debug.c

  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	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				  u16 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}