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Subject[patch 42/46] hrtimers: add high resolution timer support
From: Thomas Gleixner <tglx@linutronix.de>

Implement high resolution timers on top of the hrtimers infrastructure
and the clockevents / tick-management framework. This provides accurate
timers for all hrtimer subsystem users.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
Documentation/kernel-parameters.txt | 4
include/linux/hrtimer.h | 116 ++++++-
include/linux/interrupt.h | 3
include/linux/ktime.h | 3
kernel/hrtimer.c | 572 ++++++++++++++++++++++++++++++++----
kernel/itimer.c | 2
kernel/posix-timers.c | 2
kernel/time/Kconfig | 10
8 files changed, 652 insertions(+), 60 deletions(-)

Index: linux-2.6.20-rc4-mm1-bo/Documentation/kernel-parameters.txt
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/Documentation/kernel-parameters.txt
+++ linux-2.6.20-rc4-mm1-bo/Documentation/kernel-parameters.txt
@@ -610,6 +610,10 @@ and is between 256 and 4096 characters.
highmem otherwise. This also works to reduce highmem
size on bigger boxes.

+ highres= [KNL] Enable/disable high resolution timer mode.
+ Valid parameters: "on", "off"
+ Default: "on"
+
hisax= [HW,ISDN]
See Documentation/isdn/README.HiSax.

Index: linux-2.6.20-rc4-mm1-bo/include/linux/hrtimer.h
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/include/linux/hrtimer.h
+++ linux-2.6.20-rc4-mm1-bo/include/linux/hrtimer.h
@@ -41,16 +41,35 @@ enum hrtimer_restart {
};

/*
- * Bit values to track state of the timer
+ * hrtimer callback modes:
+ *
+ * HRTIMER_CB_SOFTIRQ: Callback must run in softirq context
+ * HRTIMER_CB_IRQSAFE: Callback may run in hardirq context
+ * HRTIMER_CB_IRQSAFE_NO_RESTART: Callback may run in hardirq context and
+ * does not restart the timer
+ * HRTIMER_CB_IRQSAFE_NO_SOFTIRQ: Callback must run in softirq context
+ * Special mode for tick emultation
+ */
+enum hrtimer_cb_mode {
+ HRTIMER_CB_SOFTIRQ,
+ HRTIMER_CB_IRQSAFE,
+ HRTIMER_CB_IRQSAFE_NO_RESTART,
+ HRTIMER_CB_IRQSAFE_NO_SOFTIRQ,
+};
+
+/*
+ * Values to track state of the timer
*
* Possible states:
*
* 0x00 inactive
* 0x01 enqueued into rbtree
* 0x02 callback function running
+ * 0x04 callback pending (high resolution mode)
+ *
+ * Special case:
* 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
@@ -67,6 +86,7 @@ enum hrtimer_restart {
#define HRTIMER_STATE_INACTIVE 0x00
#define HRTIMER_STATE_ENQUEUED 0x01
#define HRTIMER_STATE_CALLBACK 0x02
+#define HRTIMER_STATE_PENDING 0x04

/**
* struct hrtimer - the basic hrtimer structure
@@ -77,8 +97,17 @@ enum hrtimer_restart {
* @function: timer expiry callback function
* @base: pointer to the timer base (per cpu and per clock)
* @state: state information (See bit values above)
+ * @cb_mode: high resolution timer feature to select the callback execution
+ * mode
+ * @cb_entry: list head to enqueue an expired timer into the callback list
+ * @start_site: timer statistics field to store the site where the timer
+ * was started
+ * @start_comm: timer statistics field to store the name of the process which
+ * started the timer
+ * @start_pid: timer statistics field to store the pid of the task which
+ * started the timer
*
- * The hrtimer structure must be initialized by init_hrtimer_#CLOCKTYPE()
+ * The hrtimer structure must be initialized by hrtimer_init()
*/
struct hrtimer {
struct rb_node node;
@@ -86,6 +115,10 @@ struct hrtimer {
enum hrtimer_restart (*function)(struct hrtimer *);
struct hrtimer_clock_base *base;
unsigned long state;
+#ifdef CONFIG_HIGH_RES_TIMERS
+ enum hrtimer_cb_mode cb_mode;
+ struct list_head cb_entry;
+#endif
};

/**
@@ -110,6 +143,9 @@ struct hrtimer_sleeper {
* @get_time: function to retrieve the current time of the clock
* @get_softirq_time: function to retrieve the current time from the softirq
* @softirq_time: the time when running the hrtimer queue in the softirq
+ * @cb_pending: list of timers where the callback is pending
+ * @offset: offset of this clock to the monotonic base
+ * @reprogram: function to reprogram the timer event
*/
struct hrtimer_clock_base {
struct hrtimer_cpu_base *cpu_base;
@@ -120,6 +156,12 @@ struct hrtimer_clock_base {
ktime_t (*get_time)(void);
ktime_t (*get_softirq_time)(void);
ktime_t softirq_time;
+#ifdef CONFIG_HIGH_RES_TIMERS
+ ktime_t offset;
+ int (*reprogram)(struct hrtimer *t,
+ struct hrtimer_clock_base *b,
+ ktime_t n);
+#endif
};

#define HRTIMER_MAX_CLOCK_BASES 2
@@ -131,19 +173,74 @@ struct hrtimer_clock_base {
* @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
+ * @expires_next: absolute time of the next event which was scheduled
+ * via clock_set_next_event()
+ * @hres_active: State of high resolution mode
+ * @check_clocks: Indictator, when set evaluate time source and clock
+ * event devices whether high resolution mode can be
+ * activated.
+ * @cb_pending: Expired timers are moved from the rbtree to this
+ * list in the timer interrupt. The list is processed
+ * in the softirq.
+ * @nr_events: Total number of timer interrupt events
*/
struct hrtimer_cpu_base {
spinlock_t lock;
struct lock_class_key lock_key;
struct hrtimer_clock_base clock_base[HRTIMER_MAX_CLOCK_BASES];
+#ifdef CONFIG_HIGH_RES_TIMERS
+ ktime_t expires_next;
+ int hres_active;
+ struct list_head cb_pending;
+ unsigned long nr_events;
+#endif
};

+#ifdef CONFIG_HIGH_RES_TIMERS
+struct clock_event_device;
+
+extern void clock_was_set(void);
+extern void hrtimer_interrupt(struct clock_event_device *dev);
+
+/*
+ * In high resolution mode the time reference must be read accurate
+ */
+static inline ktime_t hrtimer_cb_get_time(struct hrtimer *timer)
+{
+ return timer->base->get_time();
+}
+
+/*
+ * The resolution of the clocks. The resolution value is returned in
+ * the clock_getres() system call to give application programmers an
+ * idea of the (in)accuracy of timers. Timer values are rounded up to
+ * this resolution values.
+ */
+# define KTIME_HIGH_RES (ktime_t) { .tv64 = 1 }
+# define KTIME_MONOTONIC_RES KTIME_HIGH_RES
+
+#else
+
+# define KTIME_MONOTONIC_RES KTIME_LOW_RES
+
/*
* clock_was_set() is a NOP for non- high-resolution systems. The
* time-sorted order guarantees that a timer does not expire early and
* is expired in the next softirq when the clock was advanced.
*/
-#define clock_was_set() do { } while (0)
+static inline void clock_was_set(void) { }
+
+/*
+ * In non high resolution mode the time reference is taken from
+ * the base softirq time variable.
+ */
+static inline ktime_t hrtimer_cb_get_time(struct hrtimer *timer)
+{
+ return timer->base->softirq_time;
+}
+
+#endif
+
extern ktime_t ktime_get(void);
extern ktime_t ktime_get_real(void);

@@ -168,9 +265,7 @@ static inline int hrtimer_restart(struct
extern ktime_t hrtimer_get_remaining(const struct hrtimer *timer);
extern int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp);

-#ifdef CONFIG_NO_IDLE_HZ
extern ktime_t hrtimer_get_next_event(void);
-#endif

/*
* A timer is active, when it is enqueued into the rbtree or the callback
@@ -181,6 +276,15 @@ static inline int hrtimer_active(const s
return timer->state != HRTIMER_STATE_INACTIVE;
}

+/*
+ * 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 | HRTIMER_STATE_PENDING);
+}
+
/* Forward a hrtimer so it expires after now: */
extern unsigned long
hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval);
Index: linux-2.6.20-rc4-mm1-bo/include/linux/interrupt.h
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/include/linux/interrupt.h
+++ linux-2.6.20-rc4-mm1-bo/include/linux/interrupt.h
@@ -220,6 +220,9 @@ enum
BLOCK_SOFTIRQ,
TASKLET_SOFTIRQ,
SCHED_SOFTIRQ,
+#ifdef CONFIG_HIGH_RES_TIMERS
+ HRTIMER_SOFTIRQ,
+#endif
};

/* softirq mask and active fields moved to irq_cpustat_t in
Index: linux-2.6.20-rc4-mm1-bo/include/linux/ktime.h
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/include/linux/ktime.h
+++ linux-2.6.20-rc4-mm1-bo/include/linux/ktime.h
@@ -261,8 +261,7 @@ static inline s64 ktime_to_ns(const ktim
* idea of the (in)accuracy of timers. Timer values are rounded up to
* this resolution values.
*/
-#define KTIME_REALTIME_RES (ktime_t){ .tv64 = TICK_NSEC }
-#define KTIME_MONOTONIC_RES (ktime_t){ .tv64 = TICK_NSEC }
+#define KTIME_LOW_RES (ktime_t){ .tv64 = TICK_NSEC }

/* Get the monotonic time in timespec format: */
extern void ktime_get_ts(struct timespec *ts);
Index: linux-2.6.20-rc4-mm1-bo/kernel/hrtimer.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/hrtimer.c
+++ linux-2.6.20-rc4-mm1-bo/kernel/hrtimer.c
@@ -3,7 +3,7 @@
*
* Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
* Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
- * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
+ * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner
*
* High-resolution kernel timers
*
@@ -32,13 +32,17 @@
*/

#include <linux/cpu.h>
+#include <linux/irq.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/hrtimer.h>
#include <linux/notifier.h>
#include <linux/syscalls.h>
+#include <linux/kallsyms.h>
#include <linux/interrupt.h>
#include <linux/tick.h>
+#include <linux/seq_file.h>
+#include <linux/err.h>

#include <asm/uaccess.h>

@@ -81,7 +85,7 @@ 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.
*/
-static DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
+DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
{

.clock_base =
@@ -89,12 +93,12 @@ static DEFINE_PER_CPU(struct hrtimer_cpu
{
.index = CLOCK_REALTIME,
.get_time = &ktime_get_real,
- .resolution = KTIME_REALTIME_RES,
+ .resolution = KTIME_LOW_RES,
},
{
.index = CLOCK_MONOTONIC,
.get_time = &ktime_get,
- .resolution = KTIME_MONOTONIC_RES,
+ .resolution = KTIME_LOW_RES,
},
}
};
@@ -151,14 +155,6 @@ static void hrtimer_get_softirq_time(str
}

/*
- * 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
*/
@@ -226,7 +222,7 @@ switch_hrtimer_base(struct hrtimer *time
* completed. There is no conflict as we hold the lock until
* the timer is enqueued.
*/
- if (unlikely(timer->state & HRTIMER_STATE_CALLBACK))
+ if (unlikely(hrtimer_callback_running(timer)))
return base;

/* See the comment in lock_timer_base() */
@@ -250,7 +246,7 @@ lock_hrtimer_base(const struct hrtimer *
return base;
}

-#define switch_hrtimer_base(t, b) (b)
+# define switch_hrtimer_base(t, b) (b)

#endif /* !CONFIG_SMP */

@@ -281,9 +277,6 @@ ktime_t ktime_add_ns(const ktime_t kt, u

return ktime_add(kt, tmp);
}
-
-#else /* CONFIG_KTIME_SCALAR */
-
# endif /* !CONFIG_KTIME_SCALAR */

/*
@@ -308,6 +301,290 @@ unsigned long ktime_divns(const ktime_t
}
#endif /* BITS_PER_LONG >= 64 */

+/* High resolution timer related functions */
+#ifdef CONFIG_HIGH_RES_TIMERS
+
+/*
+ * High resolution timer enabled ?
+ */
+static int hrtimer_hres_enabled __read_mostly = 1;
+
+/*
+ * Enable / Disable high resolution mode
+ */
+static int __init setup_hrtimer_hres(char *str)
+{
+ if (!strcmp(str, "off"))
+ hrtimer_hres_enabled = 0;
+ else if (!strcmp(str, "on"))
+ hrtimer_hres_enabled = 1;
+ else
+ return 0;
+ return 1;
+}
+
+__setup("highres=", setup_hrtimer_hres);
+
+/*
+ * hrtimer_high_res_enabled - query, if the highres mode is enabled
+ */
+static inline int hrtimer_is_hres_enabled(void)
+{
+ return hrtimer_hres_enabled;
+}
+
+/*
+ * Is the high resolution mode active ?
+ */
+static inline int hrtimer_hres_active(void)
+{
+ return __get_cpu_var(hrtimer_bases).hres_active;
+}
+
+/*
+ * Reprogram the event source with checking both queues for the
+ * next event
+ * Called with interrupts disabled and base->lock held
+ */
+static void hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base)
+{
+ int i;
+ struct hrtimer_clock_base *base = cpu_base->clock_base;
+ ktime_t expires;
+
+ cpu_base->expires_next.tv64 = KTIME_MAX;
+
+ for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
+ struct hrtimer *timer;
+
+ if (!base->first)
+ continue;
+ timer = rb_entry(base->first, struct hrtimer, node);
+ expires = ktime_sub(timer->expires, base->offset);
+ if (expires.tv64 < cpu_base->expires_next.tv64)
+ cpu_base->expires_next = expires;
+ }
+
+ if (cpu_base->expires_next.tv64 != KTIME_MAX)
+ tick_program_event(cpu_base->expires_next, 1);
+}
+
+/*
+ * Shared reprogramming for clock_realtime and clock_monotonic
+ *
+ * When a timer is enqueued and expires earlier than the already enqueued
+ * timers, we have to check, whether it expires earlier than the timer for
+ * which the clock event device was armed.
+ *
+ * Called with interrupts disabled and base->cpu_base.lock held
+ */
+static int hrtimer_reprogram(struct hrtimer *timer,
+ struct hrtimer_clock_base *base)
+{
+ ktime_t *expires_next = &__get_cpu_var(hrtimer_bases).expires_next;
+ ktime_t expires = ktime_sub(timer->expires, base->offset);
+ int res;
+
+ /*
+ * When the callback is running, we do not reprogram the clock event
+ * device. The timer callback is either running on a different CPU or
+ * the callback is executed in the hrtimer_interupt context. The
+ * reprogramming is handled either by the softirq, which called the
+ * callback or at the end of the hrtimer_interrupt.
+ */
+ if (hrtimer_callback_running(timer))
+ return 0;
+
+ if (expires.tv64 >= expires_next->tv64)
+ return 0;
+
+ /*
+ * Clockevents returns -ETIME, when the event was in the past.
+ */
+ res = tick_program_event(expires, 0);
+ if (!IS_ERR_VALUE(res))
+ *expires_next = expires;
+ return res;
+}
+
+
+/*
+ * Retrigger next event is called after clock was set
+ *
+ * Called with interrupts disabled via on_each_cpu()
+ */
+static void retrigger_next_event(void *arg)
+{
+ struct hrtimer_cpu_base *base;
+ struct timespec realtime_offset;
+ unsigned long seq;
+
+ if (!hrtimer_hres_active())
+ return;
+
+ do {
+ seq = read_seqbegin(&xtime_lock);
+ set_normalized_timespec(&realtime_offset,
+ -wall_to_monotonic.tv_sec,
+ -wall_to_monotonic.tv_nsec);
+ } while (read_seqretry(&xtime_lock, seq));
+
+ base = &__get_cpu_var(hrtimer_bases);
+
+ /* Adjust CLOCK_REALTIME offset */
+ spin_lock(&base->lock);
+ base->clock_base[CLOCK_REALTIME].offset =
+ timespec_to_ktime(realtime_offset);
+
+ hrtimer_force_reprogram(base);
+ spin_unlock(&base->lock);
+}
+
+/*
+ * Clock realtime was set
+ *
+ * Change the offset of the realtime clock vs. the monotonic
+ * clock.
+ *
+ * We might have to reprogram the high resolution timer interrupt. On
+ * SMP we call the architecture specific code to retrigger _all_ high
+ * resolution timer interrupts. On UP we just disable interrupts and
+ * call the high resolution interrupt code.
+ */
+void clock_was_set(void)
+{
+ /* Retrigger the CPU local events everywhere */
+ on_each_cpu(retrigger_next_event, NULL, 0, 1);
+}
+
+/*
+ * Check, whether the timer is on the callback pending list
+ */
+static inline int hrtimer_cb_pending(const struct hrtimer *timer)
+{
+ return timer->state & HRTIMER_STATE_PENDING;
+}
+
+/*
+ * Remove a timer from the callback pending list
+ */
+static inline void hrtimer_remove_cb_pending(struct hrtimer *timer)
+{
+ list_del_init(&timer->cb_entry);
+}
+
+/*
+ * Initialize the high resolution related parts of cpu_base
+ */
+static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base)
+{
+ base->expires_next.tv64 = KTIME_MAX;
+ base->hres_active = 0;
+ INIT_LIST_HEAD(&base->cb_pending);
+}
+
+/*
+ * Initialize the high resolution related parts of a hrtimer
+ */
+static inline void hrtimer_init_timer_hres(struct hrtimer *timer)
+{
+ INIT_LIST_HEAD(&timer->cb_entry);
+}
+
+/*
+ * When High resolution timers are active, try to reprogram. Note, that in case
+ * the state has HRTIMER_STATE_CALLBACK set, no reprogramming and no expiry
+ * check happens. The timer gets enqueued into the rbtree. The reprogramming
+ * and expiry check is done in the hrtimer_interrupt or in the softirq.
+ */
+static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
+ struct hrtimer_clock_base *base)
+{
+ if (base->cpu_base->hres_active && hrtimer_reprogram(timer, base)) {
+
+ /* Timer is expired, act upon the callback mode */
+ switch(timer->cb_mode) {
+ case HRTIMER_CB_IRQSAFE_NO_RESTART:
+ /*
+ * We can call the callback from here. No restart
+ * happens, so no danger of recursion
+ */
+ BUG_ON(timer->function(timer) != HRTIMER_NORESTART);
+ return 1;
+ case HRTIMER_CB_IRQSAFE_NO_SOFTIRQ:
+ /*
+ * This is solely for the sched tick emulation with
+ * dynamic tick support to ensure that we do not
+ * restart the tick right on the edge and end up with
+ * the tick timer in the softirq ! The calling site
+ * takes care of this.
+ */
+ return 1;
+ case HRTIMER_CB_IRQSAFE:
+ case HRTIMER_CB_SOFTIRQ:
+ /*
+ * Move everything else into the softirq pending list !
+ */
+ list_add_tail(&timer->cb_entry,
+ &base->cpu_base->cb_pending);
+ timer->state = HRTIMER_STATE_PENDING;
+ raise_softirq(HRTIMER_SOFTIRQ);
+ return 1;
+ default:
+ BUG();
+ }
+ }
+ return 0;
+}
+
+/*
+ * Switch to high resolution mode
+ */
+static void hrtimer_switch_to_hres(void)
+{
+ struct hrtimer_cpu_base *base = &__get_cpu_var(hrtimer_bases);
+ unsigned long flags;
+
+ if (base->hres_active)
+ return;
+
+ local_irq_save(flags);
+
+ if (tick_init_highres()) {
+ local_irq_restore(flags);
+ return;
+ }
+ base->hres_active = 1;
+ base->clock_base[CLOCK_REALTIME].resolution = KTIME_HIGH_RES;
+ base->clock_base[CLOCK_MONOTONIC].resolution = KTIME_HIGH_RES;
+
+ tick_setup_sched_timer();
+
+ /* "Retrigger" the interrupt to get things going */
+ retrigger_next_event(NULL);
+ local_irq_restore(flags);
+ printk(KERN_INFO "Switched to high resolution mode on CPU %d\n",
+ smp_processor_id());
+}
+
+#else
+
+static inline int hrtimer_hres_active(void) { return 0; }
+static inline int hrtimer_is_hres_enabled(void) { return 0; }
+static inline void hrtimer_switch_to_hres(void) { }
+static inline void hrtimer_force_reprogram(struct hrtimer_cpu_base *base) { }
+static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
+ struct hrtimer_clock_base *base)
+{
+ return 0;
+}
+static inline int hrtimer_cb_pending(struct hrtimer *timer) { return 0; }
+static inline void hrtimer_remove_cb_pending(struct hrtimer *timer) { }
+static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base) { }
+static inline void hrtimer_init_timer_hres(struct hrtimer *timer) { }
+
+#endif /* CONFIG_HIGH_RES_TIMERS */
+
/*
* Counterpart to lock_timer_base above:
*/
@@ -365,7 +642,7 @@ hrtimer_forward(struct hrtimer *timer, k
* red black tree is O(log(n)). Must hold the base lock.
*/
static void enqueue_hrtimer(struct hrtimer *timer,
- struct hrtimer_clock_base *base)
+ struct hrtimer_clock_base *base, int reprogram)
{
struct rb_node **link = &base->active.rb_node;
struct rb_node *parent = NULL;
@@ -391,6 +668,22 @@ static void enqueue_hrtimer(struct hrtim
* Insert the timer to the rbtree and check whether it
* replaces the first pending timer
*/
+ if (!base->first || timer->expires.tv64 <
+ rb_entry(base->first, struct hrtimer, node)->expires.tv64) {
+ /*
+ * Reprogram the clock event device. When the timer is already
+ * expired hrtimer_enqueue_reprogram has either called the
+ * callback or added it to the pending list and raised the
+ * softirq.
+ *
+ * This is a NOP for !HIGHRES
+ */
+ if (reprogram && hrtimer_enqueue_reprogram(timer, base))
+ return;
+
+ base->first = &timer->node;
+ }
+
rb_link_node(&timer->node, parent, link);
rb_insert_color(&timer->node, &base->active);
/*
@@ -398,28 +691,38 @@ static void enqueue_hrtimer(struct hrtim
* 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)
- base->first = &timer->node;
}

/*
* __remove_hrtimer - internal function to remove a timer
*
* Caller must hold the base lock.
+ *
+ * High resolution timer mode reprograms the clock event device when the
+ * timer is the one which expires next. The caller can disable this by setting
+ * reprogram to zero. This is useful, when the context does a reprogramming
+ * anyway (e.g. timer interrupt)
*/
static void __remove_hrtimer(struct hrtimer *timer,
struct hrtimer_clock_base *base,
- unsigned long newstate)
+ unsigned long newstate, int reprogram)
{
- /*
- * Remove the timer from the rbtree and replace the
- * first entry pointer if necessary.
- */
- if (base->first == &timer->node)
- base->first = rb_next(&timer->node);
- rb_erase(&timer->node, &base->active);
+ /* High res. callback list. NOP for !HIGHRES */
+ if (hrtimer_cb_pending(timer))
+ hrtimer_remove_cb_pending(timer);
+ else {
+ /*
+ * Remove the timer from the rbtree and replace the
+ * first entry pointer if necessary.
+ */
+ if (base->first == &timer->node) {
+ base->first = rb_next(&timer->node);
+ /* Reprogram the clock event device. if enabled */
+ if (reprogram && hrtimer_hres_active())
+ hrtimer_force_reprogram(base->cpu_base);
+ }
+ rb_erase(&timer->node, &base->active);
+ }
timer->state = newstate;
}

@@ -430,7 +733,19 @@ static inline int
remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
{
if (hrtimer_is_queued(timer)) {
- __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE);
+ int reprogram;
+
+ /*
+ * Remove the timer and force reprogramming when high
+ * resolution mode is active and the timer is on the current
+ * CPU. If we remove a timer on another CPU, reprogramming is
+ * skipped. The interrupt event on this CPU is fired and
+ * reprogramming happens in the interrupt handler. This is a
+ * rare case and less expensive than a smp call.
+ */
+ reprogram = base->cpu_base == &__get_cpu_var(hrtimer_bases);
+ __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE,
+ reprogram);
return 1;
}
return 0;
@@ -476,7 +791,7 @@ hrtimer_start(struct hrtimer *timer, kti
}
timer->expires = tim;

- enqueue_hrtimer(timer, new_base);
+ enqueue_hrtimer(timer, new_base, base == new_base);

unlock_hrtimer_base(timer, &flags);

@@ -567,17 +882,19 @@ ktime_t hrtimer_get_next_event(void)

spin_lock_irqsave(&cpu_base->lock, flags);

- for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
- struct hrtimer *timer;
-
- if (!base->first)
- continue;
-
- timer = rb_entry(base->first, struct hrtimer, node);
- delta.tv64 = timer->expires.tv64;
- delta = ktime_sub(delta, base->get_time());
- if (delta.tv64 < mindelta.tv64)
- mindelta.tv64 = delta.tv64;
+ if (!hrtimer_hres_active()) {
+ for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
+ struct hrtimer *timer;
+
+ if (!base->first)
+ continue;
+
+ timer = rb_entry(base->first, struct hrtimer, node);
+ delta.tv64 = timer->expires.tv64;
+ delta = ktime_sub(delta, base->get_time());
+ if (delta.tv64 < mindelta.tv64)
+ mindelta.tv64 = delta.tv64;
+ }
}

spin_unlock_irqrestore(&cpu_base->lock, flags);
@@ -607,6 +924,7 @@ void hrtimer_init(struct hrtimer *timer,
clock_id = CLOCK_MONOTONIC;

timer->base = &cpu_base->clock_base[clock_id];
+ hrtimer_init_timer_hres(timer);
}
EXPORT_SYMBOL_GPL(hrtimer_init);

@@ -629,6 +947,139 @@ int hrtimer_get_res(const clockid_t whic
}
EXPORT_SYMBOL_GPL(hrtimer_get_res);

+#ifdef CONFIG_HIGH_RES_TIMERS
+
+/*
+ * High resolution timer interrupt
+ * Called with interrupts disabled
+ */
+void hrtimer_interrupt(struct clock_event_device *dev)
+{
+ struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
+ struct hrtimer_clock_base *base;
+ ktime_t expires_next, now;
+ int i, raise = 0;
+
+ BUG_ON(!cpu_base->hres_active);
+ cpu_base->nr_events++;
+ dev->next_event.tv64 = KTIME_MAX;
+
+ retry:
+ now = ktime_get();
+
+ expires_next.tv64 = KTIME_MAX;
+
+ base = cpu_base->clock_base;
+
+ for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
+ ktime_t basenow;
+ struct rb_node *node;
+
+ spin_lock(&cpu_base->lock);
+
+ basenow = ktime_add(now, base->offset);
+
+ while ((node = base->first)) {
+ struct hrtimer *timer;
+
+ timer = rb_entry(node, struct hrtimer, node);
+
+ if (basenow.tv64 < timer->expires.tv64) {
+ ktime_t expires;
+
+ expires = ktime_sub(timer->expires,
+ base->offset);
+ if (expires.tv64 < expires_next.tv64)
+ expires_next = expires;
+ break;
+ }
+
+ /* Move softirq callbacks to the pending list */
+ if (timer->cb_mode == HRTIMER_CB_SOFTIRQ) {
+ __remove_hrtimer(timer, base,
+ HRTIMER_STATE_PENDING, 0);
+ list_add_tail(&timer->cb_entry,
+ &base->cpu_base->cb_pending);
+ raise = 1;
+ continue;
+ }
+
+ __remove_hrtimer(timer, base,
+ HRTIMER_STATE_CALLBACK, 0);
+
+ /*
+ * Note: We clear the CALLBACK bit after
+ * enqueue_hrtimer to avoid reprogramming of
+ * the event hardware. This happens at the end
+ * of this function anyway.
+ */
+ if (timer->function(timer) != HRTIMER_NORESTART) {
+ BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
+ enqueue_hrtimer(timer, base, 0);
+ }
+ timer->state &= ~HRTIMER_STATE_CALLBACK;
+ }
+ spin_unlock(&cpu_base->lock);
+ base++;
+ }
+
+ cpu_base->expires_next = expires_next;
+
+ /* Reprogramming necessary ? */
+ if (expires_next.tv64 != KTIME_MAX) {
+ if (tick_program_event(expires_next, 0))
+ goto retry;
+ }
+
+ /* Raise softirq ? */
+ if (raise)
+ raise_softirq(HRTIMER_SOFTIRQ);
+}
+
+static void run_hrtimer_softirq(struct softirq_action *h)
+{
+ struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
+
+ spin_lock_irq(&cpu_base->lock);
+
+ while (!list_empty(&cpu_base->cb_pending)) {
+ enum hrtimer_restart (*fn)(struct hrtimer *);
+ struct hrtimer *timer;
+ int restart;
+
+ timer = list_entry(cpu_base->cb_pending.next,
+ struct hrtimer, cb_entry);
+
+ fn = timer->function;
+ __remove_hrtimer(timer, timer->base, HRTIMER_STATE_CALLBACK, 0);
+ spin_unlock_irq(&cpu_base->lock);
+
+ restart = fn(timer);
+
+ spin_lock_irq(&cpu_base->lock);
+
+ timer->state &= ~HRTIMER_STATE_CALLBACK;
+ if (restart == HRTIMER_RESTART) {
+ BUG_ON(hrtimer_active(timer));
+ /*
+ * Enqueue the timer, allow reprogramming of the event
+ * device
+ */
+ enqueue_hrtimer(timer, timer->base, 1);
+ } else if (hrtimer_active(timer)) {
+ /*
+ * If the timer was rearmed on another CPU, reprogram
+ * the event device.
+ */
+ if (timer->base->first == &timer->node)
+ hrtimer_reprogram(timer, timer->base);
+ }
+ }
+ spin_unlock_irq(&cpu_base->lock);
+}
+
+#endif /* CONFIG_HIGH_RES_TIMERS */
+
/*
* Expire the per base hrtimer-queue:
*/
@@ -656,7 +1107,7 @@ static inline void run_hrtimer_queue(str
break;

fn = timer->function;
- __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK);
+ __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
spin_unlock_irq(&cpu_base->lock);

restart = fn(timer);
@@ -666,7 +1117,7 @@ static inline void run_hrtimer_queue(str
timer->state &= ~HRTIMER_STATE_CALLBACK;
if (restart != HRTIMER_NORESTART) {
BUG_ON(hrtimer_active(timer));
- enqueue_hrtimer(timer, base);
+ enqueue_hrtimer(timer, base, 0);
}
}
spin_unlock_irq(&cpu_base->lock);
@@ -674,12 +1125,19 @@ static inline void run_hrtimer_queue(str

/*
* Called from timer softirq every jiffy, expire hrtimers:
+ *
+ * For HRT its the fall back code to run the softirq in the timer
+ * softirq context in case the hrtimer initialization failed or has
+ * not been done yet.
*/
void hrtimer_run_queues(void)
{
struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
int i;

+ if (hrtimer_hres_active())
+ return;
+
/*
* This _is_ ugly: We have to check in the softirq context,
* whether we can switch to highres and / or nohz mode. The
@@ -688,7 +1146,8 @@ void hrtimer_run_queues(void)
* check bit in the tick_oneshot code, otherwise we might
* deadlock vs. xtime_lock.
*/
- tick_check_oneshot_change(1);
+ if (tick_check_oneshot_change(!hrtimer_is_hres_enabled()))
+ hrtimer_switch_to_hres();

hrtimer_get_softirq_time(cpu_base);

@@ -716,6 +1175,9 @@ void hrtimer_init_sleeper(struct hrtimer
{
sl->timer.function = hrtimer_wakeup;
sl->task = task;
+#ifdef CONFIG_HIGH_RES_TIMERS
+ sl->timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_RESTART;
+#endif
}

static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
@@ -726,7 +1188,8 @@ static int __sched do_nanosleep(struct h
set_current_state(TASK_INTERRUPTIBLE);
hrtimer_start(&t->timer, t->timer.expires, mode);

- schedule();
+ if (likely(t->task))
+ schedule();

hrtimer_cancel(&t->timer);
mode = HRTIMER_MODE_ABS;
@@ -831,6 +1294,7 @@ static void __devinit init_hrtimers_cpu(
for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
cpu_base->clock_base[i].cpu_base = cpu_base;

+ hrtimer_init_hres(cpu_base);
}

#ifdef CONFIG_HOTPLUG_CPU
@@ -843,10 +1307,13 @@ static void migrate_hrtimer_list(struct

while ((node = rb_first(&old_base->active))) {
timer = rb_entry(node, struct hrtimer, node);
- BUG_ON(timer->state & HRTIMER_STATE_CALLBACK);
- __remove_hrtimer(timer, old_base, HRTIMER_STATE_INACTIVE);
+ BUG_ON(hrtimer_callback_running(timer));
+ __remove_hrtimer(timer, old_base, HRTIMER_STATE_INACTIVE, 0);
timer->base = new_base;
- enqueue_hrtimer(timer, new_base);
+ /*
+ * Enqueue the timer. Allow reprogramming of the event device
+ */
+ enqueue_hrtimer(timer, new_base, 1);
}
}

@@ -859,6 +1326,8 @@ static void migrate_hrtimers(int cpu)
old_base = &per_cpu(hrtimer_bases, cpu);
new_base = &get_cpu_var(hrtimer_bases);

+ tick_cancel_sched_timer(cpu);
+
local_irq_disable();

spin_lock(&new_base->lock);
@@ -909,5 +1378,8 @@ void __init hrtimers_init(void)
hrtimer_cpu_notify(&hrtimers_nb, (unsigned long)CPU_UP_PREPARE,
(void *)(long)smp_processor_id());
register_cpu_notifier(&hrtimers_nb);
+#ifdef CONFIG_HIGH_RES_TIMERS
+ open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq, NULL);
+#endif
}

Index: linux-2.6.20-rc4-mm1-bo/kernel/itimer.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/itimer.c
+++ linux-2.6.20-rc4-mm1-bo/kernel/itimer.c
@@ -136,7 +136,7 @@ enum hrtimer_restart it_real_fn(struct h
send_group_sig_info(SIGALRM, SEND_SIG_PRIV, sig->tsk);

if (sig->it_real_incr.tv64 != 0) {
- hrtimer_forward(timer, timer->base->softirq_time,
+ hrtimer_forward(timer, hrtimer_cb_get_time(timer),
sig->it_real_incr);
return HRTIMER_RESTART;
}
Index: linux-2.6.20-rc4-mm1-bo/kernel/posix-timers.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/posix-timers.c
+++ linux-2.6.20-rc4-mm1-bo/kernel/posix-timers.c
@@ -356,7 +356,7 @@ static enum hrtimer_restart posix_timer_
if (timr->it.real.interval.tv64 != 0) {
timr->it_overrun +=
hrtimer_forward(timer,
- timer->base->softirq_time,
+ hrtimer_cb_get_time(timer),
timr->it.real.interval);
ret = HRTIMER_RESTART;
++timr->it_requeue_pending;
Index: linux-2.6.20-rc4-mm1-bo/kernel/time/Kconfig
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/time/Kconfig
+++ linux-2.6.20-rc4-mm1-bo/kernel/time/Kconfig
@@ -13,3 +13,13 @@ config NO_HZ
This option enables a tickless system: timer interrupts will
only trigger on an as-needed basis both when the system is
busy and when the system is idle.
+
+config HIGH_RES_TIMERS
+ bool "High Resolution Timer Support"
+ depends on GENERIC_TIME && GENERIC_CLOCKEVENTS
+ select TICK_ONESHOT
+ help
+ This option enables high resolution timer support. If your
+ hardware is not capable then this option only increases
+ the size of the kernel image.
+
--

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