Commit 303e967f authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Linus Torvalds
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[PATCH] hrtimers; add state tracking



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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3c8aa39d
......@@ -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: */
......
......@@ -149,6 +149,23 @@ static void hrtimer_get_softirq_time(struct hrtimer_cpu_base *base)
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
......@@ -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);
}
......
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