[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: 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/include/linux/hrtimer.h b/include/linux/hrtimer.h
index e95c96c9..4ecd991 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -41,16 +41,35 @@
};
/*
- * 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 @@
#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 @@
* @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 @@
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 @@
* @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 @@
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 @@
* @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 @@
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 @@
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);