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