WUSB: correct format of wusb_chid sysfs file
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / sched_clock.c
blob819f17ac796efeeee1068efe3e6a27ac952d3a16
1 /*
2 * sched_clock for unstable cpu clocks
4 * Copyright (C) 2008 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
6 * Updates and enhancements:
7 * Copyright (C) 2008 Red Hat, Inc. Steven Rostedt <srostedt@redhat.com>
9 * Based on code by:
10 * Ingo Molnar <mingo@redhat.com>
11 * Guillaume Chazarain <guichaz@gmail.com>
13 * Create a semi stable clock from a mixture of other events, including:
14 * - gtod
15 * - sched_clock()
16 * - explicit idle events
18 * We use gtod as base and the unstable clock deltas. The deltas are filtered,
19 * making it monotonic and keeping it within an expected window.
21 * Furthermore, explicit sleep and wakeup hooks allow us to account for time
22 * that is otherwise invisible (TSC gets stopped).
24 * The clock: sched_clock_cpu() is monotonic per cpu, and should be somewhat
25 * consistent between cpus (never more than 2 jiffies difference).
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>
35 * Scheduler clock - returns current time in nanosec units.
36 * This is default implementation.
37 * Architectures and sub-architectures can override this.
39 unsigned long long __attribute__((weak)) sched_clock(void)
41 return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ);
44 static __read_mostly int sched_clock_running;
46 #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
47 __read_mostly int sched_clock_stable;
49 struct sched_clock_data {
51 * Raw spinlock - this is a special case: this might be called
52 * from within instrumentation code so we dont want to do any
53 * instrumentation ourselves.
55 raw_spinlock_t lock;
57 u64 tick_raw;
58 u64 tick_gtod;
59 u64 clock;
62 static DEFINE_PER_CPU_SHARED_ALIGNED(struct sched_clock_data, sched_clock_data);
64 static inline struct sched_clock_data *this_scd(void)
66 return &__get_cpu_var(sched_clock_data);
69 static inline struct sched_clock_data *cpu_sdc(int cpu)
71 return &per_cpu(sched_clock_data, cpu);
74 void sched_clock_init(void)
76 u64 ktime_now = ktime_to_ns(ktime_get());
77 int cpu;
79 for_each_possible_cpu(cpu) {
80 struct sched_clock_data *scd = cpu_sdc(cpu);
82 scd->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
83 scd->tick_raw = 0;
84 scd->tick_gtod = ktime_now;
85 scd->clock = ktime_now;
88 sched_clock_running = 1;
92 * min, max except they take wrapping into account
95 static inline u64 wrap_min(u64 x, u64 y)
97 return (s64)(x - y) < 0 ? x : y;
100 static inline u64 wrap_max(u64 x, u64 y)
102 return (s64)(x - y) > 0 ? x : y;
106 * update the percpu scd from the raw @now value
108 * - filter out backward motion
109 * - use the GTOD tick value to create a window to filter crazy TSC values
111 static u64 __update_sched_clock(struct sched_clock_data *scd, u64 now)
113 s64 delta = now - scd->tick_raw;
114 u64 clock, min_clock, max_clock;
116 if (unlikely(delta < 0))
117 delta = 0;
120 * scd->clock = clamp(scd->tick_gtod + delta,
121 * max(scd->tick_gtod, scd->clock),
122 * scd->tick_gtod + TICK_NSEC);
125 clock = scd->tick_gtod + delta;
126 min_clock = wrap_max(scd->tick_gtod, scd->clock);
127 max_clock = wrap_max(scd->clock, scd->tick_gtod + TICK_NSEC);
129 clock = wrap_max(clock, min_clock);
130 clock = wrap_min(clock, max_clock);
132 scd->clock = clock;
134 return scd->clock;
137 static void lock_double_clock(struct sched_clock_data *data1,
138 struct sched_clock_data *data2)
140 if (data1 < data2) {
141 __raw_spin_lock(&data1->lock);
142 __raw_spin_lock(&data2->lock);
143 } else {
144 __raw_spin_lock(&data2->lock);
145 __raw_spin_lock(&data1->lock);
149 u64 sched_clock_cpu(int cpu)
151 u64 now, clock, this_clock, remote_clock;
152 struct sched_clock_data *scd;
154 if (sched_clock_stable)
155 return sched_clock();
157 scd = cpu_sdc(cpu);
160 * Normally this is not called in NMI context - but if it is,
161 * trying to do any locking here is totally lethal.
163 if (unlikely(in_nmi()))
164 return scd->clock;
166 if (unlikely(!sched_clock_running))
167 return 0ull;
169 WARN_ON_ONCE(!irqs_disabled());
170 now = sched_clock();
172 if (cpu != raw_smp_processor_id()) {
173 struct sched_clock_data *my_scd = this_scd();
175 lock_double_clock(scd, my_scd);
177 this_clock = __update_sched_clock(my_scd, now);
178 remote_clock = scd->clock;
181 * Use the opportunity that we have both locks
182 * taken to couple the two clocks: we take the
183 * larger time as the latest time for both
184 * runqueues. (this creates monotonic movement)
186 if (likely((s64)(remote_clock - this_clock) < 0)) {
187 clock = this_clock;
188 scd->clock = clock;
189 } else {
191 * Should be rare, but possible:
193 clock = remote_clock;
194 my_scd->clock = remote_clock;
197 __raw_spin_unlock(&my_scd->lock);
198 } else {
199 __raw_spin_lock(&scd->lock);
200 clock = __update_sched_clock(scd, now);
203 __raw_spin_unlock(&scd->lock);
205 return clock;
208 void sched_clock_tick(void)
210 struct sched_clock_data *scd;
211 u64 now, now_gtod;
213 if (sched_clock_stable)
214 return;
216 if (unlikely(!sched_clock_running))
217 return;
219 WARN_ON_ONCE(!irqs_disabled());
221 scd = this_scd();
222 now_gtod = ktime_to_ns(ktime_get());
223 now = sched_clock();
225 __raw_spin_lock(&scd->lock);
226 scd->tick_raw = now;
227 scd->tick_gtod = now_gtod;
228 __update_sched_clock(scd, now);
229 __raw_spin_unlock(&scd->lock);
233 * We are going deep-idle (irqs are disabled):
235 void sched_clock_idle_sleep_event(void)
237 sched_clock_cpu(smp_processor_id());
239 EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event);
242 * We just idled delta nanoseconds (called with irqs disabled):
244 void sched_clock_idle_wakeup_event(u64 delta_ns)
246 if (timekeeping_suspended)
247 return;
249 sched_clock_tick();
250 touch_softlockup_watchdog();
252 EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
254 #else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */
256 void sched_clock_init(void)
258 sched_clock_running = 1;
261 u64 sched_clock_cpu(int cpu)
263 if (unlikely(!sched_clock_running))
264 return 0;
266 return sched_clock();
269 #endif /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */
271 unsigned long long cpu_clock(int cpu)
273 unsigned long long clock;
274 unsigned long flags;
276 local_irq_save(flags);
277 clock = sched_clock_cpu(cpu);
278 local_irq_restore(flags);
280 return clock;
282 EXPORT_SYMBOL_GPL(cpu_clock);