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 */
29__bpf_kfunc void 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(cgrp: 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(cgrp: pos, cpu)->updated_next)
108 return NULL;
109 } else {
110 pos = cgroup_parent(cgrp: pos);
111 }
112
113 /* walk down to the first leaf */
114 while (true) {
115 rstatc = cgroup_rstat_cpu(cgrp: 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(cgrp: pos);
128 if (parent) {
129 struct cgroup_rstat_cpu *prstatc;
130 struct cgroup **nextp;
131
132 prstatc = cgroup_rstat_cpu(cgrp: parent, cpu);
133 nextp = &prstatc->updated_children;
134 while (*nextp != pos) {
135 struct cgroup_rstat_cpu *nrstatc;
136
137 nrstatc = cgroup_rstat_cpu(cgrp: *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)
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, root: cgrp, cpu))) {
197 struct cgroup_subsys_state *css;
198
199 cgroup_base_stat_flush(cgrp: pos, cpu);
200 bpf_rstat_flush(cgrp: pos, parent: cgroup_parent(cgrp: 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 /* play nice and yield if necessary */
211 if (need_resched() || spin_needbreak(lock: &cgroup_rstat_lock)) {
212 spin_unlock_irq(lock: &cgroup_rstat_lock);
213 if (!cond_resched())
214 cpu_relax();
215 spin_lock_irq(lock: &cgroup_rstat_lock);
216 }
217 }
218}
219
220/**
221 * cgroup_rstat_flush - flush stats in @cgrp's subtree
222 * @cgrp: target cgroup
223 *
224 * Collect all per-cpu stats in @cgrp's subtree into the global counters
225 * and propagate them upwards. After this function returns, all cgroups in
226 * the subtree have up-to-date ->stat.
227 *
228 * This also gets all cgroups in the subtree including @cgrp off the
229 * ->updated_children lists.
230 *
231 * This function may block.
232 */
233__bpf_kfunc void cgroup_rstat_flush(struct cgroup *cgrp)
234{
235 might_sleep();
236
237 spin_lock_irq(lock: &cgroup_rstat_lock);
238 cgroup_rstat_flush_locked(cgrp);
239 spin_unlock_irq(lock: &cgroup_rstat_lock);
240}
241
242/**
243 * cgroup_rstat_flush_hold - flush stats in @cgrp's subtree and hold
244 * @cgrp: target cgroup
245 *
246 * Flush stats in @cgrp's subtree and prevent further flushes. Must be
247 * paired with cgroup_rstat_flush_release().
248 *
249 * This function may block.
250 */
251void cgroup_rstat_flush_hold(struct cgroup *cgrp)
252 __acquires(&cgroup_rstat_lock)
253{
254 might_sleep();
255 spin_lock_irq(lock: &cgroup_rstat_lock);
256 cgroup_rstat_flush_locked(cgrp);
257}
258
259/**
260 * cgroup_rstat_flush_release - release cgroup_rstat_flush_hold()
261 */
262void cgroup_rstat_flush_release(void)
263 __releases(&cgroup_rstat_lock)
264{
265 spin_unlock_irq(lock: &cgroup_rstat_lock);
266}
267
268int cgroup_rstat_init(struct cgroup *cgrp)
269{
270 int cpu;
271
272 /* the root cgrp has rstat_cpu preallocated */
273 if (!cgrp->rstat_cpu) {
274 cgrp->rstat_cpu = alloc_percpu(struct cgroup_rstat_cpu);
275 if (!cgrp->rstat_cpu)
276 return -ENOMEM;
277 }
278
279 /* ->updated_children list is self terminated */
280 for_each_possible_cpu(cpu) {
281 struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
282
283 rstatc->updated_children = cgrp;
284 u64_stats_init(syncp: &rstatc->bsync);
285 }
286
287 return 0;
288}
289
290void cgroup_rstat_exit(struct cgroup *cgrp)
291{
292 int cpu;
293
294 cgroup_rstat_flush(cgrp);
295
296 /* sanity check */
297 for_each_possible_cpu(cpu) {
298 struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
299
300 if (WARN_ON_ONCE(rstatc->updated_children != cgrp) ||
301 WARN_ON_ONCE(rstatc->updated_next))
302 return;
303 }
304
305 free_percpu(pdata: cgrp->rstat_cpu);
306 cgrp->rstat_cpu = NULL;
307}
308
309void __init cgroup_rstat_boot(void)
310{
311 int cpu;
312
313 for_each_possible_cpu(cpu)
314 raw_spin_lock_init(per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu));
315}
316
317/*
318 * Functions for cgroup basic resource statistics implemented on top of
319 * rstat.
320 */
321static void cgroup_base_stat_add(struct cgroup_base_stat *dst_bstat,
322 struct cgroup_base_stat *src_bstat)
323{
324 dst_bstat->cputime.utime += src_bstat->cputime.utime;
325 dst_bstat->cputime.stime += src_bstat->cputime.stime;
326 dst_bstat->cputime.sum_exec_runtime += src_bstat->cputime.sum_exec_runtime;
327#ifdef CONFIG_SCHED_CORE
328 dst_bstat->forceidle_sum += src_bstat->forceidle_sum;
329#endif
330}
331
332static void cgroup_base_stat_sub(struct cgroup_base_stat *dst_bstat,
333 struct cgroup_base_stat *src_bstat)
334{
335 dst_bstat->cputime.utime -= src_bstat->cputime.utime;
336 dst_bstat->cputime.stime -= src_bstat->cputime.stime;
337 dst_bstat->cputime.sum_exec_runtime -= src_bstat->cputime.sum_exec_runtime;
338#ifdef CONFIG_SCHED_CORE
339 dst_bstat->forceidle_sum -= src_bstat->forceidle_sum;
340#endif
341}
342
343static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)
344{
345 struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
346 struct cgroup *parent = cgroup_parent(cgrp);
347 struct cgroup_rstat_cpu *prstatc;
348 struct cgroup_base_stat delta;
349 unsigned seq;
350
351 /* Root-level stats are sourced from system-wide CPU stats */
352 if (!parent)
353 return;
354
355 /* fetch the current per-cpu values */
356 do {
357 seq = __u64_stats_fetch_begin(syncp: &rstatc->bsync);
358 delta = rstatc->bstat;
359 } while (__u64_stats_fetch_retry(syncp: &rstatc->bsync, start: seq));
360
361 /* propagate per-cpu delta to cgroup and per-cpu global statistics */
362 cgroup_base_stat_sub(dst_bstat: &delta, src_bstat: &rstatc->last_bstat);
363 cgroup_base_stat_add(dst_bstat: &cgrp->bstat, src_bstat: &delta);
364 cgroup_base_stat_add(dst_bstat: &rstatc->last_bstat, src_bstat: &delta);
365 cgroup_base_stat_add(dst_bstat: &rstatc->subtree_bstat, src_bstat: &delta);
366
367 /* propagate cgroup and per-cpu global delta to parent (unless that's root) */
368 if (cgroup_parent(cgrp: parent)) {
369 delta = cgrp->bstat;
370 cgroup_base_stat_sub(dst_bstat: &delta, src_bstat: &cgrp->last_bstat);
371 cgroup_base_stat_add(dst_bstat: &parent->bstat, src_bstat: &delta);
372 cgroup_base_stat_add(dst_bstat: &cgrp->last_bstat, src_bstat: &delta);
373
374 delta = rstatc->subtree_bstat;
375 prstatc = cgroup_rstat_cpu(cgrp: parent, cpu);
376 cgroup_base_stat_sub(dst_bstat: &delta, src_bstat: &rstatc->last_subtree_bstat);
377 cgroup_base_stat_add(dst_bstat: &prstatc->subtree_bstat, src_bstat: &delta);
378 cgroup_base_stat_add(dst_bstat: &rstatc->last_subtree_bstat, src_bstat: &delta);
379 }
380}
381
382static struct cgroup_rstat_cpu *
383cgroup_base_stat_cputime_account_begin(struct cgroup *cgrp, unsigned long *flags)
384{
385 struct cgroup_rstat_cpu *rstatc;
386
387 rstatc = get_cpu_ptr(cgrp->rstat_cpu);
388 *flags = u64_stats_update_begin_irqsave(syncp: &rstatc->bsync);
389 return rstatc;
390}
391
392static void cgroup_base_stat_cputime_account_end(struct cgroup *cgrp,
393 struct cgroup_rstat_cpu *rstatc,
394 unsigned long flags)
395{
396 u64_stats_update_end_irqrestore(syncp: &rstatc->bsync, flags);
397 cgroup_rstat_updated(cgrp, smp_processor_id());
398 put_cpu_ptr(rstatc);
399}
400
401void __cgroup_account_cputime(struct cgroup *cgrp, u64 delta_exec)
402{
403 struct cgroup_rstat_cpu *rstatc;
404 unsigned long flags;
405
406 rstatc = cgroup_base_stat_cputime_account_begin(cgrp, flags: &flags);
407 rstatc->bstat.cputime.sum_exec_runtime += delta_exec;
408 cgroup_base_stat_cputime_account_end(cgrp, rstatc, flags);
409}
410
411void __cgroup_account_cputime_field(struct cgroup *cgrp,
412 enum cpu_usage_stat index, u64 delta_exec)
413{
414 struct cgroup_rstat_cpu *rstatc;
415 unsigned long flags;
416
417 rstatc = cgroup_base_stat_cputime_account_begin(cgrp, flags: &flags);
418
419 switch (index) {
420 case CPUTIME_USER:
421 case CPUTIME_NICE:
422 rstatc->bstat.cputime.utime += delta_exec;
423 break;
424 case CPUTIME_SYSTEM:
425 case CPUTIME_IRQ:
426 case CPUTIME_SOFTIRQ:
427 rstatc->bstat.cputime.stime += delta_exec;
428 break;
429#ifdef CONFIG_SCHED_CORE
430 case CPUTIME_FORCEIDLE:
431 rstatc->bstat.forceidle_sum += delta_exec;
432 break;
433#endif
434 default:
435 break;
436 }
437
438 cgroup_base_stat_cputime_account_end(cgrp, rstatc, flags);
439}
440
441/*
442 * compute the cputime for the root cgroup by getting the per cpu data
443 * at a global level, then categorizing the fields in a manner consistent
444 * with how it is done by __cgroup_account_cputime_field for each bit of
445 * cpu time attributed to a cgroup.
446 */
447static void root_cgroup_cputime(struct cgroup_base_stat *bstat)
448{
449 struct task_cputime *cputime = &bstat->cputime;
450 int i;
451
452 memset(bstat, 0, sizeof(*bstat));
453 for_each_possible_cpu(i) {
454 struct kernel_cpustat kcpustat;
455 u64 *cpustat = kcpustat.cpustat;
456 u64 user = 0;
457 u64 sys = 0;
458
459 kcpustat_cpu_fetch(dst: &kcpustat, cpu: i);
460
461 user += cpustat[CPUTIME_USER];
462 user += cpustat[CPUTIME_NICE];
463 cputime->utime += user;
464
465 sys += cpustat[CPUTIME_SYSTEM];
466 sys += cpustat[CPUTIME_IRQ];
467 sys += cpustat[CPUTIME_SOFTIRQ];
468 cputime->stime += sys;
469
470 cputime->sum_exec_runtime += user;
471 cputime->sum_exec_runtime += sys;
472 cputime->sum_exec_runtime += cpustat[CPUTIME_STEAL];
473
474#ifdef CONFIG_SCHED_CORE
475 bstat->forceidle_sum += cpustat[CPUTIME_FORCEIDLE];
476#endif
477 }
478}
479
480void cgroup_base_stat_cputime_show(struct seq_file *seq)
481{
482 struct cgroup *cgrp = seq_css(seq)->cgroup;
483 u64 usage, utime, stime;
484 struct cgroup_base_stat bstat;
485#ifdef CONFIG_SCHED_CORE
486 u64 forceidle_time;
487#endif
488
489 if (cgroup_parent(cgrp)) {
490 cgroup_rstat_flush_hold(cgrp);
491 usage = cgrp->bstat.cputime.sum_exec_runtime;
492 cputime_adjust(curr: &cgrp->bstat.cputime, prev: &cgrp->prev_cputime,
493 ut: &utime, st: &stime);
494#ifdef CONFIG_SCHED_CORE
495 forceidle_time = cgrp->bstat.forceidle_sum;
496#endif
497 cgroup_rstat_flush_release();
498 } else {
499 root_cgroup_cputime(bstat: &bstat);
500 usage = bstat.cputime.sum_exec_runtime;
501 utime = bstat.cputime.utime;
502 stime = bstat.cputime.stime;
503#ifdef CONFIG_SCHED_CORE
504 forceidle_time = bstat.forceidle_sum;
505#endif
506 }
507
508 do_div(usage, NSEC_PER_USEC);
509 do_div(utime, NSEC_PER_USEC);
510 do_div(stime, NSEC_PER_USEC);
511#ifdef CONFIG_SCHED_CORE
512 do_div(forceidle_time, NSEC_PER_USEC);
513#endif
514
515 seq_printf(m: seq, fmt: "usage_usec %llu\n"
516 "user_usec %llu\n"
517 "system_usec %llu\n",
518 usage, utime, stime);
519
520#ifdef CONFIG_SCHED_CORE
521 seq_printf(m: seq, fmt: "core_sched.force_idle_usec %llu\n", forceidle_time);
522#endif
523}
524
525/* Add bpf kfuncs for cgroup_rstat_updated() and cgroup_rstat_flush() */
526BTF_SET8_START(bpf_rstat_kfunc_ids)
527BTF_ID_FLAGS(func, cgroup_rstat_updated)
528BTF_ID_FLAGS(func, cgroup_rstat_flush, KF_SLEEPABLE)
529BTF_SET8_END(bpf_rstat_kfunc_ids)
530
531static const struct btf_kfunc_id_set bpf_rstat_kfunc_set = {
532 .owner = THIS_MODULE,
533 .set = &bpf_rstat_kfunc_ids,
534};
535
536static int __init bpf_rstat_kfunc_init(void)
537{
538 return register_btf_kfunc_id_set(prog_type: BPF_PROG_TYPE_TRACING,
539 s: &bpf_rstat_kfunc_set);
540}
541late_initcall(bpf_rstat_kfunc_init);
542

source code of linux/kernel/cgroup/rstat.c