xref: /openbmc/linux/kernel/cgroup/debug.c (revision 1900da52)
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 *
debug_css_alloc(struct cgroup_subsys_state * parent_css)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 
debug_css_free(struct cgroup_subsys_state * css)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  */
debug_taskcount_read(struct cgroup_subsys_state * css,struct cftype * cft)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 
current_css_set_read(struct seq_file * seq,void * v)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 
current_css_set_refcount_read(struct cgroup_subsys_state * css,struct cftype * cft)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 
current_css_set_cg_links_read(struct seq_file * seq,void * v)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
cgroup_css_links_read(struct seq_file * seq,void * v)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 
cgroup_subsys_states_read(struct seq_file * seq,void * v)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 
cgroup_masks_read_one(struct seq_file * seq,const char * name,u16 mask)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 
cgroup_masks_read(struct seq_file * seq,void * v)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 
releasable_read(struct cgroup_subsys_state * css,struct cftype * cft)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  */
enable_debug_cgroup(void)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