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27#include <linux/spinlock.h>
28#include <linux/hardirq.h>
29#include <linux/module.h>
30#include <linux/percpu.h>
31#include <linux/ktime.h>
32#include <linux/sched.h>
33
34
35
36
37
38
39unsigned long long __attribute__((weak)) sched_clock(void)
40{
41 return (unsigned long long)(jiffies - INITIAL_JIFFIES)
42 * (NSEC_PER_SEC / HZ);
43}
44
45static __read_mostly int sched_clock_running;
46
47#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
48__read_mostly int sched_clock_stable;
49
50struct sched_clock_data {
51 u64 tick_raw;
52 u64 tick_gtod;
53 u64 clock;
54};
55
56static DEFINE_PER_CPU_SHARED_ALIGNED(struct sched_clock_data, sched_clock_data);
57
58static inline struct sched_clock_data *this_scd(void)
59{
60 return &__get_cpu_var(sched_clock_data);
61}
62
63static inline struct sched_clock_data *cpu_sdc(int cpu)
64{
65 return &per_cpu(sched_clock_data, cpu);
66}
67
68void sched_clock_init(void)
69{
70 u64 ktime_now = ktime_to_ns(ktime_get());
71 int cpu;
72
73 for_each_possible_cpu(cpu) {
74 struct sched_clock_data *scd = cpu_sdc(cpu);
75
76 scd->tick_raw = 0;
77 scd->tick_gtod = ktime_now;
78 scd->clock = ktime_now;
79 }
80
81 sched_clock_running = 1;
82}
83
84
85
86
87
88static inline u64 wrap_min(u64 x, u64 y)
89{
90 return (s64)(x - y) < 0 ? x : y;
91}
92
93static inline u64 wrap_max(u64 x, u64 y)
94{
95 return (s64)(x - y) > 0 ? x : y;
96}
97
98
99
100
101
102
103
104static u64 sched_clock_local(struct sched_clock_data *scd)
105{
106 u64 now, clock, old_clock, min_clock, max_clock;
107 s64 delta;
108
109again:
110 now = sched_clock();
111 delta = now - scd->tick_raw;
112 if (unlikely(delta < 0))
113 delta = 0;
114
115 old_clock = scd->clock;
116
117
118
119
120
121
122
123 clock = scd->tick_gtod + delta;
124 min_clock = wrap_max(scd->tick_gtod, old_clock);
125 max_clock = wrap_max(old_clock, scd->tick_gtod + TICK_NSEC);
126
127 clock = wrap_max(clock, min_clock);
128 clock = wrap_min(clock, max_clock);
129
130 if (cmpxchg64(&scd->clock, old_clock, clock) != old_clock)
131 goto again;
132
133 return clock;
134}
135
136static u64 sched_clock_remote(struct sched_clock_data *scd)
137{
138 struct sched_clock_data *my_scd = this_scd();
139 u64 this_clock, remote_clock;
140 u64 *ptr, old_val, val;
141
142 sched_clock_local(my_scd);
143again:
144 this_clock = my_scd->clock;
145 remote_clock = scd->clock;
146
147
148
149
150
151
152
153 if (likely((s64)(remote_clock - this_clock) < 0)) {
154 ptr = &scd->clock;
155 old_val = remote_clock;
156 val = this_clock;
157 } else {
158
159
160
161 ptr = &my_scd->clock;
162 old_val = this_clock;
163 val = remote_clock;
164 }
165
166 if (cmpxchg64(ptr, old_val, val) != old_val)
167 goto again;
168
169 return val;
170}
171
172u64 sched_clock_cpu(int cpu)
173{
174 struct sched_clock_data *scd;
175 u64 clock;
176
177 WARN_ON_ONCE(!irqs_disabled());
178
179 if (sched_clock_stable)
180 return sched_clock();
181
182 if (unlikely(!sched_clock_running))
183 return 0ull;
184
185 scd = cpu_sdc(cpu);
186
187 if (cpu != smp_processor_id())
188 clock = sched_clock_remote(scd);
189 else
190 clock = sched_clock_local(scd);
191
192 return clock;
193}
194
195void sched_clock_tick(void)
196{
197 struct sched_clock_data *scd;
198 u64 now, now_gtod;
199
200 if (sched_clock_stable)
201 return;
202
203 if (unlikely(!sched_clock_running))
204 return;
205
206 WARN_ON_ONCE(!irqs_disabled());
207
208 scd = this_scd();
209 now_gtod = ktime_to_ns(ktime_get());
210 now = sched_clock();
211
212 scd->tick_raw = now;
213 scd->tick_gtod = now_gtod;
214 sched_clock_local(scd);
215}
216
217
218
219
220void sched_clock_idle_sleep_event(void)
221{
222 sched_clock_cpu(smp_processor_id());
223}
224EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event);
225
226
227
228
229void sched_clock_idle_wakeup_event(u64 delta_ns)
230{
231 if (timekeeping_suspended)
232 return;
233
234 sched_clock_tick();
235 touch_softlockup_watchdog();
236}
237EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
238
239#else
240
241void sched_clock_init(void)
242{
243 sched_clock_running = 1;
244}
245
246u64 sched_clock_cpu(int cpu)
247{
248 if (unlikely(!sched_clock_running))
249 return 0;
250
251 return sched_clock();
252}
253
254#endif
255
256unsigned long long cpu_clock(int cpu)
257{
258 unsigned long long clock;
259 unsigned long flags;
260
261 local_irq_save(flags);
262 clock = sched_clock_cpu(cpu);
263 local_irq_restore(flags);
264
265 return clock;
266}
267EXPORT_SYMBOL_GPL(cpu_clock);
268