[PATCH] hrtimers: cleanup locking
Improve kernel/hrtimers.c locking: use a per-CPU base with a lock to control
locking of all clocks belonging to a CPU. This simplifies code that needs to
lock all clocks at once. This makes life easier for high-res timers and
dyntick.
No functional changes.
[ optimization change from Andrew Morton <akpm@osdl.org> ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 83fc504..89a9f53 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1,8 +1,9 @@
/*
* linux/kernel/hrtimer.c
*
- * Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
- * Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
+ * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
+ * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
+ * Copyright(C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
*
* High-resolution kernel timers
*
@@ -79,21 +80,22 @@
* This ensures that we capture erroneous accesses to these clock ids
* rather than moving them into the range of valid clock id's.
*/
-
-#define MAX_HRTIMER_BASES 2
-
-static DEFINE_PER_CPU(struct hrtimer_base, hrtimer_bases[MAX_HRTIMER_BASES]) =
+static DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
{
+
+ .clock_base =
{
- .index = CLOCK_REALTIME,
- .get_time = &ktime_get_real,
- .resolution = KTIME_REALTIME_RES,
- },
- {
- .index = CLOCK_MONOTONIC,
- .get_time = &ktime_get,
- .resolution = KTIME_MONOTONIC_RES,
- },
+ {
+ .index = CLOCK_REALTIME,
+ .get_time = &ktime_get_real,
+ .resolution = KTIME_REALTIME_RES,
+ },
+ {
+ .index = CLOCK_MONOTONIC,
+ .get_time = &ktime_get,
+ .resolution = KTIME_MONOTONIC_RES,
+ },
+ }
};
/**
@@ -125,7 +127,7 @@
* Get the coarse grained time at the softirq based on xtime and
* wall_to_monotonic.
*/
-static void hrtimer_get_softirq_time(struct hrtimer_base *base)
+static void hrtimer_get_softirq_time(struct hrtimer_cpu_base *base)
{
ktime_t xtim, tomono;
struct timespec xts;
@@ -142,8 +144,9 @@
xtim = timespec_to_ktime(xts);
tomono = timespec_to_ktime(wall_to_monotonic);
- base[CLOCK_REALTIME].softirq_time = xtim;
- base[CLOCK_MONOTONIC].softirq_time = ktime_add(xtim, tomono);
+ base->clock_base[CLOCK_REALTIME].softirq_time = xtim;
+ base->clock_base[CLOCK_MONOTONIC].softirq_time =
+ ktime_add(xtim, tomono);
}
/*
@@ -166,19 +169,20 @@
* possible to set timer->base = NULL and drop the lock: the timer remains
* locked.
*/
-static struct hrtimer_base *lock_hrtimer_base(const struct hrtimer *timer,
- unsigned long *flags)
+static
+struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
+ unsigned long *flags)
{
- struct hrtimer_base *base;
+ struct hrtimer_clock_base *base;
for (;;) {
base = timer->base;
if (likely(base != NULL)) {
- spin_lock_irqsave(&base->lock, *flags);
+ spin_lock_irqsave(&base->cpu_base->lock, *flags);
if (likely(base == timer->base))
return base;
/* The timer has migrated to another CPU: */
- spin_unlock_irqrestore(&base->lock, *flags);
+ spin_unlock_irqrestore(&base->cpu_base->lock, *flags);
}
cpu_relax();
}
@@ -187,12 +191,14 @@
/*
* Switch the timer base to the current CPU when possible.
*/
-static inline struct hrtimer_base *
-switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_base *base)
+static inline struct hrtimer_clock_base *
+switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base)
{
- struct hrtimer_base *new_base;
+ struct hrtimer_clock_base *new_base;
+ struct hrtimer_cpu_base *new_cpu_base;
- new_base = &__get_cpu_var(hrtimer_bases)[base->index];
+ new_cpu_base = &__get_cpu_var(hrtimer_bases);
+ new_base = &new_cpu_base->clock_base[base->index];
if (base != new_base) {
/*
@@ -204,13 +210,13 @@
* completed. There is no conflict as we hold the lock until
* the timer is enqueued.
*/
- if (unlikely(base->curr_timer == timer))
+ if (unlikely(base->cpu_base->curr_timer == timer))
return base;
/* See the comment in lock_timer_base() */
timer->base = NULL;
- spin_unlock(&base->lock);
- spin_lock(&new_base->lock);
+ spin_unlock(&base->cpu_base->lock);
+ spin_lock(&new_base->cpu_base->lock);
timer->base = new_base;
}
return new_base;
@@ -220,12 +226,12 @@
#define set_curr_timer(b, t) do { } while (0)
-static inline struct hrtimer_base *
+static inline struct hrtimer_clock_base *
lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
{
- struct hrtimer_base *base = timer->base;
+ struct hrtimer_clock_base *base = timer->base;
- spin_lock_irqsave(&base->lock, *flags);
+ spin_lock_irqsave(&base->cpu_base->lock, *flags);
return base;
}
@@ -305,7 +311,7 @@
static inline
void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
{
- spin_unlock_irqrestore(&timer->base->lock, *flags);
+ spin_unlock_irqrestore(&timer->base->cpu_base->lock, *flags);
}
/**
@@ -355,7 +361,8 @@
* The timer is inserted in expiry order. Insertion into the
* red black tree is O(log(n)). Must hold the base lock.
*/
-static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
+static void enqueue_hrtimer(struct hrtimer *timer,
+ struct hrtimer_clock_base *base)
{
struct rb_node **link = &base->active.rb_node;
struct rb_node *parent = NULL;
@@ -394,7 +401,8 @@
*
* Caller must hold the base lock.
*/
-static void __remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
+static void __remove_hrtimer(struct hrtimer *timer,
+ struct hrtimer_clock_base *base)
{
/*
* Remove the timer from the rbtree and replace the
@@ -410,7 +418,7 @@
* remove hrtimer, called with base lock held
*/
static inline int
-remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
+remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
{
if (hrtimer_active(timer)) {
__remove_hrtimer(timer, base);
@@ -432,7 +440,7 @@
int
hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
{
- struct hrtimer_base *base, *new_base;
+ struct hrtimer_clock_base *base, *new_base;
unsigned long flags;
int ret;
@@ -479,13 +487,13 @@
*/
int hrtimer_try_to_cancel(struct hrtimer *timer)
{
- struct hrtimer_base *base;
+ struct hrtimer_clock_base *base;
unsigned long flags;
int ret = -1;
base = lock_hrtimer_base(timer, &flags);
- if (base->curr_timer != timer)
+ if (base->cpu_base->curr_timer != timer)
ret = remove_hrtimer(timer, base);
unlock_hrtimer_base(timer, &flags);
@@ -521,12 +529,12 @@
*/
ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
{
- struct hrtimer_base *base;
+ struct hrtimer_clock_base *base;
unsigned long flags;
ktime_t rem;
base = lock_hrtimer_base(timer, &flags);
- rem = ktime_sub(timer->expires, timer->base->get_time());
+ rem = ktime_sub(timer->expires, base->get_time());
unlock_hrtimer_base(timer, &flags);
return rem;
@@ -542,26 +550,29 @@
*/
ktime_t hrtimer_get_next_event(void)
{
- struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);
+ struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
+ struct hrtimer_clock_base *base = cpu_base->clock_base;
ktime_t delta, mindelta = { .tv64 = KTIME_MAX };
unsigned long flags;
int i;
- for (i = 0; i < MAX_HRTIMER_BASES; i++, base++) {
+ spin_lock_irqsave(&cpu_base->lock, flags);
+
+ for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
struct hrtimer *timer;
- spin_lock_irqsave(&base->lock, flags);
- if (!base->first) {
- spin_unlock_irqrestore(&base->lock, flags);
+ if (!base->first)
continue;
- }
+
timer = rb_entry(base->first, struct hrtimer, node);
delta.tv64 = timer->expires.tv64;
- spin_unlock_irqrestore(&base->lock, flags);
delta = ktime_sub(delta, base->get_time());
if (delta.tv64 < mindelta.tv64)
mindelta.tv64 = delta.tv64;
}
+
+ spin_unlock_irqrestore(&cpu_base->lock, flags);
+
if (mindelta.tv64 < 0)
mindelta.tv64 = 0;
return mindelta;
@@ -577,16 +588,16 @@
void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
enum hrtimer_mode mode)
{
- struct hrtimer_base *bases;
+ struct hrtimer_cpu_base *cpu_base;
memset(timer, 0, sizeof(struct hrtimer));
- bases = __raw_get_cpu_var(hrtimer_bases);
+ cpu_base = &__raw_get_cpu_var(hrtimer_bases);
if (clock_id == CLOCK_REALTIME && mode != HRTIMER_MODE_ABS)
clock_id = CLOCK_MONOTONIC;
- timer->base = &bases[clock_id];
+ timer->base = &cpu_base->clock_base[clock_id];
rb_set_parent(&timer->node, &timer->node);
}
EXPORT_SYMBOL_GPL(hrtimer_init);
@@ -601,10 +612,10 @@
*/
int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
{
- struct hrtimer_base *bases;
+ struct hrtimer_cpu_base *cpu_base;
- bases = __raw_get_cpu_var(hrtimer_bases);
- *tp = ktime_to_timespec(bases[which_clock].resolution);
+ cpu_base = &__raw_get_cpu_var(hrtimer_bases);
+ *tp = ktime_to_timespec(cpu_base->clock_base[which_clock].resolution);
return 0;
}
@@ -613,9 +624,11 @@
/*
* Expire the per base hrtimer-queue:
*/
-static inline void run_hrtimer_queue(struct hrtimer_base *base)
+static inline void run_hrtimer_queue(struct hrtimer_cpu_base *cpu_base,
+ int index)
{
struct rb_node *node;
+ struct hrtimer_clock_base *base = &cpu_base->clock_base[index];
if (!base->first)
return;
@@ -623,7 +636,7 @@
if (base->get_softirq_time)
base->softirq_time = base->get_softirq_time();
- spin_lock_irq(&base->lock);
+ spin_lock_irq(&cpu_base->lock);
while ((node = base->first)) {
struct hrtimer *timer;
@@ -635,21 +648,21 @@
break;
fn = timer->function;
- set_curr_timer(base, timer);
+ set_curr_timer(cpu_base, timer);
__remove_hrtimer(timer, base);
- spin_unlock_irq(&base->lock);
+ spin_unlock_irq(&cpu_base->lock);
restart = fn(timer);
- spin_lock_irq(&base->lock);
+ spin_lock_irq(&cpu_base->lock);
if (restart != HRTIMER_NORESTART) {
BUG_ON(hrtimer_active(timer));
enqueue_hrtimer(timer, base);
}
}
- set_curr_timer(base, NULL);
- spin_unlock_irq(&base->lock);
+ set_curr_timer(cpu_base, NULL);
+ spin_unlock_irq(&cpu_base->lock);
}
/*
@@ -657,13 +670,13 @@
*/
void hrtimer_run_queues(void)
{
- struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);
+ struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
int i;
- hrtimer_get_softirq_time(base);
+ hrtimer_get_softirq_time(cpu_base);
- for (i = 0; i < MAX_HRTIMER_BASES; i++)
- run_hrtimer_queue(&base[i]);
+ for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
+ run_hrtimer_queue(cpu_base, i);
}
/*
@@ -792,19 +805,21 @@
*/
static void __devinit init_hrtimers_cpu(int cpu)
{
- struct hrtimer_base *base = per_cpu(hrtimer_bases, cpu);
+ struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);
int i;
- for (i = 0; i < MAX_HRTIMER_BASES; i++, base++) {
- spin_lock_init(&base->lock);
- lockdep_set_class(&base->lock, &base->lock_key);
- }
+ spin_lock_init(&cpu_base->lock);
+ lockdep_set_class(&cpu_base->lock, &cpu_base->lock_key);
+
+ for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
+ cpu_base->clock_base[i].cpu_base = cpu_base;
+
}
#ifdef CONFIG_HOTPLUG_CPU
-static void migrate_hrtimer_list(struct hrtimer_base *old_base,
- struct hrtimer_base *new_base)
+static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
+ struct hrtimer_clock_base *new_base)
{
struct hrtimer *timer;
struct rb_node *node;
@@ -819,29 +834,26 @@
static void migrate_hrtimers(int cpu)
{
- struct hrtimer_base *old_base, *new_base;
+ struct hrtimer_cpu_base *old_base, *new_base;
int i;
BUG_ON(cpu_online(cpu));
- old_base = per_cpu(hrtimer_bases, cpu);
- new_base = get_cpu_var(hrtimer_bases);
+ old_base = &per_cpu(hrtimer_bases, cpu);
+ new_base = &get_cpu_var(hrtimer_bases);
local_irq_disable();
- for (i = 0; i < MAX_HRTIMER_BASES; i++) {
+ spin_lock(&new_base->lock);
+ spin_lock(&old_base->lock);
- spin_lock(&new_base->lock);
- spin_lock(&old_base->lock);
-
+ for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
BUG_ON(old_base->curr_timer);
- migrate_hrtimer_list(old_base, new_base);
-
- spin_unlock(&old_base->lock);
- spin_unlock(&new_base->lock);
- old_base++;
- new_base++;
+ migrate_hrtimer_list(&old_base->clock_base[i],
+ &new_base->clock_base[i]);
}
+ spin_unlock(&old_base->lock);
+ spin_unlock(&new_base->lock);
local_irq_enable();
put_cpu_var(hrtimer_bases);