kernel/cgroup/debug.c

   1 /*
   2  * Debug controller
   3  *
   4  * WARNING: This controller is for cgroup core debugging only.
   5  * Its interfaces are unstable and subject to changes at any time.
   6  */
   7 #include <linux/ctype.h>
   8 #include <linux/mm.h>
   9 #include <linux/slab.h>
  10
  11 #include "cgroup-internal.h"
  12
  13 static struct cgroup_subsys_state *
  14 debug_css_alloc(struct cgroup_subsys_state *parent_css)
  15 {
  16         struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
  17
  18         if (!css)
  19                 return ERR_PTR(-ENOMEM);
  20
  21         return css;
  22 }
  23
  24 static void debug_css_free(struct cgroup_subsys_state *css)
  25 {
  26         kfree(css);
  27 }
  28
  29 /*
  30  * debug_taskcount_read - return the number of tasks in a cgroup.
  31  * @cgrp: the cgroup in question
  32  */
  33 static u64 debug_taskcount_read(struct cgroup_subsys_state *css,
  34                                 struct cftype *cft)
  35 {
  36         return cgroup_task_count(css->cgroup);
  37 }
  38
  39 static int current_css_set_read(struct seq_file *seq, void *v)
  40 {
  41         struct kernfs_open_file *of = seq->private;
  42         struct css_set *cset;
  43         struct cgroup_subsys *ss;
  44         struct cgroup_subsys_state *css;
  45         int i, refcnt;
  46
  47         if (!cgroup_kn_lock_live(of->kn, false))
  48                 return -ENODEV;
  49
  50         spin_lock_irq(&css_set_lock);
  51         rcu_read_lock();
  52         cset = rcu_dereference(current->cgroups);
  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- %lx[%d]\n", ss->id, ss->name,
  67                           (unsigned long)css, css->id);
  68         }
  69         rcu_read_unlock();
  70         spin_unlock_irq(&css_set_lock);
  71         cgroup_kn_unlock(of->kn);
  72         return 0;
  73 }
  74
  75 static u64 current_css_set_refcount_read(struct cgroup_subsys_state *css,
  76                                          struct cftype *cft)
  77 {
  78         u64 count;
  79
  80         rcu_read_lock();
  81         count = refcount_read(&task_css_set(current)->refcount);
  82         rcu_read_unlock();
  83         return count;
  84 }
  85
  86 static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
  87 {
  88         struct cgrp_cset_link *link;
  89         struct css_set *cset;
  90         char *name_buf;
  91
  92         name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
  93         if (!name_buf)
  94                 return -ENOMEM;
  95
  96         spin_lock_irq(&css_set_lock);
  97         rcu_read_lock();
  98         cset = rcu_dereference(current->cgroups);
  99         list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
 100                 struct cgroup *c = link->cgrp;
 101
 102                 cgroup_name(c, name_buf, NAME_MAX + 1);
 103                 seq_printf(seq, "Root %d group %s\n",
 104                            c->root->hierarchy_id, name_buf);
 105         }
 106         rcu_read_unlock();
 107         spin_unlock_irq(&css_set_lock);
 108         kfree(name_buf);
 109         return 0;
 110 }
 111
 112 #define MAX_TASKS_SHOWN_PER_CSS 25
 113 static int cgroup_css_links_read(struct seq_file *seq, void *v)
 114 {
 115         struct cgroup_subsys_state *css = seq_css(seq);
 116         struct cgrp_cset_link *link;
 117         int dead_cnt = 0, extra_refs = 0;
 118
 119         spin_lock_irq(&css_set_lock);
 120         list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
 121                 struct css_set *cset = link->cset;
 122                 struct task_struct *task;
 123                 int count = 0;
 124                 int refcnt = refcount_read(&cset->refcount);
 125
 126                 seq_printf(seq, " %d", refcnt);
 127                 if (refcnt - cset->nr_tasks > 0) {
 128                         int extra = refcnt - cset->nr_tasks;
 129
 130                         seq_printf(seq, " +%d", extra);
 131                         /*
 132                          * Take out the one additional reference in
 133                          * init_css_set.
 134                          */
 135                         if (cset == &init_css_set)
 136                                 extra--;
 137                         extra_refs += extra;
 138                 }
 139                 seq_puts(seq, "\n");
 140
 141                 list_for_each_entry(task, &cset->tasks, cg_list) {
 142                         if (count++ <= MAX_TASKS_SHOWN_PER_CSS)
 143                                 seq_printf(seq, "  task %d\n",
 144                                            task_pid_vnr(task));
 145                 }
 146
 147                 list_for_each_entry(task, &cset->mg_tasks, cg_list) {
 148                         if (count++ <= MAX_TASKS_SHOWN_PER_CSS)
 149                                 seq_printf(seq, "  task %d\n",
 150                                            task_pid_vnr(task));
 151                 }
 152                 /* show # of overflowed tasks */
 153                 if (count > MAX_TASKS_SHOWN_PER_CSS)
 154                         seq_printf(seq, "  ... (%d)\n",
 155                                    count - MAX_TASKS_SHOWN_PER_CSS);
 156
 157                 if (cset->dead) {
 158                         seq_puts(seq, "    [dead]\n");
 159                         dead_cnt++;
 160                 }
 161
 162                 WARN_ON(count != cset->nr_tasks);
 163         }
 164         spin_unlock_irq(&css_set_lock);
 165
 166         if (!dead_cnt && !extra_refs)
 167                 return 0;
 168
 169         seq_puts(seq, "\n");
 170         if (extra_refs)
 171                 seq_printf(seq, "extra references = %d\n", extra_refs);
 172         if (dead_cnt)
 173                 seq_printf(seq, "dead css_sets = %d\n", dead_cnt);
 174
 175         return 0;
 176 }
 177
 178 static int cgroup_subsys_states_read(struct seq_file *seq, void *v)
 179 {
 180         struct kernfs_open_file *of = seq->private;
 181         struct cgroup *cgrp;
 182         struct cgroup_subsys *ss;
 183         struct cgroup_subsys_state *css;
 184         char pbuf[16];
 185         int i;
 186
 187         cgrp = cgroup_kn_lock_live(of->kn, false);
 188         if (!cgrp)
 189                 return -ENODEV;
 190
 191         for_each_subsys(ss, i) {
 192                 css = rcu_dereference_check(cgrp->subsys[ss->id], true);
 193                 if (!css)
 194                         continue;
 195
 196                 pbuf[0] = '\0';
 197
 198                 /* Show the parent CSS if applicable*/
 199                 if (css->parent)
 200                         snprintf(pbuf, sizeof(pbuf) - 1, " P=%d",
 201                                  css->parent->id);
 202                 seq_printf(seq, "%2d: %-4s\t- %lx[%d] %d%s\n", ss->id, ss->name,
 203                           (unsigned long)css, css->id,
 204                           atomic_read(&css->online_cnt), pbuf);
 205         }
 206
 207         cgroup_kn_unlock(of->kn);
 208         return 0;
 209 }
 210
 211 static void cgroup_masks_read_one(struct seq_file *seq, const char *name,
 212                                   u16 mask)
 213 {
 214         struct cgroup_subsys *ss;
 215         int ssid;
 216         bool first = true;
 217
 218         seq_printf(seq, "%-17s: ", name);
 219         for_each_subsys(ss, ssid) {
 220                 if (!(mask & (1 << ssid)))
 221                         continue;
 222                 if (!first)
 223                         seq_puts(seq, ", ");
 224                 seq_puts(seq, ss->name);
 225                 first = false;
 226         }
 227         seq_putc(seq, '\n');
 228 }
 229
 230 static int cgroup_masks_read(struct seq_file *seq, void *v)
 231 {
 232         struct kernfs_open_file *of = seq->private;
 233         struct cgroup *cgrp;
 234
 235         cgrp = cgroup_kn_lock_live(of->kn, false);
 236         if (!cgrp)
 237                 return -ENODEV;
 238
 239         cgroup_masks_read_one(seq, "subtree_control", cgrp->subtree_control);
 240         cgroup_masks_read_one(seq, "subtree_ss_mask", cgrp->subtree_ss_mask);
 241
 242         cgroup_kn_unlock(of->kn);
 243         return 0;
 244 }
 245
 246 static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
 247 {
 248         return (!cgroup_is_populated(css->cgroup) &&
 249                 !css_has_online_children(&css->cgroup->self));
 250 }
 251
 252 static struct cftype debug_legacy_files[] =  {
 253         {
 254                 .name = "taskcount",
 255                 .read_u64 = debug_taskcount_read,
 256         },
 257
 258         {
 259                 .name = "current_css_set",
 260                 .seq_show = current_css_set_read,
 261                 .flags = CFTYPE_ONLY_ON_ROOT,
 262         },
 263
 264         {
 265                 .name = "current_css_set_refcount",
 266                 .read_u64 = current_css_set_refcount_read,
 267                 .flags = CFTYPE_ONLY_ON_ROOT,
 268         },
 269
 270         {
 271                 .name = "current_css_set_cg_links",
 272                 .seq_show = current_css_set_cg_links_read,
 273                 .flags = CFTYPE_ONLY_ON_ROOT,
 274         },
 275
 276         {
 277                 .name = "cgroup_css_links",
 278                 .seq_show = cgroup_css_links_read,
 279         },
 280
 281         {
 282                 .name = "cgroup_subsys_states",
 283                 .seq_show = cgroup_subsys_states_read,
 284         },
 285
 286         {
 287                 .name = "cgroup_masks",
 288                 .seq_show = cgroup_masks_read,
 289         },
 290
 291         {
 292                 .name = "releasable",
 293                 .read_u64 = releasable_read,
 294         },
 295
 296         { }     /* terminate */
 297 };
 298
 299 static struct cftype debug_files[] =  {
 300         {
 301                 .name = "taskcount",
 302                 .read_u64 = debug_taskcount_read,
 303         },
 304
 305         {
 306                 .name = "current_css_set",
 307                 .seq_show = current_css_set_read,
 308                 .flags = CFTYPE_ONLY_ON_ROOT,
 309         },
 310
 311         {
 312                 .name = "current_css_set_refcount",
 313                 .read_u64 = current_css_set_refcount_read,
 314                 .flags = CFTYPE_ONLY_ON_ROOT,
 315         },
 316
 317         {
 318                 .name = "current_css_set_cg_links",
 319                 .seq_show = current_css_set_cg_links_read,
 320                 .flags = CFTYPE_ONLY_ON_ROOT,
 321         },
 322
 323         {
 324                 .name = "css_links",
 325                 .seq_show = cgroup_css_links_read,
 326         },
 327
 328         {
 329                 .name = "csses",
 330                 .seq_show = cgroup_subsys_states_read,
 331         },
 332
 333         {
 334                 .name = "masks",
 335                 .seq_show = cgroup_masks_read,
 336         },
 337
 338         { }     /* terminate */
 339 };
 340
 341 struct cgroup_subsys debug_cgrp_subsys = {
 342         .css_alloc      = debug_css_alloc,
 343         .css_free       = debug_css_free,
 344         .legacy_cftypes = debug_legacy_files,
 345 };
 346
 347 /*
 348  * On v2, debug is an implicit controller enabled by "cgroup_debug" boot
 349  * parameter.
 350  */
 351 static int __init enable_cgroup_debug(char *str)
 352 {
 353         debug_cgrp_subsys.dfl_cftypes = debug_files;
 354         debug_cgrp_subsys.implicit_on_dfl = true;
 355         return 1;
 356 }
 357 __setup("cgroup_debug", enable_cgroup_debug);