diff options
| -rw-r--r-- | include/linux/hrtimer.h | 36 | ||||
| -rw-r--r-- | kernel/hrtimer.c | 40 |
2 files changed, 67 insertions, 9 deletions
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index e00fc4d..d8cdac2 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -40,6 +40,34 @@ enum hrtimer_restart { 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 @@ -48,6 +76,7 @@ enum hrtimer_restart { * 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() */ @@ -56,6 +85,7 @@ struct hrtimer { ktime_t expires; enum hrtimer_restart (*function)(struct hrtimer *); struct hrtimer_clock_base *base; + unsigned long state; }; /** @@ -141,9 +171,13 @@ extern int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp); 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: */ diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 89a9f53..fee18b2 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -150,6 +150,23 @@ static void hrtimer_get_softirq_time(struct hrtimer_cpu_base *base) } /* + * 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 */ @@ -390,6 +407,11 @@ static void enqueue_hrtimer(struct hrtimer *timer, */ 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) @@ -402,7 +424,8 @@ static void enqueue_hrtimer(struct hrtimer *timer, * 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 @@ -411,7 +434,7 @@ static void __remove_hrtimer(struct hrtimer *timer, 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; } /* @@ -420,8 +443,8 @@ static void __remove_hrtimer(struct hrtimer *timer, 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; @@ -493,7 +516,7 @@ int hrtimer_try_to_cancel(struct hrtimer *timer) 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); @@ -598,7 +621,6 @@ void hrtimer_init(struct hrtimer *timer, clockid_t clock_id, clock_id = CLOCK_MONOTONIC; timer->base = &cpu_base->clock_base[clock_id]; - rb_set_parent(&timer->node, &timer->node); } EXPORT_SYMBOL_GPL(hrtimer_init); @@ -649,13 +671,14 @@ static inline void run_hrtimer_queue(struct hrtimer_cpu_base *cpu_base, 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); @@ -826,7 +849,8 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_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); } |