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-rw-r--r--kernel/time/tick-common.c277
1 files changed, 277 insertions, 0 deletions
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
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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 <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/irq.h>
18#include <linux/percpu.h>
19#include <linux/profile.h>
20#include <linux/sched.h>
21#include <linux/tick.h>
22
23/*
24 * Tick devices
25 */
26static DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
27/*
28 * Tick next event: keeps track of the tick time
29 */
30static ktime_t tick_next_period;
31static ktime_t tick_period;
32static int tick_do_timer_cpu = -1;
33static DEFINE_SPINLOCK(tick_device_lock);
34
35/*
36 * Periodic tick
37 */
38static void tick_periodic(int cpu)
39{
40 if (tick_do_timer_cpu == cpu) {
41 write_seqlock(&xtime_lock);
42
43 /* Keep track of the next tick event */
44 tick_next_period = ktime_add(tick_next_period, tick_period);
45
46 do_timer(1);
47 write_sequnlock(&xtime_lock);
48 }
49
50 update_process_times(user_mode(get_irq_regs()));
51 profile_tick(CPU_PROFILING);
52}
53
54/*
55 * Event handler for periodic ticks
56 */
57void tick_handle_periodic(struct clock_event_device *dev)
58{
59 int cpu = smp_processor_id();
60
61 tick_periodic(cpu);
62
63 if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
64 return;
65 /*
66 * Setup the next period for devices, which do not have
67 * periodic mode:
68 */
69 for (;;) {
70 ktime_t next = ktime_add(dev->next_event, tick_period);
71
72 if (!clockevents_program_event(dev, next, ktime_get()))
73 return;
74 tick_periodic(cpu);
75 }
76}
77
78/*
79 * Setup the device for a periodic tick
80 */
81void tick_setup_periodic(struct clock_event_device *dev)
82{
83 dev->event_handler = tick_handle_periodic;
84
85 if (dev->features & CLOCK_EVT_FEAT_PERIODIC) {
86 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
87 } else {
88 unsigned long seq;
89 ktime_t next;
90
91 do {
92 seq = read_seqbegin(&xtime_lock);
93 next = tick_next_period;
94 } while (read_seqretry(&xtime_lock, seq));
95
96 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
97
98 for (;;) {
99 if (!clockevents_program_event(dev, next, ktime_get()))
100 return;
101 next = ktime_add(next, tick_period);
102 }
103 }
104}
105
106/*
107 * Setup the tick device
108 */
109static void tick_setup_device(struct tick_device *td,
110 struct clock_event_device *newdev, int cpu,
111 cpumask_t cpumask)
112{
113 ktime_t next_event;
114 void (*handler)(struct clock_event_device *) = NULL;
115
116 /*
117 * First device setup ?
118 */
119 if (!td->evtdev) {
120 /*
121 * If no cpu took the do_timer update, assign it to
122 * this cpu:
123 */
124 if (tick_do_timer_cpu == -1) {
125 tick_do_timer_cpu = cpu;
126 tick_next_period = ktime_get();
127 tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
128 }
129
130 /*
131 * Startup in periodic mode first.
132 */
133 td->mode = TICKDEV_MODE_PERIODIC;
134 } else {
135 handler = td->evtdev->event_handler;
136 next_event = td->evtdev->next_event;
137 }
138
139 td->evtdev = newdev;
140
141 /*
142 * When the device is not per cpu, pin the interrupt to the
143 * current cpu:
144 */
145 if (!cpus_equal(newdev->cpumask, cpumask))
146 irq_set_affinity(newdev->irq, cpumask);
147
148 if (td->mode == TICKDEV_MODE_PERIODIC)
149 tick_setup_periodic(newdev, 0);
150}
151
152/*
153 * Check, if the new registered device should be used.
154 */
155static int tick_check_new_device(struct clock_event_device *newdev)
156{
157 struct clock_event_device *curdev;
158 struct tick_device *td;
159 int cpu, ret = NOTIFY_OK;
160 unsigned long flags;
161 cpumask_t cpumask;
162
163 spin_lock_irqsave(&tick_device_lock, flags);
164
165 cpu = smp_processor_id();
166 if (!cpu_isset(cpu, newdev->cpumask))
167 goto out;
168
169 td = &per_cpu(tick_cpu_device, cpu);
170 curdev = td->evtdev;
171 cpumask = cpumask_of_cpu(cpu);
172
173 /* cpu local device ? */
174 if (!cpus_equal(newdev->cpumask, cpumask)) {
175
176 /*
177 * If the cpu affinity of the device interrupt can not
178 * be set, ignore it.
179 */
180 if (!irq_can_set_affinity(newdev->irq))
181 goto out_bc;
182
183 /*
184 * If we have a cpu local device already, do not replace it
185 * by a non cpu local device
186 */
187 if (curdev && cpus_equal(curdev->cpumask, cpumask))
188 goto out_bc;
189 }
190
191 /*
192 * If we have an active device, then check the rating and the oneshot
193 * feature.
194 */
195 if (curdev) {
196 /*
197 * Check the rating
198 */
199 if (curdev->rating >= newdev->rating)
200 goto out;
201 }
202
203 /*
204 * Replace the eventually existing device by the new
205 * device.
206 */
207 clockevents_exchange_device(curdev, newdev);
208 tick_setup_device(td, newdev, cpu, cpumask);
209 ret = NOTIFY_STOP;
210
211out:
212 spin_unlock_irqrestore(&tick_device_lock, flags);
213 return ret;
214}
215
216/*
217 * Shutdown an event device on a given cpu:
218 *
219 * This is called on a life CPU, when a CPU is dead. So we cannot
220 * access the hardware device itself.
221 * We just set the mode and remove it from the lists.
222 */
223static void tick_shutdown(unsigned int *cpup)
224{
225 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
226 struct clock_event_device *dev = td->evtdev;
227 unsigned long flags;
228
229 spin_lock_irqsave(&tick_device_lock, flags);
230 td->mode = TICKDEV_MODE_PERIODIC;
231 if (dev) {
232 /*
233 * Prevent that the clock events layer tries to call
234 * the set mode function!
235 */
236 dev->mode = CLOCK_EVT_MODE_UNUSED;
237 clockevents_exchange_device(dev, NULL);
238 td->evtdev = NULL;
239 }
240 spin_unlock_irqrestore(&tick_device_lock, flags);
241}
242
243/*
244 * Notification about clock event devices
245 */
246static int tick_notify(struct notifier_block *nb, unsigned long reason,
247 void *dev)
248{
249 switch (reason) {
250
251 case CLOCK_EVT_NOTIFY_ADD:
252 return tick_check_new_device(dev);
253
254 case CLOCK_EVT_NOTIFY_CPU_DEAD:
255 tick_shutdown(dev);
256 break;
257
258 default:
259 break;
260 }
261
262 return NOTIFY_OK;
263}
264
265static struct notifier_block tick_notifier = {
266 .notifier_call = tick_notify,
267};
268
269/**
270 * tick_init - initialize the tick control
271 *
272 * Register the notifier with the clockevents framework
273 */
274void __init tick_init(void)
275{
276 clockevents_register_notifier(&tick_notifier);
277}