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
14 static struct cgroup_subsys_state *
15 debug_css_alloc(struct cgroup_subsys_state *parent_css)
16 {
17 struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
18
19 if (!css)
20 return ERR_PTR(-ENOMEM);
21
22 return css;
23 }
24
25 static 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 */
34 static u64 debug_taskcount_read(struct cgroup_subsys_state *css,
35 struct cftype *cft)
36 {
37 return cgroup_task_count(css->cgroup);
38 }
39
40 static 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 rcu_read_lock();
53 cset = task_css_set(current);
54 refcnt = refcount_read(&cset->refcount);
55 seq_printf(seq, "css_set %pK %d", cset, refcnt);
56 if (refcnt > cset->nr_tasks)
57 seq_printf(seq, " +%d", refcnt - cset->nr_tasks);
58 seq_puts(seq, "\n");
59
60 /*
61 * Print the css'es stored in the current css_set.
62 */
63 for_each_subsys(ss, i) {
64 css = cset->subsys[ss->id];
65 if (!css)
66 continue;
67 seq_printf(seq, "%2d: %-4s\t- %p[%d]\n", ss->id, ss->name,
68 css, css->id);
69 }
70 rcu_read_unlock();
71 spin_unlock_irq(&css_set_lock);
72 cgroup_kn_unlock(of->kn);
73 return 0;
74 }
75
76 static u64 current_css_set_refcount_read(struct cgroup_subsys_state *css,
77 struct cftype *cft)
78 {
79 u64 count;
80
81 rcu_read_lock();
82 count = refcount_read(&task_css_set(current)->refcount);
83 rcu_read_unlock();
84 return count;
85 }
86
87 static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
88 {
89 struct cgrp_cset_link *link;
90 struct css_set *cset;
91 char *name_buf;
92
93 name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
94 if (!name_buf)
95 return -ENOMEM;
96
97 spin_lock_irq(&css_set_lock);
98 rcu_read_lock();
99 cset = task_css_set(current);
100 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
101 struct cgroup *c = link->cgrp;
102
103 cgroup_name(c, name_buf, NAME_MAX + 1);
104 seq_printf(seq, "Root %d group %s\n",
105 c->root->hierarchy_id, name_buf);
106 }
107 rcu_read_unlock();
108 spin_unlock_irq(&css_set_lock);
109 kfree(name_buf);
110 return 0;
111 }
112
113 #define MAX_TASKS_SHOWN_PER_CSS 25
114 static int cgroup_css_links_read(struct seq_file *seq, void *v)
115 {
116 struct cgroup_subsys_state *css = seq_css(seq);
117 struct cgrp_cset_link *link;
118 int dead_cnt = 0, extra_refs = 0, threaded_csets = 0;
119
120 spin_lock_irq(&css_set_lock);
121
122 list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
123 struct css_set *cset = link->cset;
124 struct task_struct *task;
125 int count = 0;
126 int refcnt = refcount_read(&cset->refcount);
127
128 /*
129 * Print out the proc_cset and threaded_cset relationship
130 * and highlight difference between refcount and task_count.
131 */
132 seq_printf(seq, "css_set %pK", cset);
133 if (rcu_dereference_protected(cset->dom_cset, 1) != cset) {
134 threaded_csets++;
135 seq_printf(seq, "=>%pK", cset->dom_cset);
136 }
137 if (!list_empty(&cset->threaded_csets)) {
138 struct css_set *tcset;
139 int idx = 0;
140
141 list_for_each_entry(tcset, &cset->threaded_csets,
142 threaded_csets_node) {
143 seq_puts(seq, idx ? "," : "<=");
144 seq_printf(seq, "%pK", tcset);
145 idx++;
146 }
147 } else {
148 seq_printf(seq, " %d", refcnt);
149 if (refcnt - cset->nr_tasks > 0) {
150 int extra = refcnt - cset->nr_tasks;
151
152 seq_printf(seq, " +%d", extra);
153 /*
154 * Take out the one additional reference in
155 * init_css_set.
156 */
157 if (cset == &init_css_set)
158 extra--;
159 extra_refs += extra;
160 }
161 }
162 seq_puts(seq, "\n");
163
164 list_for_each_entry(task, &cset->tasks, cg_list) {
165 if (count++ <= MAX_TASKS_SHOWN_PER_CSS)
166 seq_printf(seq, " task %d\n",
167 task_pid_vnr(task));
168 }
169
170 list_for_each_entry(task, &cset->mg_tasks, cg_list) {
171 if (count++ <= MAX_TASKS_SHOWN_PER_CSS)
172 seq_printf(seq, " task %d\n",
173 task_pid_vnr(task));
174 }
175 /* show # of overflowed tasks */
176 if (count > MAX_TASKS_SHOWN_PER_CSS)
177 seq_printf(seq, " ... (%d)\n",
178 count - MAX_TASKS_SHOWN_PER_CSS);
179
180 if (cset->dead) {
181 seq_puts(seq, " [dead]\n");
182 dead_cnt++;
183 }
184
185 WARN_ON(count != cset->nr_tasks);
186 }
187 spin_unlock_irq(&css_set_lock);
188
189 if (!dead_cnt && !extra_refs && !threaded_csets)
190 return 0;
191
192 seq_puts(seq, "\n");
193 if (threaded_csets)
194 seq_printf(seq, "threaded css_sets = %d\n", threaded_csets);
195 if (extra_refs)
196 seq_printf(seq, "extra references = %d\n", extra_refs);
197 if (dead_cnt)
198 seq_printf(seq, "dead css_sets = %d\n", dead_cnt);
199
200 return 0;
201 }
202
203 static int cgroup_subsys_states_read(struct seq_file *seq, void *v)
204 {
205 struct kernfs_open_file *of = seq->private;
206 struct cgroup *cgrp;
207 struct cgroup_subsys *ss;
208 struct cgroup_subsys_state *css;
209 char pbuf[16];
210 int i;
211
212 cgrp = cgroup_kn_lock_live(of->kn, false);
213 if (!cgrp)
214 return -ENODEV;
215
216 for_each_subsys(ss, i) {
217 css = rcu_dereference_check(cgrp->subsys[ss->id], true);
218 if (!css)
219 continue;
220
221 pbuf[0] = '\0';
222
223 /* Show the parent CSS if applicable*/
224 if (css->parent)
225 snprintf(pbuf, sizeof(pbuf) - 1, " P=%d",
226 css->parent->id);
227 seq_printf(seq, "%2d: %-4s\t- %p[%d] %d%s\n", ss->id, ss->name,
228 css, css->id,
229 atomic_read(&css->online_cnt), pbuf);
230 }
231
232 cgroup_kn_unlock(of->kn);
233 return 0;
234 }
235
236 static void cgroup_masks_read_one(struct seq_file *seq, const char *name,
237 u16 mask)
238 {
239 struct cgroup_subsys *ss;
240 int ssid;
241 bool first = true;
242
243 seq_printf(seq, "%-17s: ", name);
244 for_each_subsys(ss, ssid) {
245 if (!(mask & (1 << ssid)))
246 continue;
247 if (!first)
248 seq_puts(seq, ", ");
249 seq_puts(seq, ss->name);
250 first = false;
251 }
252 seq_putc(seq, '\n');
253 }
254
255 static int cgroup_masks_read(struct seq_file *seq, void *v)
256 {
257 struct kernfs_open_file *of = seq->private;
258 struct cgroup *cgrp;
259
260 cgrp = cgroup_kn_lock_live(of->kn, false);
261 if (!cgrp)
262 return -ENODEV;
263
264 cgroup_masks_read_one(seq, "subtree_control", cgrp->subtree_control);
265 cgroup_masks_read_one(seq, "subtree_ss_mask", cgrp->subtree_ss_mask);
266
267 cgroup_kn_unlock(of->kn);
268 return 0;
269 }
270
271 static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
272 {
273 return (!cgroup_is_populated(css->cgroup) &&
274 !css_has_online_children(&css->cgroup->self));
275 }
276
277 static struct cftype debug_legacy_files[] = {
278 {
279 .name = "taskcount",
280 .read_u64 = debug_taskcount_read,
281 },
282
283 {
284 .name = "current_css_set",
285 .seq_show = current_css_set_read,
286 .flags = CFTYPE_ONLY_ON_ROOT,
287 },
288
289 {
290 .name = "current_css_set_refcount",
291 .read_u64 = current_css_set_refcount_read,
292 .flags = CFTYPE_ONLY_ON_ROOT,
293 },
294
295 {
296 .name = "current_css_set_cg_links",
297 .seq_show = current_css_set_cg_links_read,
298 .flags = CFTYPE_ONLY_ON_ROOT,
299 },
300
301 {
302 .name = "cgroup_css_links",
303 .seq_show = cgroup_css_links_read,
304 },
305
306 {
307 .name = "cgroup_subsys_states",
308 .seq_show = cgroup_subsys_states_read,
309 },
310
311 {
312 .name = "cgroup_masks",
313 .seq_show = cgroup_masks_read,
314 },
315
316 {
317 .name = "releasable",
318 .read_u64 = releasable_read,
319 },
320
321 { } /* terminate */
322 };
323
324 static struct cftype debug_files[] = {
325 {
326 .name = "taskcount",
327 .read_u64 = debug_taskcount_read,
328 },
329
330 {
331 .name = "current_css_set",
332 .seq_show = current_css_set_read,
333 .flags = CFTYPE_ONLY_ON_ROOT,
334 },
335
336 {
337 .name = "current_css_set_refcount",
338 .read_u64 = current_css_set_refcount_read,
339 .flags = CFTYPE_ONLY_ON_ROOT,
340 },
341
342 {
343 .name = "current_css_set_cg_links",
344 .seq_show = current_css_set_cg_links_read,
345 .flags = CFTYPE_ONLY_ON_ROOT,
346 },
347
348 {
349 .name = "css_links",
350 .seq_show = cgroup_css_links_read,
351 },
352
353 {
354 .name = "csses",
355 .seq_show = cgroup_subsys_states_read,
356 },
357
358 {
359 .name = "masks",
360 .seq_show = cgroup_masks_read,
361 },
362
363 { } /* terminate */
364 };
365
366 struct cgroup_subsys debug_cgrp_subsys = {
367 .css_alloc = debug_css_alloc,
368 .css_free = debug_css_free,
369 .legacy_cftypes = debug_legacy_files,
370 };
371
372 /*
373 * On v2, debug is an implicit controller enabled by "cgroup_debug" boot
374 * parameter.
375 */
376 void __init enable_debug_cgroup(void)
377 {
378 debug_cgrp_subsys.dfl_cftypes = debug_files;
379 debug_cgrp_subsys.implicit_on_dfl = true;
380 debug_cgrp_subsys.threaded = true;
381 }
382
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