xen: add static initialization of steal_clock op to xen_time_ops
[sfrench/cifs-2.6.git] / kernel / sched / cputime.c
1 #include <linux/export.h>
2 #include <linux/sched.h>
3 #include <linux/tsacct_kern.h>
4 #include <linux/kernel_stat.h>
5 #include <linux/static_key.h>
6 #include <linux/context_tracking.h>
7 #include "sched.h"
8 #ifdef CONFIG_PARAVIRT
9 #include <asm/paravirt.h>
10 #endif
11
12
13 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
14
15 /*
16  * There are no locks covering percpu hardirq/softirq time.
17  * They are only modified in vtime_account, on corresponding CPU
18  * with interrupts disabled. So, writes are safe.
19  * They are read and saved off onto struct rq in update_rq_clock().
20  * This may result in other CPU reading this CPU's irq time and can
21  * race with irq/vtime_account on this CPU. We would either get old
22  * or new value with a side effect of accounting a slice of irq time to wrong
23  * task when irq is in progress while we read rq->clock. That is a worthy
24  * compromise in place of having locks on each irq in account_system_time.
25  */
26 DEFINE_PER_CPU(u64, cpu_hardirq_time);
27 DEFINE_PER_CPU(u64, cpu_softirq_time);
28
29 static DEFINE_PER_CPU(u64, irq_start_time);
30 static int sched_clock_irqtime;
31
32 void enable_sched_clock_irqtime(void)
33 {
34         sched_clock_irqtime = 1;
35 }
36
37 void disable_sched_clock_irqtime(void)
38 {
39         sched_clock_irqtime = 0;
40 }
41
42 #ifndef CONFIG_64BIT
43 DEFINE_PER_CPU(seqcount_t, irq_time_seq);
44 #endif /* CONFIG_64BIT */
45
46 /*
47  * Called before incrementing preempt_count on {soft,}irq_enter
48  * and before decrementing preempt_count on {soft,}irq_exit.
49  */
50 void irqtime_account_irq(struct task_struct *curr)
51 {
52         unsigned long flags;
53         s64 delta;
54         int cpu;
55
56         if (!sched_clock_irqtime)
57                 return;
58
59         local_irq_save(flags);
60
61         cpu = smp_processor_id();
62         delta = sched_clock_cpu(cpu) - __this_cpu_read(irq_start_time);
63         __this_cpu_add(irq_start_time, delta);
64
65         irq_time_write_begin();
66         /*
67          * We do not account for softirq time from ksoftirqd here.
68          * We want to continue accounting softirq time to ksoftirqd thread
69          * in that case, so as not to confuse scheduler with a special task
70          * that do not consume any time, but still wants to run.
71          */
72         if (hardirq_count())
73                 __this_cpu_add(cpu_hardirq_time, delta);
74         else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
75                 __this_cpu_add(cpu_softirq_time, delta);
76
77         irq_time_write_end();
78         local_irq_restore(flags);
79 }
80 EXPORT_SYMBOL_GPL(irqtime_account_irq);
81
82 static int irqtime_account_hi_update(void)
83 {
84         u64 *cpustat = kcpustat_this_cpu->cpustat;
85         unsigned long flags;
86         u64 latest_ns;
87         int ret = 0;
88
89         local_irq_save(flags);
90         latest_ns = this_cpu_read(cpu_hardirq_time);
91         if (nsecs_to_cputime64(latest_ns) > cpustat[CPUTIME_IRQ])
92                 ret = 1;
93         local_irq_restore(flags);
94         return ret;
95 }
96
97 static int irqtime_account_si_update(void)
98 {
99         u64 *cpustat = kcpustat_this_cpu->cpustat;
100         unsigned long flags;
101         u64 latest_ns;
102         int ret = 0;
103
104         local_irq_save(flags);
105         latest_ns = this_cpu_read(cpu_softirq_time);
106         if (nsecs_to_cputime64(latest_ns) > cpustat[CPUTIME_SOFTIRQ])
107                 ret = 1;
108         local_irq_restore(flags);
109         return ret;
110 }
111
112 #else /* CONFIG_IRQ_TIME_ACCOUNTING */
113
114 #define sched_clock_irqtime     (0)
115
116 #endif /* !CONFIG_IRQ_TIME_ACCOUNTING */
117
118 static inline void task_group_account_field(struct task_struct *p, int index,
119                                             u64 tmp)
120 {
121         /*
122          * Since all updates are sure to touch the root cgroup, we
123          * get ourselves ahead and touch it first. If the root cgroup
124          * is the only cgroup, then nothing else should be necessary.
125          *
126          */
127         __this_cpu_add(kernel_cpustat.cpustat[index], tmp);
128
129         cpuacct_account_field(p, index, tmp);
130 }
131
132 /*
133  * Account user cpu time to a process.
134  * @p: the process that the cpu time gets accounted to
135  * @cputime: the cpu time spent in user space since the last update
136  * @cputime_scaled: cputime scaled by cpu frequency
137  */
138 void account_user_time(struct task_struct *p, cputime_t cputime,
139                        cputime_t cputime_scaled)
140 {
141         int index;
142
143         /* Add user time to process. */
144         p->utime += cputime;
145         p->utimescaled += cputime_scaled;
146         account_group_user_time(p, cputime);
147
148         index = (task_nice(p) > 0) ? CPUTIME_NICE : CPUTIME_USER;
149
150         /* Add user time to cpustat. */
151         task_group_account_field(p, index, (__force u64) cputime);
152
153         /* Account for user time used */
154         acct_account_cputime(p);
155 }
156
157 /*
158  * Account guest cpu time to a process.
159  * @p: the process that the cpu time gets accounted to
160  * @cputime: the cpu time spent in virtual machine since the last update
161  * @cputime_scaled: cputime scaled by cpu frequency
162  */
163 static void account_guest_time(struct task_struct *p, cputime_t cputime,
164                                cputime_t cputime_scaled)
165 {
166         u64 *cpustat = kcpustat_this_cpu->cpustat;
167
168         /* Add guest time to process. */
169         p->utime += cputime;
170         p->utimescaled += cputime_scaled;
171         account_group_user_time(p, cputime);
172         p->gtime += cputime;
173
174         /* Add guest time to cpustat. */
175         if (task_nice(p) > 0) {
176                 cpustat[CPUTIME_NICE] += (__force u64) cputime;
177                 cpustat[CPUTIME_GUEST_NICE] += (__force u64) cputime;
178         } else {
179                 cpustat[CPUTIME_USER] += (__force u64) cputime;
180                 cpustat[CPUTIME_GUEST] += (__force u64) cputime;
181         }
182 }
183
184 /*
185  * Account system cpu time to a process and desired cpustat field
186  * @p: the process that the cpu time gets accounted to
187  * @cputime: the cpu time spent in kernel space since the last update
188  * @cputime_scaled: cputime scaled by cpu frequency
189  * @target_cputime64: pointer to cpustat field that has to be updated
190  */
191 static inline
192 void __account_system_time(struct task_struct *p, cputime_t cputime,
193                         cputime_t cputime_scaled, int index)
194 {
195         /* Add system time to process. */
196         p->stime += cputime;
197         p->stimescaled += cputime_scaled;
198         account_group_system_time(p, cputime);
199
200         /* Add system time to cpustat. */
201         task_group_account_field(p, index, (__force u64) cputime);
202
203         /* Account for system time used */
204         acct_account_cputime(p);
205 }
206
207 /*
208  * Account system cpu time to a process.
209  * @p: the process that the cpu time gets accounted to
210  * @hardirq_offset: the offset to subtract from hardirq_count()
211  * @cputime: the cpu time spent in kernel space since the last update
212  * @cputime_scaled: cputime scaled by cpu frequency
213  */
214 void account_system_time(struct task_struct *p, int hardirq_offset,
215                          cputime_t cputime, cputime_t cputime_scaled)
216 {
217         int index;
218
219         if ((p->flags & PF_VCPU) && (irq_count() - hardirq_offset == 0)) {
220                 account_guest_time(p, cputime, cputime_scaled);
221                 return;
222         }
223
224         if (hardirq_count() - hardirq_offset)
225                 index = CPUTIME_IRQ;
226         else if (in_serving_softirq())
227                 index = CPUTIME_SOFTIRQ;
228         else
229                 index = CPUTIME_SYSTEM;
230
231         __account_system_time(p, cputime, cputime_scaled, index);
232 }
233
234 /*
235  * Account for involuntary wait time.
236  * @cputime: the cpu time spent in involuntary wait
237  */
238 void account_steal_time(cputime_t cputime)
239 {
240         u64 *cpustat = kcpustat_this_cpu->cpustat;
241
242         cpustat[CPUTIME_STEAL] += (__force u64) cputime;
243 }
244
245 /*
246  * Account for idle time.
247  * @cputime: the cpu time spent in idle wait
248  */
249 void account_idle_time(cputime_t cputime)
250 {
251         u64 *cpustat = kcpustat_this_cpu->cpustat;
252         struct rq *rq = this_rq();
253
254         if (atomic_read(&rq->nr_iowait) > 0)
255                 cpustat[CPUTIME_IOWAIT] += (__force u64) cputime;
256         else
257                 cpustat[CPUTIME_IDLE] += (__force u64) cputime;
258 }
259
260 static __always_inline bool steal_account_process_tick(void)
261 {
262 #ifdef CONFIG_PARAVIRT
263         if (static_key_false(&paravirt_steal_enabled)) {
264                 u64 steal;
265                 unsigned long steal_jiffies;
266
267                 steal = paravirt_steal_clock(smp_processor_id());
268                 steal -= this_rq()->prev_steal_time;
269
270                 /*
271                  * steal is in nsecs but our caller is expecting steal
272                  * time in jiffies. Lets cast the result to jiffies
273                  * granularity and account the rest on the next rounds.
274                  */
275                 steal_jiffies = nsecs_to_jiffies(steal);
276                 this_rq()->prev_steal_time += jiffies_to_nsecs(steal_jiffies);
277
278                 account_steal_time(jiffies_to_cputime(steal_jiffies));
279                 return steal_jiffies;
280         }
281 #endif
282         return false;
283 }
284
285 /*
286  * Accumulate raw cputime values of dead tasks (sig->[us]time) and live
287  * tasks (sum on group iteration) belonging to @tsk's group.
288  */
289 void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
290 {
291         struct signal_struct *sig = tsk->signal;
292         cputime_t utime, stime;
293         struct task_struct *t;
294         unsigned int seq, nextseq;
295         unsigned long flags;
296
297         rcu_read_lock();
298         /* Attempt a lockless read on the first round. */
299         nextseq = 0;
300         do {
301                 seq = nextseq;
302                 flags = read_seqbegin_or_lock_irqsave(&sig->stats_lock, &seq);
303                 times->utime = sig->utime;
304                 times->stime = sig->stime;
305                 times->sum_exec_runtime = sig->sum_sched_runtime;
306
307                 for_each_thread(tsk, t) {
308                         task_cputime(t, &utime, &stime);
309                         times->utime += utime;
310                         times->stime += stime;
311                         times->sum_exec_runtime += task_sched_runtime(t);
312                 }
313                 /* If lockless access failed, take the lock. */
314                 nextseq = 1;
315         } while (need_seqretry(&sig->stats_lock, seq));
316         done_seqretry_irqrestore(&sig->stats_lock, seq, flags);
317         rcu_read_unlock();
318 }
319
320 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
321 /*
322  * Account a tick to a process and cpustat
323  * @p: the process that the cpu time gets accounted to
324  * @user_tick: is the tick from userspace
325  * @rq: the pointer to rq
326  *
327  * Tick demultiplexing follows the order
328  * - pending hardirq update
329  * - pending softirq update
330  * - user_time
331  * - idle_time
332  * - system time
333  *   - check for guest_time
334  *   - else account as system_time
335  *
336  * Check for hardirq is done both for system and user time as there is
337  * no timer going off while we are on hardirq and hence we may never get an
338  * opportunity to update it solely in system time.
339  * p->stime and friends are only updated on system time and not on irq
340  * softirq as those do not count in task exec_runtime any more.
341  */
342 static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
343                                          struct rq *rq, int ticks)
344 {
345         cputime_t scaled = cputime_to_scaled(cputime_one_jiffy);
346         u64 cputime = (__force u64) cputime_one_jiffy;
347         u64 *cpustat = kcpustat_this_cpu->cpustat;
348
349         if (steal_account_process_tick())
350                 return;
351
352         cputime *= ticks;
353         scaled *= ticks;
354
355         if (irqtime_account_hi_update()) {
356                 cpustat[CPUTIME_IRQ] += cputime;
357         } else if (irqtime_account_si_update()) {
358                 cpustat[CPUTIME_SOFTIRQ] += cputime;
359         } else if (this_cpu_ksoftirqd() == p) {
360                 /*
361                  * ksoftirqd time do not get accounted in cpu_softirq_time.
362                  * So, we have to handle it separately here.
363                  * Also, p->stime needs to be updated for ksoftirqd.
364                  */
365                 __account_system_time(p, cputime, scaled, CPUTIME_SOFTIRQ);
366         } else if (user_tick) {
367                 account_user_time(p, cputime, scaled);
368         } else if (p == rq->idle) {
369                 account_idle_time(cputime);
370         } else if (p->flags & PF_VCPU) { /* System time or guest time */
371                 account_guest_time(p, cputime, scaled);
372         } else {
373                 __account_system_time(p, cputime, scaled,       CPUTIME_SYSTEM);
374         }
375 }
376
377 static void irqtime_account_idle_ticks(int ticks)
378 {
379         struct rq *rq = this_rq();
380
381         irqtime_account_process_tick(current, 0, rq, ticks);
382 }
383 #else /* CONFIG_IRQ_TIME_ACCOUNTING */
384 static inline void irqtime_account_idle_ticks(int ticks) {}
385 static inline void irqtime_account_process_tick(struct task_struct *p, int user_tick,
386                                                 struct rq *rq, int nr_ticks) {}
387 #endif /* CONFIG_IRQ_TIME_ACCOUNTING */
388
389 /*
390  * Use precise platform statistics if available:
391  */
392 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
393
394 #ifndef __ARCH_HAS_VTIME_TASK_SWITCH
395 void vtime_common_task_switch(struct task_struct *prev)
396 {
397         if (is_idle_task(prev))
398                 vtime_account_idle(prev);
399         else
400                 vtime_account_system(prev);
401
402 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
403         vtime_account_user(prev);
404 #endif
405         arch_vtime_task_switch(prev);
406 }
407 #endif
408
409 /*
410  * Archs that account the whole time spent in the idle task
411  * (outside irq) as idle time can rely on this and just implement
412  * vtime_account_system() and vtime_account_idle(). Archs that
413  * have other meaning of the idle time (s390 only includes the
414  * time spent by the CPU when it's in low power mode) must override
415  * vtime_account().
416  */
417 #ifndef __ARCH_HAS_VTIME_ACCOUNT
418 void vtime_common_account_irq_enter(struct task_struct *tsk)
419 {
420         if (!in_interrupt()) {
421                 /*
422                  * If we interrupted user, context_tracking_in_user()
423                  * is 1 because the context tracking don't hook
424                  * on irq entry/exit. This way we know if
425                  * we need to flush user time on kernel entry.
426                  */
427                 if (context_tracking_in_user()) {
428                         vtime_account_user(tsk);
429                         return;
430                 }
431
432                 if (is_idle_task(tsk)) {
433                         vtime_account_idle(tsk);
434                         return;
435                 }
436         }
437         vtime_account_system(tsk);
438 }
439 EXPORT_SYMBOL_GPL(vtime_common_account_irq_enter);
440 #endif /* __ARCH_HAS_VTIME_ACCOUNT */
441 #endif /* CONFIG_VIRT_CPU_ACCOUNTING */
442
443
444 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
445 void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
446 {
447         *ut = p->utime;
448         *st = p->stime;
449 }
450 EXPORT_SYMBOL_GPL(task_cputime_adjusted);
451
452 void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
453 {
454         struct task_cputime cputime;
455
456         thread_group_cputime(p, &cputime);
457
458         *ut = cputime.utime;
459         *st = cputime.stime;
460 }
461 #else /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
462 /*
463  * Account a single tick of cpu time.
464  * @p: the process that the cpu time gets accounted to
465  * @user_tick: indicates if the tick is a user or a system tick
466  */
467 void account_process_tick(struct task_struct *p, int user_tick)
468 {
469         cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
470         struct rq *rq = this_rq();
471
472         if (vtime_accounting_cpu_enabled())
473                 return;
474
475         if (sched_clock_irqtime) {
476                 irqtime_account_process_tick(p, user_tick, rq, 1);
477                 return;
478         }
479
480         if (steal_account_process_tick())
481                 return;
482
483         if (user_tick)
484                 account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
485         else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
486                 account_system_time(p, HARDIRQ_OFFSET, cputime_one_jiffy,
487                                     one_jiffy_scaled);
488         else
489                 account_idle_time(cputime_one_jiffy);
490 }
491
492 /*
493  * Account multiple ticks of idle time.
494  * @ticks: number of stolen ticks
495  */
496 void account_idle_ticks(unsigned long ticks)
497 {
498
499         if (sched_clock_irqtime) {
500                 irqtime_account_idle_ticks(ticks);
501                 return;
502         }
503
504         account_idle_time(jiffies_to_cputime(ticks));
505 }
506
507 /*
508  * Perform (stime * rtime) / total, but avoid multiplication overflow by
509  * loosing precision when the numbers are big.
510  */
511 static cputime_t scale_stime(u64 stime, u64 rtime, u64 total)
512 {
513         u64 scaled;
514
515         for (;;) {
516                 /* Make sure "rtime" is the bigger of stime/rtime */
517                 if (stime > rtime)
518                         swap(rtime, stime);
519
520                 /* Make sure 'total' fits in 32 bits */
521                 if (total >> 32)
522                         goto drop_precision;
523
524                 /* Does rtime (and thus stime) fit in 32 bits? */
525                 if (!(rtime >> 32))
526                         break;
527
528                 /* Can we just balance rtime/stime rather than dropping bits? */
529                 if (stime >> 31)
530                         goto drop_precision;
531
532                 /* We can grow stime and shrink rtime and try to make them both fit */
533                 stime <<= 1;
534                 rtime >>= 1;
535                 continue;
536
537 drop_precision:
538                 /* We drop from rtime, it has more bits than stime */
539                 rtime >>= 1;
540                 total >>= 1;
541         }
542
543         /*
544          * Make sure gcc understands that this is a 32x32->64 multiply,
545          * followed by a 64/32->64 divide.
546          */
547         scaled = div_u64((u64) (u32) stime * (u64) (u32) rtime, (u32)total);
548         return (__force cputime_t) scaled;
549 }
550
551 /*
552  * Adjust tick based cputime random precision against scheduler runtime
553  * accounting.
554  *
555  * Tick based cputime accounting depend on random scheduling timeslices of a
556  * task to be interrupted or not by the timer.  Depending on these
557  * circumstances, the number of these interrupts may be over or
558  * under-optimistic, matching the real user and system cputime with a variable
559  * precision.
560  *
561  * Fix this by scaling these tick based values against the total runtime
562  * accounted by the CFS scheduler.
563  *
564  * This code provides the following guarantees:
565  *
566  *   stime + utime == rtime
567  *   stime_i+1 >= stime_i, utime_i+1 >= utime_i
568  *
569  * Assuming that rtime_i+1 >= rtime_i.
570  */
571 static void cputime_adjust(struct task_cputime *curr,
572                            struct prev_cputime *prev,
573                            cputime_t *ut, cputime_t *st)
574 {
575         cputime_t rtime, stime, utime;
576         unsigned long flags;
577
578         /* Serialize concurrent callers such that we can honour our guarantees */
579         raw_spin_lock_irqsave(&prev->lock, flags);
580         rtime = nsecs_to_cputime(curr->sum_exec_runtime);
581
582         /*
583          * This is possible under two circumstances:
584          *  - rtime isn't monotonic after all (a bug);
585          *  - we got reordered by the lock.
586          *
587          * In both cases this acts as a filter such that the rest of the code
588          * can assume it is monotonic regardless of anything else.
589          */
590         if (prev->stime + prev->utime >= rtime)
591                 goto out;
592
593         stime = curr->stime;
594         utime = curr->utime;
595
596         if (utime == 0) {
597                 stime = rtime;
598                 goto update;
599         }
600
601         if (stime == 0) {
602                 utime = rtime;
603                 goto update;
604         }
605
606         stime = scale_stime((__force u64)stime, (__force u64)rtime,
607                             (__force u64)(stime + utime));
608
609         /*
610          * Make sure stime doesn't go backwards; this preserves monotonicity
611          * for utime because rtime is monotonic.
612          *
613          *  utime_i+1 = rtime_i+1 - stime_i
614          *            = rtime_i+1 - (rtime_i - utime_i)
615          *            = (rtime_i+1 - rtime_i) + utime_i
616          *            >= utime_i
617          */
618         if (stime < prev->stime)
619                 stime = prev->stime;
620         utime = rtime - stime;
621
622         /*
623          * Make sure utime doesn't go backwards; this still preserves
624          * monotonicity for stime, analogous argument to above.
625          */
626         if (utime < prev->utime) {
627                 utime = prev->utime;
628                 stime = rtime - utime;
629         }
630
631 update:
632         prev->stime = stime;
633         prev->utime = utime;
634 out:
635         *ut = prev->utime;
636         *st = prev->stime;
637         raw_spin_unlock_irqrestore(&prev->lock, flags);
638 }
639
640 void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
641 {
642         struct task_cputime cputime = {
643                 .sum_exec_runtime = p->se.sum_exec_runtime,
644         };
645
646         task_cputime(p, &cputime.utime, &cputime.stime);
647         cputime_adjust(&cputime, &p->prev_cputime, ut, st);
648 }
649 EXPORT_SYMBOL_GPL(task_cputime_adjusted);
650
651 void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
652 {
653         struct task_cputime cputime;
654
655         thread_group_cputime(p, &cputime);
656         cputime_adjust(&cputime, &p->signal->prev_cputime, ut, st);
657 }
658 #endif /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
659
660 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
661 static cputime_t vtime_delta(struct task_struct *tsk)
662 {
663         unsigned long now = READ_ONCE(jiffies);
664
665         if (time_before(now, (unsigned long)tsk->vtime_snap))
666                 return 0;
667
668         return jiffies_to_cputime(now - tsk->vtime_snap);
669 }
670
671 static cputime_t get_vtime_delta(struct task_struct *tsk)
672 {
673         unsigned long now = READ_ONCE(jiffies);
674         unsigned long delta = now - tsk->vtime_snap;
675
676         WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_INACTIVE);
677         tsk->vtime_snap = now;
678
679         return jiffies_to_cputime(delta);
680 }
681
682 static void __vtime_account_system(struct task_struct *tsk)
683 {
684         cputime_t delta_cpu = get_vtime_delta(tsk);
685
686         account_system_time(tsk, irq_count(), delta_cpu, cputime_to_scaled(delta_cpu));
687 }
688
689 void vtime_account_system(struct task_struct *tsk)
690 {
691         if (!vtime_delta(tsk))
692                 return;
693
694         write_seqcount_begin(&tsk->vtime_seqcount);
695         __vtime_account_system(tsk);
696         write_seqcount_end(&tsk->vtime_seqcount);
697 }
698
699 void vtime_gen_account_irq_exit(struct task_struct *tsk)
700 {
701         write_seqcount_begin(&tsk->vtime_seqcount);
702         if (vtime_delta(tsk))
703                 __vtime_account_system(tsk);
704         if (context_tracking_in_user())
705                 tsk->vtime_snap_whence = VTIME_USER;
706         write_seqcount_end(&tsk->vtime_seqcount);
707 }
708
709 void vtime_account_user(struct task_struct *tsk)
710 {
711         cputime_t delta_cpu;
712
713         write_seqcount_begin(&tsk->vtime_seqcount);
714         tsk->vtime_snap_whence = VTIME_SYS;
715         if (vtime_delta(tsk)) {
716                 delta_cpu = get_vtime_delta(tsk);
717                 account_user_time(tsk, delta_cpu, cputime_to_scaled(delta_cpu));
718         }
719         write_seqcount_end(&tsk->vtime_seqcount);
720 }
721
722 void vtime_user_enter(struct task_struct *tsk)
723 {
724         write_seqcount_begin(&tsk->vtime_seqcount);
725         if (vtime_delta(tsk))
726                 __vtime_account_system(tsk);
727         tsk->vtime_snap_whence = VTIME_USER;
728         write_seqcount_end(&tsk->vtime_seqcount);
729 }
730
731 void vtime_guest_enter(struct task_struct *tsk)
732 {
733         /*
734          * The flags must be updated under the lock with
735          * the vtime_snap flush and update.
736          * That enforces a right ordering and update sequence
737          * synchronization against the reader (task_gtime())
738          * that can thus safely catch up with a tickless delta.
739          */
740         write_seqcount_begin(&tsk->vtime_seqcount);
741         if (vtime_delta(tsk))
742                 __vtime_account_system(tsk);
743         current->flags |= PF_VCPU;
744         write_seqcount_end(&tsk->vtime_seqcount);
745 }
746 EXPORT_SYMBOL_GPL(vtime_guest_enter);
747
748 void vtime_guest_exit(struct task_struct *tsk)
749 {
750         write_seqcount_begin(&tsk->vtime_seqcount);
751         __vtime_account_system(tsk);
752         current->flags &= ~PF_VCPU;
753         write_seqcount_end(&tsk->vtime_seqcount);
754 }
755 EXPORT_SYMBOL_GPL(vtime_guest_exit);
756
757 void vtime_account_idle(struct task_struct *tsk)
758 {
759         cputime_t delta_cpu = get_vtime_delta(tsk);
760
761         account_idle_time(delta_cpu);
762 }
763
764 void arch_vtime_task_switch(struct task_struct *prev)
765 {
766         write_seqcount_begin(&prev->vtime_seqcount);
767         prev->vtime_snap_whence = VTIME_INACTIVE;
768         write_seqcount_end(&prev->vtime_seqcount);
769
770         write_seqcount_begin(&current->vtime_seqcount);
771         current->vtime_snap_whence = VTIME_SYS;
772         current->vtime_snap = jiffies;
773         write_seqcount_end(&current->vtime_seqcount);
774 }
775
776 void vtime_init_idle(struct task_struct *t, int cpu)
777 {
778         unsigned long flags;
779
780         local_irq_save(flags);
781         write_seqcount_begin(&t->vtime_seqcount);
782         t->vtime_snap_whence = VTIME_SYS;
783         t->vtime_snap = jiffies;
784         write_seqcount_end(&t->vtime_seqcount);
785         local_irq_restore(flags);
786 }
787
788 cputime_t task_gtime(struct task_struct *t)
789 {
790         unsigned int seq;
791         cputime_t gtime;
792
793         if (!vtime_accounting_enabled())
794                 return t->gtime;
795
796         do {
797                 seq = read_seqcount_begin(&t->vtime_seqcount);
798
799                 gtime = t->gtime;
800                 if (t->vtime_snap_whence == VTIME_SYS && t->flags & PF_VCPU)
801                         gtime += vtime_delta(t);
802
803         } while (read_seqcount_retry(&t->vtime_seqcount, seq));
804
805         return gtime;
806 }
807
808 /*
809  * Fetch cputime raw values from fields of task_struct and
810  * add up the pending nohz execution time since the last
811  * cputime snapshot.
812  */
813 static void
814 fetch_task_cputime(struct task_struct *t,
815                    cputime_t *u_dst, cputime_t *s_dst,
816                    cputime_t *u_src, cputime_t *s_src,
817                    cputime_t *udelta, cputime_t *sdelta)
818 {
819         unsigned int seq;
820         unsigned long long delta;
821
822         do {
823                 *udelta = 0;
824                 *sdelta = 0;
825
826                 seq = read_seqcount_begin(&t->vtime_seqcount);
827
828                 if (u_dst)
829                         *u_dst = *u_src;
830                 if (s_dst)
831                         *s_dst = *s_src;
832
833                 /* Task is sleeping, nothing to add */
834                 if (t->vtime_snap_whence == VTIME_INACTIVE ||
835                     is_idle_task(t))
836                         continue;
837
838                 delta = vtime_delta(t);
839
840                 /*
841                  * Task runs either in user or kernel space, add pending nohz time to
842                  * the right place.
843                  */
844                 if (t->vtime_snap_whence == VTIME_USER || t->flags & PF_VCPU) {
845                         *udelta = delta;
846                 } else {
847                         if (t->vtime_snap_whence == VTIME_SYS)
848                                 *sdelta = delta;
849                 }
850         } while (read_seqcount_retry(&t->vtime_seqcount, seq));
851 }
852
853
854 void task_cputime(struct task_struct *t, cputime_t *utime, cputime_t *stime)
855 {
856         cputime_t udelta, sdelta;
857
858         if (!vtime_accounting_enabled()) {
859                 if (utime)
860                         *utime = t->utime;
861                 if (stime)
862                         *stime = t->stime;
863                 return;
864         }
865
866         fetch_task_cputime(t, utime, stime, &t->utime,
867                            &t->stime, &udelta, &sdelta);
868         if (utime)
869                 *utime += udelta;
870         if (stime)
871                 *stime += sdelta;
872 }
873
874 void task_cputime_scaled(struct task_struct *t,
875                          cputime_t *utimescaled, cputime_t *stimescaled)
876 {
877         cputime_t udelta, sdelta;
878
879         if (!vtime_accounting_enabled()) {
880                 if (utimescaled)
881                         *utimescaled = t->utimescaled;
882                 if (stimescaled)
883                         *stimescaled = t->stimescaled;
884                 return;
885         }
886
887         fetch_task_cputime(t, utimescaled, stimescaled,
888                            &t->utimescaled, &t->stimescaled, &udelta, &sdelta);
889         if (utimescaled)
890                 *utimescaled += cputime_to_scaled(udelta);
891         if (stimescaled)
892                 *stimescaled += cputime_to_scaled(sdelta);
893 }
894 #endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */