer.c
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*
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* For licencing details see kernel-base/COPYING
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*/
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#include <linux/cpu.h>
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#include <linux/module.h>
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#include <linux/percpu.h>
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#include <linux/hrtimer.h>
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#include <linux/notifier.h>
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#include <linux/syscalls.h>
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#include <linux/interrupt.h>
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#include <asm/uaccess.h>
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/**
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* ktime_get - get the monotonic time in ktime_t format
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*
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* returns the time in ktime_t format
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*/
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static ktime_t ktime_get(void)
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{
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struct timespec now;
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ktime_get_ts(&now);
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return timespec_to_ktime(now);
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}
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/**
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* ktime_get_real - get the real (wall-) time in ktime_t format
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*
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* returns the time in ktime_t format
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*/
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static ktime_t ktime_get_real(void)
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{
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struct timespec now;
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getnstimeofday(&now);
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return timespec_to_ktime(now);
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}
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EXPORT_SYMBOL_GPL(ktime_get_real);
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/*
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* The timer bases:
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*/
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#define MAX_HRTIMER_BASES 2
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static DEFINE_PER_CPU(struct hrtimer_base, hrtimer_bases[MAX_HRTIMER_BASES]) =
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{
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{
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.index = CLOCK_REALTIME,
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.get_time = &ktime_get_real,
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.resolution = KTIME_REALTIME_RES,
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},
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{
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.index = CLOCK_MONOTONIC,
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.get_time = &ktime_get,
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.resolution = KTIME_MONOTONIC_RES,
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},
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};
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/**
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* ktime_get_ts - get the monotonic clock in timespec format
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*
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* @ts: pointer to timespec variable
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*
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* The function calculates the monotonic clock from the realtime
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* clock and the wall_to_monotonic offset and stores the result
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* in normalized timespec format in the variable pointed to by ts.
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*/
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void ktime_get_ts(struct timespec *ts)
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{
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struct timespec tomono;
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unsigned long seq;
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do {
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seq = read_seqbegin(&xtime_lock);
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getnstimeofday(ts);
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tomono = wall_to_monotonic;
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} while (read_seqretry(&xtime_lock, seq));
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set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
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ts->tv_nsec + tomono.tv_nsec);
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}
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/*
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* Functions and macros which are different for UP/SMP systems are kept in a
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* single place
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*/
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#ifdef CONFIG_SMP
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#define set_curr_timer(b, t) do { (b)->curr_timer = (t); } while (0)
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/*
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* We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
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* means that all timers which are tied to this base via timer->base are
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* locked, and the base itself is locked too.
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*
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* So __run_timers/migrate_timers can safely modify all timers which could
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* be found on the lists/queues.
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*
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* When the timer's base is locked, and the timer removed from list, it is
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* possible to set timer->base = NULL and drop the lock: the timer remains
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* locked.
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*/
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static struct hrtimer_base *lock_hrtimer_base(const struct hrtimer *timer,
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unsigned long *flags)
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{
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struct hrtimer_base *base;
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for (;;) {
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base = timer->base;
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if (likely(base != NULL)) {
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spin_lock_irqsave(&base->lock, *flags);
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if (likely(base == timer->base))
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return base;
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/* The timer has migrated to another CPU: */
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spin_unlock_irqrestore(&base->lock, *flags);
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}
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cpu_relax();
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}
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}
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/*
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* Switch the timer base to the current CPU when possible.
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*/
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static inline struct hrtimer_base *
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switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_base *base)
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{
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struct hrtimer_base *new_base;
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new_base = &__get_cpu_var(hrtimer_bases[base->index]);
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if (base != new_base) {
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/*
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* We are trying to schedule the timer on the local CPU.
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* However we can't change timer's base while it is running,
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* so we keep it on the same CPU. No hassle vs. reprogramming
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* the event source in the high resolution case. The softirq
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* code will take care of this when the timer function has
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* completed. There is no conflict as we hold the lock until
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* the timer is enqueued.
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*/
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if (unlikely(base->curr_timer == timer))
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return base;
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/* See the comment in lock_timer_base() */
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timer->base = NULL;
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spin_unlock(&base->lock);
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spin_lock(&new_base->lock);
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timer->base = new_base;
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}
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return new_base;
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}
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#else /* CONFIG_SMP */
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#define set_curr_timer(b, t) do { } while (0)
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static inline struct hrtimer_base *
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lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
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{
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struct hrtimer_base *base = timer->base;
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spin_lock_irqsave(&base->lock, *flags);
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return base;
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}
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#define switch_hrtimer_base(t, b) (b)
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#endif /* !CONFIG_SMP */
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/*
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* Functions for the union type storage format of ktime_t which are
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* too large for inlining:
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*/
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#if BITS_PER_LONG < 64
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# ifndef CONFIG_KTIME_SCALAR
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/**
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* ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
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*
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* @kt: addend
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* @nsec: the scalar nsec value to add
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*
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* Returns the sum of kt and nsec in ktime_t format
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*/
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ktime_t ktime_add_ns(const ktime_t kt, u64 nsec)
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{
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ktime_t tmp;
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if (likely(nsec < NSEC_PER_SEC)) {
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tmp.tv64 = nsec;
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} else {
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unsigned long rem = do_div(nsec, NSEC_PER_SEC);
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tmp = ktime_set((long)nsec, rem);
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}
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return ktime_add(kt, tmp);
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}
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#else /* CONFIG_KTIME_SCALAR */
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# endif /* !CONFIG_KTIME_SCALAR */
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/*
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* Divide a ktime value by a nanosecond value
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*/
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static unsigned long ktime_divns(const ktime_t kt, nsec_t div)
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{
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u64 dclc, inc, dns;
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int sft = 0;
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dclc = dns = ktime_to_ns(kt);
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inc = div;
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/* Make sure the divisor is less than 2^32: */
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while (div >> 32) {
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sft++;
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div >>= 1;
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}
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dclc >>= sft;
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do_div(dclc, (unsigned long) div);
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return (unsigned long) dclc;
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}
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#else /* BITS_PER_LONG < 64 */
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# define ktime_divns(kt, div) (unsigned long)((kt).tv64 / (div))
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#endif /* BITS_PER_LONG >= 64 */
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/*
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* Counterpart to lock_timer_base above:
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*/
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static inline
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void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
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{
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spin_unlock_irqrestore(&timer->base->lock, *flags);
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}
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/**
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* hrtimer_forward - forward the timer expiry
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*
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* @timer: hrtimer to forward
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* @interval: the interval to forward
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*
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* Forward the timer expiry so it will expire in the future.
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* The number of overruns is added to the overrun field.
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*/
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unsigned long
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hrtimer_forward(struct hrtimer *timer, const ktime_t interval)
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{
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unsigned long orun = 1;
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ktime_t delta, now;
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now = timer->base->get_time();
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delta = ktime_sub(now, timer->expires);
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if (delta.tv64 < 0)
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return 0;
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if (unlikely(delta.tv64 >= interval.tv64)) {
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nsec_t incr = ktime_to_ns(interval);
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orun = ktime_divns(delta, incr);
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timer->expires = ktime_add_ns(timer->expires, incr * orun);
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if (timer->expires.tv64 > now.tv64)
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return orun;
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/*
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* This (and the ktime_add() below) is the
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* correction for exact:
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*/
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orun++;
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}
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timer->expires = ktime_add(timer->expires, interval);
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return orun;
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}
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/*
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* enqueue_hrtimer - internal function to (re)start a timer
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*
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* The timer is inserted in expiry order. Insertion into the
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* red black tree is O(log(n)). Must hold the base lock.
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*/
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static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
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{
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struct rb_node **link = &base->active.rb_node;
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struct list_head *prev = &base->pending;
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struct rb_node *parent = NULL;
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struct hrtimer *entry;
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/*
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* Find the right place in the rbtree:
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*/
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while (*link) {
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parent = *link;
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entry = rb_entry(parent, struct hrtimer, node);
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/*
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* We dont care about collisions. Nodes with
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* the same expiry time stay together.
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*/
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if (timer->expires.tv64 < entry->expires.tv64)
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link = &(*link)->rb_left;
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else {
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link = &(*link)->rb_right;
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prev = &entry->list;
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}
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}
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/*
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* Insert the timer to the rbtree and to the sorted list:
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*/
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rb_link_node(&timer->node, parent, link);
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rb_insert_color(&timer->node, &base->active);
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list_add(&timer->list, prev);
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timer->state = HRTIMER_PENDING;
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}
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/*
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* __remove_hrtimer - internal function to remove a timer
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*
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* Caller must hold the base lock.
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*/
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static void __remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
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{
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/*
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* Remove the timer from the sorted list and from the rbtree:
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*/
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list_del(&timer->list);
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rb_erase(&timer->node, &base->active);
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}
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/*
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* remove hrtimer, called with base lock held
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*/
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static inline int
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remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
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{
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if (hrtimer_active(timer)) {
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__remove_hrtimer(timer, base);
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timer->state = HRTIMER_INACTIVE;
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return 1;
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}
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return 0;
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}
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/**
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* hrtimer_start - (re)start an relative timer on the current CPU
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*
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* @timer: the timer to be added
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* @tim: expiry time
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* @mode: expiry mode: absolute (HRTIMER_ABS) or relative (HRTIMER_REL)
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*
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* Returns:
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* 0 on success
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* 1 when the timer was active
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*/
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int
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hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
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{
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struct hrtimer_base *base, *new_base;
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unsigned long flags;
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int ret;
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base = lock_hrtimer_base(timer, &flags);
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/* Remove an active timer from the queue: */
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ret = remove_hrtimer(timer, base);
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/* Switch the timer base, if necessary: */
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new_base = switch_hrtimer_base(timer, base);
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if (mode == HRTIMER_REL)
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tim = ktime_add(tim, new_base->get_time());
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timer->expires = tim;
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enqueue_hrtimer(timer, new_base);
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unlock_hrtimer_base(timer, &flags);
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return ret;
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}
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/**
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* hrtimer_try_to_cancel - try to deactivate a timer
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*
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* @timer: hrtimer to stop
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*
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* Returns:
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* 0 when the timer was not active
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* 1 when the timer was active
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* -1 when the timer is currently excuting the callback function and
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* can not be stopped
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*/
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int hrtimer_try_to_cancel(struct hrtimer *timer)
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{
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struct hrtimer_base *base;
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unsigned long flags;
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int ret = -1;
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base = lock_hrtimer_base(timer, &flags);
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if (base->curr_timer != timer)
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ret = remove_hrtimer(timer, base);
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unlock_hrtimer_base(timer, &flags);
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return ret;
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}
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/**
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* hrtimer_cancel - cancel a timer and wait for the handler to finish.
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*
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* @timer: the timer to be cancelled
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*
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* Returns:
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* 0 when the timer was not active
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* 1 when the timer was active
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*/
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int hrtimer_cancel(struct hrtimer *timer)
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{
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for (;;) {
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int ret = hrtimer_try_to_cancel(timer);
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if (ret >= 0)
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return ret;
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}
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}
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/**
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* hrtimer_get_remaining - get remaining time for the timer
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*
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* @timer: the timer to read
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*/
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ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
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{
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struct hrtimer_base *base;
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unsigned long flags;
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ktime_t rem;
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base = lock_hrtimer_base(timer, &flags);
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rem = ktime_sub(timer->expires, timer->base->get_time());
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unlock_hrtimer_base(timer, &flags);
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return rem;
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}
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/**
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* hrtimer_rebase - rebase an initialized hrtimer to a different base
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*
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* @timer: the timer to be rebased
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* @clock_id: the clock to be used
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*/
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void hrtimer_rebase(struct hrtimer *timer, const clockid_t clock_id)
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{
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struct hrtimer_base *bases;
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bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
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timer->base = &bases[clock_id];
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}
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/**
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* hrtimer_init - initialize a timer to the given clock
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*
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* @timer: the timer to be initialized
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* @clock_id: the clock to be used
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*/
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void hrtimer_init(struct hrtimer *timer, const clockid_t clock_id)
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{
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memset(timer, 0, sizeof(struct hrtimer));
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hrtimer_rebase(timer, clock_id);
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}
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/**
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* hrtimer_get_res - get the timer resolution for a clock
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*
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* @which_clock: which clock to query
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* @tp: pointer to timespec variable to store the resolution
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*
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* Store the resolution of the clock selected by which_clock in the
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* variable pointed to by tp.
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*/
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int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
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{
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struct hrtimer_base *bases;
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tp->tv_sec = 0;
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bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
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tp->tv_nsec = bases[which_clock].resolution;
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return 0;
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}
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/*
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* Expire the per base hrtimer-queue:
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*/
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static inline void run_hrtimer_queue(struct hrtimer_base *base)
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{
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ktime_t now = base->get_time();
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spin_lock_irq(&base->lock);
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while (!list_empty(&base->pending)) {
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struct hrtimer *timer;
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int (*fn)(void *);
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int restart;
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void *data;
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timer = list_entry(base->pending.next, struct hrtimer, list);
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if (now.tv64 <= timer->expires.tv64)
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break;
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fn = timer->function;
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data = timer->data;
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set_curr_timer(base, timer);
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__remove_hrtimer(timer, base);
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spin_unlock_irq(&base->lock);
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/*
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* fn == NULL is special case for the simplest timer
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* variant - wake up process and do not restart:
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*/
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if (!fn) {
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wake_up_process(data);
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restart = HRTIMER_NORESTART;
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} else
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restart = fn(data);
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spin_lock_irq(&base->lock);
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if (restart == HRTIMER_RESTART)
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enqueue_hrtimer(timer, base);
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|
else
|
|
timer->state = HRTIMER_EXPIRED;
|
|
}
|
|
set_curr_timer(base, NULL);
|
|
spin_unlock_irq(&base->lock);
|
|
}
|
|
|
|
/*
|
|
* Called from timer softirq every jiffy, expire hrtimers:
|
|
*/
|
|
void hrtimer_run_queues(void)
|
|
{
|
|
struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);
|
|
int i;
|
|
|
|
for (i = 0; i < MAX_HRTIMER_BASES; i++)
|
|
run_hrtimer_queue(&base[i]);
|
|
}
|
|
|
|
/*
|
|
* Sleep related functions:
|
|
*/
|
|
|
|
/**
|
|
* schedule_hrtimer - sleep until timeout
|
|
*
|
|
* @timer: hrtimer variable initialized with the correct clock base
|
|
* @mode: timeout value is abs/rel
|
|
*
|
|
* Make the current task sleep until @timeout is
|
|
* elapsed.
|
|
*
|
|
* You can set the task state as follows -
|
|
*
|
|
* %TASK_UNINTERRUPTIBLE - at least @timeout is guaranteed to
|
|
* pass before the routine returns. The routine will return 0
|
|
*
|
|
* %TASK_INTERRUPTIBLE - the routine may return early if a signal is
|
|
* delivered to the current task. In this case the remaining time
|
|
* will be returned
|
|
*
|
|
* The current task state is guaranteed to be TASK_RUNNING when this
|
|
* routine returns.
|
|
*/
|
|
static ktime_t __sched
|
|
schedule_hrtimer(struct hrtimer *timer, const enum hrtimer_mode mode)
|
|
{
|
|
/* fn stays NULL, meaning single-shot wakeup: */
|
|
timer->data = current;
|
|
|
|
hrtimer_start(timer, timer->expires, mode);
|
|
|
|
schedule();
|
|
hrtimer_cancel(timer);
|
|
|
|
/* Return the remaining time: */
|
|
if (timer->state != HRTIMER_EXPIRED)
|
|
return ktime_sub(timer->expires, timer->base->get_time());
|
|
else
|
|
return (ktime_t) {.tv64 = 0 };
|
|
}
|
|
|
|
static inline ktime_t __sched
|
|
schedule_hrtimer_interruptible(struct hrtimer *timer,
|
|
const enum hrtimer_mode mode)
|
|
{
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
|
|
return schedule_hrtimer(timer, mode);
|
|
}
|
|
|
|
static long __sched
|
|
nanosleep_restart(struct restart_block *restart, clockid_t clockid)
|
|
{
|
|
struct timespec __user *rmtp, tu;
|
|
void *rfn_save = restart->fn;
|
|
struct hrtimer timer;
|
|
ktime_t rem;
|
|
|
|
restart->fn = do_no_restart_syscall;
|
|
|
|
hrtimer_init(&timer, clockid);
|
|
|
|
timer.expires.tv64 = ((u64)restart->arg1 << 32) | (u64) restart->arg0;
|
|
|
|
rem = schedule_hrtimer_interruptible(&timer, HRTIMER_ABS);
|
|
|
|
if (rem.tv64 <= 0)
|
|
return 0;
|
|
|
|
rmtp = (struct timespec __user *) restart->arg2;
|
|
tu = ktime_to_timespec(rem);
|
|
if (rmtp && copy_to_user(rmtp, &tu, sizeof(tu)))
|
|
return -EFAULT;
|
|
|
|
restart->fn = rfn_save;
|
|
|
|
/* The other values in restart are already filled in */
|
|
return -ERESTART_RESTARTBLOCK;
|
|
}
|
|
|
|
static long __sched nanosleep_restart_mono(struct restart_block *restart)
|
|
{
|
|
return nanosleep_restart(restart, CLOCK_MONOTONIC);
|
|
}
|
|
|
|
static long __sched nanosleep_restart_real(struct restart_block *restart)
|
|
{
|
|
return nanosleep_restart(restart, CLOCK_REALTIME);
|
|
}
|
|
|
|
long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
|
|
const enum hrtimer_mode mode, const clockid_t clockid)
|
|
{
|
|
struct restart_block *restart;
|
|
struct hrtimer timer;
|
|
struct timespec tu;
|
|
ktime_t rem;
|
|
|
|
hrtimer_init(&timer, clockid);
|
|
|
|
timer.expires = timespec_to_ktime(*rqtp);
|
|
|
|
rem = schedule_hrtimer_interruptible(&timer, mode);
|
|
if (rem.tv64 <= 0)
|
|
return 0;
|
|
|
|
/* Absolute timers do not update the rmtp value: */
|
|
if (mode == HRTIMER_ABS)
|
|
return -ERESTARTNOHAND;
|
|
|
|
tu = ktime_to_timespec(rem);
|
|
|
|
if (rmtp && copy_to_user(rmtp, &tu, sizeof(tu)))
|
|
return -EFAULT;
|
|
|
|
restart = ¤t_thread_info()->restart_block;
|
|
restart->fn = (clockid == CLOCK_MONOTONIC) ?
|
|
nanosleep_restart_mono : nanosleep_restart_real;
|
|
restart->arg0 = timer.expires.tv64 & 0xFFFFFFFF;
|
|
restart->arg1 = timer.expires.tv64 >> 32;
|
|
restart->arg2 = (unsigned long) rmtp;
|
|
|
|
return -ERESTART_RESTARTBLOCK;
|
|
}
|
|
|
|
/*
|
|
* Functions related to boot-time initialization:
|
|
*/
|
|
static void __devinit init_hrtimers_cpu(int cpu)
|
|
{
|
|
struct hrtimer_base *base = per_cpu(hrtimer_bases, cpu);
|
|
int i;
|
|
|
|
for (i = 0; i < MAX_HRTIMER_BASES; i++) {
|
|
spin_lock_init(&base->lock);
|
|
INIT_LIST_HEAD(&base->pending);
|
|
base++;
|
|
}
|
|
}
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
|
|
static void migrate_hrtimer_list(struct hrtimer_base *old_base,
|
|
struct hrtimer_base *new_base)
|
|
{
|
|
struct hrtimer *timer;
|
|
struct rb_node *node;
|
|
|
|
while ((node = rb_first(&old_base->active))) {
|
|
timer = rb_entry(node, struct hrtimer, node);
|
|
__remove_hrtimer(timer, old_base);
|
|
timer->base = new_base;
|
|
enqueue_hrtimer(timer, new_base);
|
|
}
|
|
}
|
|
|
|
static void migrate_hrtimers(int cpu)
|
|
{
|
|
struct hrtimer_base *old_base, *new_base;
|
|
int i;
|
|
|
|
BUG_ON(cpu_online(cpu));
|
|
old_base = per_cpu(hrtimer_bases, cpu);
|
|
new_base = get_cpu_var(hrtimer_bases);
|
|
|
|
local_irq_disable();
|
|
|
|
for (i = 0; i < MAX_HRTIMER_BASES; i++) {
|
|
|
|
spin_lock(&new_base->lock);
|
|
spin_lock(&old_base->lock);
|
|
|
|
BUG_ON(old_base->curr_timer);
|
|
|
|
migrate_hrtimer_list(old_base, new_base);
|
|
|
|
spin_unlock(&old_base->lock);
|
|
spin_unlock(&new_base->lock);
|
|
old_base++;
|
|
new_base++;
|
|
}
|
|
|
|
local_irq_enable();
|
|
put_cpu_var(hrtimer_bases);
|
|
}
|
|
#endif /* CONFIG_HOTPLUG_CPU */
|
|
|
|
static int __devinit hrtimer_cpu_notify(struct notifier_block *self,
|
|
unsigned long action, void *hcpu)
|
|
{
|
|
long cpu = (long)hcpu;
|
|
|
|
switch (action) {
|
|
|
|
case CPU_UP_PREPARE:
|
|
init_hrtimers_cpu(cpu);
|
|
break;
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
case CPU_DEAD:
|
|
migrate_hrtimers(cpu);
|
|
break;
|
|
#endif
|
|
|
|
default:
|
|
break;
|
|
}
|
|
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
static struct notifier_block __devinitdata hrtimers_nb = {
|
|
.notifier_call = hrtimer_cpu_notify,
|
|
};
|
|
|
|
void __init hrtimers_init(void)
|
|
{
|
|
hrtimer_cpu_notify(&hrtimers_nb, (unsigned long)CPU_UP_PREPARE,
|
|
(void *)(long)smp_processor_id());
|
|
register_cpu_notifier(&hrtimers_nb);
|
|
}
|
|
|