Commit 3c8aa39d authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Linus Torvalds
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[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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c9cb2e3d
......@@ -21,6 +21,9 @@
#include <linux/list.h>
#include <linux/wait.h>
struct hrtimer_clock_base;
struct hrtimer_cpu_base;
/*
* Mode arguments of xxx_hrtimer functions:
*/
......@@ -37,8 +40,6 @@ enum hrtimer_restart {
HRTIMER_RESTART, /* Timer must be restarted */
};
struct hrtimer_base;
/**
* struct hrtimer - the basic hrtimer structure
* @node: red black tree node for time ordered insertion
......@@ -51,10 +52,10 @@ struct hrtimer_base;
* The hrtimer structure must be initialized by init_hrtimer_#CLOCKTYPE()
*/
struct hrtimer {
struct rb_node node;
ktime_t expires;
enum hrtimer_restart (*function)(struct hrtimer *);
struct hrtimer_base *base;
struct rb_node node;
ktime_t expires;
enum hrtimer_restart (*function)(struct hrtimer *);
struct hrtimer_clock_base *base;
};
/**
......@@ -71,29 +72,41 @@ struct hrtimer_sleeper {
/**
* struct hrtimer_base - the timer base for a specific clock
* @index: clock type index for per_cpu support when moving a timer
* to a base on another cpu.
* @lock: lock protecting the base and associated timers
* @index: clock type index for per_cpu support when moving a
* timer to a base on another cpu.
* @active: red black tree root node for the active timers
* @first: pointer to the timer node which expires first
* @resolution: the resolution of the clock, in nanoseconds
* @get_time: function to retrieve the current time of the clock
* @get_softirq_time: function to retrieve the current time from the softirq
* @curr_timer: the timer which is executing a callback right now
* @softirq_time: the time when running the hrtimer queue in the softirq
* @lock_key: the lock_class_key for use with lockdep
*/
struct hrtimer_base {
struct hrtimer_clock_base {
struct hrtimer_cpu_base *cpu_base;
clockid_t index;
spinlock_t lock;
struct rb_root active;
struct rb_node *first;
ktime_t resolution;
ktime_t (*get_time)(void);
ktime_t (*get_softirq_time)(void);
struct hrtimer *curr_timer;
ktime_t softirq_time;
struct lock_class_key lock_key;
};
#define HRTIMER_MAX_CLOCK_BASES 2
/*
* struct hrtimer_cpu_base - the per cpu clock bases
* @lock: lock protecting the base and associated clock bases
* and timers
* @lock_key: the lock_class_key for use with lockdep
* @clock_base: array of clock bases for this cpu
* @curr_timer: the timer which is executing a callback right now
*/
struct hrtimer_cpu_base {
spinlock_t lock;
struct lock_class_key lock_key;
struct hrtimer_clock_base clock_base[HRTIMER_MAX_CLOCK_BASES];
struct hrtimer *curr_timer;
};
/*
......
/*
* 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 @@ EXPORT_SYMBOL_GPL(ktime_get_real);
* 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 @@ EXPORT_SYMBOL_GPL(ktime_get_ts);
* 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 @@ static void hrtimer_get_softirq_time(struct hrtimer_base *base)
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 @@ static void hrtimer_get_softirq_time(struct hrtimer_base *base)
* 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 @@ static struct hrtimer_base *lock_hrtimer_base(const struct hrtimer *timer,
/*
* 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 @@ switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_base *base)
* 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 @@ switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_base *base)
#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 @@ void hrtimer_notify_resume(void)
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 @@ hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
* 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 @@ static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
*
* 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 @@ static void __remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
* 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 @@ remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
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 @@ EXPORT_SYMBOL_GPL(hrtimer_start);
*/
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 @@ EXPORT_SYMBOL_GPL(hrtimer_cancel);
*/
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 @@ EXPORT_SYMBOL_GPL(hrtimer_get_remaining);
*/
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 @@ ktime_t hrtimer_get_next_event(void)
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 @@ EXPORT_SYMBOL_GPL(hrtimer_init);
*/
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 @@ EXPORT_SYMBOL_GPL(hrtimer_get_res);
/*
* 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 @@ static inline void run_hrtimer_queue(struct hrtimer_base *base)
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 @@ static inline void run_hrtimer_queue(struct hrtimer_base *base)
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 @@ static inline void run_hrtimer_queue(struct hrtimer_base *base)
*/
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 @@ sys_nanosleep(struct timespec __user *rqtp, struct timespec __user *rmtp)
*/
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_hrtimer_list(struct hrtimer_base *old_base,
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);
......
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