1 /*
2 * linux/kernel/time/tick-common.c
3 *
4 * This file contains the base functions to manage periodic tick
5 * related events.
6 *
7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
10 *
11 * This code is licenced under the GPL version 2. For details see
12 * kernel-base/COPYING.
13 */
14 #include <linux/cpu.h>
15 #include <linux/err.h>
16 #include <linux/hrtimer.h>
17 #include <linux/interrupt.h>
18 #include <linux/percpu.h>
19 #include <linux/profile.h>
20 #include <linux/sched.h>
21 #include <linux/tick.h>
22
23 #include <asm/irq_regs.h>
24
25 #include "tick-internal.h"
26
27 /*
28 * Tick devices
29 */
30 DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
31 /*
32 * Tick next event: keeps track of the tick time
33 */
34 ktime_t tick_next_period;
35 ktime_t tick_period;
36 int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
37 DEFINE_SPINLOCK(tick_device_lock);
38
39 /*
40 * Debugging: see timer_list.c
41 */
42 struct tick_device *tick_get_device(int cpu)
43 {
44 return &per_cpu(tick_cpu_device, cpu);
45 }
46
47 /**
48 * tick_is_oneshot_available - check for a oneshot capable event device
49 */
50 int tick_is_oneshot_available(void)
51 {
52 struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
53
54 return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
55 }
56
57 /*
58 * Periodic tick
59 */
60 static void tick_periodic(int cpu)
61 {
62 if (tick_do_timer_cpu == cpu) {
63 write_seqlock(&xtime_lock);
64
65 /* Keep track of the next tick event */
66 tick_next_period = ktime_add(tick_next_period, tick_period);
67
68 do_timer(1);
69 write_sequnlock(&xtime_lock);
70 }
71
72 update_process_times(user_mode(get_irq_regs()));
73 profile_tick(CPU_PROFILING);
74 }
75
76 /*
77 * Event handler for periodic ticks
78 */
79 void tick_handle_periodic(struct clock_event_device *dev)
80 {
81 int cpu = smp_processor_id();
82 ktime_t next;
83
84 tick_periodic(cpu);
85
86 if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
87 return;
88 /*
89 * Setup the next period for devices, which do not have
90 * periodic mode:
91 */
92 next = ktime_add(dev->next_event, tick_period);
93 for (;;) {
94 if (!clockevents_program_event(dev, next, ktime_get()))
95 return;
96 /*
97 * Have to be careful here. If we're in oneshot mode,
98 * before we call tick_periodic() in a loop, we need
99 * to be sure we're using a real hardware clocksource.
100 * Otherwise we could get trapped in an infinite
101 * loop, as the tick_periodic() increments jiffies,
102 * when then will increment time, posibly causing
103 * the loop to trigger again and again.
104 */
105 if (timekeeping_valid_for_hres())
106 tick_periodic(cpu);
107 next = ktime_add(next, tick_period);
108 }
109 }
110
111 /*
112 * Setup the device for a periodic tick
113 */
114 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
115 {
116 tick_set_periodic_handler(dev, broadcast);
117
118 /* Broadcast setup ? */
119 if (!tick_device_is_functional(dev))
120 return;
121
122 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
123 !tick_broadcast_oneshot_active()) {
124 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
125 } else {
126 unsigned long seq;
127 ktime_t next;
128
129 do {
130 seq = read_seqbegin(&xtime_lock);
131 next = tick_next_period;
132 } while (read_seqretry(&xtime_lock, seq));
133
134 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
135
136 for (;;) {
137 if (!clockevents_program_event(dev, next, ktime_get()))
138 return;
139 next = ktime_add(next, tick_period);
140 }
141 }
142 }
143
144 /*
145 * Setup the tick device
146 */
147 static void tick_setup_device(struct tick_device *td,
148 struct clock_event_device *newdev, int cpu,
149 const struct cpumask *cpumask)
150 {
151 ktime_t next_event;
152 void (*handler)(struct clock_event_device *) = NULL;
153
154 /*
155 * First device setup ?
156 */
157 if (!td->evtdev) {
158 /*
159 * If no cpu took the do_timer update, assign it to
160 * this cpu:
161 */
162 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
163 tick_do_timer_cpu = cpu;
164 tick_next_period = ktime_get();
165 tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
166 }
167
168 /*
169 * Startup in periodic mode first.
170 */
171 td->mode = TICKDEV_MODE_PERIODIC;
172 } else {
173 handler = td->evtdev->event_handler;
174 next_event = td->evtdev->next_event;
175 td->evtdev->event_handler = clockevents_handle_noop;
176 }
177
178 td->evtdev = newdev;
179
180 /*
181 * When the device is not per cpu, pin the interrupt to the
182 * current cpu:
183 */
184 if (!cpumask_equal(newdev->cpumask, cpumask))
185 irq_set_affinity(newdev->irq, cpumask);
186
187 /*
188 * When global broadcasting is active, check if the current
189 * device is registered as a placeholder for broadcast mode.
190 * This allows us to handle this x86 misfeature in a generic
191 * way.
192 */
193 if (tick_device_uses_broadcast(newdev, cpu))
194 return;
195
196 if (td->mode == TICKDEV_MODE_PERIODIC)
197 tick_setup_periodic(newdev, 0);
198 else
199 tick_setup_oneshot(newdev, handler, next_event);
200 }
201
202 /*
203 * Check, if the new registered device should be used.
204 */
205 static int tick_check_new_device(struct clock_event_device *newdev)
206 {
207 struct clock_event_device *curdev;
208 struct tick_device *td;
209 int cpu, ret = NOTIFY_OK;
210 unsigned long flags;
211
212 spin_lock_irqsave(&tick_device_lock, flags);
213
214 cpu = smp_processor_id();
215 if (!cpumask_test_cpu(cpu, newdev->cpumask))
216 goto out_bc;
217
218 td = &per_cpu(tick_cpu_device, cpu);
219 curdev = td->evtdev;
220
221 /* cpu local device ? */
222 if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) {
223
224 /*
225 * If the cpu affinity of the device interrupt can not
226 * be set, ignore it.
227 */
228 if (!irq_can_set_affinity(newdev->irq))
229 goto out_bc;
230
231 /*
232 * If we have a cpu local device already, do not replace it
233 * by a non cpu local device
234 */
235 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
236 goto out_bc;
237 }
238
239 /*
240 * If we have an active device, then check the rating and the oneshot
241 * feature.
242 */
243 if (curdev) {
244 /*
245 * Prefer one shot capable devices !
246 */
247 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
248 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
249 goto out_bc;
250 /*
251 * Check the rating
252 */
253 if (curdev->rating >= newdev->rating)
254 goto out_bc;
255 }
256
257 /*
258 * Replace the eventually existing device by the new
259 * device. If the current device is the broadcast device, do
260 * not give it back to the clockevents layer !
261 */
262 if (tick_is_broadcast_device(curdev)) {
263 clockevents_shutdown(curdev);
264 curdev = NULL;
265 }
266 clockevents_exchange_device(curdev, newdev);
267 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
268 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
269 tick_oneshot_notify();
270
271 spin_unlock_irqrestore(&tick_device_lock, flags);
272 return NOTIFY_STOP;
273
274 out_bc:
275 /*
276 * Can the new device be used as a broadcast device ?
277 */
278 if (tick_check_broadcast_device(newdev))
279 ret = NOTIFY_STOP;
280
281 spin_unlock_irqrestore(&tick_device_lock, flags);
282
283 return ret;
284 }
285
286 /*
287 * Transfer the do_timer job away from a dying cpu.
288 *
289 * Called with interrupts disabled.
290 */
291 static void tick_handover_do_timer(int *cpup)
292 {
293 if (*cpup == tick_do_timer_cpu) {
294 int cpu = cpumask_first(cpu_online_mask);
295
296 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
297 TICK_DO_TIMER_NONE;
298 }
299 }
300
301 /*
302 * Shutdown an event device on a given cpu:
303 *
304 * This is called on a life CPU, when a CPU is dead. So we cannot
305 * access the hardware device itself.
306 * We just set the mode and remove it from the lists.
307 */
308 static void tick_shutdown(unsigned int *cpup)
309 {
310 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
311 struct clock_event_device *dev = td->evtdev;
312 unsigned long flags;
313
314 spin_lock_irqsave(&tick_device_lock, flags);
315 td->mode = TICKDEV_MODE_PERIODIC;
316 if (dev) {
317 /*
318 * Prevent that the clock events layer tries to call
319 * the set mode function!
320 */
321 dev->mode = CLOCK_EVT_MODE_UNUSED;
322 clockevents_exchange_device(dev, NULL);
323 td->evtdev = NULL;
324 }
325 spin_unlock_irqrestore(&tick_device_lock, flags);
326 }
327
328 static void tick_suspend(void)
329 {
330 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
331 unsigned long flags;
332
333 spin_lock_irqsave(&tick_device_lock, flags);
334 clockevents_shutdown(td->evtdev);
335 spin_unlock_irqrestore(&tick_device_lock, flags);
336 }
337
338 static void tick_resume(void)
339 {
340 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
341 unsigned long flags;
342 int broadcast = tick_resume_broadcast();
343
344 spin_lock_irqsave(&tick_device_lock, flags);
345 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
346
347 if (!broadcast) {
348 if (td->mode == TICKDEV_MODE_PERIODIC)
349 tick_setup_periodic(td->evtdev, 0);
350 else
351 tick_resume_oneshot();
352 }
353 spin_unlock_irqrestore(&tick_device_lock, flags);
354 }
355
356 /*
357 * Notification about clock event devices
358 */
359 static int tick_notify(struct notifier_block *nb, unsigned long reason,
360 void *dev)
361 {
362 switch (reason) {
363
364 case CLOCK_EVT_NOTIFY_ADD:
365 return tick_check_new_device(dev);
366
367 case CLOCK_EVT_NOTIFY_BROADCAST_ON:
368 case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
369 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
370 tick_broadcast_on_off(reason, dev);
371 break;
372
373 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
374 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
375 tick_broadcast_oneshot_control(reason);
376 break;
377
378 case CLOCK_EVT_NOTIFY_CPU_DYING:
379 tick_handover_do_timer(dev);
380 break;
381
382 case CLOCK_EVT_NOTIFY_CPU_DEAD:
383 tick_shutdown_broadcast_oneshot(dev);
384 tick_shutdown_broadcast(dev);
385 tick_shutdown(dev);
386 break;
387
388 case CLOCK_EVT_NOTIFY_SUSPEND:
389 tick_suspend();
390 tick_suspend_broadcast();
391 break;
392
393 case CLOCK_EVT_NOTIFY_RESUME:
394 tick_resume();
395 break;
396
397 default:
398 break;
399 }
400
401 return NOTIFY_OK;
402 }
403
404 static struct notifier_block tick_notifier = {
405 .notifier_call = tick_notify,
406 };
407
408 /**
409 * tick_init - initialize the tick control
410 *
411 * Register the notifier with the clockevents framework
412 */
413 void __init tick_init(void)
414 {
415 clockevents_register_notifier(&tick_notifier);
416 }
417
|
This page was automatically generated by the
LXR engine.
|