1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Simple CPU accounting cgroup controller
4 */
5#include <linux/sched/cputime.h>
6#include <linux/tsacct_kern.h>
7#include "sched.h"
8
9#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
10 #include <asm/cputime.h>
11#endif
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 */
26DEFINE_PER_CPU(struct irqtime, cpu_irqtime);
27
28int sched_clock_irqtime;
29
30void enable_sched_clock_irqtime(void)
31{
32 sched_clock_irqtime = 1;
33}
34
35void disable_sched_clock_irqtime(void)
36{
37 sched_clock_irqtime = 0;
38}
39
40static void irqtime_account_delta(struct irqtime *irqtime, u64 delta,
41 enum cpu_usage_stat idx)
42{
43 u64 *cpustat = kcpustat_this_cpu->cpustat;
44
45 u64_stats_update_begin(syncp: &irqtime->sync);
46 cpustat[idx] += delta;
47 irqtime->total += delta;
48 irqtime->tick_delta += delta;
49 u64_stats_update_end(syncp: &irqtime->sync);
50}
51
52/*
53 * Called after incrementing preempt_count on {soft,}irq_enter
54 * and before decrementing preempt_count on {soft,}irq_exit.
55 */
56void irqtime_account_irq(struct task_struct *curr, unsigned int offset)
57{
58 struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);
59 unsigned int pc;
60 s64 delta;
61 int cpu;
62
63 if (!irqtime_enabled())
64 return;
65
66 cpu = smp_processor_id();
67 delta = sched_clock_cpu(cpu) - irqtime->irq_start_time;
68 irqtime->irq_start_time += delta;
69 pc = irq_count() - offset;
70
71 /*
72 * We do not account for softirq time from ksoftirqd here.
73 * We want to continue accounting softirq time to ksoftirqd thread
74 * in that case, so as not to confuse scheduler with a special task
75 * that do not consume any time, but still wants to run.
76 */
77 if (pc & HARDIRQ_MASK)
78 irqtime_account_delta(irqtime, delta, idx: CPUTIME_IRQ);
79 else if ((pc & SOFTIRQ_OFFSET) && curr != this_cpu_ksoftirqd())
80 irqtime_account_delta(irqtime, delta, idx: CPUTIME_SOFTIRQ);
81}
82
83static u64 irqtime_tick_accounted(u64 maxtime)
84{
85 struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);
86 u64 delta;
87
88 delta = min(irqtime->tick_delta, maxtime);
89 irqtime->tick_delta -= delta;
90
91 return delta;
92}
93
94#else /* !CONFIG_IRQ_TIME_ACCOUNTING: */
95
96static u64 irqtime_tick_accounted(u64 dummy)
97{
98 return 0;
99}
100
101#endif /* !CONFIG_IRQ_TIME_ACCOUNTING */
102
103static inline void task_group_account_field(struct task_struct *p, int index,
104 u64 tmp)
105{
106 /*
107 * Since all updates are sure to touch the root cgroup, we
108 * get ourselves ahead and touch it first. If the root cgroup
109 * is the only cgroup, then nothing else should be necessary.
110 *
111 */
112 __this_cpu_add(kernel_cpustat.cpustat[index], tmp);
113
114 cgroup_account_cputime_field(task: p, index, delta_exec: tmp);
115}
116
117/*
118 * Account user CPU time to a process.
119 * @p: the process that the CPU time gets accounted to
120 * @cputime: the CPU time spent in user space since the last update
121 */
122void account_user_time(struct task_struct *p, u64 cputime)
123{
124 int index;
125
126 /* Add user time to process. */
127 p->utime += cputime;
128 account_group_user_time(tsk: p, cputime);
129
130 index = (task_nice(p) > 0) ? CPUTIME_NICE : CPUTIME_USER;
131
132 /* Add user time to cpustat. */
133 task_group_account_field(p, index, tmp: cputime);
134
135 /* Account for user time used */
136 acct_account_cputime(tsk: p);
137}
138
139/*
140 * Account guest CPU time to a process.
141 * @p: the process that the CPU time gets accounted to
142 * @cputime: the CPU time spent in virtual machine since the last update
143 */
144void account_guest_time(struct task_struct *p, u64 cputime)
145{
146 u64 *cpustat = kcpustat_this_cpu->cpustat;
147
148 /* Add guest time to process. */
149 p->utime += cputime;
150 account_group_user_time(tsk: p, cputime);
151 p->gtime += cputime;
152
153 /* Add guest time to cpustat. */
154 if (task_nice(p) > 0) {
155 task_group_account_field(p, index: CPUTIME_NICE, tmp: cputime);
156 cpustat[CPUTIME_GUEST_NICE] += cputime;
157 } else {
158 task_group_account_field(p, index: CPUTIME_USER, tmp: cputime);
159 cpustat[CPUTIME_GUEST] += cputime;
160 }
161}
162
163/*
164 * Account system CPU time to a process and desired cpustat field
165 * @p: the process that the CPU time gets accounted to
166 * @cputime: the CPU time spent in kernel space since the last update
167 * @index: pointer to cpustat field that has to be updated
168 */
169void account_system_index_time(struct task_struct *p,
170 u64 cputime, enum cpu_usage_stat index)
171{
172 /* Add system time to process. */
173 p->stime += cputime;
174 account_group_system_time(tsk: p, cputime);
175
176 /* Add system time to cpustat. */
177 task_group_account_field(p, index, tmp: cputime);
178
179 /* Account for system time used */
180 acct_account_cputime(tsk: p);
181}
182
183/*
184 * Account system CPU time to a process.
185 * @p: the process that the CPU time gets accounted to
186 * @hardirq_offset: the offset to subtract from hardirq_count()
187 * @cputime: the CPU time spent in kernel space since the last update
188 */
189void account_system_time(struct task_struct *p, int hardirq_offset, u64 cputime)
190{
191 int index;
192
193 if ((p->flags & PF_VCPU) && (irq_count() - hardirq_offset == 0)) {
194 account_guest_time(p, cputime);
195 return;
196 }
197
198 if (hardirq_count() - hardirq_offset)
199 index = CPUTIME_IRQ;
200 else if (in_serving_softirq())
201 index = CPUTIME_SOFTIRQ;
202 else
203 index = CPUTIME_SYSTEM;
204
205 account_system_index_time(p, cputime, index);
206}
207
208/*
209 * Account for involuntary wait time.
210 * @cputime: the CPU time spent in involuntary wait
211 */
212void account_steal_time(u64 cputime)
213{
214 u64 *cpustat = kcpustat_this_cpu->cpustat;
215
216 cpustat[CPUTIME_STEAL] += cputime;
217}
218
219/*
220 * Account for idle time.
221 * @cputime: the CPU time spent in idle wait
222 */
223void account_idle_time(u64 cputime)
224{
225 u64 *cpustat = kcpustat_this_cpu->cpustat;
226 struct rq *rq = this_rq();
227
228 if (atomic_read(v: &rq->nr_iowait) > 0)
229 cpustat[CPUTIME_IOWAIT] += cputime;
230 else
231 cpustat[CPUTIME_IDLE] += cputime;
232}
233
234
235#ifdef CONFIG_SCHED_CORE
236/*
237 * Account for forceidle time due to core scheduling.
238 *
239 * REQUIRES: schedstat is enabled.
240 */
241void __account_forceidle_time(struct task_struct *p, u64 delta)
242{
243 __schedstat_add(p->stats.core_forceidle_sum, delta);
244
245 task_group_account_field(p, index: CPUTIME_FORCEIDLE, tmp: delta);
246}
247#endif /* CONFIG_SCHED_CORE */
248
249/*
250 * When a guest is interrupted for a longer amount of time, missed clock
251 * ticks are not redelivered later. Due to that, this function may on
252 * occasion account more time than the calling functions think elapsed.
253 */
254static __always_inline u64 steal_account_process_time(u64 maxtime)
255{
256#ifdef CONFIG_PARAVIRT
257 if (static_key_false(key: &paravirt_steal_enabled)) {
258 u64 steal;
259
260 steal = paravirt_steal_clock(smp_processor_id());
261 steal -= this_rq()->prev_steal_time;
262 steal = min(steal, maxtime);
263 account_steal_time(cputime: steal);
264 this_rq()->prev_steal_time += steal;
265
266 return steal;
267 }
268#endif /* CONFIG_PARAVIRT */
269 return 0;
270}
271
272/*
273 * Account how much elapsed time was spent in steal, IRQ, or softirq time.
274 */
275static inline u64 account_other_time(u64 max)
276{
277 u64 accounted;
278
279 lockdep_assert_irqs_disabled();
280
281 accounted = steal_account_process_time(maxtime: max);
282
283 if (accounted < max)
284 accounted += irqtime_tick_accounted(maxtime: max - accounted);
285
286 return accounted;
287}
288
289#ifdef CONFIG_64BIT
290static inline u64 read_sum_exec_runtime(struct task_struct *t)
291{
292 return t->se.sum_exec_runtime;
293}
294#else /* !CONFIG_64BIT: */
295static u64 read_sum_exec_runtime(struct task_struct *t)
296{
297 u64 ns;
298 struct rq_flags rf;
299 struct rq *rq;
300
301 rq = task_rq_lock(t, &rf);
302 ns = t->se.sum_exec_runtime;
303 task_rq_unlock(rq, t, &rf);
304
305 return ns;
306}
307#endif /* !CONFIG_64BIT */
308
309/*
310 * Accumulate raw cputime values of dead tasks (sig->[us]time) and live
311 * tasks (sum on group iteration) belonging to @tsk's group.
312 */
313void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
314{
315 struct signal_struct *sig = tsk->signal;
316 struct task_struct *t;
317 u64 utime, stime;
318
319 /*
320 * Update current task runtime to account pending time since last
321 * scheduler action or thread_group_cputime() call. This thread group
322 * might have other running tasks on different CPUs, but updating
323 * their runtime can affect syscall performance, so we skip account
324 * those pending times and rely only on values updated on tick or
325 * other scheduler action.
326 */
327 if (same_thread_group(current, p2: tsk))
328 (void) task_sched_runtime(current);
329
330 guard(rcu)();
331 scoped_seqlock_read (&sig->stats_lock, ss_lock_irqsave) {
332 times->utime = sig->utime;
333 times->stime = sig->stime;
334 times->sum_exec_runtime = sig->sum_sched_runtime;
335
336 __for_each_thread(sig, t) {
337 task_cputime(t, utime: &utime, stime: &stime);
338 times->utime += utime;
339 times->stime += stime;
340 times->sum_exec_runtime += read_sum_exec_runtime(t);
341 }
342 }
343}
344
345#ifdef CONFIG_IRQ_TIME_ACCOUNTING
346/*
347 * Account a tick to a process and cpustat
348 * @p: the process that the CPU time gets accounted to
349 * @user_tick: is the tick from userspace
350 * @rq: the pointer to rq
351 *
352 * Tick demultiplexing follows the order
353 * - pending hardirq update
354 * - pending softirq update
355 * - user_time
356 * - idle_time
357 * - system time
358 * - check for guest_time
359 * - else account as system_time
360 *
361 * Check for hardirq is done both for system and user time as there is
362 * no timer going off while we are on hardirq and hence we may never get an
363 * opportunity to update it solely in system time.
364 * p->stime and friends are only updated on system time and not on IRQ
365 * softirq as those do not count in task exec_runtime any more.
366 */
367static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
368 int ticks)
369{
370 u64 other, cputime = TICK_NSEC * ticks;
371
372 /*
373 * When returning from idle, many ticks can get accounted at
374 * once, including some ticks of steal, IRQ, and softirq time.
375 * Subtract those ticks from the amount of time accounted to
376 * idle, or potentially user or system time. Due to rounding,
377 * other time can exceed ticks occasionally.
378 */
379 other = account_other_time(ULONG_MAX);
380 if (other >= cputime)
381 return;
382
383 cputime -= other;
384
385 if (this_cpu_ksoftirqd() == p) {
386 /*
387 * ksoftirqd time do not get accounted in cpu_softirq_time.
388 * So, we have to handle it separately here.
389 * Also, p->stime needs to be updated for ksoftirqd.
390 */
391 account_system_index_time(p, cputime, index: CPUTIME_SOFTIRQ);
392 } else if (user_tick) {
393 account_user_time(p, cputime);
394 } else if (p == this_rq()->idle) {
395 account_idle_time(cputime);
396 } else if (p->flags & PF_VCPU) { /* System time or guest time */
397 account_guest_time(p, cputime);
398 } else {
399 account_system_index_time(p, cputime, index: CPUTIME_SYSTEM);
400 }
401}
402
403static void irqtime_account_idle_ticks(int ticks)
404{
405 irqtime_account_process_tick(current, user_tick: 0, ticks);
406}
407#else /* !CONFIG_IRQ_TIME_ACCOUNTING: */
408static inline void irqtime_account_idle_ticks(int ticks) { }
409static inline void irqtime_account_process_tick(struct task_struct *p, int user_tick,
410 int nr_ticks) { }
411#endif /* !CONFIG_IRQ_TIME_ACCOUNTING */
412
413/*
414 * Use precise platform statistics if available:
415 */
416#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
417
418void vtime_account_irq(struct task_struct *tsk, unsigned int offset)
419{
420 unsigned int pc = irq_count() - offset;
421
422 if (pc & HARDIRQ_OFFSET) {
423 vtime_account_hardirq(tsk);
424 } else if (pc & SOFTIRQ_OFFSET) {
425 vtime_account_softirq(tsk);
426 } else if (!IS_ENABLED(CONFIG_HAVE_VIRT_CPU_ACCOUNTING_IDLE) &&
427 is_idle_task(tsk)) {
428 vtime_account_idle(tsk);
429 } else {
430 vtime_account_kernel(tsk);
431 }
432}
433
434void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev,
435 u64 *ut, u64 *st)
436{
437 *ut = curr->utime;
438 *st = curr->stime;
439}
440
441void task_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
442{
443 *ut = p->utime;
444 *st = p->stime;
445}
446EXPORT_SYMBOL_GPL(task_cputime_adjusted);
447
448void thread_group_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
449{
450 struct task_cputime cputime;
451
452 thread_group_cputime(p, &cputime);
453
454 *ut = cputime.utime;
455 *st = cputime.stime;
456}
457
458#else /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE: */
459
460/*
461 * Account a single tick of CPU time.
462 * @p: the process that the CPU time gets accounted to
463 * @user_tick: indicates if the tick is a user or a system tick
464 */
465void account_process_tick(struct task_struct *p, int user_tick)
466{
467 u64 cputime, steal;
468
469 if (vtime_accounting_enabled_this_cpu())
470 return;
471
472 if (irqtime_enabled()) {
473 irqtime_account_process_tick(p, user_tick, ticks: 1);
474 return;
475 }
476
477 cputime = TICK_NSEC;
478 steal = steal_account_process_time(ULONG_MAX);
479
480 if (steal >= cputime)
481 return;
482
483 cputime -= steal;
484
485 if (user_tick)
486 account_user_time(p, cputime);
487 else if ((p != this_rq()->idle) || (irq_count() != HARDIRQ_OFFSET))
488 account_system_time(p, HARDIRQ_OFFSET, cputime);
489 else
490 account_idle_time(cputime);
491}
492
493/*
494 * Account multiple ticks of idle time.
495 * @ticks: number of stolen ticks
496 */
497void account_idle_ticks(unsigned long ticks)
498{
499 u64 cputime, steal;
500
501 if (irqtime_enabled()) {
502 irqtime_account_idle_ticks(ticks);
503 return;
504 }
505
506 cputime = ticks * TICK_NSEC;
507 steal = steal_account_process_time(ULONG_MAX);
508
509 if (steal >= cputime)
510 return;
511
512 cputime -= steal;
513 account_idle_time(cputime);
514}
515
516/*
517 * Adjust tick based cputime random precision against scheduler runtime
518 * accounting.
519 *
520 * Tick based cputime accounting depend on random scheduling timeslices of a
521 * task to be interrupted or not by the timer. Depending on these
522 * circumstances, the number of these interrupts may be over or
523 * under-optimistic, matching the real user and system cputime with a variable
524 * precision.
525 *
526 * Fix this by scaling these tick based values against the total runtime
527 * accounted by the CFS scheduler.
528 *
529 * This code provides the following guarantees:
530 *
531 * stime + utime == rtime
532 * stime_i+1 >= stime_i, utime_i+1 >= utime_i
533 *
534 * Assuming that rtime_i+1 >= rtime_i.
535 */
536void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev,
537 u64 *ut, u64 *st)
538{
539 u64 rtime, stime, utime;
540 unsigned long flags;
541
542 /* Serialize concurrent callers such that we can honour our guarantees */
543 raw_spin_lock_irqsave(&prev->lock, flags);
544 rtime = curr->sum_exec_runtime;
545
546 /*
547 * This is possible under two circumstances:
548 * - rtime isn't monotonic after all (a bug);
549 * - we got reordered by the lock.
550 *
551 * In both cases this acts as a filter such that the rest of the code
552 * can assume it is monotonic regardless of anything else.
553 */
554 if (prev->stime + prev->utime >= rtime)
555 goto out;
556
557 stime = curr->stime;
558 utime = curr->utime;
559
560 /*
561 * If either stime or utime are 0, assume all runtime is userspace.
562 * Once a task gets some ticks, the monotonicity code at 'update:'
563 * will ensure things converge to the observed ratio.
564 */
565 if (stime == 0) {
566 utime = rtime;
567 goto update;
568 }
569
570 if (utime == 0) {
571 stime = rtime;
572 goto update;
573 }
574
575 stime = mul_u64_u64_div_u64(stime, rtime, stime + utime);
576 /*
577 * Because mul_u64_u64_div_u64() can approximate on some
578 * achitectures; enforce the constraint that: a*b/(b+c) <= a.
579 */
580 if (unlikely(stime > rtime))
581 stime = rtime;
582
583update:
584 /*
585 * Make sure stime doesn't go backwards; this preserves monotonicity
586 * for utime because rtime is monotonic.
587 *
588 * utime_i+1 = rtime_i+1 - stime_i
589 * = rtime_i+1 - (rtime_i - utime_i)
590 * = (rtime_i+1 - rtime_i) + utime_i
591 * >= utime_i
592 */
593 if (stime < prev->stime)
594 stime = prev->stime;
595 utime = rtime - stime;
596
597 /*
598 * Make sure utime doesn't go backwards; this still preserves
599 * monotonicity for stime, analogous argument to above.
600 */
601 if (utime < prev->utime) {
602 utime = prev->utime;
603 stime = rtime - utime;
604 }
605
606 prev->stime = stime;
607 prev->utime = utime;
608out:
609 *ut = prev->utime;
610 *st = prev->stime;
611 raw_spin_unlock_irqrestore(&prev->lock, flags);
612}
613
614void task_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
615{
616 struct task_cputime cputime = {
617 .sum_exec_runtime = p->se.sum_exec_runtime,
618 };
619
620 if (task_cputime(t: p, utime: &cputime.utime, stime: &cputime.stime))
621 cputime.sum_exec_runtime = task_sched_runtime(task: p);
622 cputime_adjust(curr: &cputime, prev: &p->prev_cputime, ut, st);
623}
624EXPORT_SYMBOL_GPL(task_cputime_adjusted);
625
626void thread_group_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
627{
628 struct task_cputime cputime;
629
630 thread_group_cputime(tsk: p, times: &cputime);
631 cputime_adjust(curr: &cputime, prev: &p->signal->prev_cputime, ut, st);
632}
633#endif /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
634
635#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
636static u64 vtime_delta(struct vtime *vtime)
637{
638 unsigned long long clock;
639
640 clock = sched_clock();
641 if (clock < vtime->starttime)
642 return 0;
643
644 return clock - vtime->starttime;
645}
646
647static u64 get_vtime_delta(struct vtime *vtime)
648{
649 u64 delta = vtime_delta(vtime);
650 u64 other;
651
652 /*
653 * Unlike tick based timing, vtime based timing never has lost
654 * ticks, and no need for steal time accounting to make up for
655 * lost ticks. Vtime accounts a rounded version of actual
656 * elapsed time. Limit account_other_time to prevent rounding
657 * errors from causing elapsed vtime to go negative.
658 */
659 other = account_other_time(delta);
660 WARN_ON_ONCE(vtime->state == VTIME_INACTIVE);
661 vtime->starttime += delta;
662
663 return delta - other;
664}
665
666static void vtime_account_system(struct task_struct *tsk,
667 struct vtime *vtime)
668{
669 vtime->stime += get_vtime_delta(vtime);
670 if (vtime->stime >= TICK_NSEC) {
671 account_system_time(tsk, irq_count(), vtime->stime);
672 vtime->stime = 0;
673 }
674}
675
676static void vtime_account_guest(struct task_struct *tsk,
677 struct vtime *vtime)
678{
679 vtime->gtime += get_vtime_delta(vtime);
680 if (vtime->gtime >= TICK_NSEC) {
681 account_guest_time(tsk, vtime->gtime);
682 vtime->gtime = 0;
683 }
684}
685
686static void __vtime_account_kernel(struct task_struct *tsk,
687 struct vtime *vtime)
688{
689 /* We might have scheduled out from guest path */
690 if (vtime->state == VTIME_GUEST)
691 vtime_account_guest(tsk, vtime);
692 else
693 vtime_account_system(tsk, vtime);
694}
695
696void vtime_account_kernel(struct task_struct *tsk)
697{
698 struct vtime *vtime = &tsk->vtime;
699
700 if (!vtime_delta(vtime))
701 return;
702
703 write_seqcount_begin(&vtime->seqcount);
704 __vtime_account_kernel(tsk, vtime);
705 write_seqcount_end(&vtime->seqcount);
706}
707
708void vtime_user_enter(struct task_struct *tsk)
709{
710 struct vtime *vtime = &tsk->vtime;
711
712 write_seqcount_begin(&vtime->seqcount);
713 vtime_account_system(tsk, vtime);
714 vtime->state = VTIME_USER;
715 write_seqcount_end(&vtime->seqcount);
716}
717
718void vtime_user_exit(struct task_struct *tsk)
719{
720 struct vtime *vtime = &tsk->vtime;
721
722 write_seqcount_begin(&vtime->seqcount);
723 vtime->utime += get_vtime_delta(vtime);
724 if (vtime->utime >= TICK_NSEC) {
725 account_user_time(tsk, vtime->utime);
726 vtime->utime = 0;
727 }
728 vtime->state = VTIME_SYS;
729 write_seqcount_end(&vtime->seqcount);
730}
731
732void vtime_guest_enter(struct task_struct *tsk)
733{
734 struct vtime *vtime = &tsk->vtime;
735 /*
736 * The flags must be updated under the lock with
737 * the vtime_starttime flush and update.
738 * That enforces a right ordering and update sequence
739 * synchronization against the reader (task_gtime())
740 * that can thus safely catch up with a tickless delta.
741 */
742 write_seqcount_begin(&vtime->seqcount);
743 vtime_account_system(tsk, vtime);
744 tsk->flags |= PF_VCPU;
745 vtime->state = VTIME_GUEST;
746 write_seqcount_end(&vtime->seqcount);
747}
748EXPORT_SYMBOL_GPL(vtime_guest_enter);
749
750void vtime_guest_exit(struct task_struct *tsk)
751{
752 struct vtime *vtime = &tsk->vtime;
753
754 write_seqcount_begin(&vtime->seqcount);
755 vtime_account_guest(tsk, vtime);
756 tsk->flags &= ~PF_VCPU;
757 vtime->state = VTIME_SYS;
758 write_seqcount_end(&vtime->seqcount);
759}
760EXPORT_SYMBOL_GPL(vtime_guest_exit);
761
762void vtime_account_idle(struct task_struct *tsk)
763{
764 account_idle_time(get_vtime_delta(&tsk->vtime));
765}
766
767void vtime_task_switch_generic(struct task_struct *prev)
768{
769 struct vtime *vtime = &prev->vtime;
770
771 write_seqcount_begin(&vtime->seqcount);
772 if (vtime->state == VTIME_IDLE)
773 vtime_account_idle(prev);
774 else
775 __vtime_account_kernel(prev, vtime);
776 vtime->state = VTIME_INACTIVE;
777 vtime->cpu = -1;
778 write_seqcount_end(&vtime->seqcount);
779
780 vtime = &current->vtime;
781
782 write_seqcount_begin(&vtime->seqcount);
783 if (is_idle_task(current))
784 vtime->state = VTIME_IDLE;
785 else if (current->flags & PF_VCPU)
786 vtime->state = VTIME_GUEST;
787 else
788 vtime->state = VTIME_SYS;
789 vtime->starttime = sched_clock();
790 vtime->cpu = smp_processor_id();
791 write_seqcount_end(&vtime->seqcount);
792}
793
794void vtime_init_idle(struct task_struct *t, int cpu)
795{
796 struct vtime *vtime = &t->vtime;
797 unsigned long flags;
798
799 local_irq_save(flags);
800 write_seqcount_begin(&vtime->seqcount);
801 vtime->state = VTIME_IDLE;
802 vtime->starttime = sched_clock();
803 vtime->cpu = cpu;
804 write_seqcount_end(&vtime->seqcount);
805 local_irq_restore(flags);
806}
807
808u64 task_gtime(struct task_struct *t)
809{
810 struct vtime *vtime = &t->vtime;
811 unsigned int seq;
812 u64 gtime;
813
814 if (!vtime_accounting_enabled())
815 return t->gtime;
816
817 do {
818 seq = read_seqcount_begin(&vtime->seqcount);
819
820 gtime = t->gtime;
821 if (vtime->state == VTIME_GUEST)
822 gtime += vtime->gtime + vtime_delta(vtime);
823
824 } while (read_seqcount_retry(&vtime->seqcount, seq));
825
826 return gtime;
827}
828
829/*
830 * Fetch cputime raw values from fields of task_struct and
831 * add up the pending nohz execution time since the last
832 * cputime snapshot.
833 */
834bool task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
835{
836 struct vtime *vtime = &t->vtime;
837 unsigned int seq;
838 u64 delta;
839 int ret;
840
841 if (!vtime_accounting_enabled()) {
842 *utime = t->utime;
843 *stime = t->stime;
844 return false;
845 }
846
847 do {
848 ret = false;
849 seq = read_seqcount_begin(&vtime->seqcount);
850
851 *utime = t->utime;
852 *stime = t->stime;
853
854 /* Task is sleeping or idle, nothing to add */
855 if (vtime->state < VTIME_SYS)
856 continue;
857
858 ret = true;
859 delta = vtime_delta(vtime);
860
861 /*
862 * Task runs either in user (including guest) or kernel space,
863 * add pending nohz time to the right place.
864 */
865 if (vtime->state == VTIME_SYS)
866 *stime += vtime->stime + delta;
867 else
868 *utime += vtime->utime + delta;
869 } while (read_seqcount_retry(&vtime->seqcount, seq));
870
871 return ret;
872}
873
874static int vtime_state_fetch(struct vtime *vtime, int cpu)
875{
876 int state = READ_ONCE(vtime->state);
877
878 /*
879 * We raced against a context switch, fetch the
880 * kcpustat task again.
881 */
882 if (vtime->cpu != cpu && vtime->cpu != -1)
883 return -EAGAIN;
884
885 /*
886 * Two possible things here:
887 * 1) We are seeing the scheduling out task (prev) or any past one.
888 * 2) We are seeing the scheduling in task (next) but it hasn't
889 * passed though vtime_task_switch() yet so the pending
890 * cputime of the prev task may not be flushed yet.
891 *
892 * Case 1) is ok but 2) is not. So wait for a safe VTIME state.
893 */
894 if (state == VTIME_INACTIVE)
895 return -EAGAIN;
896
897 return state;
898}
899
900static u64 kcpustat_user_vtime(struct vtime *vtime)
901{
902 if (vtime->state == VTIME_USER)
903 return vtime->utime + vtime_delta(vtime);
904 else if (vtime->state == VTIME_GUEST)
905 return vtime->gtime + vtime_delta(vtime);
906 return 0;
907}
908
909static int kcpustat_field_vtime(u64 *cpustat,
910 struct task_struct *tsk,
911 enum cpu_usage_stat usage,
912 int cpu, u64 *val)
913{
914 struct vtime *vtime = &tsk->vtime;
915 unsigned int seq;
916
917 do {
918 int state;
919
920 seq = read_seqcount_begin(&vtime->seqcount);
921
922 state = vtime_state_fetch(vtime, cpu);
923 if (state < 0)
924 return state;
925
926 *val = cpustat[usage];
927
928 /*
929 * Nice VS unnice cputime accounting may be inaccurate if
930 * the nice value has changed since the last vtime update.
931 * But proper fix would involve interrupting target on nice
932 * updates which is a no go on nohz_full (although the scheduler
933 * may still interrupt the target if rescheduling is needed...)
934 */
935 switch (usage) {
936 case CPUTIME_SYSTEM:
937 if (state == VTIME_SYS)
938 *val += vtime->stime + vtime_delta(vtime);
939 break;
940 case CPUTIME_USER:
941 if (task_nice(tsk) <= 0)
942 *val += kcpustat_user_vtime(vtime);
943 break;
944 case CPUTIME_NICE:
945 if (task_nice(tsk) > 0)
946 *val += kcpustat_user_vtime(vtime);
947 break;
948 case CPUTIME_GUEST:
949 if (state == VTIME_GUEST && task_nice(tsk) <= 0)
950 *val += vtime->gtime + vtime_delta(vtime);
951 break;
952 case CPUTIME_GUEST_NICE:
953 if (state == VTIME_GUEST && task_nice(tsk) > 0)
954 *val += vtime->gtime + vtime_delta(vtime);
955 break;
956 default:
957 break;
958 }
959 } while (read_seqcount_retry(&vtime->seqcount, seq));
960
961 return 0;
962}
963
964u64 kcpustat_field(struct kernel_cpustat *kcpustat,
965 enum cpu_usage_stat usage, int cpu)
966{
967 u64 *cpustat = kcpustat->cpustat;
968 u64 val = cpustat[usage];
969 struct rq *rq;
970 int err;
971
972 if (!vtime_accounting_enabled_cpu(cpu))
973 return val;
974
975 rq = cpu_rq(cpu);
976
977 for (;;) {
978 struct task_struct *curr;
979
980 rcu_read_lock();
981 curr = rcu_dereference(rq->curr);
982 if (WARN_ON_ONCE(!curr)) {
983 rcu_read_unlock();
984 return cpustat[usage];
985 }
986
987 err = kcpustat_field_vtime(cpustat, curr, usage, cpu, &val);
988 rcu_read_unlock();
989
990 if (!err)
991 return val;
992
993 cpu_relax();
994 }
995}
996EXPORT_SYMBOL_GPL(kcpustat_field);
997
998static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
999 const struct kernel_cpustat *src,
1000 struct task_struct *tsk, int cpu)
1001{
1002 struct vtime *vtime = &tsk->vtime;
1003 unsigned int seq;
1004
1005 do {
1006 u64 *cpustat;
1007 u64 delta;
1008 int state;
1009
1010 seq = read_seqcount_begin(&vtime->seqcount);
1011
1012 state = vtime_state_fetch(vtime, cpu);
1013 if (state < 0)
1014 return state;
1015
1016 *dst = *src;
1017 cpustat = dst->cpustat;
1018
1019 /* Task is sleeping, dead or idle, nothing to add */
1020 if (state < VTIME_SYS)
1021 continue;
1022
1023 delta = vtime_delta(vtime);
1024
1025 /*
1026 * Task runs either in user (including guest) or kernel space,
1027 * add pending nohz time to the right place.
1028 */
1029 if (state == VTIME_SYS) {
1030 cpustat[CPUTIME_SYSTEM] += vtime->stime + delta;
1031 } else if (state == VTIME_USER) {
1032 if (task_nice(tsk) > 0)
1033 cpustat[CPUTIME_NICE] += vtime->utime + delta;
1034 else
1035 cpustat[CPUTIME_USER] += vtime->utime + delta;
1036 } else {
1037 WARN_ON_ONCE(state != VTIME_GUEST);
1038 if (task_nice(tsk) > 0) {
1039 cpustat[CPUTIME_GUEST_NICE] += vtime->gtime + delta;
1040 cpustat[CPUTIME_NICE] += vtime->gtime + delta;
1041 } else {
1042 cpustat[CPUTIME_GUEST] += vtime->gtime + delta;
1043 cpustat[CPUTIME_USER] += vtime->gtime + delta;
1044 }
1045 }
1046 } while (read_seqcount_retry(&vtime->seqcount, seq));
1047
1048 return 0;
1049}
1050
1051void kcpustat_cpu_fetch(struct kernel_cpustat *dst, int cpu)
1052{
1053 const struct kernel_cpustat *src = &kcpustat_cpu(cpu);
1054 struct rq *rq;
1055 int err;
1056
1057 if (!vtime_accounting_enabled_cpu(cpu)) {
1058 *dst = *src;
1059 return;
1060 }
1061
1062 rq = cpu_rq(cpu);
1063
1064 for (;;) {
1065 struct task_struct *curr;
1066
1067 rcu_read_lock();
1068 curr = rcu_dereference(rq->curr);
1069 if (WARN_ON_ONCE(!curr)) {
1070 rcu_read_unlock();
1071 *dst = *src;
1072 return;
1073 }
1074
1075 err = kcpustat_cpu_fetch_vtime(dst, src, curr, cpu);
1076 rcu_read_unlock();
1077
1078 if (!err)
1079 return;
1080
1081 cpu_relax();
1082 }
1083}
1084EXPORT_SYMBOL_GPL(kcpustat_cpu_fetch);
1085
1086#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */
1087

source code of linux/kernel/sched/cputime.c