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63#include <linux/spinlock.h>
64#include <linux/hardirq.h>
65#include <linux/module.h>
66#include <linux/percpu.h>
67#include <linux/ktime.h>
68#include <linux/sched.h>
69
70
71
72
73
74
75unsigned long long __attribute__((weak)) sched_clock(void)
76{
77 return (unsigned long long)(jiffies - INITIAL_JIFFIES)
78 * (NSEC_PER_SEC / HZ);
79}
80EXPORT_SYMBOL_GPL(sched_clock);
81
82__read_mostly int sched_clock_running;
83
84#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
85__read_mostly int sched_clock_stable;
86
87struct sched_clock_data {
88 u64 tick_raw;
89 u64 tick_gtod;
90 u64 clock;
91};
92
93static DEFINE_PER_CPU_SHARED_ALIGNED(struct sched_clock_data, sched_clock_data);
94
95static inline struct sched_clock_data *this_scd(void)
96{
97 return &__get_cpu_var(sched_clock_data);
98}
99
100static inline struct sched_clock_data *cpu_sdc(int cpu)
101{
102 return &per_cpu(sched_clock_data, cpu);
103}
104
105void sched_clock_init(void)
106{
107 u64 ktime_now = ktime_to_ns(ktime_get());
108 int cpu;
109
110 for_each_possible_cpu(cpu) {
111 struct sched_clock_data *scd = cpu_sdc(cpu);
112
113 scd->tick_raw = 0;
114 scd->tick_gtod = ktime_now;
115 scd->clock = ktime_now;
116 }
117
118 sched_clock_running = 1;
119}
120
121
122
123
124
125static inline u64 wrap_min(u64 x, u64 y)
126{
127 return (s64)(x - y) < 0 ? x : y;
128}
129
130static inline u64 wrap_max(u64 x, u64 y)
131{
132 return (s64)(x - y) > 0 ? x : y;
133}
134
135
136
137
138
139
140
141static u64 sched_clock_local(struct sched_clock_data *scd)
142{
143 u64 now, clock, old_clock, min_clock, max_clock;
144 s64 delta;
145
146again:
147 now = sched_clock();
148 delta = now - scd->tick_raw;
149 if (unlikely(delta < 0))
150 delta = 0;
151
152 old_clock = scd->clock;
153
154
155
156
157
158
159
160 clock = scd->tick_gtod + delta;
161 min_clock = wrap_max(scd->tick_gtod, old_clock);
162 max_clock = wrap_max(old_clock, scd->tick_gtod + TICK_NSEC);
163
164 clock = wrap_max(clock, min_clock);
165 clock = wrap_min(clock, max_clock);
166
167 if (cmpxchg64(&scd->clock, old_clock, clock) != old_clock)
168 goto again;
169
170 return clock;
171}
172
173static u64 sched_clock_remote(struct sched_clock_data *scd)
174{
175 struct sched_clock_data *my_scd = this_scd();
176 u64 this_clock, remote_clock;
177 u64 *ptr, old_val, val;
178
179 sched_clock_local(my_scd);
180again:
181 this_clock = my_scd->clock;
182 remote_clock = scd->clock;
183
184
185
186
187
188
189
190 if (likely((s64)(remote_clock - this_clock) < 0)) {
191 ptr = &scd->clock;
192 old_val = remote_clock;
193 val = this_clock;
194 } else {
195
196
197
198 ptr = &my_scd->clock;
199 old_val = this_clock;
200 val = remote_clock;
201 }
202
203 if (cmpxchg64(ptr, old_val, val) != old_val)
204 goto again;
205
206 return val;
207}
208
209
210
211
212
213
214u64 sched_clock_cpu(int cpu)
215{
216 struct sched_clock_data *scd;
217 u64 clock;
218
219 WARN_ON_ONCE(!irqs_disabled());
220
221 if (sched_clock_stable)
222 return sched_clock();
223
224 if (unlikely(!sched_clock_running))
225 return 0ull;
226
227 scd = cpu_sdc(cpu);
228
229 if (cpu != smp_processor_id())
230 clock = sched_clock_remote(scd);
231 else
232 clock = sched_clock_local(scd);
233
234 return clock;
235}
236
237void sched_clock_tick(void)
238{
239 struct sched_clock_data *scd;
240 u64 now, now_gtod;
241
242 if (sched_clock_stable)
243 return;
244
245 if (unlikely(!sched_clock_running))
246 return;
247
248 WARN_ON_ONCE(!irqs_disabled());
249
250 scd = this_scd();
251 now_gtod = ktime_to_ns(ktime_get());
252 now = sched_clock();
253
254 scd->tick_raw = now;
255 scd->tick_gtod = now_gtod;
256 sched_clock_local(scd);
257}
258
259
260
261
262void sched_clock_idle_sleep_event(void)
263{
264 sched_clock_cpu(smp_processor_id());
265}
266EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event);
267
268
269
270
271void sched_clock_idle_wakeup_event(u64 delta_ns)
272{
273 if (timekeeping_suspended)
274 return;
275
276 sched_clock_tick();
277 touch_softlockup_watchdog();
278}
279EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
280
281
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288
289
290
291u64 cpu_clock(int cpu)
292{
293 u64 clock;
294 unsigned long flags;
295
296 local_irq_save(flags);
297 clock = sched_clock_cpu(cpu);
298 local_irq_restore(flags);
299
300 return clock;
301}
302
303
304
305
306
307
308
309
310u64 local_clock(void)
311{
312 u64 clock;
313 unsigned long flags;
314
315 local_irq_save(flags);
316 clock = sched_clock_cpu(smp_processor_id());
317 local_irq_restore(flags);
318
319 return clock;
320}
321
322#else
323
324void sched_clock_init(void)
325{
326 sched_clock_running = 1;
327}
328
329u64 sched_clock_cpu(int cpu)
330{
331 if (unlikely(!sched_clock_running))
332 return 0;
333
334 return sched_clock();
335}
336
337u64 cpu_clock(int cpu)
338{
339 return sched_clock_cpu(cpu);
340}
341
342u64 local_clock(void)
343{
344 return sched_clock_cpu(0);
345}
346
347#endif
348
349EXPORT_SYMBOL_GPL(cpu_clock);
350EXPORT_SYMBOL_GPL(local_clock);
351