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[PATCH] hrtimers; add state tracking

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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.)

No functional changes.

Build-fixes-from: Andrew Morton <akpm@osdl.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Thomas Gleixner 2007-02-16 01:27:51 -08:00 • committed by Linus Torvalds
parent 3c8aa39d7c
commit 303e967ff9
2 changed files with 67 additions and 9 deletions
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36
include/linux/hrtimer.h
View file

@ -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: */