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1// SPDX-License-Identifier: GPL-2.0-only
2#include "cgroup-internal.h"
3
4#include <linux/sched/cputime.h>
5
6#include <linux/bpf.h>
7#include <linux/btf.h>
8#include <linux/btf_ids.h>
9
10static DEFINE_SPINLOCK(cgroup_rstat_lock);
11static DEFINE_PER_CPU(raw_spinlock_t, cgroup_rstat_cpu_lock);
12
13static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu);
14
15static struct cgroup_rstat_cpu *cgroup_rstat_cpu(struct cgroup *cgrp, int cpu)
16{
17 return per_cpu_ptr(cgrp->rstat_cpu, cpu);
18}
19
20/**
21 * cgroup_rstat_updated - keep track of updated rstat_cpu
22 * @cgrp: target cgroup
23 * @cpu: cpu on which rstat_cpu was updated
24 *
25 * @cgrp's rstat_cpu on @cpu was updated. Put it on the parent's matching
26 * rstat_cpu->updated_children list. See the comment on top of
27 * cgroup_rstat_cpu definition for details.
28 */
29void cgroup_rstat_updated(struct cgroup *cgrp, int cpu)
30{
31 raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu);
32 unsigned long flags;
33
34 /*
35 * Speculative already-on-list test. This may race leading to
36 * temporary inaccuracies, which is fine.
37 *
38 * Because @parent's updated_children is terminated with @parent
39 * instead of NULL, we can tell whether @cgrp is on the list by
40 * testing the next pointer for NULL.
41 */
42 if (data_race(cgroup_rstat_cpu(cgrp, cpu)->updated_next))
43 return;
44
45 raw_spin_lock_irqsave(cpu_lock, flags);
46
47 /* put @cgrp and all ancestors on the corresponding updated lists */
48 while (true) {
49 struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
50 struct cgroup *parent = cgroup_parent(cgrp);
51 struct cgroup_rstat_cpu *prstatc;
52
53 /*
54 * Both additions and removals are bottom-up. If a cgroup
55 * is already in the tree, all ancestors are.
56 */
57 if (rstatc->updated_next)
58 break;
59
60 /* Root has no parent to link it to, but mark it busy */
61 if (!parent) {
62 rstatc->updated_next = cgrp;
63 break;
64 }
65
66 prstatc = cgroup_rstat_cpu(parent, cpu);
67 rstatc->updated_next = prstatc->updated_children;
68 prstatc->updated_children = cgrp;
69
70 cgrp = parent;
71 }
72
73 raw_spin_unlock_irqrestore(cpu_lock, flags);
74}
75
76/**
77 * cgroup_rstat_cpu_pop_updated - iterate and dismantle rstat_cpu updated tree
78 * @pos: current position
79 * @root: root of the tree to traversal
80 * @cpu: target cpu
81 *
82 * Walks the updated rstat_cpu tree on @cpu from @root. %NULL @pos starts
83 * the traversal and %NULL return indicates the end. During traversal,
84 * each returned cgroup is unlinked from the tree. Must be called with the
85 * matching cgroup_rstat_cpu_lock held.
86 *
87 * The only ordering guarantee is that, for a parent and a child pair
88 * covered by a given traversal, if a child is visited, its parent is
89 * guaranteed to be visited afterwards.
90 */
91static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos,
92 struct cgroup *root, int cpu)
93{
94 struct cgroup_rstat_cpu *rstatc;
95 struct cgroup *parent;
96
97 if (pos == root)
98 return NULL;
99
100 /*
101 * We're gonna walk down to the first leaf and visit/remove it. We
102 * can pick whatever unvisited node as the starting point.
103 */
104 if (!pos) {
105 pos = root;
106 /* return NULL if this subtree is not on-list */
107 if (!cgroup_rstat_cpu(pos, cpu)->updated_next)
108 return NULL;
109 } else {
110 pos = cgroup_parent(pos);
111 }
112
113 /* walk down to the first leaf */
114 while (true) {
115 rstatc = cgroup_rstat_cpu(pos, cpu);
116 if (rstatc->updated_children == pos)
117 break;
118 pos = rstatc->updated_children;
119 }
120
121 /*
122 * Unlink @pos from the tree. As the updated_children list is
123 * singly linked, we have to walk it to find the removal point.
124 * However, due to the way we traverse, @pos will be the first
125 * child in most cases. The only exception is @root.
126 */
127 parent = cgroup_parent(pos);
128 if (parent) {
129 struct cgroup_rstat_cpu *prstatc;
130 struct cgroup **nextp;
131
132 prstatc = cgroup_rstat_cpu(parent, cpu);
133 nextp = &prstatc->updated_children;
134 while (*nextp != pos) {
135 struct cgroup_rstat_cpu *nrstatc;
136
137 nrstatc = cgroup_rstat_cpu(*nextp, cpu);
138 WARN_ON_ONCE(*nextp == parent);
139 nextp = &nrstatc->updated_next;
140 }
141 *nextp = rstatc->updated_next;
142 }
143
144 rstatc->updated_next = NULL;
145 return pos;
146}
147
148/*
149 * A hook for bpf stat collectors to attach to and flush their stats.
150 * Together with providing bpf kfuncs for cgroup_rstat_updated() and
151 * cgroup_rstat_flush(), this enables a complete workflow where bpf progs that
152 * collect cgroup stats can integrate with rstat for efficient flushing.
153 *
154 * A static noinline declaration here could cause the compiler to optimize away
155 * the function. A global noinline declaration will keep the definition, but may
156 * optimize away the callsite. Therefore, __weak is needed to ensure that the
157 * call is still emitted, by telling the compiler that we don't know what the
158 * function might eventually be.
159 *
160 * __diag_* below are needed to dismiss the missing prototype warning.
161 */
162__diag_push();
163__diag_ignore_all("-Wmissing-prototypes",
164 "kfuncs which will be used in BPF programs");
165
166__weak noinline void bpf_rstat_flush(struct cgroup *cgrp,
167 struct cgroup *parent, int cpu)
168{
169}
170
171__diag_pop();
172
173/* see cgroup_rstat_flush() */
174static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep)
175 __releases(&cgroup_rstat_lock) __acquires(&cgroup_rstat_lock)
176{
177 int cpu;
178
179 lockdep_assert_held(&cgroup_rstat_lock);
180
181 for_each_possible_cpu(cpu) {
182 raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock,
183 cpu);
184 struct cgroup *pos = NULL;
185 unsigned long flags;
186
187 /*
188 * The _irqsave() is needed because cgroup_rstat_lock is
189 * spinlock_t which is a sleeping lock on PREEMPT_RT. Acquiring
190 * this lock with the _irq() suffix only disables interrupts on
191 * a non-PREEMPT_RT kernel. The raw_spinlock_t below disables
192 * interrupts on both configurations. The _irqsave() ensures
193 * that interrupts are always disabled and later restored.
194 */
195 raw_spin_lock_irqsave(cpu_lock, flags);
196 while ((pos = cgroup_rstat_cpu_pop_updated(pos, cgrp, cpu))) {
197 struct cgroup_subsys_state *css;
198
199 cgroup_base_stat_flush(pos, cpu);
200 bpf_rstat_flush(pos, cgroup_parent(pos), cpu);
201
202 rcu_read_lock();
203 list_for_each_entry_rcu(css, &pos->rstat_css_list,
204 rstat_css_node)
205 css->ss->css_rstat_flush(css, cpu);
206 rcu_read_unlock();
207 }
208 raw_spin_unlock_irqrestore(cpu_lock, flags);
209
210 /* if @may_sleep, play nice and yield if necessary */
211 if (may_sleep && (need_resched() ||
212 spin_needbreak(&cgroup_rstat_lock))) {
213 spin_unlock_irq(&cgroup_rstat_lock);
214 if (!cond_resched())
215 cpu_relax();
216 spin_lock_irq(&cgroup_rstat_lock);
217 }
218 }
219}
220
221/**
222 * cgroup_rstat_flush - flush stats in @cgrp's subtree
223 * @cgrp: target cgroup
224 *
225 * Collect all per-cpu stats in @cgrp's subtree into the global counters
226 * and propagate them upwards. After this function returns, all cgroups in
227 * the subtree have up-to-date ->stat.
228 *
229 * This also gets all cgroups in the subtree including @cgrp off the
230 * ->updated_children lists.
231 *
232 * This function may block.
233 */
234void cgroup_rstat_flush(struct cgroup *cgrp)
235{
236 might_sleep();
237
238 spin_lock_irq(&cgroup_rstat_lock);
239 cgroup_rstat_flush_locked(cgrp, true);
240 spin_unlock_irq(&cgroup_rstat_lock);
241}
242
243/**
244 * cgroup_rstat_flush_irqsafe - irqsafe version of cgroup_rstat_flush()
245 * @cgrp: target cgroup
246 *
247 * This function can be called from any context.
248 */
249void cgroup_rstat_flush_irqsafe(struct cgroup *cgrp)
250{
251 unsigned long flags;
252
253 spin_lock_irqsave(&cgroup_rstat_lock, flags);
254 cgroup_rstat_flush_locked(cgrp, false);
255 spin_unlock_irqrestore(&cgroup_rstat_lock, flags);
256}
257
258/**
259 * cgroup_rstat_flush_hold - flush stats in @cgrp's subtree and hold
260 * @cgrp: target cgroup
261 *
262 * Flush stats in @cgrp's subtree and prevent further flushes. Must be
263 * paired with cgroup_rstat_flush_release().
264 *
265 * This function may block.
266 */
267void cgroup_rstat_flush_hold(struct cgroup *cgrp)
268 __acquires(&cgroup_rstat_lock)
269{
270 might_sleep();
271 spin_lock_irq(&cgroup_rstat_lock);
272 cgroup_rstat_flush_locked(cgrp, true);
273}
274
275/**
276 * cgroup_rstat_flush_release - release cgroup_rstat_flush_hold()
277 */
278void cgroup_rstat_flush_release(void)
279 __releases(&cgroup_rstat_lock)
280{
281 spin_unlock_irq(&cgroup_rstat_lock);
282}
283
284int cgroup_rstat_init(struct cgroup *cgrp)
285{
286 int cpu;
287
288 /* the root cgrp has rstat_cpu preallocated */
289 if (!cgrp->rstat_cpu) {
290 cgrp->rstat_cpu = alloc_percpu(struct cgroup_rstat_cpu);
291 if (!cgrp->rstat_cpu)
292 return -ENOMEM;
293 }
294
295 /* ->updated_children list is self terminated */
296 for_each_possible_cpu(cpu) {
297 struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
298
299 rstatc->updated_children = cgrp;
300 u64_stats_init(&rstatc->bsync);
301 }
302
303 return 0;
304}
305
306void cgroup_rstat_exit(struct cgroup *cgrp)
307{
308 int cpu;
309
310 cgroup_rstat_flush(cgrp);
311
312 /* sanity check */
313 for_each_possible_cpu(cpu) {
314 struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
315
316 if (WARN_ON_ONCE(rstatc->updated_children != cgrp) ||
317 WARN_ON_ONCE(rstatc->updated_next))
318 return;
319 }
320
321 free_percpu(cgrp->rstat_cpu);
322 cgrp->rstat_cpu = NULL;
323}
324
325void __init cgroup_rstat_boot(void)
326{
327 int cpu;
328
329 for_each_possible_cpu(cpu)
330 raw_spin_lock_init(per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu));
331}
332
333/*
334 * Functions for cgroup basic resource statistics implemented on top of
335 * rstat.
336 */
337static void cgroup_base_stat_add(struct cgroup_base_stat *dst_bstat,
338 struct cgroup_base_stat *src_bstat)
339{
340 dst_bstat->cputime.utime += src_bstat->cputime.utime;
341 dst_bstat->cputime.stime += src_bstat->cputime.stime;
342 dst_bstat->cputime.sum_exec_runtime += src_bstat->cputime.sum_exec_runtime;
343#ifdef CONFIG_SCHED_CORE
344 dst_bstat->forceidle_sum += src_bstat->forceidle_sum;
345#endif
346}
347
348static void cgroup_base_stat_sub(struct cgroup_base_stat *dst_bstat,
349 struct cgroup_base_stat *src_bstat)
350{
351 dst_bstat->cputime.utime -= src_bstat->cputime.utime;
352 dst_bstat->cputime.stime -= src_bstat->cputime.stime;
353 dst_bstat->cputime.sum_exec_runtime -= src_bstat->cputime.sum_exec_runtime;
354#ifdef CONFIG_SCHED_CORE
355 dst_bstat->forceidle_sum -= src_bstat->forceidle_sum;
356#endif
357}
358
359static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)
360{
361 struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
362 struct cgroup *parent = cgroup_parent(cgrp);
363 struct cgroup_base_stat delta;
364 unsigned seq;
365
366 /* Root-level stats are sourced from system-wide CPU stats */
367 if (!parent)
368 return;
369
370 /* fetch the current per-cpu values */
371 do {
372 seq = __u64_stats_fetch_begin(&rstatc->bsync);
373 delta = rstatc->bstat;
374 } while (__u64_stats_fetch_retry(&rstatc->bsync, seq));
375
376 /* propagate percpu delta to global */
377 cgroup_base_stat_sub(&delta, &rstatc->last_bstat);
378 cgroup_base_stat_add(&cgrp->bstat, &delta);
379 cgroup_base_stat_add(&rstatc->last_bstat, &delta);
380
381 /* propagate global delta to parent (unless that's root) */
382 if (cgroup_parent(parent)) {
383 delta = cgrp->bstat;
384 cgroup_base_stat_sub(&delta, &cgrp->last_bstat);
385 cgroup_base_stat_add(&parent->bstat, &delta);
386 cgroup_base_stat_add(&cgrp->last_bstat, &delta);
387 }
388}
389
390static struct cgroup_rstat_cpu *
391cgroup_base_stat_cputime_account_begin(struct cgroup *cgrp, unsigned long *flags)
392{
393 struct cgroup_rstat_cpu *rstatc;
394
395 rstatc = get_cpu_ptr(cgrp->rstat_cpu);
396 *flags = u64_stats_update_begin_irqsave(&rstatc->bsync);
397 return rstatc;
398}
399
400static void cgroup_base_stat_cputime_account_end(struct cgroup *cgrp,
401 struct cgroup_rstat_cpu *rstatc,
402 unsigned long flags)
403{
404 u64_stats_update_end_irqrestore(&rstatc->bsync, flags);
405 cgroup_rstat_updated(cgrp, smp_processor_id());
406 put_cpu_ptr(rstatc);
407}
408
409void __cgroup_account_cputime(struct cgroup *cgrp, u64 delta_exec)
410{
411 struct cgroup_rstat_cpu *rstatc;
412 unsigned long flags;
413
414 rstatc = cgroup_base_stat_cputime_account_begin(cgrp, &flags);
415 rstatc->bstat.cputime.sum_exec_runtime += delta_exec;
416 cgroup_base_stat_cputime_account_end(cgrp, rstatc, flags);
417}
418
419void __cgroup_account_cputime_field(struct cgroup *cgrp,
420 enum cpu_usage_stat index, u64 delta_exec)
421{
422 struct cgroup_rstat_cpu *rstatc;
423 unsigned long flags;
424
425 rstatc = cgroup_base_stat_cputime_account_begin(cgrp, &flags);
426
427 switch (index) {
428 case CPUTIME_USER:
429 case CPUTIME_NICE:
430 rstatc->bstat.cputime.utime += delta_exec;
431 break;
432 case CPUTIME_SYSTEM:
433 case CPUTIME_IRQ:
434 case CPUTIME_SOFTIRQ:
435 rstatc->bstat.cputime.stime += delta_exec;
436 break;
437#ifdef CONFIG_SCHED_CORE
438 case CPUTIME_FORCEIDLE:
439 rstatc->bstat.forceidle_sum += delta_exec;
440 break;
441#endif
442 default:
443 break;
444 }
445
446 cgroup_base_stat_cputime_account_end(cgrp, rstatc, flags);
447}
448
449/*
450 * compute the cputime for the root cgroup by getting the per cpu data
451 * at a global level, then categorizing the fields in a manner consistent
452 * with how it is done by __cgroup_account_cputime_field for each bit of
453 * cpu time attributed to a cgroup.
454 */
455static void root_cgroup_cputime(struct cgroup_base_stat *bstat)
456{
457 struct task_cputime *cputime = &bstat->cputime;
458 int i;
459
460 cputime->stime = 0;
461 cputime->utime = 0;
462 cputime->sum_exec_runtime = 0;
463 for_each_possible_cpu(i) {
464 struct kernel_cpustat kcpustat;
465 u64 *cpustat = kcpustat.cpustat;
466 u64 user = 0;
467 u64 sys = 0;
468
469 kcpustat_cpu_fetch(&kcpustat, i);
470
471 user += cpustat[CPUTIME_USER];
472 user += cpustat[CPUTIME_NICE];
473 cputime->utime += user;
474
475 sys += cpustat[CPUTIME_SYSTEM];
476 sys += cpustat[CPUTIME_IRQ];
477 sys += cpustat[CPUTIME_SOFTIRQ];
478 cputime->stime += sys;
479
480 cputime->sum_exec_runtime += user;
481 cputime->sum_exec_runtime += sys;
482 cputime->sum_exec_runtime += cpustat[CPUTIME_STEAL];
483
484#ifdef CONFIG_SCHED_CORE
485 bstat->forceidle_sum += cpustat[CPUTIME_FORCEIDLE];
486#endif
487 }
488}
489
490void cgroup_base_stat_cputime_show(struct seq_file *seq)
491{
492 struct cgroup *cgrp = seq_css(seq)->cgroup;
493 u64 usage, utime, stime;
494 struct cgroup_base_stat bstat;
495#ifdef CONFIG_SCHED_CORE
496 u64 forceidle_time;
497#endif
498
499 if (cgroup_parent(cgrp)) {
500 cgroup_rstat_flush_hold(cgrp);
501 usage = cgrp->bstat.cputime.sum_exec_runtime;
502 cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime,
503 &utime, &stime);
504#ifdef CONFIG_SCHED_CORE
505 forceidle_time = cgrp->bstat.forceidle_sum;
506#endif
507 cgroup_rstat_flush_release();
508 } else {
509 root_cgroup_cputime(&bstat);
510 usage = bstat.cputime.sum_exec_runtime;
511 utime = bstat.cputime.utime;
512 stime = bstat.cputime.stime;
513#ifdef CONFIG_SCHED_CORE
514 forceidle_time = bstat.forceidle_sum;
515#endif
516 }
517
518 do_div(usage, NSEC_PER_USEC);
519 do_div(utime, NSEC_PER_USEC);
520 do_div(stime, NSEC_PER_USEC);
521#ifdef CONFIG_SCHED_CORE
522 do_div(forceidle_time, NSEC_PER_USEC);
523#endif
524
525 seq_printf(seq, "usage_usec %llu\n"
526 "user_usec %llu\n"
527 "system_usec %llu\n",
528 usage, utime, stime);
529
530#ifdef CONFIG_SCHED_CORE
531 seq_printf(seq, "core_sched.force_idle_usec %llu\n", forceidle_time);
532#endif
533}
534
535/* Add bpf kfuncs for cgroup_rstat_updated() and cgroup_rstat_flush() */
536BTF_SET8_START(bpf_rstat_kfunc_ids)
537BTF_ID_FLAGS(func, cgroup_rstat_updated)
538BTF_ID_FLAGS(func, cgroup_rstat_flush, KF_SLEEPABLE)
539BTF_SET8_END(bpf_rstat_kfunc_ids)
540
541static const struct btf_kfunc_id_set bpf_rstat_kfunc_set = {
542 .owner = THIS_MODULE,
543 .set = &bpf_rstat_kfunc_ids,
544};
545
546static int __init bpf_rstat_kfunc_init(void)
547{
548 return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING,
549 &bpf_rstat_kfunc_set);
550}
551late_initcall(bpf_rstat_kfunc_init);