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Subject[patch 11/23] hrtimers: state tracking
From: Thomas Gleixner <tglx@linutronix.de>

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 3.)

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
--
include/linux/hrtimer.h | 7 +++++--
kernel/hrtimer.c | 17 ++++++++++-------
2 files changed, 15 insertions(+), 9 deletions(-)
Index: linux-2.6.18-mm2/include/linux/hrtimer.h
===================================================================
--- linux-2.6.18-mm2.orig/include/linux/hrtimer.h 2006-09-30 01:41:17.000000000 +0200
+++ linux-2.6.18-mm2/include/linux/hrtimer.h 2006-09-30 01:41:17.000000000 +0200
@@ -34,7 +34,9 @@ enum hrtimer_restart {
HRTIMER_RESTART,
};

-#define HRTIMER_INACTIVE ((void *)1UL)
+#define HRTIMER_INACTIVE 0x00
+#define HRTIMER_ACTIVE 0x01
+#define HRTIMER_CALLBACK 0x02

struct hrtimer_clock_base;

@@ -54,6 +56,7 @@ struct hrtimer {
ktime_t expires;
int (*function)(struct hrtimer *);
struct hrtimer_clock_base *base;
+ unsigned long state;
};

/**
@@ -139,7 +142,7 @@ extern ktime_t hrtimer_get_next_event(vo

static inline int hrtimer_active(const struct hrtimer *timer)
{
- return rb_parent(&timer->node) != &timer->node;
+ return timer->state != HRTIMER_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 2006-09-30 01:41:17.000000000 +0200
+++ linux-2.6.18-mm2/kernel/hrtimer.c 2006-09-30 01:41:17.000000000 +0200
@@ -384,6 +384,7 @@ static void enqueue_hrtimer(struct hrtim
*/
rb_link_node(&timer->node, parent, link);
rb_insert_color(&timer->node, &base->active);
+ timer->state |= HRTIMER_ACTIVE;

if (!base->first || timer->expires.tv64 <
rb_entry(base->first, struct hrtimer, node)->expires.tv64)
@@ -396,7 +397,8 @@ 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
@@ -405,7 +407,7 @@ 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;
}

/*
@@ -415,7 +417,7 @@ 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_INACTIVE);
return 1;
}
return 0;
@@ -487,7 +489,7 @@ int hrtimer_try_to_cancel(struct hrtimer

base = lock_hrtimer_base(timer, &flags);

- if (base->cpu_base->curr_timer != timer)
+ if (!(timer->state & HRTIMER_CALLBACK))
ret = remove_hrtimer(timer, base);

unlock_hrtimer_base(timer, &flags);
@@ -592,7 +594,6 @@ 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);

@@ -643,13 +644,14 @@ 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_CALLBACK);
spin_unlock_irq(&cpu_base->lock);

restart = fn(timer);

spin_lock_irq(&cpu_base->lock);

+ timer->state &= ~HRTIMER_CALLBACK;
if (restart != HRTIMER_NORESTART) {
BUG_ON(hrtimer_active(timer));
enqueue_hrtimer(timer, base);
@@ -820,7 +822,8 @@ 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);
}
--

-
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