HRTIMER_RESTART, /* Timer must be restarted */
};
+/*
+ * Bit values to track state of the timer
+ *
+ * Possible states:
+ *
+ * 0x00 inactive
+ * 0x01 enqueued into rbtree
+ * 0x02 callback function running
+ * 0x03 callback function running and enqueued
+ * (was requeued on another CPU)
+ *
+ * The "callback function running and enqueued" status is only possible on
+ * SMP. It happens for example when a posix timer expired and the callback
+ * queued a signal. Between dropping the lock which protects the posix timer
+ * and reacquiring the base lock of the hrtimer, another CPU can deliver the
+ * signal and rearm the timer. We have to preserve the callback running state,
+ * as otherwise the timer could be removed before the softirq code finishes the
+ * the handling of the timer.
+ *
+ * The HRTIMER_STATE_ENQUEUE bit is always or'ed to the current state to
+ * preserve the HRTIMER_STATE_CALLBACK bit in the above scenario.
+ *
+ * All state transitions are protected by cpu_base->lock.
+ */
+#define HRTIMER_STATE_INACTIVE 0x00
+#define HRTIMER_STATE_ENQUEUED 0x01
+#define HRTIMER_STATE_CALLBACK 0x02
+
/**
* struct hrtimer - the basic hrtimer structure
* @node: red black tree node for time ordered insertion
* which the timer is based.
* @function: timer expiry callback function
* @base: pointer to the timer base (per cpu and per clock)
+ * @state: state information (See bit values above)
*
* The hrtimer structure must be initialized by init_hrtimer_#CLOCKTYPE()
*/
ktime_t expires;
enum hrtimer_restart (*function)(struct hrtimer *);
struct hrtimer_clock_base *base;
+ unsigned long state;
};
/**
extern ktime_t hrtimer_get_next_event(void);
#endif
+/*
+ * A timer is active, when it is enqueued into the rbtree or the callback
+ * function is running.
+ */
static inline int hrtimer_active(const struct hrtimer *timer)
{
- return rb_parent(&timer->node) != &timer->node;
+ return timer->state != HRTIMER_STATE_INACTIVE;
}
/* Forward a hrtimer so it expires after now: */
ktime_add(xtim, tomono);
}
+/*
+ * Helper function to check, whether the timer is on one of the queues
+ */
+static inline int hrtimer_is_queued(struct hrtimer *timer)
+{
+ return timer->state & HRTIMER_STATE_ENQUEUED;
+}
+
+/*
+ * Helper function to check, whether the timer is running the callback
+ * function
+ */
+static inline int hrtimer_callback_running(struct hrtimer *timer)
+{
+ return timer->state & HRTIMER_STATE_CALLBACK;
+}
+
/*
* Functions and macros which are different for UP/SMP systems are kept in a
* single place
*/
rb_link_node(&timer->node, parent, link);
rb_insert_color(&timer->node, &base->active);
+ /*
+ * HRTIMER_STATE_ENQUEUED is or'ed to the current state to preserve the
+ * state of a possibly running callback.
+ */
+ timer->state |= HRTIMER_STATE_ENQUEUED;
if (!base->first || timer->expires.tv64 <
rb_entry(base->first, struct hrtimer, node)->expires.tv64)
* Caller must hold the base lock.
*/
static void __remove_hrtimer(struct hrtimer *timer,
- struct hrtimer_clock_base *base)
+ struct hrtimer_clock_base *base,
+ unsigned long newstate)
{
/*
* Remove the timer from the rbtree and replace the
if (base->first == &timer->node)
base->first = rb_next(&timer->node);
rb_erase(&timer->node, &base->active);
- rb_set_parent(&timer->node, &timer->node);
+ timer->state = newstate;
}
/*
static inline int
remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
{
- if (hrtimer_active(timer)) {
- __remove_hrtimer(timer, base);
+ if (hrtimer_is_queued(timer)) {
+ __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE);
return 1;
}
return 0;
base = lock_hrtimer_base(timer, &flags);
- if (base->cpu_base->curr_timer != timer)
+ if (!hrtimer_callback_running(timer))
ret = remove_hrtimer(timer, base);
unlock_hrtimer_base(timer, &flags);
clock_id = CLOCK_MONOTONIC;
timer->base = &cpu_base->clock_base[clock_id];
- rb_set_parent(&timer->node, &timer->node);
}
EXPORT_SYMBOL_GPL(hrtimer_init);
fn = timer->function;
set_curr_timer(cpu_base, timer);
- __remove_hrtimer(timer, base);
+ __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK);
spin_unlock_irq(&cpu_base->lock);
restart = fn(timer);
spin_lock_irq(&cpu_base->lock);
+ timer->state &= ~HRTIMER_STATE_CALLBACK;
if (restart != HRTIMER_NORESTART) {
BUG_ON(hrtimer_active(timer));
enqueue_hrtimer(timer, base);
while ((node = rb_first(&old_base->active))) {
timer = rb_entry(node, struct hrtimer, node);
- __remove_hrtimer(timer, old_base);
+ BUG_ON(timer->state & HRTIMER_STATE_CALLBACK);
+ __remove_hrtimer(timer, old_base, HRTIMER_STATE_INACTIVE);
timer->base = new_base;
enqueue_hrtimer(timer, new_base);
}