114 строки
3.0 KiB
C
114 строки
3.0 KiB
C
/*
|
|
* linux/kernel/time/tick-broadcast-hrtimer.c
|
|
* This file emulates a local clock event device
|
|
* via a pseudo clock device.
|
|
*/
|
|
#include <linux/cpu.h>
|
|
#include <linux/err.h>
|
|
#include <linux/hrtimer.h>
|
|
#include <linux/interrupt.h>
|
|
#include <linux/percpu.h>
|
|
#include <linux/profile.h>
|
|
#include <linux/clockchips.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/smp.h>
|
|
#include <linux/module.h>
|
|
|
|
#include "tick-internal.h"
|
|
|
|
static struct hrtimer bctimer;
|
|
|
|
static void bc_set_mode(enum clock_event_mode mode,
|
|
struct clock_event_device *bc)
|
|
{
|
|
switch (mode) {
|
|
case CLOCK_EVT_MODE_SHUTDOWN:
|
|
/*
|
|
* Note, we cannot cancel the timer here as we might
|
|
* run into the following live lock scenario:
|
|
*
|
|
* cpu 0 cpu1
|
|
* lock(broadcast_lock);
|
|
* hrtimer_interrupt()
|
|
* bc_handler()
|
|
* tick_handle_oneshot_broadcast();
|
|
* lock(broadcast_lock);
|
|
* hrtimer_cancel()
|
|
* wait_for_callback()
|
|
*/
|
|
hrtimer_try_to_cancel(&bctimer);
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This is called from the guts of the broadcast code when the cpu
|
|
* which is about to enter idle has the earliest broadcast timer event.
|
|
*/
|
|
static int bc_set_next(ktime_t expires, struct clock_event_device *bc)
|
|
{
|
|
int bc_moved;
|
|
/*
|
|
* We try to cancel the timer first. If the callback is on
|
|
* flight on some other cpu then we let it handle it. If we
|
|
* were able to cancel the timer nothing can rearm it as we
|
|
* own broadcast_lock.
|
|
*
|
|
* However we can also be called from the event handler of
|
|
* ce_broadcast_hrtimer itself when it expires. We cannot
|
|
* restart the timer because we are in the callback, but we
|
|
* can set the expiry time and let the callback return
|
|
* HRTIMER_RESTART.
|
|
*
|
|
* Since we are in the idle loop at this point and because
|
|
* hrtimer_{start/cancel} functions call into tracing,
|
|
* calls to these functions must be bound within RCU_NONIDLE.
|
|
*/
|
|
RCU_NONIDLE(bc_moved = (hrtimer_try_to_cancel(&bctimer) >= 0) ?
|
|
!hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED) :
|
|
0);
|
|
if (bc_moved) {
|
|
/* Bind the "device" to the cpu */
|
|
bc->bound_on = smp_processor_id();
|
|
} else if (bc->bound_on == smp_processor_id()) {
|
|
hrtimer_set_expires(&bctimer, expires);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static struct clock_event_device ce_broadcast_hrtimer = {
|
|
.set_mode = bc_set_mode,
|
|
.set_next_ktime = bc_set_next,
|
|
.features = CLOCK_EVT_FEAT_ONESHOT |
|
|
CLOCK_EVT_FEAT_KTIME |
|
|
CLOCK_EVT_FEAT_HRTIMER,
|
|
.rating = 0,
|
|
.bound_on = -1,
|
|
.min_delta_ns = 1,
|
|
.max_delta_ns = KTIME_MAX,
|
|
.min_delta_ticks = 1,
|
|
.max_delta_ticks = ULONG_MAX,
|
|
.mult = 1,
|
|
.shift = 0,
|
|
.cpumask = cpu_all_mask,
|
|
};
|
|
|
|
static enum hrtimer_restart bc_handler(struct hrtimer *t)
|
|
{
|
|
ce_broadcast_hrtimer.event_handler(&ce_broadcast_hrtimer);
|
|
|
|
if (ce_broadcast_hrtimer.next_event.tv64 == KTIME_MAX)
|
|
return HRTIMER_NORESTART;
|
|
|
|
return HRTIMER_RESTART;
|
|
}
|
|
|
|
void tick_setup_hrtimer_broadcast(void)
|
|
{
|
|
hrtimer_init(&bctimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
|
|
bctimer.function = bc_handler;
|
|
clockevents_register_device(&ce_broadcast_hrtimer);
|
|
}
|