kernel/cgroup/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
  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 }