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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Debug controller
4 *
5 * WARNING: This controller is for cgroup core debugging only.
6 * Its interfaces are unstable and subject to changes at any time.
7 */
8#include <linux/ctype.h>
9#include <linux/mm.h>
10#include <linux/slab.h>
11
12#include "cgroup-internal.h"
13
14static struct cgroup_subsys_state *
15debug_css_alloc(struct cgroup_subsys_state *parent_css)
16{
17 struct cgroup_subsys_state *css = kzalloc_obj(*css);
18
19 if (!css)
20 return ERR_PTR(-ENOMEM);
21
22 return css;
23}
24
25static void debug_css_free(struct cgroup_subsys_state *css)
26{
27 kfree(css);
28}
29
30/*
31 * debug_taskcount_read - return the number of tasks in a cgroup.
32 * @cgrp: the cgroup in question
33 */
34static u64 debug_taskcount_read(struct cgroup_subsys_state *css,
35 struct cftype *cft)
36{
37 return cgroup_task_count(css->cgroup);
38}
39
40static int current_css_set_read(struct seq_file *seq, void *v)
41{
42 struct kernfs_open_file *of = seq->private;
43 struct css_set *cset;
44 struct cgroup_subsys *ss;
45 struct cgroup_subsys_state *css;
46 int i, refcnt;
47
48 if (!cgroup_kn_lock_live(of->kn, false))
49 return -ENODEV;
50
51 spin_lock_irq(&css_set_lock);
52 cset = task_css_set(current);
53 refcnt = refcount_read(&cset->refcount);
54 seq_printf(seq, "css_set %pK %d", cset, refcnt);
55 if (refcnt > cset->nr_tasks)
56 seq_printf(seq, " +%d", refcnt - cset->nr_tasks);
57 seq_puts(seq, "\n");
58
59 /*
60 * Print the css'es stored in the current css_set.
61 */
62 for_each_subsys(ss, i) {
63 css = cset->subsys[ss->id];
64 if (!css)
65 continue;
66 seq_printf(seq, "%2d: %-4s\t- %p[%d]\n", ss->id, ss->name,
67 css, css->id);
68 }
69 spin_unlock_irq(&css_set_lock);
70 cgroup_kn_unlock(of->kn);
71 return 0;
72}
73
74static u64 current_css_set_refcount_read(struct cgroup_subsys_state *css,
75 struct cftype *cft)
76{
77 u64 count;
78
79 rcu_read_lock();
80 count = refcount_read(&task_css_set(current)->refcount);
81 rcu_read_unlock();
82 return count;
83}
84
85static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
86{
87 struct cgrp_cset_link *link;
88 struct css_set *cset;
89 char *name_buf;
90
91 name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
92 if (!name_buf)
93 return -ENOMEM;
94
95 spin_lock_irq(&css_set_lock);
96 cset = task_css_set(current);
97 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
98 struct cgroup *c = link->cgrp;
99
100 cgroup_name(c, name_buf, NAME_MAX + 1);
101 seq_printf(seq, "Root %d group %s\n",
102 c->root->hierarchy_id, name_buf);
103 }
104 spin_unlock_irq(&css_set_lock);
105 kfree(name_buf);
106 return 0;
107}
108
109#define MAX_TASKS_SHOWN_PER_CSS 25
110static int cgroup_css_links_read(struct seq_file *seq, void *v)
111{
112 struct cgroup_subsys_state *css = seq_css(seq);
113 struct cgrp_cset_link *link;
114 int dead_cnt = 0, extra_refs = 0, threaded_csets = 0;
115
116 spin_lock_irq(&css_set_lock);
117
118 list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
119 struct css_set *cset = link->cset;
120 struct task_struct *task;
121 int count = 0;
122 int refcnt = refcount_read(&cset->refcount);
123
124 /*
125 * Print out the proc_cset and threaded_cset relationship
126 * and highlight difference between refcount and task_count.
127 */
128 seq_printf(seq, "css_set %pK", cset);
129 if (rcu_dereference_protected(cset->dom_cset, 1) != cset) {
130 threaded_csets++;
131 seq_printf(seq, "=>%pK", cset->dom_cset);
132 }
133 if (!list_empty(&cset->threaded_csets)) {
134 struct css_set *tcset;
135 int idx = 0;
136
137 list_for_each_entry(tcset, &cset->threaded_csets,
138 threaded_csets_node) {
139 seq_puts(seq, idx ? "," : "<=");
140 seq_printf(seq, "%pK", tcset);
141 idx++;
142 }
143 } else {
144 seq_printf(seq, " %d", refcnt);
145 if (refcnt - cset->nr_tasks > 0) {
146 int extra = refcnt - cset->nr_tasks;
147
148 seq_printf(seq, " +%d", extra);
149 /*
150 * Take out the one additional reference in
151 * init_css_set.
152 */
153 if (cset == &init_css_set)
154 extra--;
155 extra_refs += extra;
156 }
157 }
158 seq_puts(seq, "\n");
159
160 list_for_each_entry(task, &cset->tasks, cg_list) {
161 if (count++ <= MAX_TASKS_SHOWN_PER_CSS)
162 seq_printf(seq, " task %d\n",
163 task_pid_vnr(task));
164 }
165
166 list_for_each_entry(task, &cset->mg_tasks, cg_list) {
167 if (count++ <= MAX_TASKS_SHOWN_PER_CSS)
168 seq_printf(seq, " task %d\n",
169 task_pid_vnr(task));
170 }
171 /* show # of overflowed tasks */
172 if (count > MAX_TASKS_SHOWN_PER_CSS)
173 seq_printf(seq, " ... (%d)\n",
174 count - MAX_TASKS_SHOWN_PER_CSS);
175
176 if (cset->dead) {
177 seq_puts(seq, " [dead]\n");
178 dead_cnt++;
179 }
180
181 WARN_ON(count != cset->nr_tasks);
182 }
183 spin_unlock_irq(&css_set_lock);
184
185 if (!dead_cnt && !extra_refs && !threaded_csets)
186 return 0;
187
188 seq_puts(seq, "\n");
189 if (threaded_csets)
190 seq_printf(seq, "threaded css_sets = %d\n", threaded_csets);
191 if (extra_refs)
192 seq_printf(seq, "extra references = %d\n", extra_refs);
193 if (dead_cnt)
194 seq_printf(seq, "dead css_sets = %d\n", dead_cnt);
195
196 return 0;
197}
198
199static int cgroup_subsys_states_read(struct seq_file *seq, void *v)
200{
201 struct kernfs_open_file *of = seq->private;
202 struct cgroup *cgrp;
203 struct cgroup_subsys *ss;
204 struct cgroup_subsys_state *css;
205 char pbuf[16];
206 int i;
207
208 cgrp = cgroup_kn_lock_live(of->kn, false);
209 if (!cgrp)
210 return -ENODEV;
211
212 for_each_subsys(ss, i) {
213 css = rcu_dereference_check(cgrp->subsys[ss->id], true);
214 if (!css)
215 continue;
216
217 pbuf[0] = '\0';
218
219 /* Show the parent CSS if applicable*/
220 if (css->parent)
221 snprintf(pbuf, sizeof(pbuf) - 1, " P=%d",
222 css->parent->id);
223 seq_printf(seq, "%2d: %-4s\t- %p[%d] %d%s\n", ss->id, ss->name,
224 css, css->id,
225 atomic_read(&css->online_cnt), pbuf);
226 }
227
228 cgroup_kn_unlock(of->kn);
229 return 0;
230}
231
232static void cgroup_masks_read_one(struct seq_file *seq, const char *name,
233 u32 mask)
234{
235 struct cgroup_subsys *ss;
236 int ssid;
237 bool first = true;
238
239 seq_printf(seq, "%-17s: ", name);
240 for_each_subsys(ss, ssid) {
241 if (!(mask & (1 << ssid)))
242 continue;
243 if (!first)
244 seq_puts(seq, ", ");
245 seq_puts(seq, ss->name);
246 first = false;
247 }
248 seq_putc(seq, '\n');
249}
250
251static int cgroup_masks_read(struct seq_file *seq, void *v)
252{
253 struct kernfs_open_file *of = seq->private;
254 struct cgroup *cgrp;
255
256 cgrp = cgroup_kn_lock_live(of->kn, false);
257 if (!cgrp)
258 return -ENODEV;
259
260 cgroup_masks_read_one(seq, "subtree_control", cgrp->subtree_control);
261 cgroup_masks_read_one(seq, "subtree_ss_mask", cgrp->subtree_ss_mask);
262
263 cgroup_kn_unlock(of->kn);
264 return 0;
265}
266
267static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
268{
269 return (!cgroup_is_populated(css->cgroup) &&
270 !css_has_online_children(&css->cgroup->self));
271}
272
273static struct cftype debug_legacy_files[] = {
274 {
275 .name = "taskcount",
276 .read_u64 = debug_taskcount_read,
277 },
278
279 {
280 .name = "current_css_set",
281 .seq_show = current_css_set_read,
282 .flags = CFTYPE_ONLY_ON_ROOT,
283 },
284
285 {
286 .name = "current_css_set_refcount",
287 .read_u64 = current_css_set_refcount_read,
288 .flags = CFTYPE_ONLY_ON_ROOT,
289 },
290
291 {
292 .name = "current_css_set_cg_links",
293 .seq_show = current_css_set_cg_links_read,
294 .flags = CFTYPE_ONLY_ON_ROOT,
295 },
296
297 {
298 .name = "cgroup_css_links",
299 .seq_show = cgroup_css_links_read,
300 },
301
302 {
303 .name = "cgroup_subsys_states",
304 .seq_show = cgroup_subsys_states_read,
305 },
306
307 {
308 .name = "cgroup_masks",
309 .seq_show = cgroup_masks_read,
310 },
311
312 {
313 .name = "releasable",
314 .read_u64 = releasable_read,
315 },
316
317 { } /* terminate */
318};
319
320static struct cftype debug_files[] = {
321 {
322 .name = "taskcount",
323 .read_u64 = debug_taskcount_read,
324 },
325
326 {
327 .name = "current_css_set",
328 .seq_show = current_css_set_read,
329 .flags = CFTYPE_ONLY_ON_ROOT,
330 },
331
332 {
333 .name = "current_css_set_refcount",
334 .read_u64 = current_css_set_refcount_read,
335 .flags = CFTYPE_ONLY_ON_ROOT,
336 },
337
338 {
339 .name = "current_css_set_cg_links",
340 .seq_show = current_css_set_cg_links_read,
341 .flags = CFTYPE_ONLY_ON_ROOT,
342 },
343
344 {
345 .name = "css_links",
346 .seq_show = cgroup_css_links_read,
347 },
348
349 {
350 .name = "csses",
351 .seq_show = cgroup_subsys_states_read,
352 },
353
354 {
355 .name = "masks",
356 .seq_show = cgroup_masks_read,
357 },
358
359 { } /* terminate */
360};
361
362struct cgroup_subsys debug_cgrp_subsys = {
363 .css_alloc = debug_css_alloc,
364 .css_free = debug_css_free,
365 .legacy_cftypes = debug_legacy_files,
366};
367
368/*
369 * On v2, debug is an implicit controller enabled by "cgroup_debug" boot
370 * parameter.
371 */
372void __init enable_debug_cgroup(void)
373{
374 debug_cgrp_subsys.dfl_cftypes = debug_files;
375 debug_cgrp_subsys.implicit_on_dfl = true;
376 debug_cgrp_subsys.threaded = true;
377}