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(sizeof(*css), GFP_KERNEL);
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	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
76static 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
87static 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
114static 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
203static 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
236static 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
255static 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
271static 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
277static 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
324static 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
366struct 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 */
376void __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