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TOMOYO Linux Cross Reference
Linux/kernel/sched/cputime.c

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  1 /*
  2  * Simple CPU accounting cgroup controller
  3  */
  4 #include "sched.h"
  5 
  6 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
  7 
  8 /*
  9  * There are no locks covering percpu hardirq/softirq time.
 10  * They are only modified in vtime_account, on corresponding CPU
 11  * with interrupts disabled. So, writes are safe.
 12  * They are read and saved off onto struct rq in update_rq_clock().
 13  * This may result in other CPU reading this CPU's irq time and can
 14  * race with irq/vtime_account on this CPU. We would either get old
 15  * or new value with a side effect of accounting a slice of irq time to wrong
 16  * task when irq is in progress while we read rq->clock. That is a worthy
 17  * compromise in place of having locks on each irq in account_system_time.
 18  */
 19 DEFINE_PER_CPU(struct irqtime, cpu_irqtime);
 20 
 21 static int sched_clock_irqtime;
 22 
 23 void enable_sched_clock_irqtime(void)
 24 {
 25         sched_clock_irqtime = 1;
 26 }
 27 
 28 void disable_sched_clock_irqtime(void)
 29 {
 30         sched_clock_irqtime = 0;
 31 }
 32 
 33 static void irqtime_account_delta(struct irqtime *irqtime, u64 delta,
 34                                   enum cpu_usage_stat idx)
 35 {
 36         u64 *cpustat = kcpustat_this_cpu->cpustat;
 37 
 38         u64_stats_update_begin(&irqtime->sync);
 39         cpustat[idx] += delta;
 40         irqtime->total += delta;
 41         irqtime->tick_delta += delta;
 42         u64_stats_update_end(&irqtime->sync);
 43 }
 44 
 45 /*
 46  * Called before incrementing preempt_count on {soft,}irq_enter
 47  * and before decrementing preempt_count on {soft,}irq_exit.
 48  */
 49 void irqtime_account_irq(struct task_struct *curr)
 50 {
 51         struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);
 52         s64 delta;
 53         int cpu;
 54 
 55         if (!sched_clock_irqtime)
 56                 return;
 57 
 58         cpu = smp_processor_id();
 59         delta = sched_clock_cpu(cpu) - irqtime->irq_start_time;
 60         irqtime->irq_start_time += delta;
 61 
 62         /*
 63          * We do not account for softirq time from ksoftirqd here.
 64          * We want to continue accounting softirq time to ksoftirqd thread
 65          * in that case, so as not to confuse scheduler with a special task
 66          * that do not consume any time, but still wants to run.
 67          */
 68         if (hardirq_count())
 69                 irqtime_account_delta(irqtime, delta, CPUTIME_IRQ);
 70         else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
 71                 irqtime_account_delta(irqtime, delta, CPUTIME_SOFTIRQ);
 72 }
 73 EXPORT_SYMBOL_GPL(irqtime_account_irq);
 74 
 75 static u64 irqtime_tick_accounted(u64 maxtime)
 76 {
 77         struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);
 78         u64 delta;
 79 
 80         delta = min(irqtime->tick_delta, maxtime);
 81         irqtime->tick_delta -= delta;
 82 
 83         return delta;
 84 }
 85 
 86 #else /* CONFIG_IRQ_TIME_ACCOUNTING */
 87 
 88 #define sched_clock_irqtime     (0)
 89 
 90 static u64 irqtime_tick_accounted(u64 dummy)
 91 {
 92         return 0;
 93 }
 94 
 95 #endif /* !CONFIG_IRQ_TIME_ACCOUNTING */
 96 
 97 static inline void task_group_account_field(struct task_struct *p, int index,
 98                                             u64 tmp)
 99 {
100         /*
101          * Since all updates are sure to touch the root cgroup, we
102          * get ourselves ahead and touch it first. If the root cgroup
103          * is the only cgroup, then nothing else should be necessary.
104          *
105          */
106         __this_cpu_add(kernel_cpustat.cpustat[index], tmp);
107 
108         cgroup_account_cputime_field(p, index, tmp);
109 }
110 
111 /*
112  * Account user CPU time to a process.
113  * @p: the process that the CPU time gets accounted to
114  * @cputime: the CPU time spent in user space since the last update
115  */
116 void account_user_time(struct task_struct *p, u64 cputime)
117 {
118         int index;
119 
120         /* Add user time to process. */
121         p->utime += cputime;
122         account_group_user_time(p, cputime);
123 
124         index = (task_nice(p) > 0) ? CPUTIME_NICE : CPUTIME_USER;
125 
126         /* Add user time to cpustat. */
127         task_group_account_field(p, index, cputime);
128 
129         /* Account for user time used */
130         acct_account_cputime(p);
131 }
132 
133 /*
134  * Account guest CPU time to a process.
135  * @p: the process that the CPU time gets accounted to
136  * @cputime: the CPU time spent in virtual machine since the last update
137  */
138 void account_guest_time(struct task_struct *p, u64 cputime)
139 {
140         u64 *cpustat = kcpustat_this_cpu->cpustat;
141 
142         /* Add guest time to process. */
143         p->utime += cputime;
144         account_group_user_time(p, cputime);
145         p->gtime += cputime;
146 
147         /* Add guest time to cpustat. */
148         if (task_nice(p) > 0) {
149                 cpustat[CPUTIME_NICE] += cputime;
150                 cpustat[CPUTIME_GUEST_NICE] += cputime;
151         } else {
152                 cpustat[CPUTIME_USER] += cputime;
153                 cpustat[CPUTIME_GUEST] += cputime;
154         }
155 }
156 
157 /*
158  * Account system CPU time to a process and desired cpustat field
159  * @p: the process that the CPU time gets accounted to
160  * @cputime: the CPU time spent in kernel space since the last update
161  * @index: pointer to cpustat field that has to be updated
162  */
163 void account_system_index_time(struct task_struct *p,
164                                u64 cputime, enum cpu_usage_stat index)
165 {
166         /* Add system time to process. */
167         p->stime += cputime;
168         account_group_system_time(p, cputime);
169 
170         /* Add system time to cpustat. */
171         task_group_account_field(p, index, cputime);
172 
173         /* Account for system time used */
174         acct_account_cputime(p);
175 }
176 
177 /*
178  * Account system CPU time to a process.
179  * @p: the process that the CPU time gets accounted to
180  * @hardirq_offset: the offset to subtract from hardirq_count()
181  * @cputime: the CPU time spent in kernel space since the last update
182  */
183 void account_system_time(struct task_struct *p, int hardirq_offset, u64 cputime)
184 {
185         int index;
186 
187         if ((p->flags & PF_VCPU) && (irq_count() - hardirq_offset == 0)) {
188                 account_guest_time(p, cputime);
189                 return;
190         }
191 
192         if (hardirq_count() - hardirq_offset)
193                 index = CPUTIME_IRQ;
194         else if (in_serving_softirq())
195                 index = CPUTIME_SOFTIRQ;
196         else
197                 index = CPUTIME_SYSTEM;
198 
199         account_system_index_time(p, cputime, index);
200 }
201 
202 /*
203  * Account for involuntary wait time.
204  * @cputime: the CPU time spent in involuntary wait
205  */
206 void account_steal_time(u64 cputime)
207 {
208         u64 *cpustat = kcpustat_this_cpu->cpustat;
209 
210         cpustat[CPUTIME_STEAL] += cputime;
211 }
212 
213 /*
214  * Account for idle time.
215  * @cputime: the CPU time spent in idle wait
216  */
217 void account_idle_time(u64 cputime)
218 {
219         u64 *cpustat = kcpustat_this_cpu->cpustat;
220         struct rq *rq = this_rq();
221 
222         if (atomic_read(&rq->nr_iowait) > 0)
223                 cpustat[CPUTIME_IOWAIT] += cputime;
224         else
225                 cpustat[CPUTIME_IDLE] += cputime;
226 }
227 
228 /*
229  * When a guest is interrupted for a longer amount of time, missed clock
230  * ticks are not redelivered later. Due to that, this function may on
231  * occasion account more time than the calling functions think elapsed.
232  */
233 static __always_inline u64 steal_account_process_time(u64 maxtime)
234 {
235 #ifdef CONFIG_PARAVIRT
236         if (static_key_false(&paravirt_steal_enabled)) {
237                 u64 steal;
238 
239                 steal = paravirt_steal_clock(smp_processor_id());
240                 steal -= this_rq()->prev_steal_time;
241                 steal = min(steal, maxtime);
242                 account_steal_time(steal);
243                 this_rq()->prev_steal_time += steal;
244 
245                 return steal;
246         }
247 #endif
248         return 0;
249 }
250 
251 /*
252  * Account how much elapsed time was spent in steal, irq, or softirq time.
253  */
254 static inline u64 account_other_time(u64 max)
255 {
256         u64 accounted;
257 
258         lockdep_assert_irqs_disabled();
259 
260         accounted = steal_account_process_time(max);
261 
262         if (accounted < max)
263                 accounted += irqtime_tick_accounted(max - accounted);
264 
265         return accounted;
266 }
267 
268 #ifdef CONFIG_64BIT
269 static inline u64 read_sum_exec_runtime(struct task_struct *t)
270 {
271         return t->se.sum_exec_runtime;
272 }
273 #else
274 static u64 read_sum_exec_runtime(struct task_struct *t)
275 {
276         u64 ns;
277         struct rq_flags rf;
278         struct rq *rq;
279 
280         rq = task_rq_lock(t, &rf);
281         ns = t->se.sum_exec_runtime;
282         task_rq_unlock(rq, t, &rf);
283 
284         return ns;
285 }
286 #endif
287 
288 /*
289  * Accumulate raw cputime values of dead tasks (sig->[us]time) and live
290  * tasks (sum on group iteration) belonging to @tsk's group.
291  */
292 void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
293 {
294         struct signal_struct *sig = tsk->signal;
295         u64 utime, stime;
296         struct task_struct *t;
297         unsigned int seq, nextseq;
298         unsigned long flags;
299 
300         /*
301          * Update current task runtime to account pending time since last
302          * scheduler action or thread_group_cputime() call. This thread group
303          * might have other running tasks on different CPUs, but updating
304          * their runtime can affect syscall performance, so we skip account
305          * those pending times and rely only on values updated on tick or
306          * other scheduler action.
307          */
308         if (same_thread_group(current, tsk))
309                 (void) task_sched_runtime(current);
310 
311         rcu_read_lock();
312         /* Attempt a lockless read on the first round. */
313         nextseq = 0;
314         do {
315                 seq = nextseq;
316                 flags = read_seqbegin_or_lock_irqsave(&sig->stats_lock, &seq);
317                 times->utime = sig->utime;
318                 times->stime = sig->stime;
319                 times->sum_exec_runtime = sig->sum_sched_runtime;
320 
321                 for_each_thread(tsk, t) {
322                         task_cputime(t, &utime, &stime);
323                         times->utime += utime;
324                         times->stime += stime;
325                         times->sum_exec_runtime += read_sum_exec_runtime(t);
326                 }
327                 /* If lockless access failed, take the lock. */
328                 nextseq = 1;
329         } while (need_seqretry(&sig->stats_lock, seq));
330         done_seqretry_irqrestore(&sig->stats_lock, seq, flags);
331         rcu_read_unlock();
332 }
333 
334 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
335 /*
336  * Account a tick to a process and cpustat
337  * @p: the process that the CPU time gets accounted to
338  * @user_tick: is the tick from userspace
339  * @rq: the pointer to rq
340  *
341  * Tick demultiplexing follows the order
342  * - pending hardirq update
343  * - pending softirq update
344  * - user_time
345  * - idle_time
346  * - system time
347  *   - check for guest_time
348  *   - else account as system_time
349  *
350  * Check for hardirq is done both for system and user time as there is
351  * no timer going off while we are on hardirq and hence we may never get an
352  * opportunity to update it solely in system time.
353  * p->stime and friends are only updated on system time and not on irq
354  * softirq as those do not count in task exec_runtime any more.
355  */
356 static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
357                                          struct rq *rq, int ticks)
358 {
359         u64 other, cputime = TICK_NSEC * ticks;
360 
361         /*
362          * When returning from idle, many ticks can get accounted at
363          * once, including some ticks of steal, irq, and softirq time.
364          * Subtract those ticks from the amount of time accounted to
365          * idle, or potentially user or system time. Due to rounding,
366          * other time can exceed ticks occasionally.
367          */
368         other = account_other_time(ULONG_MAX);
369         if (other >= cputime)
370                 return;
371 
372         cputime -= other;
373 
374         if (this_cpu_ksoftirqd() == p) {
375                 /*
376                  * ksoftirqd time do not get accounted in cpu_softirq_time.
377                  * So, we have to handle it separately here.
378                  * Also, p->stime needs to be updated for ksoftirqd.
379                  */
380                 account_system_index_time(p, cputime, CPUTIME_SOFTIRQ);
381         } else if (user_tick) {
382                 account_user_time(p, cputime);
383         } else if (p == rq->idle) {
384                 account_idle_time(cputime);
385         } else if (p->flags & PF_VCPU) { /* System time or guest time */
386                 account_guest_time(p, cputime);
387         } else {
388                 account_system_index_time(p, cputime, CPUTIME_SYSTEM);
389         }
390 }
391 
392 static void irqtime_account_idle_ticks(int ticks)
393 {
394         struct rq *rq = this_rq();
395 
396         irqtime_account_process_tick(current, 0, rq, ticks);
397 }
398 #else /* CONFIG_IRQ_TIME_ACCOUNTING */
399 static inline void irqtime_account_idle_ticks(int ticks) { }
400 static inline void irqtime_account_process_tick(struct task_struct *p, int user_tick,
401                                                 struct rq *rq, int nr_ticks) { }
402 #endif /* CONFIG_IRQ_TIME_ACCOUNTING */
403 
404 /*
405  * Use precise platform statistics if available:
406  */
407 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
408 # ifndef __ARCH_HAS_VTIME_TASK_SWITCH
409 void vtime_common_task_switch(struct task_struct *prev)
410 {
411         if (is_idle_task(prev))
412                 vtime_account_idle(prev);
413         else
414                 vtime_account_system(prev);
415 
416         vtime_flush(prev);
417         arch_vtime_task_switch(prev);
418 }
419 # endif
420 #endif /* CONFIG_VIRT_CPU_ACCOUNTING */
421 
422 
423 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
424 /*
425  * Archs that account the whole time spent in the idle task
426  * (outside irq) as idle time can rely on this and just implement
427  * vtime_account_system() and vtime_account_idle(). Archs that
428  * have other meaning of the idle time (s390 only includes the
429  * time spent by the CPU when it's in low power mode) must override
430  * vtime_account().
431  */
432 #ifndef __ARCH_HAS_VTIME_ACCOUNT
433 void vtime_account_irq_enter(struct task_struct *tsk)
434 {
435         if (!in_interrupt() && is_idle_task(tsk))
436                 vtime_account_idle(tsk);
437         else
438                 vtime_account_system(tsk);
439 }
440 EXPORT_SYMBOL_GPL(vtime_account_irq_enter);
441 #endif /* __ARCH_HAS_VTIME_ACCOUNT */
442 
443 void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev,
444                     u64 *ut, u64 *st)
445 {
446         *ut = curr->utime;
447         *st = curr->stime;
448 }
449 
450 void task_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
451 {
452         *ut = p->utime;
453         *st = p->stime;
454 }
455 EXPORT_SYMBOL_GPL(task_cputime_adjusted);
456 
457 void thread_group_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
458 {
459         struct task_cputime cputime;
460 
461         thread_group_cputime(p, &cputime);
462 
463         *ut = cputime.utime;
464         *st = cputime.stime;
465 }
466 
467 #else /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE: */
468 
469 /*
470  * Account a single tick of CPU time.
471  * @p: the process that the CPU time gets accounted to
472  * @user_tick: indicates if the tick is a user or a system tick
473  */
474 void account_process_tick(struct task_struct *p, int user_tick)
475 {
476         u64 cputime, steal;
477         struct rq *rq = this_rq();
478 
479         if (vtime_accounting_cpu_enabled())
480                 return;
481 
482         if (sched_clock_irqtime) {
483                 irqtime_account_process_tick(p, user_tick, rq, 1);
484                 return;
485         }
486 
487         cputime = TICK_NSEC;
488         steal = steal_account_process_time(ULONG_MAX);
489 
490         if (steal >= cputime)
491                 return;
492 
493         cputime -= steal;
494 
495         if (user_tick)
496                 account_user_time(p, cputime);
497         else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
498                 account_system_time(p, HARDIRQ_OFFSET, cputime);
499         else
500                 account_idle_time(cputime);
501 }
502 
503 /*
504  * Account multiple ticks of idle time.
505  * @ticks: number of stolen ticks
506  */
507 void account_idle_ticks(unsigned long ticks)
508 {
509         u64 cputime, steal;
510 
511         if (sched_clock_irqtime) {
512                 irqtime_account_idle_ticks(ticks);
513                 return;
514         }
515 
516         cputime = ticks * TICK_NSEC;
517         steal = steal_account_process_time(ULONG_MAX);
518 
519         if (steal >= cputime)
520                 return;
521 
522         cputime -= steal;
523         account_idle_time(cputime);
524 }
525 
526 /*
527  * Perform (stime * rtime) / total, but avoid multiplication overflow by
528  * losing precision when the numbers are big.
529  */
530 static u64 scale_stime(u64 stime, u64 rtime, u64 total)
531 {
532         u64 scaled;
533 
534         for (;;) {
535                 /* Make sure "rtime" is the bigger of stime/rtime */
536                 if (stime > rtime)
537                         swap(rtime, stime);
538 
539                 /* Make sure 'total' fits in 32 bits */
540                 if (total >> 32)
541                         goto drop_precision;
542 
543                 /* Does rtime (and thus stime) fit in 32 bits? */
544                 if (!(rtime >> 32))
545                         break;
546 
547                 /* Can we just balance rtime/stime rather than dropping bits? */
548                 if (stime >> 31)
549                         goto drop_precision;
550 
551                 /* We can grow stime and shrink rtime and try to make them both fit */
552                 stime <<= 1;
553                 rtime >>= 1;
554                 continue;
555 
556 drop_precision:
557                 /* We drop from rtime, it has more bits than stime */
558                 rtime >>= 1;
559                 total >>= 1;
560         }
561 
562         /*
563          * Make sure gcc understands that this is a 32x32->64 multiply,
564          * followed by a 64/32->64 divide.
565          */
566         scaled = div_u64((u64) (u32) stime * (u64) (u32) rtime, (u32)total);
567         return scaled;
568 }
569 
570 /*
571  * Adjust tick based cputime random precision against scheduler runtime
572  * accounting.
573  *
574  * Tick based cputime accounting depend on random scheduling timeslices of a
575  * task to be interrupted or not by the timer.  Depending on these
576  * circumstances, the number of these interrupts may be over or
577  * under-optimistic, matching the real user and system cputime with a variable
578  * precision.
579  *
580  * Fix this by scaling these tick based values against the total runtime
581  * accounted by the CFS scheduler.
582  *
583  * This code provides the following guarantees:
584  *
585  *   stime + utime == rtime
586  *   stime_i+1 >= stime_i, utime_i+1 >= utime_i
587  *
588  * Assuming that rtime_i+1 >= rtime_i.
589  */
590 void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev,
591                     u64 *ut, u64 *st)
592 {
593         u64 rtime, stime, utime;
594         unsigned long flags;
595 
596         /* Serialize concurrent callers such that we can honour our guarantees */
597         raw_spin_lock_irqsave(&prev->lock, flags);
598         rtime = curr->sum_exec_runtime;
599 
600         /*
601          * This is possible under two circumstances:
602          *  - rtime isn't monotonic after all (a bug);
603          *  - we got reordered by the lock.
604          *
605          * In both cases this acts as a filter such that the rest of the code
606          * can assume it is monotonic regardless of anything else.
607          */
608         if (prev->stime + prev->utime >= rtime)
609                 goto out;
610 
611         stime = curr->stime;
612         utime = curr->utime;
613 
614         /*
615          * If either stime or utime are 0, assume all runtime is userspace.
616          * Once a task gets some ticks, the monotonicy code at 'update:'
617          * will ensure things converge to the observed ratio.
618          */
619         if (stime == 0) {
620                 utime = rtime;
621                 goto update;
622         }
623 
624         if (utime == 0) {
625                 stime = rtime;
626                 goto update;
627         }
628 
629         stime = scale_stime(stime, rtime, stime + utime);
630 
631 update:
632         /*
633          * Make sure stime doesn't go backwards; this preserves monotonicity
634          * for utime because rtime is monotonic.
635          *
636          *  utime_i+1 = rtime_i+1 - stime_i
637          *            = rtime_i+1 - (rtime_i - utime_i)
638          *            = (rtime_i+1 - rtime_i) + utime_i
639          *            >= utime_i
640          */
641         if (stime < prev->stime)
642                 stime = prev->stime;
643         utime = rtime - stime;
644 
645         /*
646          * Make sure utime doesn't go backwards; this still preserves
647          * monotonicity for stime, analogous argument to above.
648          */
649         if (utime < prev->utime) {
650                 utime = prev->utime;
651                 stime = rtime - utime;
652         }
653 
654         prev->stime = stime;
655         prev->utime = utime;
656 out:
657         *ut = prev->utime;
658         *st = prev->stime;
659         raw_spin_unlock_irqrestore(&prev->lock, flags);
660 }
661 
662 void task_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
663 {
664         struct task_cputime cputime = {
665                 .sum_exec_runtime = p->se.sum_exec_runtime,
666         };
667 
668         task_cputime(p, &cputime.utime, &cputime.stime);
669         cputime_adjust(&cputime, &p->prev_cputime, ut, st);
670 }
671 EXPORT_SYMBOL_GPL(task_cputime_adjusted);
672 
673 void thread_group_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
674 {
675         struct task_cputime cputime;
676 
677         thread_group_cputime(p, &cputime);
678         cputime_adjust(&cputime, &p->signal->prev_cputime, ut, st);
679 }
680 #endif /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
681 
682 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
683 static u64 vtime_delta(struct vtime *vtime)
684 {
685         unsigned long long clock;
686 
687         clock = sched_clock();
688         if (clock < vtime->starttime)
689                 return 0;
690 
691         return clock - vtime->starttime;
692 }
693 
694 static u64 get_vtime_delta(struct vtime *vtime)
695 {
696         u64 delta = vtime_delta(vtime);
697         u64 other;
698 
699         /*
700          * Unlike tick based timing, vtime based timing never has lost
701          * ticks, and no need for steal time accounting to make up for
702          * lost ticks. Vtime accounts a rounded version of actual
703          * elapsed time. Limit account_other_time to prevent rounding
704          * errors from causing elapsed vtime to go negative.
705          */
706         other = account_other_time(delta);
707         WARN_ON_ONCE(vtime->state == VTIME_INACTIVE);
708         vtime->starttime += delta;
709 
710         return delta - other;
711 }
712 
713 static void __vtime_account_system(struct task_struct *tsk,
714                                    struct vtime *vtime)
715 {
716         vtime->stime += get_vtime_delta(vtime);
717         if (vtime->stime >= TICK_NSEC) {
718                 account_system_time(tsk, irq_count(), vtime->stime);
719                 vtime->stime = 0;
720         }
721 }
722 
723 static void vtime_account_guest(struct task_struct *tsk,
724                                 struct vtime *vtime)
725 {
726         vtime->gtime += get_vtime_delta(vtime);
727         if (vtime->gtime >= TICK_NSEC) {
728                 account_guest_time(tsk, vtime->gtime);
729                 vtime->gtime = 0;
730         }
731 }
732 
733 void vtime_account_system(struct task_struct *tsk)
734 {
735         struct vtime *vtime = &tsk->vtime;
736 
737         if (!vtime_delta(vtime))
738                 return;
739 
740         write_seqcount_begin(&vtime->seqcount);
741         /* We might have scheduled out from guest path */
742         if (current->flags & PF_VCPU)
743                 vtime_account_guest(tsk, vtime);
744         else
745                 __vtime_account_system(tsk, vtime);
746         write_seqcount_end(&vtime->seqcount);
747 }
748 
749 void vtime_user_enter(struct task_struct *tsk)
750 {
751         struct vtime *vtime = &tsk->vtime;
752 
753         write_seqcount_begin(&vtime->seqcount);
754         __vtime_account_system(tsk, vtime);
755         vtime->state = VTIME_USER;
756         write_seqcount_end(&vtime->seqcount);
757 }
758 
759 void vtime_user_exit(struct task_struct *tsk)
760 {
761         struct vtime *vtime = &tsk->vtime;
762 
763         write_seqcount_begin(&vtime->seqcount);
764         vtime->utime += get_vtime_delta(vtime);
765         if (vtime->utime >= TICK_NSEC) {
766                 account_user_time(tsk, vtime->utime);
767                 vtime->utime = 0;
768         }
769         vtime->state = VTIME_SYS;
770         write_seqcount_end(&vtime->seqcount);
771 }
772 
773 void vtime_guest_enter(struct task_struct *tsk)
774 {
775         struct vtime *vtime = &tsk->vtime;
776         /*
777          * The flags must be updated under the lock with
778          * the vtime_starttime flush and update.
779          * That enforces a right ordering and update sequence
780          * synchronization against the reader (task_gtime())
781          * that can thus safely catch up with a tickless delta.
782          */
783         write_seqcount_begin(&vtime->seqcount);
784         __vtime_account_system(tsk, vtime);
785         current->flags |= PF_VCPU;
786         write_seqcount_end(&vtime->seqcount);
787 }
788 EXPORT_SYMBOL_GPL(vtime_guest_enter);
789 
790 void vtime_guest_exit(struct task_struct *tsk)
791 {
792         struct vtime *vtime = &tsk->vtime;
793 
794         write_seqcount_begin(&vtime->seqcount);
795         vtime_account_guest(tsk, vtime);
796         current->flags &= ~PF_VCPU;
797         write_seqcount_end(&vtime->seqcount);
798 }
799 EXPORT_SYMBOL_GPL(vtime_guest_exit);
800 
801 void vtime_account_idle(struct task_struct *tsk)
802 {
803         account_idle_time(get_vtime_delta(&tsk->vtime));
804 }
805 
806 void arch_vtime_task_switch(struct task_struct *prev)
807 {
808         struct vtime *vtime = &prev->vtime;
809 
810         write_seqcount_begin(&vtime->seqcount);
811         vtime->state = VTIME_INACTIVE;
812         write_seqcount_end(&vtime->seqcount);
813 
814         vtime = &current->vtime;
815 
816         write_seqcount_begin(&vtime->seqcount);
817         vtime->state = VTIME_SYS;
818         vtime->starttime = sched_clock();
819         write_seqcount_end(&vtime->seqcount);
820 }
821 
822 void vtime_init_idle(struct task_struct *t, int cpu)
823 {
824         struct vtime *vtime = &t->vtime;
825         unsigned long flags;
826 
827         local_irq_save(flags);
828         write_seqcount_begin(&vtime->seqcount);
829         vtime->state = VTIME_SYS;
830         vtime->starttime = sched_clock();
831         write_seqcount_end(&vtime->seqcount);
832         local_irq_restore(flags);
833 }
834 
835 u64 task_gtime(struct task_struct *t)
836 {
837         struct vtime *vtime = &t->vtime;
838         unsigned int seq;
839         u64 gtime;
840 
841         if (!vtime_accounting_enabled())
842                 return t->gtime;
843 
844         do {
845                 seq = read_seqcount_begin(&vtime->seqcount);
846 
847                 gtime = t->gtime;
848                 if (vtime->state == VTIME_SYS && t->flags & PF_VCPU)
849                         gtime += vtime->gtime + vtime_delta(vtime);
850 
851         } while (read_seqcount_retry(&vtime->seqcount, seq));
852 
853         return gtime;
854 }
855 
856 /*
857  * Fetch cputime raw values from fields of task_struct and
858  * add up the pending nohz execution time since the last
859  * cputime snapshot.
860  */
861 void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
862 {
863         struct vtime *vtime = &t->vtime;
864         unsigned int seq;
865         u64 delta;
866 
867         if (!vtime_accounting_enabled()) {
868                 *utime = t->utime;
869                 *stime = t->stime;
870                 return;
871         }
872 
873         do {
874                 seq = read_seqcount_begin(&vtime->seqcount);
875 
876                 *utime = t->utime;
877                 *stime = t->stime;
878 
879                 /* Task is sleeping, nothing to add */
880                 if (vtime->state == VTIME_INACTIVE || is_idle_task(t))
881                         continue;
882 
883                 delta = vtime_delta(vtime);
884 
885                 /*
886                  * Task runs either in user or kernel space, add pending nohz time to
887                  * the right place.
888                  */
889                 if (vtime->state == VTIME_USER || t->flags & PF_VCPU)
890                         *utime += vtime->utime + delta;
891                 else if (vtime->state == VTIME_SYS)
892                         *stime += vtime->stime + delta;
893         } while (read_seqcount_retry(&vtime->seqcount, seq));
894 }
895 #endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */
896 

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