Commit 54cdfdb4 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Linus Torvalds

[PATCH] hrtimers: add high resolution timer support

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: 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 d40891e7
......@@ -609,6 +609,10 @@ and is between 256 and 4096 characters. It is defined in the file
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.
......
......@@ -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 hrtimer *timer)
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 struct hrtimer *timer)
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);
......
......@@ -242,6 +242,9 @@ 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
......
......@@ -261,8 +261,7 @@ static inline s64 ktime_to_ns(const ktime_t kt)
* 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);
......
This diff is collapsed.
......@@ -136,7 +136,7 @@ enum hrtimer_restart it_real_fn(struct hrtimer *timer)
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;
}
......
......@@ -356,7 +356,7 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *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;
......
......@@ -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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