projects/linux·blob v2.6.21 · refs

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