From: Thomas Gleixner reintroduce ktimers feature "optimized away" by the ktimers review process: multiple hrtimer states to enable the running of hrtimers without holding the cpu-base-lock. (the "optimized" rbtree hack carried only 2 states worth of information and we need 4 for high resolution timers and dynamic ticks.) Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar -- include/linux/hrtimer.h | 36 +++++++++++++++++++++++++++++++++++- kernel/hrtimer.c | 21 ++++++++++++++------- 2 files changed, 49 insertions(+), 8 deletions(-) Index: linux-2.6.18-mm2/include/linux/hrtimer.h =================================================================== --- linux-2.6.18-mm2.orig/include/linux/hrtimer.h 2006-10-02 00:55:52.000000000 +0200 +++ linux-2.6.18-mm2/include/linux/hrtimer.h 2006-10-02 00:55:52.000000000 +0200 @@ -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 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: */ Index: linux-2.6.18-mm2/kernel/hrtimer.c =================================================================== --- linux-2.6.18-mm2.orig/kernel/hrtimer.c 2006-10-02 00:55:52.000000000 +0200 +++ linux-2.6.18-mm2/kernel/hrtimer.c 2006-10-02 00:55:52.000000000 +0200 @@ -385,6 +385,11 @@ static void enqueue_hrtimer(struct hrtim */ 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) @@ -397,7 +402,8 @@ static void enqueue_hrtimer(struct hrtim * 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 @@ -406,7 +412,7 @@ static void __remove_hrtimer(struct hrti 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; } /* @@ -416,7 +422,7 @@ static inline int remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base) { if (hrtimer_active(timer)) { - __remove_hrtimer(timer, base); + __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE); return 1; } return 0; @@ -488,7 +494,7 @@ int hrtimer_try_to_cancel(struct hrtimer base = lock_hrtimer_base(timer, &flags); - if (base->cpu_base->curr_timer != timer) + if (!(timer->state & HRTIMER_STATE_CALLBACK)) ret = remove_hrtimer(timer, base); unlock_hrtimer_base(timer, &flags); @@ -593,7 +599,6 @@ void hrtimer_init(struct hrtimer *timer, clock_id = CLOCK_MONOTONIC; timer->base = &cpu_base->clock_base[clock_id]; - rb_set_parent(&timer->node, &timer->node); } EXPORT_SYMBOL_GPL(hrtimer_init); @@ -644,13 +649,14 @@ static inline void run_hrtimer_queue(str 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); @@ -821,7 +827,8 @@ static void migrate_hrtimer_list(struct while ((node = rb_first(&old_base->active))) { timer = rb_entry(node, struct hrtimer, node); - __remove_hrtimer(timer, old_base); + BUG_ON(timer->state & HRTIMER_CALLBACK); + __remove_hrtimer(timer, old_base, HRTIMER_INACTIVE); timer->base = new_base; enqueue_hrtimer(timer, new_base); } -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/