diff options
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/hrtimer.h | 36 |
1 files changed, 35 insertions, 1 deletions
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index e00fc4d3d74f..d8cdac2d28d6 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: */ |