[PATCH] hrtimer: hrtimer core code

hrtimer subsystem core.  It is initialized at bootup and expired by the timer
interrupt, but is otherwise not utilized by any other subsystem yet.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 679 insertions, 0 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
new file mode 100644
index 000000000000..690efd9d9adf
--- /dev/null
+++ b/kernel/hrtimer.c
@@ -0,0 +1,679 @@
+/*
+ *  linux/kernel/hrtimer.c
+ *
+ *  Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
+ *  Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
+ *
+ *  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
+ *
+ *  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/interrupt.h>
+
+#include <asm/uaccess.h>
+
+/**
+ * ktime_get - get the monotonic time in ktime_t format
+ *
+ * returns the time in ktime_t format
+ */
+static ktime_t ktime_get(void)
+{
+        struct timespec now;
+
+        ktime_get_ts(&now);
+
+        return timespec_to_ktime(now);
+}
+
+/**
+ * ktime_get_real - get the real (wall-) time in ktime_t format
+ *
+ * returns the time in ktime_t format
+ */
+static 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:
+ */
+
+#define MAX_HRTIMER_BASES 2
+
+static DEFINE_PER_CPU(struct hrtimer_base, hrtimer_bases[MAX_HRTIMER_BASES]) =
+{
+        {
+                .index = CLOCK_REALTIME,
+                .get_time = &ktime_get_real,
+                .resolution = KTIME_REALTIME_RES,
+        },
+        {
+                .index = CLOCK_MONOTONIC,
+                .get_time = &ktime_get,
+                .resolution = KTIME_MONOTONIC_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);
+}
+
+/*
+ * Functions and macros which are different for UP/SMP systems are kept in a
+ * single place
+ */
+#ifdef CONFIG_SMP
+
+#define set_curr_timer(b, t)            do { (b)->curr_timer = (t); } while (0)
+
+/*
+ * 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.
+ */
+static struct hrtimer_base *lock_hrtimer_base(const struct hrtimer *timer,
+                                              unsigned long *flags)
+{
+        struct hrtimer_base *base;
+
+        for (;;) {
+                base = timer->base;
+                if (likely(base != NULL)) {
+                        spin_lock_irqsave(&base->lock, *flags);
+                        if (likely(base == timer->base))
+                                return base;
+                        /* The timer has migrated to another CPU: */
+                        spin_unlock_irqrestore(&base->lock, *flags);
+                }
+                cpu_relax();
+        }
+}
+
+/*
+ * Switch the timer base to the current CPU when possible.
+ */
+static inline struct hrtimer_base *
+switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_base *base)
+{
+        struct hrtimer_base *new_base;
+
+        new_base = &__get_cpu_var(hrtimer_bases[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(base->curr_timer == timer))
+                        return base;
+
+                /* See the comment in lock_timer_base() */
+                timer->base = NULL;
+                spin_unlock(&base->lock);
+                spin_lock(&new_base->lock);
+                timer->base = new_base;
+        }
+        return new_base;
+}
+
+#else /* CONFIG_SMP */
+
+#define set_curr_timer(b, t)            do { } while (0)
+
+static inline struct hrtimer_base *
+lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
+{
+        struct hrtimer_base *base = timer->base;
+
+        spin_lock_irqsave(&base->lock, *flags);
+
+        return base;
+}
+
+#define switch_hrtimer_base(t, b)       (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);
+}
+
+#else /* CONFIG_KTIME_SCALAR */
+
+# endif /* !CONFIG_KTIME_SCALAR */
+
+/*
+ * Divide a ktime value by a nanosecond value
+ */
+static unsigned long ktime_divns(const ktime_t kt, nsec_t div)
+{
+        u64 dclc, inc, dns;
+        int sft = 0;
+
+        dclc = dns = ktime_to_ns(kt);
+        inc = div;
+        /* Make sure the divisor is less than 2^32: */
+        while (div >> 32) {
+                sft++;
+                div >>= 1;
+        }
+        dclc >>= sft;
+        do_div(dclc, (unsigned long) div);
+
+        return (unsigned long) dclc;
+}
+
+#else /* BITS_PER_LONG < 64 */
+# define ktime_divns(kt, div)           (unsigned long)((kt).tv64 / (div))
+#endif /* BITS_PER_LONG >= 64 */
+
+/*
+ * Counterpart to lock_timer_base above:
+ */
+static inline
+void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
+{
+        spin_unlock_irqrestore(&timer->base->lock, *flags);
+}
+
+/**
+ * hrtimer_forward - forward the timer expiry
+ *
+ * @timer:      hrtimer to forward
+ * @interval:   the interval to forward
+ *
+ * Forward the timer expiry so it will expire in the future.
+ * The number of overruns is added to the overrun field.
+ */
+unsigned long
+hrtimer_forward(struct hrtimer *timer, const ktime_t interval)
+{
+        unsigned long orun = 1;
+        ktime_t delta, now;
+
+        now = timer->base->get_time();
+
+        delta = ktime_sub(now, timer->expires);
+
+        if (delta.tv64 < 0)
+                return 0;
+
+        if (unlikely(delta.tv64 >= interval.tv64)) {
+                nsec_t incr = ktime_to_ns(interval);
+
+                orun = ktime_divns(delta, incr);
+                timer->expires = ktime_add_ns(timer->expires, incr * orun);
+                if (timer->expires.tv64 > now.tv64)
+                        return orun;
+                /*
+                 * This (and the ktime_add() below) is the
+                 * correction for exact:
+                 */
+                orun++;
+        }
+        timer->expires = ktime_add(timer->expires, interval);
+
+        return orun;
+}
+
+/*
+ * enqueue_hrtimer - internal function to (re)start a timer
+ *
+ * The timer is inserted in expiry order. Insertion into the
+ * red black tree is O(log(n)). Must hold the base lock.
+ */
+static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
+{
+        struct rb_node **link = &base->active.rb_node;
+        struct list_head *prev = &base->pending;
+        struct rb_node *parent = NULL;
+        struct hrtimer *entry;
+
+        /*
+         * Find the right place in the rbtree:
+         */
+        while (*link) {
+                parent = *link;
+                entry = rb_entry(parent, struct hrtimer, node);
+                /*
+                 * We dont care about collisions. Nodes with
+                 * the same expiry time stay together.
+                 */
+                if (timer->expires.tv64 < entry->expires.tv64)
+                        link = &(*link)->rb_left;
+                else {
+                        link = &(*link)->rb_right;
+                        prev = &entry->list;
+                }
+        }
+
+        /*
+         * Insert the timer to the rbtree and to the sorted list:
+         */
+        rb_link_node(&timer->node, parent, link);
+        rb_insert_color(&timer->node, &base->active);
+        list_add(&timer->list, prev);
+
+        timer->state = HRTIMER_PENDING;
+}
+
+
+/*
+ * __remove_hrtimer - internal function to remove a timer
+ *
+ * Caller must hold the base lock.
+ */
+static void __remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
+{
+        /*
+         * Remove the timer from the sorted list and from the rbtree:
+         */
+        list_del(&timer->list);
+        rb_erase(&timer->node, &base->active);
+}
+
+/*
+ * remove hrtimer, called with base lock held
+ */
+static inline int
+remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
+{
+        if (hrtimer_active(timer)) {
+                __remove_hrtimer(timer, base);
+                timer->state = HRTIMER_INACTIVE;
+                return 1;
+        }
+        return 0;
+}
+
+/**
+ * hrtimer_start - (re)start an relative timer on the current CPU
+ *
+ * @timer:      the timer to be added
+ * @tim:        expiry time
+ * @mode:       expiry mode: absolute (HRTIMER_ABS) or relative (HRTIMER_REL)
+ *
+ * Returns:
+ *  0 on success
+ *  1 when the timer was active
+ */
+int
+hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
+{
+        struct hrtimer_base *base, *new_base;
+        unsigned long flags;
+        int ret;
+
+        base = lock_hrtimer_base(timer, &flags);
+
+        /* Remove an active timer from the queue: */
+        ret = remove_hrtimer(timer, base);
+
+        /* Switch the timer base, if necessary: */
+        new_base = switch_hrtimer_base(timer, base);
+
+        if (mode == HRTIMER_REL)
+                tim = ktime_add(tim, new_base->get_time());
+        timer->expires = tim;
+
+        enqueue_hrtimer(timer, new_base);
+
+        unlock_hrtimer_base(timer, &flags);
+
+        return ret;
+}
+
+/**
+ * hrtimer_try_to_cancel - try to deactivate a timer
+ *
+ * @timer:      hrtimer to stop
+ *
+ * Returns:
+ *  0 when the timer was not active
+ *  1 when the timer was active
+ * -1 when the timer is currently excuting the callback function and
+ *    can not be stopped
+ */
+int hrtimer_try_to_cancel(struct hrtimer *timer)
+{
+        struct hrtimer_base *base;
+        unsigned long flags;
+        int ret = -1;
+
+        base = lock_hrtimer_base(timer, &flags);
+
+        if (base->curr_timer != timer)
+                ret = remove_hrtimer(timer, base);
+
+        unlock_hrtimer_base(timer, &flags);
+
+        return ret;
+
+}
+
+/**
+ * hrtimer_cancel - cancel a timer and wait for the handler to finish.
+ *
+ * @timer:      the timer to be cancelled
+ *
+ * Returns:
+ *  0 when the timer was not active
+ *  1 when the timer was active
+ */
+int hrtimer_cancel(struct hrtimer *timer)
+{
+        for (;;) {
+                int ret = hrtimer_try_to_cancel(timer);
+
+                if (ret >= 0)
+                        return ret;
+        }
+}
+
+/**
+ * hrtimer_get_remaining - get remaining time for the timer
+ *
+ * @timer:      the timer to read
+ */
+ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
+{
+        struct hrtimer_base *base;
+        unsigned long flags;
+        ktime_t rem;
+
+        base = lock_hrtimer_base(timer, &flags);
+        rem = ktime_sub(timer->expires, timer->base->get_time());
+        unlock_hrtimer_base(timer, &flags);
+
+        return rem;
+}
+
+/**
+ * hrtimer_rebase - rebase an initialized hrtimer to a different base
+ *
+ * @timer:      the timer to be rebased
+ * @clock_id:   the clock to be used
+ */
+void hrtimer_rebase(struct hrtimer *timer, const clockid_t clock_id)
+{
+        struct hrtimer_base *bases;
+
+        bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
+        timer->base = &bases[clock_id];
+}
+
+/**
+ * hrtimer_init - initialize a timer to the given clock
+ *
+ * @timer:      the timer to be initialized
+ * @clock_id:   the clock to be used
+ */
+void hrtimer_init(struct hrtimer *timer, const clockid_t clock_id)
+{
+        memset(timer, 0, sizeof(struct hrtimer));
+        hrtimer_rebase(timer, clock_id);
+}
+
+/**
+ * hrtimer_get_res - get the timer resolution for a clock
+ *
+ * @which_clock: which clock to query
+ * @tp:          pointer to timespec variable to store the resolution
+ *
+ * Store the resolution of the clock selected by which_clock in the
+ * variable pointed to by tp.
+ */
+int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
+{
+        struct hrtimer_base *bases;
+
+        tp->tv_sec = 0;
+        bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
+        tp->tv_nsec = bases[which_clock].resolution;
+
+        return 0;
+}
+
+/*
+ * Expire the per base hrtimer-queue:
+ */
+static inline void run_hrtimer_queue(struct hrtimer_base *base)
+{
+        ktime_t now = base->get_time();
+
+        spin_lock_irq(&base->lock);
+
+        while (!list_empty(&base->pending)) {
+                struct hrtimer *timer;
+                int (*fn)(void *);
+                int restart;
+                void *data;
+
+                timer = list_entry(base->pending.next, struct hrtimer, list);
+                if (now.tv64 <= timer->expires.tv64)
+                        break;
+
+                fn = timer->function;
+                data = timer->data;
+                set_curr_timer(base, timer);
+                __remove_hrtimer(timer, base);
+                spin_unlock_irq(&base->lock);
+
+                /*
+                 * fn == NULL is special case for the simplest timer
+                 * variant - wake up process and do not restart:
+                 */
+                if (!fn) {
+                        wake_up_process(data);
+                        restart = HRTIMER_NORESTART;
+                } else
+                        restart = fn(data);
+
+                spin_lock_irq(&base->lock);
+
+                if (restart == HRTIMER_RESTART)
+                        enqueue_hrtimer(timer, base);
+                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]);
+}
+
+/*
+ * 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);
+}
+