aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/time/tick-common.c
blob: bf43284d6855ad083319d653d1b0fbc3235dde08 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
/*
 * linux/kernel/time/tick-common.c
 *
 * This file contains the base functions to manage periodic tick
 * related events.
 *
 * 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
 *
 * This code is licenced under the GPL version 2. For details see
 * kernel-base/COPYING.
 */
#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/sched.h>
#include <linux/tick.h>

#include <asm/irq_regs.h>

#include "tick-internal.h"

/*
 * Tick devices
 */
DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
/*
 * Tick next event: keeps track of the tick time
 */
ktime_t tick_next_period;
ktime_t tick_period;
int tick_do_timer_cpu __read_mostly = -1;
DEFINE_SPINLOCK(tick_device_lock);

/*
 * Debugging: see timer_list.c
 */
struct tick_device *tick_get_device(int cpu)
{
	return &per_cpu(tick_cpu_device, cpu);
}

/**
 * tick_is_oneshot_available - check for a oneshot capable event device
 */
int tick_is_oneshot_available(void)
{
	struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;

	return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
}

/*
 * Periodic tick
 */
static void tick_periodic(int cpu)
{
	if (tick_do_timer_cpu == cpu) {
		write_seqlock(&xtime_lock);

		/* Keep track of the next tick event */
		tick_next_period = ktime_add(tick_next_period, tick_period);

		do_timer(1);
		write_sequnlock(&xtime_lock);
	}

	update_process_times(user_mode(get_irq_regs()));
	profile_tick(CPU_PROFILING);
}

/*
 * Event handler for periodic ticks
 */
void tick_handle_periodic(struct clock_event_device *dev)
{
	int cpu = smp_processor_id();
	ktime_t next;

	tick_periodic(cpu);

	if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
		return;
	/*
	 * Setup the next period for devices, which do not have
	 * periodic mode:
	 */
	next = ktime_add(dev->next_event, tick_period);
	for (;;) {
		if (!clockevents_program_event(dev, next, ktime_get()))
			return;
		tick_periodic(cpu);
		next = ktime_add(next, tick_period);
	}
}

/*
 * Setup the device for a periodic tick
 */
void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
{
	tick_set_periodic_handler(dev, broadcast);

	/* Broadcast setup ? */
	if (!tick_device_is_functional(dev))
		return;

	if (dev->features & CLOCK_EVT_FEAT_PERIODIC) {
		clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
	} else {
		unsigned long seq;
		ktime_t next;

		do {
			seq = read_seqbegin(&xtime_lock);
			next = tick_next_period;
		} while (read_seqretry(&xtime_lock, seq));

		clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);

		for (;;) {
			if (!clockevents_program_event(dev, next, ktime_get()))
				return;
			next = ktime_add(next, tick_period);
		}
	}
}

/*
 * Setup the tick device
 */
static void tick_setup_device(struct tick_device *td,
			      struct clock_event_device *newdev, int cpu,
			      const cpumask_t *cpumask)
{
	ktime_t next_event;
	void (*handler)(struct clock_event_device *) = NULL;

	/*
	 * First device setup ?
	 */
	if (!td->evtdev) {
		/*
		 * If no cpu took the do_timer update, assign it to
		 * this cpu:
		 */
		if (tick_do_timer_cpu == -1) {
			tick_do_timer_cpu = cpu;
			tick_next_period = ktime_get();
			tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
		}

		/*
		 * Startup in periodic mode first.
		 */
		td->mode = TICKDEV_MODE_PERIODIC;
	} else {
		handler = td->evtdev->event_handler;
		next_event = td->evtdev->next_event;
	}

	td->evtdev = newdev;

	/*
	 * When the device is not per cpu, pin the interrupt to the
	 * current cpu:
	 */
	if (!cpus_equal(newdev->cpumask, *cpumask))
		irq_set_affinity(newdev->irq, *cpumask);

	/*
	 * When global broadcasting is active, check if the current
	 * device is registered as a placeholder for broadcast mode.
	 * This allows us to handle this x86 misfeature in a generic
	 * way.
	 */
	if (tick_device_uses_broadcast(newdev, cpu))
		return;

	if (td->mode == TICKDEV_MODE_PERIODIC)
		tick_setup_periodic(newdev, 0);
	else
		tick_setup_oneshot(newdev, handler, next_event);
}

/*
 * Check, if the new registered device should be used.
 */
static int tick_check_new_device(struct clock_event_device *newdev)
{
	struct clock_event_device *curdev;
	struct tick_device *td;
	int cpu, ret = NOTIFY_OK;
	unsigned long flags;
	cpumask_of_cpu_ptr_declare(cpumask);

	spin_lock_irqsave(&tick_device_lock, flags);

	cpu = smp_processor_id();
	cpumask_of_cpu_ptr_next(cpumask, cpu);
	if (!cpu_isset(cpu, newdev->cpumask))
		goto out_bc;

	td = &per_cpu(tick_cpu_device, cpu);
	curdev = td->evtdev;

	/* cpu local device ? */
	if (!cpus_equal(newdev->cpumask, *cpumask)) {

		/*
		 * If the cpu affinity of the device interrupt can not
		 * be set, ignore it.
		 */
		if (!irq_can_set_affinity(newdev->irq))
			goto out_bc;

		/*
		 * If we have a cpu local device already, do not replace it
		 * by a non cpu local device
		 */
		if (curdev && cpus_equal(curdev->cpumask, *cpumask))
			goto out_bc;
	}

	/*
	 * If we have an active device, then check the rating and the oneshot
	 * feature.
	 */
	if (curdev) {
		/*
		 * Prefer one shot capable devices !
		 */
		if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
		    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
			goto out_bc;
		/*
		 * Check the rating
		 */
		if (curdev->rating >= newdev->rating)
			goto out_bc;
	}

	/*
	 * Replace the eventually existing device by the new
	 * device. If the current device is the broadcast device, do
	 * not give it back to the clockevents layer !
	 */
	if (tick_is_broadcast_device(curdev)) {
		clockevents_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN);
		curdev = NULL;
	}
	clockevents_exchange_device(curdev, newdev);
	tick_setup_device(td, newdev, cpu, cpumask);
	if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
		tick_oneshot_notify();

	spin_unlock_irqrestore(&tick_device_lock, flags);
	return NOTIFY_STOP;

out_bc:
	/*
	 * Can the new device be used as a broadcast device ?
	 */
	if (tick_check_broadcast_device(newdev))
		ret = NOTIFY_STOP;

	spin_unlock_irqrestore(&tick_device_lock, flags);

	return ret;
}

/*
 * Shutdown an event device on a given cpu:
 *
 * This is called on a life CPU, when a CPU is dead. So we cannot
 * access the hardware device itself.
 * We just set the mode and remove it from the lists.
 */
static void tick_shutdown(unsigned int *cpup)
{
	struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
	struct clock_event_device *dev = td->evtdev;
	unsigned long flags;

	spin_lock_irqsave(&tick_device_lock, flags);
	td->mode = TICKDEV_MODE_PERIODIC;
	if (dev) {
		/*
		 * Prevent that the clock events layer tries to call
		 * the set mode function!
		 */
		dev->mode = CLOCK_EVT_MODE_UNUSED;
		clockevents_exchange_device(dev, NULL);
		td->evtdev = NULL;
	}
	/* Transfer the do_timer job away from this cpu */
	if (*cpup == tick_do_timer_cpu) {
		int cpu = first_cpu(cpu_online_map);

		tick_do_timer_cpu = (cpu != NR_CPUS) ? cpu : -1;
	}
	spin_unlock_irqrestore(&tick_device_lock, flags);
}

static void tick_suspend(void)
{
	struct tick_device *td = &__get_cpu_var(tick_cpu_device);
	unsigned long flags;

	spin_lock_irqsave(&tick_device_lock, flags);
	clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_SHUTDOWN);
	spin_unlock_irqrestore(&tick_device_lock, flags);
}

static void tick_resume(void)
{
	struct tick_device *td = &__get_cpu_var(tick_cpu_device);
	unsigned long flags;
	int broadcast = tick_resume_broadcast();

	spin_lock_irqsave(&tick_device_lock, flags);
	clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);

	if (!broadcast) {
		if (td->mode == TICKDEV_MODE_PERIODIC)
			tick_setup_periodic(td->evtdev, 0);
		else
			tick_resume_oneshot();
	}
	spin_unlock_irqrestore(&tick_device_lock, flags);
}

/*
 * Notification about clock event devices
 */
static int tick_notify(struct notifier_block *nb, unsigned long reason,
			       void *dev)
{
	switch (reason) {

	case CLOCK_EVT_NOTIFY_ADD:
		return tick_check_new_device(dev);

	case CLOCK_EVT_NOTIFY_BROADCAST_ON:
	case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
	case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
		tick_broadcast_on_off(reason, dev);
		break;

	case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
	case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
		tick_broadcast_oneshot_control(reason);
		break;

	case CLOCK_EVT_NOTIFY_CPU_DEAD:
		tick_shutdown_broadcast_oneshot(dev);
		tick_shutdown_broadcast(dev);
		tick_shutdown(dev);
		break;

	case CLOCK_EVT_NOTIFY_SUSPEND:
		tick_suspend();
		tick_suspend_broadcast();
		break;

	case CLOCK_EVT_NOTIFY_RESUME:
		tick_resume();
		break;

	default:
		break;
	}

	return NOTIFY_OK;
}

static struct notifier_block tick_notifier = {
	.notifier_call = tick_notify,
};

/**
 * tick_init - initialize the tick control
 *
 * Register the notifier with the clockevents framework
 */
void __init tick_init(void)
{
	clockevents_register_notifier(&tick_notifier);
}

Privacy Policy