clockevents: prevent endless loop in periodic broadcast handler
[linux-3.10.git] / kernel / time / tick-broadcast.c
1 /*
2  * linux/kernel/time/tick-broadcast.c
3  *
4  * This file contains functions which emulate a local clock-event
5  * device via a broadcast event source.
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 "tick-internal.h"
24
25 /*
26  * Broadcast support for broken x86 hardware, where the local apic
27  * timer stops in C3 state.
28  */
29
30 struct tick_device tick_broadcast_device;
31 static cpumask_t tick_broadcast_mask;
32 static DEFINE_SPINLOCK(tick_broadcast_lock);
33 static int tick_broadcast_force;
34
35 #ifdef CONFIG_TICK_ONESHOT
36 static void tick_broadcast_clear_oneshot(int cpu);
37 #else
38 static inline void tick_broadcast_clear_oneshot(int cpu) { }
39 #endif
40
41 /*
42  * Debugging: see timer_list.c
43  */
44 struct tick_device *tick_get_broadcast_device(void)
45 {
46         return &tick_broadcast_device;
47 }
48
49 cpumask_t *tick_get_broadcast_mask(void)
50 {
51         return &tick_broadcast_mask;
52 }
53
54 /*
55  * Start the device in periodic mode
56  */
57 static void tick_broadcast_start_periodic(struct clock_event_device *bc)
58 {
59         if (bc)
60                 tick_setup_periodic(bc, 1);
61 }
62
63 /*
64  * Check, if the device can be utilized as broadcast device:
65  */
66 int tick_check_broadcast_device(struct clock_event_device *dev)
67 {
68         if ((tick_broadcast_device.evtdev &&
69              tick_broadcast_device.evtdev->rating >= dev->rating) ||
70              (dev->features & CLOCK_EVT_FEAT_C3STOP))
71                 return 0;
72
73         clockevents_exchange_device(NULL, dev);
74         tick_broadcast_device.evtdev = dev;
75         if (!cpus_empty(tick_broadcast_mask))
76                 tick_broadcast_start_periodic(dev);
77         return 1;
78 }
79
80 /*
81  * Check, if the device is the broadcast device
82  */
83 int tick_is_broadcast_device(struct clock_event_device *dev)
84 {
85         return (dev && tick_broadcast_device.evtdev == dev);
86 }
87
88 /*
89  * Check, if the device is disfunctional and a place holder, which
90  * needs to be handled by the broadcast device.
91  */
92 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
93 {
94         unsigned long flags;
95         int ret = 0;
96
97         spin_lock_irqsave(&tick_broadcast_lock, flags);
98
99         /*
100          * Devices might be registered with both periodic and oneshot
101          * mode disabled. This signals, that the device needs to be
102          * operated from the broadcast device and is a placeholder for
103          * the cpu local device.
104          */
105         if (!tick_device_is_functional(dev)) {
106                 dev->event_handler = tick_handle_periodic;
107                 cpu_set(cpu, tick_broadcast_mask);
108                 tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
109                 ret = 1;
110         } else {
111                 /*
112                  * When the new device is not affected by the stop
113                  * feature and the cpu is marked in the broadcast mask
114                  * then clear the broadcast bit.
115                  */
116                 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) {
117                         int cpu = smp_processor_id();
118
119                         cpu_clear(cpu, tick_broadcast_mask);
120                         tick_broadcast_clear_oneshot(cpu);
121                 }
122         }
123         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
124         return ret;
125 }
126
127 /*
128  * Broadcast the event to the cpus, which are set in the mask
129  */
130 static void tick_do_broadcast(cpumask_t mask)
131 {
132         int cpu = smp_processor_id();
133         struct tick_device *td;
134
135         /*
136          * Check, if the current cpu is in the mask
137          */
138         if (cpu_isset(cpu, mask)) {
139                 cpu_clear(cpu, mask);
140                 td = &per_cpu(tick_cpu_device, cpu);
141                 td->evtdev->event_handler(td->evtdev);
142         }
143
144         if (!cpus_empty(mask)) {
145                 /*
146                  * It might be necessary to actually check whether the devices
147                  * have different broadcast functions. For now, just use the
148                  * one of the first device. This works as long as we have this
149                  * misfeature only on x86 (lapic)
150                  */
151                 cpu = first_cpu(mask);
152                 td = &per_cpu(tick_cpu_device, cpu);
153                 td->evtdev->broadcast(mask);
154         }
155 }
156
157 /*
158  * Periodic broadcast:
159  * - invoke the broadcast handlers
160  */
161 static void tick_do_periodic_broadcast(void)
162 {
163         cpumask_t mask;
164
165         spin_lock(&tick_broadcast_lock);
166
167         cpus_and(mask, cpu_online_map, tick_broadcast_mask);
168         tick_do_broadcast(mask);
169
170         spin_unlock(&tick_broadcast_lock);
171 }
172
173 /*
174  * Event handler for periodic broadcast ticks
175  */
176 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
177 {
178         ktime_t next;
179
180         tick_do_periodic_broadcast();
181
182         /*
183          * The device is in periodic mode. No reprogramming necessary:
184          */
185         if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
186                 return;
187
188         /*
189          * Setup the next period for devices, which do not have
190          * periodic mode. We read dev->next_event first and add to it
191          * when the event alrady expired. clockevents_program_event()
192          * sets dev->next_event only when the event is really
193          * programmed to the device.
194          */
195         for (next = dev->next_event; ;) {
196                 next = ktime_add(next, tick_period);
197
198                 if (!clockevents_program_event(dev, next, ktime_get()))
199                         return;
200                 tick_do_periodic_broadcast();
201         }
202 }
203
204 /*
205  * Powerstate information: The system enters/leaves a state, where
206  * affected devices might stop
207  */
208 static void tick_do_broadcast_on_off(void *why)
209 {
210         struct clock_event_device *bc, *dev;
211         struct tick_device *td;
212         unsigned long flags, *reason = why;
213         int cpu;
214
215         spin_lock_irqsave(&tick_broadcast_lock, flags);
216
217         cpu = smp_processor_id();
218         td = &per_cpu(tick_cpu_device, cpu);
219         dev = td->evtdev;
220         bc = tick_broadcast_device.evtdev;
221
222         /*
223          * Is the device not affected by the powerstate ?
224          */
225         if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
226                 goto out;
227
228         if (!tick_device_is_functional(dev))
229                 goto out;
230
231         switch (*reason) {
232         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
233         case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
234                 if (!cpu_isset(cpu, tick_broadcast_mask)) {
235                         cpu_set(cpu, tick_broadcast_mask);
236                         if (td->mode == TICKDEV_MODE_PERIODIC)
237                                 clockevents_set_mode(dev,
238                                                      CLOCK_EVT_MODE_SHUTDOWN);
239                 }
240                 if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
241                         tick_broadcast_force = 1;
242                 break;
243         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
244                 if (!tick_broadcast_force &&
245                     cpu_isset(cpu, tick_broadcast_mask)) {
246                         cpu_clear(cpu, tick_broadcast_mask);
247                         if (td->mode == TICKDEV_MODE_PERIODIC)
248                                 tick_setup_periodic(dev, 0);
249                 }
250                 break;
251         }
252
253         if (cpus_empty(tick_broadcast_mask))
254                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
255         else {
256                 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
257                         tick_broadcast_start_periodic(bc);
258                 else
259                         tick_broadcast_setup_oneshot(bc);
260         }
261 out:
262         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
263 }
264
265 /*
266  * Powerstate information: The system enters/leaves a state, where
267  * affected devices might stop.
268  */
269 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
270 {
271         if (!cpu_isset(*oncpu, cpu_online_map))
272                 printk(KERN_ERR "tick-broadcast: ignoring broadcast for "
273                        "offline CPU #%d\n", *oncpu);
274         else
275                 smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
276                                          &reason, 1);
277 }
278
279 /*
280  * Set the periodic handler depending on broadcast on/off
281  */
282 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
283 {
284         if (!broadcast)
285                 dev->event_handler = tick_handle_periodic;
286         else
287                 dev->event_handler = tick_handle_periodic_broadcast;
288 }
289
290 /*
291  * Remove a CPU from broadcasting
292  */
293 void tick_shutdown_broadcast(unsigned int *cpup)
294 {
295         struct clock_event_device *bc;
296         unsigned long flags;
297         unsigned int cpu = *cpup;
298
299         spin_lock_irqsave(&tick_broadcast_lock, flags);
300
301         bc = tick_broadcast_device.evtdev;
302         cpu_clear(cpu, tick_broadcast_mask);
303
304         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
305                 if (bc && cpus_empty(tick_broadcast_mask))
306                         clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
307         }
308
309         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
310 }
311
312 void tick_suspend_broadcast(void)
313 {
314         struct clock_event_device *bc;
315         unsigned long flags;
316
317         spin_lock_irqsave(&tick_broadcast_lock, flags);
318
319         bc = tick_broadcast_device.evtdev;
320         if (bc)
321                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
322
323         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
324 }
325
326 int tick_resume_broadcast(void)
327 {
328         struct clock_event_device *bc;
329         unsigned long flags;
330         int broadcast = 0;
331
332         spin_lock_irqsave(&tick_broadcast_lock, flags);
333
334         bc = tick_broadcast_device.evtdev;
335
336         if (bc) {
337                 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
338
339                 switch (tick_broadcast_device.mode) {
340                 case TICKDEV_MODE_PERIODIC:
341                         if(!cpus_empty(tick_broadcast_mask))
342                                 tick_broadcast_start_periodic(bc);
343                         broadcast = cpu_isset(smp_processor_id(),
344                                               tick_broadcast_mask);
345                         break;
346                 case TICKDEV_MODE_ONESHOT:
347                         broadcast = tick_resume_broadcast_oneshot(bc);
348                         break;
349                 }
350         }
351         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
352
353         return broadcast;
354 }
355
356
357 #ifdef CONFIG_TICK_ONESHOT
358
359 static cpumask_t tick_broadcast_oneshot_mask;
360
361 /*
362  * Debugging: see timer_list.c
363  */
364 cpumask_t *tick_get_broadcast_oneshot_mask(void)
365 {
366         return &tick_broadcast_oneshot_mask;
367 }
368
369 static int tick_broadcast_set_event(ktime_t expires, int force)
370 {
371         struct clock_event_device *bc = tick_broadcast_device.evtdev;
372         ktime_t now = ktime_get();
373         int res;
374
375         for(;;) {
376                 res = clockevents_program_event(bc, expires, now);
377                 if (!res || !force)
378                         return res;
379                 now = ktime_get();
380                 expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
381         }
382 }
383
384 int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
385 {
386         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
387         return 0;
388 }
389
390 /*
391  * Handle oneshot mode broadcasting
392  */
393 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
394 {
395         struct tick_device *td;
396         cpumask_t mask;
397         ktime_t now, next_event;
398         int cpu;
399
400         spin_lock(&tick_broadcast_lock);
401 again:
402         dev->next_event.tv64 = KTIME_MAX;
403         next_event.tv64 = KTIME_MAX;
404         mask = CPU_MASK_NONE;
405         now = ktime_get();
406         /* Find all expired events */
407         for_each_cpu_mask_nr(cpu, tick_broadcast_oneshot_mask) {
408                 td = &per_cpu(tick_cpu_device, cpu);
409                 if (td->evtdev->next_event.tv64 <= now.tv64)
410                         cpu_set(cpu, mask);
411                 else if (td->evtdev->next_event.tv64 < next_event.tv64)
412                         next_event.tv64 = td->evtdev->next_event.tv64;
413         }
414
415         /*
416          * Wakeup the cpus which have an expired event.
417          */
418         tick_do_broadcast(mask);
419
420         /*
421          * Two reasons for reprogram:
422          *
423          * - The global event did not expire any CPU local
424          * events. This happens in dyntick mode, as the maximum PIT
425          * delta is quite small.
426          *
427          * - There are pending events on sleeping CPUs which were not
428          * in the event mask
429          */
430         if (next_event.tv64 != KTIME_MAX) {
431                 /*
432                  * Rearm the broadcast device. If event expired,
433                  * repeat the above
434                  */
435                 if (tick_broadcast_set_event(next_event, 0))
436                         goto again;
437         }
438         spin_unlock(&tick_broadcast_lock);
439 }
440
441 /*
442  * Powerstate information: The system enters/leaves a state, where
443  * affected devices might stop
444  */
445 void tick_broadcast_oneshot_control(unsigned long reason)
446 {
447         struct clock_event_device *bc, *dev;
448         struct tick_device *td;
449         unsigned long flags;
450         int cpu;
451
452         spin_lock_irqsave(&tick_broadcast_lock, flags);
453
454         /*
455          * Periodic mode does not care about the enter/exit of power
456          * states
457          */
458         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
459                 goto out;
460
461         bc = tick_broadcast_device.evtdev;
462         cpu = smp_processor_id();
463         td = &per_cpu(tick_cpu_device, cpu);
464         dev = td->evtdev;
465
466         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
467                 goto out;
468
469         if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
470                 if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
471                         cpu_set(cpu, tick_broadcast_oneshot_mask);
472                         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
473                         if (dev->next_event.tv64 < bc->next_event.tv64)
474                                 tick_broadcast_set_event(dev->next_event, 1);
475                 }
476         } else {
477                 if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
478                         cpu_clear(cpu, tick_broadcast_oneshot_mask);
479                         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
480                         if (dev->next_event.tv64 != KTIME_MAX)
481                                 tick_program_event(dev->next_event, 1);
482                 }
483         }
484
485 out:
486         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
487 }
488
489 /*
490  * Reset the one shot broadcast for a cpu
491  *
492  * Called with tick_broadcast_lock held
493  */
494 static void tick_broadcast_clear_oneshot(int cpu)
495 {
496         cpu_clear(cpu, tick_broadcast_oneshot_mask);
497 }
498
499 /**
500  * tick_broadcast_setup_oneshot - setup the broadcast device
501  */
502 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
503 {
504         bc->event_handler = tick_handle_oneshot_broadcast;
505         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
506         bc->next_event.tv64 = KTIME_MAX;
507 }
508
509 /*
510  * Select oneshot operating mode for the broadcast device
511  */
512 void tick_broadcast_switch_to_oneshot(void)
513 {
514         struct clock_event_device *bc;
515         unsigned long flags;
516
517         spin_lock_irqsave(&tick_broadcast_lock, flags);
518
519         tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
520         bc = tick_broadcast_device.evtdev;
521         if (bc)
522                 tick_broadcast_setup_oneshot(bc);
523         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
524 }
525
526
527 /*
528  * Remove a dead CPU from broadcasting
529  */
530 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
531 {
532         unsigned long flags;
533         unsigned int cpu = *cpup;
534
535         spin_lock_irqsave(&tick_broadcast_lock, flags);
536
537         /*
538          * Clear the broadcast mask flag for the dead cpu, but do not
539          * stop the broadcast device!
540          */
541         cpu_clear(cpu, tick_broadcast_oneshot_mask);
542
543         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
544 }
545
546 #endif