/*
* The timer bases:
*
- * There are more clockids then hrtimer bases. Thus, we index
+ * There are more clockids than hrtimer bases. Thus, we index
* into the timer bases by the hrtimer_base_type enum. When trying
* to reach a base using a clockid, hrtimer_clockid_to_base()
* is used to convert from clockid to the proper hrtimer_base_type.
*/
DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
{
-
.lock = __RAW_SPIN_LOCK_UNLOCKED(hrtimer_bases.lock),
+ .seq = SEQCNT_ZERO(hrtimer_bases.seq),
.clock_base =
{
{
.index = HRTIMER_BASE_MONOTONIC,
.clockid = CLOCK_MONOTONIC,
.get_time = &ktime_get,
- .resolution = KTIME_LOW_RES,
},
{
.index = HRTIMER_BASE_REALTIME,
.clockid = CLOCK_REALTIME,
.get_time = &ktime_get_real,
- .resolution = KTIME_LOW_RES,
},
{
.index = HRTIMER_BASE_BOOTTIME,
.clockid = CLOCK_BOOTTIME,
.get_time = &ktime_get_boottime,
- .resolution = KTIME_LOW_RES,
},
{
.index = HRTIMER_BASE_TAI,
.clockid = CLOCK_TAI,
.get_time = &ktime_get_clocktai,
- .resolution = KTIME_LOW_RES,
},
}
};
return hrtimer_clock_to_base_table[clock_id];
}
-
-/*
- * 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, mono, boot, tai;
- ktime_t off_real, off_boot, off_tai;
-
- mono = ktime_get_update_offsets_tick(&off_real, &off_boot, &off_tai);
- boot = ktime_add(mono, off_boot);
- xtim = ktime_add(mono, off_real);
- tai = ktime_add(mono, off_tai);
-
- base->clock_base[HRTIMER_BASE_REALTIME].softirq_time = xtim;
- base->clock_base[HRTIMER_BASE_MONOTONIC].softirq_time = mono;
- base->clock_base[HRTIMER_BASE_BOOTTIME].softirq_time = boot;
- base->clock_base[HRTIMER_BASE_TAI].softirq_time = tai;
-}
-
/*
* Functions and macros which are different for UP/SMP systems are kept in a
* single place
*/
#ifdef CONFIG_SMP
+/*
+ * We require the migration_base for lock_hrtimer_base()/switch_hrtimer_base()
+ * such that hrtimer_callback_running() can unconditionally dereference
+ * timer->base->cpu_base
+ */
+static struct hrtimer_cpu_base migration_cpu_base = {
+ .seq = SEQCNT_ZERO(migration_cpu_base),
+ .clock_base = { { .cpu_base = &migration_cpu_base, }, },
+};
+
+#define migration_base migration_cpu_base.clock_base[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
* 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.
+ * possible to set timer->base = &migration_base and drop the lock: the timer
+ * remains locked.
*/
static
struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
for (;;) {
base = timer->base;
- if (likely(base != NULL)) {
+ if (likely(base != &migration_base)) {
raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);
if (likely(base == timer->base))
return base;
#endif
}
+#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
+static inline
+struct hrtimer_cpu_base *get_target_base(struct hrtimer_cpu_base *base,
+ int pinned)
+{
+ if (pinned || !base->migration_enabled)
+ return base;
+ return &per_cpu(hrtimer_bases, get_nohz_timer_target());
+}
+#else
+static inline
+struct hrtimer_cpu_base *get_target_base(struct hrtimer_cpu_base *base,
+ int pinned)
+{
+ return base;
+}
+#endif
+
/*
- * Switch the timer base to the current CPU when possible.
+ * We switch the timer base to a power-optimized selected CPU target,
+ * if:
+ * - NO_HZ_COMMON is enabled
+ * - timer migration is enabled
+ * - the timer callback is not running
+ * - the timer is not the first expiring timer on the new target
+ *
+ * If one of the above requirements is not fulfilled we move the timer
+ * to the current CPU or leave it on the previously assigned CPU if
+ * the timer callback is currently running.
*/
static inline struct hrtimer_clock_base *
switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
int pinned)
{
+ struct hrtimer_cpu_base *new_cpu_base, *this_cpu_base;
struct hrtimer_clock_base *new_base;
- struct hrtimer_cpu_base *new_cpu_base;
- int this_cpu = smp_processor_id();
- int cpu = get_nohz_timer_target(pinned);
int basenum = base->index;
+ this_cpu_base = this_cpu_ptr(&hrtimer_bases);
+ new_cpu_base = get_target_base(this_cpu_base, pinned);
again:
- new_cpu_base = &per_cpu(hrtimer_bases, cpu);
new_base = &new_cpu_base->clock_base[basenum];
if (base != new_base) {
if (unlikely(hrtimer_callback_running(timer)))
return base;
- /* See the comment in lock_timer_base() */
- timer->base = NULL;
+ /* See the comment in lock_hrtimer_base() */
+ timer->base = &migration_base;
raw_spin_unlock(&base->cpu_base->lock);
raw_spin_lock(&new_base->cpu_base->lock);
- if (cpu != this_cpu && hrtimer_check_target(timer, new_base)) {
- cpu = this_cpu;
+ if (new_cpu_base != this_cpu_base &&
+ hrtimer_check_target(timer, new_base)) {
raw_spin_unlock(&new_base->cpu_base->lock);
raw_spin_lock(&base->cpu_base->lock);
+ new_cpu_base = this_cpu_base;
timer->base = base;
goto again;
}
timer->base = new_base;
} else {
- if (cpu != this_cpu && hrtimer_check_target(timer, new_base)) {
- cpu = this_cpu;
+ if (new_cpu_base != this_cpu_base &&
+ hrtimer_check_target(timer, new_base)) {
+ new_cpu_base = this_cpu_base;
goto again;
}
}
}
#if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS)
+static inline void hrtimer_update_next_timer(struct hrtimer_cpu_base *cpu_base,
+ struct hrtimer *timer)
+{
+#ifdef CONFIG_HIGH_RES_TIMERS
+ cpu_base->next_timer = timer;
+#endif
+}
+
static ktime_t __hrtimer_get_next_event(struct hrtimer_cpu_base *cpu_base)
{
struct hrtimer_clock_base *base = cpu_base->clock_base;
ktime_t expires, expires_next = { .tv64 = KTIME_MAX };
- int i;
+ unsigned int active = cpu_base->active_bases;
- for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
+ hrtimer_update_next_timer(cpu_base, NULL);
+ for (; active; base++, active >>= 1) {
struct timerqueue_node *next;
struct hrtimer *timer;
- next = timerqueue_getnext(&base->active);
- if (!next)
+ if (!(active & 0x01))
continue;
+ next = timerqueue_getnext(&base->active);
timer = container_of(next, struct hrtimer, node);
expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
- if (expires.tv64 < expires_next.tv64)
+ if (expires.tv64 < expires_next.tv64) {
expires_next = expires;
+ hrtimer_update_next_timer(cpu_base, timer);
+ }
}
/*
* clock_was_set() might have changed base->offset of any of
}
#endif
+static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
+{
+ ktime_t *offs_real = &base->clock_base[HRTIMER_BASE_REALTIME].offset;
+ ktime_t *offs_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset;
+ ktime_t *offs_tai = &base->clock_base[HRTIMER_BASE_TAI].offset;
+
+ return ktime_get_update_offsets_now(&base->clock_was_set_seq,
+ offs_real, offs_boot, offs_tai);
+}
+
/* High resolution timer related functions */
#ifdef CONFIG_HIGH_RES_TIMERS
* High resolution timer enabled ?
*/
static int hrtimer_hres_enabled __read_mostly = 1;
+unsigned int hrtimer_resolution __read_mostly = LOW_RES_NSEC;
+EXPORT_SYMBOL_GPL(hrtimer_resolution);
/*
* Enable / Disable high resolution mode
/*
* Is the high resolution mode active ?
*/
+static inline int __hrtimer_hres_active(struct hrtimer_cpu_base *cpu_base)
+{
+ return cpu_base->hres_active;
+}
+
static inline int hrtimer_hres_active(void)
{
- return __this_cpu_read(hrtimer_bases.hres_active);
+ return __hrtimer_hres_active(this_cpu_ptr(&hrtimer_bases));
}
/*
static void
hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
{
- ktime_t expires_next = __hrtimer_get_next_event(cpu_base);
+ ktime_t expires_next;
+
+ if (!cpu_base->hres_active)
+ return;
+
+ expires_next = __hrtimer_get_next_event(cpu_base);
if (skip_equal && expires_next.tv64 == cpu_base->expires_next.tv64)
return;
if (cpu_base->hang_detected)
return;
- if (cpu_base->expires_next.tv64 != KTIME_MAX)
- tick_program_event(cpu_base->expires_next, 1);
+ tick_program_event(cpu_base->expires_next, 1);
}
/*
- * Shared reprogramming for clock_realtime and clock_monotonic
- *
* When a timer is enqueued and expires earlier than the already enqueued
* timers, we have to check, whether it expires earlier than the timer for
* which the clock event device was armed.
*
- * Note, that in case the state has HRTIMER_STATE_CALLBACK set, no reprogramming
- * and no expiry check happens. The timer gets enqueued into the rbtree. The
- * reprogramming and expiry check is done in the hrtimer_interrupt or in the
- * softirq.
- *
* Called with interrupts disabled and base->cpu_base.lock held
*/
-static int hrtimer_reprogram(struct hrtimer *timer,
- struct hrtimer_clock_base *base)
+static void hrtimer_reprogram(struct hrtimer *timer,
+ struct hrtimer_clock_base *base)
{
struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
ktime_t expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
- int res;
WARN_ON_ONCE(hrtimer_get_expires_tv64(timer) < 0);
/*
- * When the callback is running, we do not reprogram the clock event
- * device. The timer callback is either running on a different CPU or
- * the callback is executed in the hrtimer_interrupt context. The
- * reprogramming is handled at the end of the hrtimer_interrupt.
+ * If the timer is not on the current cpu, we cannot reprogram
+ * the other cpus clock event device.
*/
- if (hrtimer_callback_running(timer))
- return 0;
+ if (base->cpu_base != cpu_base)
+ return;
+
+ /*
+ * If the hrtimer interrupt is running, then it will
+ * reevaluate the clock bases and reprogram the clock event
+ * device. The callbacks are always executed in hard interrupt
+ * context so we don't need an extra check for a running
+ * callback.
+ */
+ if (cpu_base->in_hrtirq)
+ return;
if (base->cpu_base != cpu_base)
return 0;
/*
* CLOCK_REALTIME timer might be requested with an absolute
- * expiry time which is less than base->offset. Nothing wrong
- * about that, just avoid to call into the tick code, which
- * has now objections against negative expiry values.
+ * expiry time which is less than base->offset. Set it to 0.
*/
if (expires.tv64 < 0)
- return -ETIME;
+ expires.tv64 = 0;
if (expires.tv64 >= cpu_base->expires_next.tv64)
- return 0;
+ return;
- /*
- * When the target cpu of the timer is currently executing
- * hrtimer_interrupt(), then we do not touch the clock event
- * device. hrtimer_interrupt() will reevaluate all clock bases
- * before reprogramming the device.
- */
- if (cpu_base->in_hrtirq)
- return 0;
+ /* Update the pointer to the next expiring timer */
+ cpu_base->next_timer = timer;
/*
* If a hang was detected in the last timer interrupt then we
* to make progress.
*/
if (cpu_base->hang_detected)
- return 0;
+ return;
cpu_base->expires_next = expires;
/*
- * Clockevents returns -ETIME, when the event was in the past.
+ * Program the timer hardware. We enforce the expiry for
+ * events which are already in the past.
*/
- res = tick_program_event(expires, 1);
- return res;
+ tick_program_event(expires, 1);
}
-static void __run_hrtimer(struct hrtimer *timer, ktime_t *now);
-static int hrtimer_rt_defer(struct hrtimer *timer);
-
/*
* Initialize the high resolution related parts of cpu_base
*/
base->hres_active = 0;
}
-static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
- struct hrtimer_clock_base *base,
- int wakeup)
-{
- if (!hrtimer_reprogram(timer, base))
- return 0;
- if (!wakeup)
- return -ETIME;
-#ifdef CONFIG_PREEMPT_RT_BASE
- if (!hrtimer_rt_defer(timer))
- return -ETIME;
-#endif
- return 1;
-}
-
-static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
-{
- ktime_t *offs_real = &base->clock_base[HRTIMER_BASE_REALTIME].offset;
- ktime_t *offs_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset;
- ktime_t *offs_tai = &base->clock_base[HRTIMER_BASE_TAI].offset;
-
- return ktime_get_update_offsets_now(offs_real, offs_boot, offs_tai);
-}
-
/*
* Retrigger next event is called after clock was set
*
{
struct hrtimer_cpu_base *base = this_cpu_ptr(&hrtimer_bases);
- if (!hrtimer_hres_active())
+ if (!base->hres_active)
return;
raw_spin_lock(&base->lock);
/*
* Switch to high resolution mode
*/
-static int hrtimer_switch_to_hres(void)
+static void hrtimer_switch_to_hres(void)
{
- int i, cpu = smp_processor_id();
- struct hrtimer_cpu_base *base = &per_cpu(hrtimer_bases, cpu);
- unsigned long flags;
-
- if (base->hres_active)
- return 1;
-
- local_irq_save(flags);
+ struct hrtimer_cpu_base *base = this_cpu_ptr(&hrtimer_bases);
if (tick_init_highres()) {
- local_irq_restore(flags);
printk(KERN_WARNING "Could not switch to high resolution "
- "mode on CPU %d\n", cpu);
- return 0;
+ "mode on CPU %d\n", base->cpu);
+ return;
}
base->hres_active = 1;
- for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
- base->clock_base[i].resolution = KTIME_HIGH_RES;
+ hrtimer_resolution = HIGH_RES_NSEC;
tick_setup_sched_timer();
/* "Retrigger" the interrupt to get things going */
retrigger_next_event(NULL);
- local_irq_restore(flags);
- return 1;
}
static void clock_was_set_work(struct work_struct *work)
#else
+static inline int __hrtimer_hres_active(struct hrtimer_cpu_base *b) { return 0; }
static inline int hrtimer_hres_active(void) { return 0; }
static inline int hrtimer_is_hres_enabled(void) { return 0; }
-static inline int hrtimer_switch_to_hres(void) { return 0; }
+static inline void hrtimer_switch_to_hres(void) { }
static inline void
hrtimer_force_reprogram(struct hrtimer_cpu_base *base, int skip_equal) { }
-static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
- struct hrtimer_clock_base *base,
- int wakeup)
-{
- return 0;
-}
-
-static inline int hrtimer_reprogram(struct hrtimer *timer,
- struct hrtimer_clock_base *base)
-{
- return 0;
-}
+static inline void hrtimer_reprogram(struct hrtimer *timer,
+ struct hrtimer_clock_base *base) { }
static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base) { }
static inline void retrigger_next_event(void *arg) { }
+
#endif /* CONFIG_HIGH_RES_TIMERS */
/*
*
* Forward the timer expiry so it will expire in the future.
* Returns the number of overruns.
+ *
+ * Can be safely called from the callback function of @timer. If
+ * called from other contexts @timer must neither be enqueued nor
+ * running the callback and the caller needs to take care of
+ * serialization.
+ *
+ * Note: This only updates the timer expiry value and does not requeue
+ * the timer.
*/
u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
{
if (delta.tv64 < 0)
return 0;
- if (interval.tv64 < timer->base->resolution.tv64)
- interval.tv64 = timer->base->resolution.tv64;
+ if (WARN_ON(timer->state & HRTIMER_STATE_ENQUEUED))
+ return 0;
+
+ if (interval.tv64 < hrtimer_resolution)
+ interval.tv64 = hrtimer_resolution;
if (unlikely(delta.tv64 >= interval.tv64)) {
s64 incr = ktime_to_ns(interval);
if (base && base->cpu_base && !timer->irqsafe)
wait_event(base->cpu_base->wait,
- !(timer->state & HRTIMER_STATE_CALLBACK));
+ !(hrtimer_callback_running(timer)));
}
#else
{
debug_activate(timer);
- timerqueue_add(&base->active, &timer->node);
base->cpu_base->active_bases |= 1 << base->index;
- /*
- * HRTIMER_STATE_ENQUEUED is or'ed to the current state to preserve the
- * state of a possibly running callback.
- */
- timer->state |= HRTIMER_STATE_ENQUEUED;
+ timer->state = HRTIMER_STATE_ENQUEUED;
- return (&timer->node == base->active.next);
+ return timerqueue_add(&base->active, &timer->node);
}
/*
*/
static void __remove_hrtimer(struct hrtimer *timer,
struct hrtimer_clock_base *base,
- unsigned long newstate, int reprogram)
+ u8 newstate, int reprogram)
{
- struct timerqueue_node *next_timer;
- if (!(timer->state & HRTIMER_STATE_ENQUEUED))
- goto out;
+ struct hrtimer_cpu_base *cpu_base = base->cpu_base;
+ u8 state = timer->state;
+
+ timer->state = newstate;
+ if (!(state & HRTIMER_STATE_ENQUEUED))
+ return;
if (unlikely(!list_empty(&timer->cb_entry))) {
list_del_init(&timer->cb_entry);
- goto out;
+ return;
}
- next_timer = timerqueue_getnext(&base->active);
- timerqueue_del(&base->active, &timer->node);
- if (&timer->node == next_timer) {
+ if (!timerqueue_del(&base->active, &timer->node))
+ cpu_base->active_bases &= ~(1 << base->index);
+
#ifdef CONFIG_HIGH_RES_TIMERS
- /* Reprogram the clock event device. if enabled */
- if (reprogram && hrtimer_hres_active()) {
- ktime_t expires;
-
- expires = ktime_sub(hrtimer_get_expires(timer),
- base->offset);
- if (base->cpu_base->expires_next.tv64 == expires.tv64)
- hrtimer_force_reprogram(base->cpu_base, 1);
- }
+ /*
+ * Note: If reprogram is false we do not update
+ * cpu_base->next_timer. This happens when we remove the first
+ * timer on a remote cpu. No harm as we never dereference
+ * cpu_base->next_timer. So the worst thing what can happen is
+ * an superflous call to hrtimer_force_reprogram() on the
+ * remote cpu later on if the same timer gets enqueued again.
+ */
+ if (reprogram && timer == cpu_base->next_timer)
+ hrtimer_force_reprogram(cpu_base, 1);
#endif
- }
- if (!timerqueue_getnext(&base->active))
- base->cpu_base->active_bases &= ~(1 << base->index);
-out:
- timer->state = newstate;
}
/*
* remove hrtimer, called with base lock held
*/
static inline int
-remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
+remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base, bool restart)
{
if (hrtimer_is_queued(timer)) {
- unsigned long state;
+ u8 state = timer->state;
int reprogram;
/*
debug_deactivate(timer);
timer_stats_hrtimer_clear_start_info(timer);
reprogram = base->cpu_base == this_cpu_ptr(&hrtimer_bases);
- /*
- * We must preserve the CALLBACK state flag here,
- * otherwise we could move the timer base in
- * switch_hrtimer_base.
- */
- state = timer->state & HRTIMER_STATE_CALLBACK;
+
+ if (!restart)
+ state = HRTIMER_STATE_INACTIVE;
+
__remove_hrtimer(timer, base, state, reprogram);
return 1;
}
return 0;
}
-int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
- unsigned long delta_ns, const enum hrtimer_mode mode,
- int wakeup)
+static inline ktime_t hrtimer_update_lowres(struct hrtimer *timer, ktime_t tim,
+ const enum hrtimer_mode mode)
+{
+#ifdef CONFIG_TIME_LOW_RES
+ /*
+ * CONFIG_TIME_LOW_RES indicates that the system has no way to return
+ * granular time values. For relative timers we add hrtimer_resolution
+ * (i.e. one jiffie) to prevent short timeouts.
+ */
+ timer->is_rel = mode & HRTIMER_MODE_REL;
+ if (timer->is_rel)
+ tim = ktime_add_safe(tim, ktime_set(0, hrtimer_resolution));
+#endif
+ return tim;
+}
+
+/**
+ * hrtimer_start_range_ns - (re)start an hrtimer on the current CPU
+ * @timer: the timer to be added
+ * @tim: expiry time
+ * @delta_ns: "slack" range for the timer
+ * @mode: expiry mode: absolute (HRTIMER_MODE_ABS) or
+ * relative (HRTIMER_MODE_REL)
+ */
+void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
+ unsigned long delta_ns, const enum hrtimer_mode mode)
{
struct hrtimer_clock_base *base, *new_base;
unsigned long flags;
- int ret, leftmost;
+ int leftmost;
base = lock_hrtimer_base(timer, &flags);
/* Remove an active timer from the queue: */
- ret = remove_hrtimer(timer, base);
+ remove_hrtimer(timer, base, true);
- if (mode & HRTIMER_MODE_REL) {
+ if (mode & HRTIMER_MODE_REL)
tim = ktime_add_safe(tim, base->get_time());
- /*
- * CONFIG_TIME_LOW_RES is a temporary way for architectures
- * to signal that they simply return xtime in
- * do_gettimeoffset(). In this case we want to round up by
- * resolution when starting a relative timer, to avoid short
- * timeouts. This will go away with the GTOD framework.
- */
-#ifdef CONFIG_TIME_LOW_RES
- tim = ktime_add_safe(tim, base->resolution);
-#endif
- }
+
+ tim = hrtimer_update_lowres(timer, tim, mode);
hrtimer_set_expires_range_ns(timer, tim, delta_ns);
}
#endif
leftmost = enqueue_hrtimer(timer, new_base);
-
- if (!leftmost) {
- unlock_hrtimer_base(timer, &flags);
- return ret;
- }
+ if (!leftmost)
+ goto unlock;
if (!hrtimer_is_hres_active(timer)) {
/*
* Kick to reschedule the next tick to handle the new timer
* on dynticks target.
*/
- wake_up_nohz_cpu(new_base->cpu_base->cpu);
- } else if (new_base->cpu_base == this_cpu_ptr(&hrtimer_bases)) {
-
- ret = hrtimer_enqueue_reprogram(timer, new_base, wakeup);
- if (ret < 0) {
- /*
- * In case we failed to reprogram the timer (mostly
- * because out current timer is already elapsed),
- * remove it again and report a failure. This avoids
- * stale base->first entries.
- */
- debug_deactivate(timer);
- __remove_hrtimer(timer, new_base,
- timer->state & HRTIMER_STATE_CALLBACK, 0);
- } else if (ret > 0) {
- /*
- * Only allow reprogramming if the new base is on this CPU.
- * (it might still be on another CPU if the timer was pending)
- *
- * XXX send_remote_softirq() ?
- */
- /*
- * We need to drop cpu_base->lock to avoid a
- * lock ordering issue vs. rq->lock.
- */
- raw_spin_unlock(&new_base->cpu_base->lock);
- raise_softirq_irqoff(HRTIMER_SOFTIRQ);
- local_irq_restore(flags);
- return 0;
- }
+ if (new_base->cpu_base->nohz_active)
+ wake_up_nohz_cpu(new_base->cpu_base->cpu);
+ } else {
+ hrtimer_reprogram(timer, new_base);
}
-
+unlock:
unlock_hrtimer_base(timer, &flags);
-
- return ret;
-}
-EXPORT_SYMBOL_GPL(__hrtimer_start_range_ns);
-
-/**
- * hrtimer_start_range_ns - (re)start an hrtimer on the current CPU
- * @timer: the timer to be added
- * @tim: expiry time
- * @delta_ns: "slack" range for the timer
- * @mode: expiry mode: absolute (HRTIMER_MODE_ABS) or
- * relative (HRTIMER_MODE_REL)
- *
- * Returns:
- * 0 on success
- * 1 when the timer was active
- */
-int hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
- unsigned long delta_ns, const enum hrtimer_mode mode)
-{
- return __hrtimer_start_range_ns(timer, tim, delta_ns, mode, 1);
}
EXPORT_SYMBOL_GPL(hrtimer_start_range_ns);
-/**
- * hrtimer_start - (re)start an hrtimer on the current CPU
- * @timer: the timer to be added
- * @tim: expiry time
- * @mode: expiry mode: absolute (HRTIMER_MODE_ABS) or
- * relative (HRTIMER_MODE_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)
-{
- return __hrtimer_start_range_ns(timer, tim, 0, mode, 1);
-}
-EXPORT_SYMBOL_GPL(hrtimer_start);
-
-
/**
* hrtimer_try_to_cancel - try to deactivate a timer
* @timer: hrtimer to stop
unsigned long flags;
int ret = -1;
+ /*
+ * Check lockless first. If the timer is not active (neither
+ * enqueued nor running the callback, nothing to do here. The
+ * base lock does not serialize against a concurrent enqueue,
+ * so we can avoid taking it.
+ */
+ if (!hrtimer_active(timer))
+ return 0;
+
base = lock_hrtimer_base(timer, &flags);
if (!hrtimer_callback_running(timer))
- ret = remove_hrtimer(timer, base);
+ ret = remove_hrtimer(timer, base, false);
unlock_hrtimer_base(timer, &flags);
/**
* hrtimer_get_remaining - get remaining time for the timer
* @timer: the timer to read
+ * @adjust: adjust relative timers when CONFIG_TIME_LOW_RES=y
*/
-ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
+ktime_t __hrtimer_get_remaining(const struct hrtimer *timer, bool adjust)
{
unsigned long flags;
ktime_t rem;
lock_hrtimer_base(timer, &flags);
- rem = hrtimer_expires_remaining(timer);
+ if (IS_ENABLED(CONFIG_TIME_LOW_RES) && adjust)
+ rem = hrtimer_expires_remaining_adjusted(timer);
+ else
+ rem = hrtimer_expires_remaining(timer);
unlock_hrtimer_base(timer, &flags);
return rem;
}
-EXPORT_SYMBOL_GPL(hrtimer_get_remaining);
+EXPORT_SYMBOL_GPL(__hrtimer_get_remaining);
#ifdef CONFIG_NO_HZ_COMMON
/**
* hrtimer_get_next_event - get the time until next expiry event
*
- * Returns the delta to the next expiry event or KTIME_MAX if no timer
- * is pending.
+ * Returns the next expiry time or KTIME_MAX if no timer is pending.
*/
-ktime_t hrtimer_get_next_event(void)
+u64 hrtimer_get_next_event(void)
{
struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
- ktime_t mindelta = { .tv64 = KTIME_MAX };
+ u64 expires = KTIME_MAX;
unsigned long flags;
raw_spin_lock_irqsave(&cpu_base->lock, flags);
- if (!hrtimer_hres_active())
- mindelta = ktime_sub(__hrtimer_get_next_event(cpu_base),
- ktime_get());
+ if (!__hrtimer_hres_active(cpu_base))
+ expires = __hrtimer_get_next_event(cpu_base).tv64;
raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
- if (mindelta.tv64 < 0)
- mindelta.tv64 = 0;
- return mindelta;
+ return expires;
}
#endif
}
EXPORT_SYMBOL_GPL(hrtimer_init);
-/**
- * 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
+/*
+ * A timer is active, when it is enqueued into the rbtree or the
+ * callback function is running or it's in the state of being migrated
+ * to another cpu.
*
- * Store the resolution of the clock selected by @which_clock in the
- * variable pointed to by @tp.
+ * It is important for this function to not return a false negative.
*/
-int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
+bool hrtimer_active(const struct hrtimer *timer)
{
struct hrtimer_cpu_base *cpu_base;
- int base = hrtimer_clockid_to_base(which_clock);
+ unsigned int seq;
- cpu_base = raw_cpu_ptr(&hrtimer_bases);
- *tp = ktime_to_timespec(cpu_base->clock_base[base].resolution);
+ do {
+ cpu_base = READ_ONCE(timer->base->cpu_base);
+ seq = raw_read_seqcount_begin(&cpu_base->seq);
- return 0;
+ if (timer->state != HRTIMER_STATE_INACTIVE ||
+ cpu_base->running_soft == timer ||
+ cpu_base->running == timer)
+ return true;
+
+ } while (read_seqcount_retry(&cpu_base->seq, seq) ||
+ cpu_base != READ_ONCE(timer->base->cpu_base));
+
+ return false;
}
-EXPORT_SYMBOL_GPL(hrtimer_get_res);
+EXPORT_SYMBOL_GPL(hrtimer_active);
+
+/*
+ * The write_seqcount_barrier()s in __run_hrtimer() split the thing into 3
+ * distinct sections:
+ *
+ * - queued: the timer is queued
+ * - callback: the timer is being ran
+ * - post: the timer is inactive or (re)queued
+ *
+ * On the read side we ensure we observe timer->state and cpu_base->running
+ * from the same section, if anything changed while we looked at it, we retry.
+ * This includes timer->base changing because sequence numbers alone are
+ * insufficient for that.
+ *
+ * The sequence numbers are required because otherwise we could still observe
+ * a false negative if the read side got smeared over multiple consequtive
+ * __run_hrtimer() invocations.
+ */
-static void __run_hrtimer(struct hrtimer *timer, ktime_t *now)
+static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base,
+ struct hrtimer_clock_base *base,
+ struct hrtimer *timer, ktime_t *now)
{
- struct hrtimer_clock_base *base = timer->base;
- struct hrtimer_cpu_base *cpu_base = base->cpu_base;
enum hrtimer_restart (*fn)(struct hrtimer *);
int restart;
- WARN_ON(!irqs_disabled());
+ lockdep_assert_held(&cpu_base->lock);
debug_deactivate(timer);
- __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
+ cpu_base->running = timer;
+
+ /*
+ * Separate the ->running assignment from the ->state assignment.
+ *
+ * As with a regular write barrier, this ensures the read side in
+ * hrtimer_active() cannot observe cpu_base->running == NULL &&
+ * timer->state == INACTIVE.
+ */
+ raw_write_seqcount_barrier(&cpu_base->seq);
+
+ __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE, 0);
timer_stats_account_hrtimer(timer);
fn = timer->function;
+ /*
+ * Clear the 'is relative' flag for the TIME_LOW_RES case. If the
+ * timer is restarted with a period then it becomes an absolute
+ * timer. If its not restarted it does not matter.
+ */
+ if (IS_ENABLED(CONFIG_TIME_LOW_RES))
+ timer->is_rel = false;
+
/*
* Because we run timers from hardirq context, there is no chance
* they get migrated to another cpu, therefore its safe to unlock
raw_spin_lock(&cpu_base->lock);
/*
- * Note: We clear the CALLBACK bit after enqueue_hrtimer and
+ * Note: We clear the running state after enqueue_hrtimer and
* we do not reprogramm the event hardware. Happens either in
* hrtimer_start_range_ns() or in hrtimer_interrupt()
+ *
+ * Note: Because we dropped the cpu_base->lock above,
+ * hrtimer_start_range_ns() can have popped in and enqueued the timer
+ * for us already.
*/
- if (restart != HRTIMER_NORESTART) {
- BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
+ if (restart != HRTIMER_NORESTART &&
+ !(timer->state & HRTIMER_STATE_ENQUEUED))
enqueue_hrtimer(timer, base);
- }
- WARN_ON_ONCE(!(timer->state & HRTIMER_STATE_CALLBACK));
+ /*
+ * Separate the ->running assignment from the ->state assignment.
+ *
+ * As with a regular write barrier, this ensures the read side in
+ * hrtimer_active() cannot observe cpu_base->running == NULL &&
+ * timer->state == INACTIVE.
+ */
+ raw_write_seqcount_barrier(&cpu_base->seq);
- timer->state &= ~HRTIMER_STATE_CALLBACK;
+ WARN_ON_ONCE(cpu_base->running != timer);
+ cpu_base->running = NULL;
}
-static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer);
-
#ifdef CONFIG_PREEMPT_RT_BASE
static void hrtimer_rt_reprogram(int restart, struct hrtimer *timer,
struct hrtimer_clock_base *base)
{
- /*
- * Note, we clear the callback flag before we requeue the
- * timer otherwise we trigger the callback_running() check
- * in hrtimer_reprogram().
- */
- timer->state &= ~HRTIMER_STATE_CALLBACK;
-
- if (restart != HRTIMER_NORESTART) {
- BUG_ON(hrtimer_active(timer));
- /*
- * Enqueue the timer, if it's the leftmost timer then
- * we need to reprogram it.
- */
- if (!enqueue_hrtimer(timer, base))
- return;
+ int leftmost;
-#ifndef CONFIG_HIGH_RES_TIMERS
- }
-#else
- if (base->cpu_base->hres_active &&
- hrtimer_reprogram(timer, base))
- goto requeue;
+ if (restart != HRTIMER_NORESTART &&
+ !(timer->state & HRTIMER_STATE_ENQUEUED)) {
- } else if (hrtimer_active(timer)) {
- /*
- * If the timer was rearmed on another CPU, reprogram
- * the event device.
- */
- if (&timer->node == base->active.next &&
- base->cpu_base->hres_active &&
- hrtimer_reprogram(timer, base))
- goto requeue;
- }
- return;
+ leftmost = enqueue_hrtimer(timer, base);
+ if (!leftmost)
+ return;
+#ifdef CONFIG_HIGH_RES_TIMERS
+ if (!hrtimer_is_hres_active(timer)) {
+ /*
+ * Kick to reschedule the next tick to handle the new timer
+ * on dynticks target.
+ */
+ if (base->cpu_base->nohz_active)
+ wake_up_nohz_cpu(base->cpu_base->cpu);
+ } else {
-requeue:
- /*
- * Timer is expired. Thus move it from tree to pending list
- * again.
- */
- __remove_hrtimer(timer, base, timer->state, 0);
- list_add_tail(&timer->cb_entry, &base->expired);
+ hrtimer_reprogram(timer, base);
+ }
#endif
+ }
}
/*
* Same as the above __run_hrtimer function
* just we run with interrupts enabled.
*/
- debug_hrtimer_deactivate(timer);
- __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
+ debug_deactivate(timer);
+ cpu_base->running_soft = timer;
+ raw_write_seqcount_barrier(&cpu_base->seq);
+
+ __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE, 0);
timer_stats_account_hrtimer(timer);
fn = timer->function;
raw_spin_lock_irq(&cpu_base->lock);
hrtimer_rt_reprogram(restart, timer, base);
+ raw_write_seqcount_barrier(&cpu_base->seq);
+
+ WARN_ON_ONCE(cpu_base->running_soft != timer);
+ cpu_base->running_soft = NULL;
}
}
#else
-static inline void hrtimer_rt_run_pending(void)
-{
- hrtimer_peek_ahead_timers();
-}
-
static inline int hrtimer_rt_defer(struct hrtimer *timer) { return 0; }
#endif
-#ifdef CONFIG_HIGH_RES_TIMERS
+static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer);
-/*
- * High resolution timer interrupt
- * Called with interrupts disabled
- */
-void hrtimer_interrupt(struct clock_event_device *dev)
+static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now)
{
- struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
- ktime_t expires_next, now, entry_time, delta;
- int i, retries = 0, raise = 0;
-
- BUG_ON(!cpu_base->hres_active);
- cpu_base->nr_events++;
- dev->next_event.tv64 = KTIME_MAX;
-
- raw_spin_lock(&cpu_base->lock);
- entry_time = now = hrtimer_update_base(cpu_base);
-retry:
- cpu_base->in_hrtirq = 1;
- /*
- * We set expires_next to KTIME_MAX here with cpu_base->lock
- * held to prevent that a timer is enqueued in our queue via
- * the migration code. This does not affect enqueueing of
- * timers which run their callback and need to be requeued on
- * this CPU.
- */
- cpu_base->expires_next.tv64 = KTIME_MAX;
+ struct hrtimer_clock_base *base = cpu_base->clock_base;
+ unsigned int active = cpu_base->active_bases;
+ int raise = 0;
- for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
- struct hrtimer_clock_base *base;
+ for (; active; base++, active >>= 1) {
struct timerqueue_node *node;
ktime_t basenow;
- if (!(cpu_base->active_bases & (1 << i)))
+ if (!(active & 0x01))
continue;
- base = cpu_base->clock_base + i;
basenow = ktime_add(now, base->offset);
while ((node = timerqueue_getnext(&base->active))) {
break;
if (!hrtimer_rt_defer(timer))
- __run_hrtimer(timer, &basenow);
+ __run_hrtimer(cpu_base, base, timer, &basenow);
else
raise = 1;
}
}
+ if (raise)
+ raise_softirq_irqoff(HRTIMER_SOFTIRQ);
+}
+
+#ifdef CONFIG_HIGH_RES_TIMERS
+
+/*
+ * High resolution timer interrupt
+ * Called with interrupts disabled
+ */
+void hrtimer_interrupt(struct clock_event_device *dev)
+{
+ struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
+ ktime_t expires_next, now, entry_time, delta;
+ int retries = 0;
+
+ BUG_ON(!cpu_base->hres_active);
+ cpu_base->nr_events++;
+ dev->next_event.tv64 = KTIME_MAX;
+
+ raw_spin_lock(&cpu_base->lock);
+ entry_time = now = hrtimer_update_base(cpu_base);
+retry:
+ cpu_base->in_hrtirq = 1;
+ /*
+ * We set expires_next to KTIME_MAX here with cpu_base->lock
+ * held to prevent that a timer is enqueued in our queue via
+ * the migration code. This does not affect enqueueing of
+ * timers which run their callback and need to be requeued on
+ * this CPU.
+ */
+ cpu_base->expires_next.tv64 = KTIME_MAX;
+
+ __hrtimer_run_queues(cpu_base, now);
+
/* Reevaluate the clock bases for the next expiry */
expires_next = __hrtimer_get_next_event(cpu_base);
/*
raw_spin_unlock(&cpu_base->lock);
/* Reprogramming necessary ? */
- if (expires_next.tv64 == KTIME_MAX ||
- !tick_program_event(expires_next, 0)) {
+ if (!tick_program_event(expires_next, 0)) {
cpu_base->hang_detected = 0;
- goto out;
+ return;
}
/*
cpu_base->hang_detected = 1;
raw_spin_unlock(&cpu_base->lock);
delta = ktime_sub(now, entry_time);
- if (delta.tv64 > cpu_base->max_hang_time.tv64)
- cpu_base->max_hang_time = delta;
+ if ((unsigned int)delta.tv64 > cpu_base->max_hang_time)
+ cpu_base->max_hang_time = (unsigned int) delta.tv64;
/*
* Limit it to a sensible value as we enforce a longer
* delay. Give the CPU at least 100ms to catch up.
tick_program_event(expires_next, 1);
printk_once(KERN_WARNING "hrtimer: interrupt took %llu ns\n",
ktime_to_ns(delta));
-out:
- if (raise)
- raise_softirq_irqoff(HRTIMER_SOFTIRQ);
}
/*
* local version of hrtimer_peek_ahead_timers() called with interrupts
* disabled.
*/
-static void __hrtimer_peek_ahead_timers(void)
+static inline void __hrtimer_peek_ahead_timers(void)
{
struct tick_device *td;
hrtimer_interrupt(td->evtdev);
}
-/**
- * hrtimer_peek_ahead_timers -- run soft-expired timers now
- *
- * hrtimer_peek_ahead_timers will peek at the timer queue of
- * the current cpu and check if there are any timers for which
- * the soft expires time has passed. If any such timers exist,
- * they are run immediately and then removed from the timer queue.
- *
- */
-void hrtimer_peek_ahead_timers(void)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- __hrtimer_peek_ahead_timers();
- local_irq_restore(flags);
-}
#else /* CONFIG_HIGH_RES_TIMERS */
static inline void __hrtimer_peek_ahead_timers(void) { }
#endif /* !CONFIG_HIGH_RES_TIMERS */
-
-static void run_hrtimer_softirq(struct softirq_action *h)
-{
- hrtimer_rt_run_pending();
-}
-
/*
- * Called from timer softirq every jiffy, expire hrtimers:
- *
- * For HRT its the fall back code to run the softirq in the timer
- * softirq context in case the hrtimer initialization failed or has
- * not been done yet.
+ * Called from run_local_timers in hardirq context every jiffy
*/
-void hrtimer_run_pending(void)
+void hrtimer_run_queues(void)
{
- if (hrtimer_hres_active())
+ struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
+ ktime_t now;
+
+ if (__hrtimer_hres_active(cpu_base))
return;
/*
- * This _is_ ugly: We have to check in the softirq context,
- * whether we can switch to highres and / or nohz mode. The
- * clocksource switch happens in the timer interrupt with
- * xtime_lock held. Notification from there only sets the
- * check bit in the tick_oneshot code, otherwise we might
- * deadlock vs. xtime_lock.
+ * This _is_ ugly: We have to check periodically, whether we
+ * can switch to highres and / or nohz mode. The clocksource
+ * switch happens with xtime_lock held. Notification from
+ * there only sets the check bit in the tick_oneshot code,
+ * otherwise we might deadlock vs. xtime_lock.
*/
- if (tick_check_oneshot_change(!hrtimer_is_hres_enabled()))
+ if (tick_check_oneshot_change(!hrtimer_is_hres_enabled())) {
hrtimer_switch_to_hres();
-}
-
-/*
- * Called from hardirq context every jiffy
- */
-void hrtimer_run_queues(void)
-{
- struct timerqueue_node *node;
- struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
- struct hrtimer_clock_base *base;
- int index, gettime = 1, raise = 0;
-
- if (hrtimer_hres_active())
return;
-
- for (index = 0; index < HRTIMER_MAX_CLOCK_BASES; index++) {
- base = &cpu_base->clock_base[index];
- if (!timerqueue_getnext(&base->active))
- continue;
-
- if (gettime) {
- hrtimer_get_softirq_time(cpu_base);
- gettime = 0;
- }
-
- raw_spin_lock(&cpu_base->lock);
-
- while ((node = timerqueue_getnext(&base->active))) {
- struct hrtimer *timer;
-
- timer = container_of(node, struct hrtimer, node);
- if (base->softirq_time.tv64 <=
- hrtimer_get_expires_tv64(timer))
- break;
-
- if (!hrtimer_rt_defer(timer))
- __run_hrtimer(timer, &base->softirq_time);
- else
- raise = 1;
- }
- raw_spin_unlock(&cpu_base->lock);
}
- if (raise)
- raise_softirq_irqoff(HRTIMER_SOFTIRQ);
+ raw_spin_lock(&cpu_base->lock);
+ now = hrtimer_update_base(cpu_base);
+ __hrtimer_run_queues(cpu_base, now);
+ raw_spin_unlock(&cpu_base->lock);
}
/*
do {
set_current_state(state);
hrtimer_start_expires(&t->timer, mode);
- if (!hrtimer_active(&t->timer))
- t->task = NULL;
if (likely(t->task))
freezable_schedule();
debug_deactivate(timer);
/*
- * Mark it as STATE_MIGRATE not INACTIVE otherwise the
+ * Mark it as ENQUEUED not INACTIVE otherwise the
* timer could be seen as !active and just vanish away
* under us on another CPU
*/
- __remove_hrtimer(timer, old_base, HRTIMER_STATE_MIGRATE, 0);
+ __remove_hrtimer(timer, old_base, HRTIMER_STATE_ENQUEUED, 0);
timer->base = new_base;
/*
* Enqueue the timers on the new cpu. This does not
* event device.
*/
enqueue_hrtimer(timer, new_base);
-
- /* Clear the migration state bit */
- timer->state &= ~HRTIMER_STATE_MIGRATE;
}
}
.notifier_call = hrtimer_cpu_notify,
};
+#ifdef CONFIG_PREEMPT_RT_BASE
+static void run_hrtimer_softirq(struct softirq_action *h)
+{
+ hrtimer_rt_run_pending();
+}
+#endif
+
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);
+#ifdef CONFIG_PREEMPT_RT_BASE
open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq);
+#endif
}
/**
hrtimer_init_sleeper(&t, current);
hrtimer_start_expires(&t.timer, mode);
- if (!hrtimer_active(&t.timer))
- t.task = NULL;
if (likely(t.task))
schedule();
Code Review / kvmfornfv.git / blobdiff