kernel/trace/trace_stat.c

   1 /*
   2  * Infrastructure for statistic tracing (histogram output).
   3  *
   4  * Copyright (C) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
   5  *
   6  * Based on the code from trace_branch.c which is
   7  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
   8  *
   9  */
  10
  11
  12 #include <linux/list.h>
  13 #include <linux/rbtree.h>
  14 #include <linux/debugfs.h>
  15 #include "trace_stat.h"
  16 #include "trace.h"
  17
  18
  19 /*
  20  * List of stat red-black nodes from a tracer
  21  * We use a such tree to sort quickly the stat
  22  * entries from the tracer.
  23  */
  24 struct stat_node {
  25         struct rb_node          node;
  26         void                    *stat;
  27 };
  28
  29 /* A stat session is the stats output in one file */
  30 struct stat_session {
  31         struct list_head        session_list;
  32         struct tracer_stat      *ts;
  33         struct rb_root          stat_root;
  34         struct mutex            stat_mutex;
  35         struct dentry           *file;
  36 };
  37
  38 /* All of the sessions currently in use. Each stat file embed one session */
  39 static LIST_HEAD(all_stat_sessions);
  40 static DEFINE_MUTEX(all_stat_sessions_mutex);
  41
  42 /* The root directory for all stat files */
  43 static struct dentry            *stat_dir;
  44
  45 /*
  46  * Iterate through the rbtree using a post order traversal path
  47  * to release the next node.
  48  * It won't necessary release one at each iteration
  49  * but it will at least advance closer to the next one
  50  * to be released.
  51  */
  52 static struct rb_node *release_next(struct rb_node *node)
  53 {
  54         struct stat_node *snode;
  55         struct rb_node *parent = rb_parent(node);
  56
  57         if (node->rb_left)
  58                 return node->rb_left;
  59         else if (node->rb_right)
  60                 return node->rb_right;
  61         else {
  62                 if (!parent)
  63                         ;
  64                 else if (parent->rb_left == node)
  65                         parent->rb_left = NULL;
  66                 else
  67                         parent->rb_right = NULL;
  68
  69                 snode = container_of(node, struct stat_node, node);
  70                 kfree(snode);
  71
  72                 return parent;
  73         }
  74 }
  75
  76 static void reset_stat_session(struct stat_session *session)
  77 {
  78         struct rb_node *node = session->stat_root.rb_node;
  79
  80         while (node)
  81                 node = release_next(node);
  82
  83         session->stat_root = RB_ROOT;
  84 }
  85
  86 static void destroy_session(struct stat_session *session)
  87 {
  88         debugfs_remove(session->file);
  89         reset_stat_session(session);
  90         mutex_destroy(&session->stat_mutex);
  91         kfree(session);
  92 }
  93
  94 typedef int (*cmp_stat_t)(void *, void *);
  95
  96 static int insert_stat(struct rb_root *root, void *stat, cmp_stat_t cmp)
  97 {
  98         struct rb_node **new = &(root->rb_node), *parent = NULL;
  99         struct stat_node *data;
 100
 101         data = kzalloc(sizeof(*data), GFP_KERNEL);
 102         if (!data)
 103                 return -ENOMEM;
 104         data->stat = stat;
 105
 106         /*
 107          * Figure out where to put new node
 108          * This is a descendent sorting
 109          */
 110         while (*new) {
 111                 struct stat_node *this;
 112                 int result;
 113
 114                 this = container_of(*new, struct stat_node, node);
 115                 result = cmp(data->stat, this->stat);
 116
 117                 parent = *new;
 118                 if (result >= 0)
 119                         new = &((*new)->rb_left);
 120                 else
 121                         new = &((*new)->rb_right);
 122         }
 123
 124         rb_link_node(&data->node, parent, new);
 125         rb_insert_color(&data->node, root);
 126         return 0;
 127 }
 128
 129 /*
 130  * For tracers that don't provide a stat_cmp callback.
 131  * This one will force an insertion as right-most node
 132  * in the rbtree.
 133  */
 134 static int dummy_cmp(void *p1, void *p2)
 135 {
 136         return -1;
 137 }
 138
 139 /*
 140  * Initialize the stat rbtree at each trace_stat file opening.
 141  * All of these copies and sorting are required on all opening
 142  * since the stats could have changed between two file sessions.
 143  */
 144 static int stat_seq_init(struct stat_session *session)
 145 {
 146         struct tracer_stat *ts = session->ts;
 147         struct rb_root *root = &session->stat_root;
 148         void *stat;
 149         int ret = 0;
 150         int i;
 151
 152         mutex_lock(&session->stat_mutex);
 153         reset_stat_session(session);
 154
 155         if (!ts->stat_cmp)
 156                 ts->stat_cmp = dummy_cmp;
 157
 158         stat = ts->stat_start(ts);
 159         if (!stat)
 160                 goto exit;
 161
 162         ret = insert_stat(root, stat, ts->stat_cmp);
 163         if (ret)
 164                 goto exit;
 165
 166         /*
 167          * Iterate over the tracer stat entries and store them in an rbtree.
 168          */
 169         for (i = 1; ; i++) {
 170                 stat = ts->stat_next(stat, i);
 171
 172                 /* End of insertion */
 173                 if (!stat)
 174                         break;
 175
 176                 ret = insert_stat(root, stat, ts->stat_cmp);
 177                 if (ret)
 178                         goto exit_free_rbtree;
 179         }
 180
 181 exit:
 182         mutex_unlock(&session->stat_mutex);
 183         return ret;
 184
 185 exit_free_rbtree:
 186         reset_stat_session(session);
 187         mutex_unlock(&session->stat_mutex);
 188         return ret;
 189 }
 190
 191
 192 static void *stat_seq_start(struct seq_file *s, loff_t *pos)
 193 {
 194         struct stat_session *session = s->private;
 195         struct rb_node *node;
 196         int i;
 197
 198         /* Prevent from tracer switch or rbtree modification */
 199         mutex_lock(&session->stat_mutex);
 200
 201         /* If we are in the beginning of the file, print the headers */
 202         if (!*pos && session->ts->stat_headers) {
 203                 (*pos)++;
 204                 return SEQ_START_TOKEN;
 205         }
 206
 207         node = rb_first(&session->stat_root);
 208         for (i = 0; node && i < *pos; i++)
 209                 node = rb_next(node);
 210
 211         (*pos)++;
 212
 213         return node;
 214 }
 215
 216 static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
 217 {
 218         struct stat_session *session = s->private;
 219         struct rb_node *node = p;
 220
 221         (*pos)++;
 222
 223         if (p == SEQ_START_TOKEN)
 224                 return rb_first(&session->stat_root);
 225
 226         return rb_next(node);
 227 }
 228
 229 static void stat_seq_stop(struct seq_file *s, void *p)
 230 {
 231         struct stat_session *session = s->private;
 232         mutex_unlock(&session->stat_mutex);
 233 }
 234
 235 static int stat_seq_show(struct seq_file *s, void *v)
 236 {
 237         struct stat_session *session = s->private;
 238         struct stat_node *l = container_of(v, struct stat_node, node);
 239
 240         if (v == SEQ_START_TOKEN)
 241                 return session->ts->stat_headers(s);
 242
 243         return session->ts->stat_show(s, l->stat);
 244 }
 245
 246 static const struct seq_operations trace_stat_seq_ops = {
 247         .start          = stat_seq_start,
 248         .next           = stat_seq_next,
 249         .stop           = stat_seq_stop,
 250         .show           = stat_seq_show
 251 };
 252
 253 /* The session stat is refilled and resorted at each stat file opening */
 254 static int tracing_stat_open(struct inode *inode, struct file *file)
 255 {
 256         int ret;
 257
 258         struct stat_session *session = inode->i_private;
 259
 260         ret = seq_open(file, &trace_stat_seq_ops);
 261         if (!ret) {
 262                 struct seq_file *m = file->private_data;
 263                 m->private = session;
 264                 ret = stat_seq_init(session);
 265         }
 266
 267         return ret;
 268 }
 269
 270 /*
 271  * Avoid consuming memory with our now useless rbtree.
 272  */
 273 static int tracing_stat_release(struct inode *i, struct file *f)
 274 {
 275         struct stat_session *session = i->i_private;
 276
 277         mutex_lock(&session->stat_mutex);
 278         reset_stat_session(session);
 279         mutex_unlock(&session->stat_mutex);
 280
 281         return 0;
 282 }
 283
 284 static const struct file_operations tracing_stat_fops = {
 285         .open           = tracing_stat_open,
 286         .read           = seq_read,
 287         .llseek         = seq_lseek,
 288         .release        = tracing_stat_release
 289 };
 290
 291 static int tracing_stat_init(void)
 292 {
 293         struct dentry *d_tracing;
 294
 295         d_tracing = tracing_init_dentry();
 296
 297         stat_dir = debugfs_create_dir("trace_stat", d_tracing);
 298         if (!stat_dir)
 299                 pr_warning("Could not create debugfs "
 300                            "'trace_stat' entry\n");
 301         return 0;
 302 }
 303
 304 static int init_stat_file(struct stat_session *session)
 305 {
 306         if (!stat_dir && tracing_stat_init())
 307                 return -ENODEV;
 308
 309         session->file = debugfs_create_file(session->ts->name, 0644,
 310                                             stat_dir,
 311                                             session, &tracing_stat_fops);
 312         if (!session->file)
 313                 return -ENOMEM;
 314         return 0;
 315 }
 316
 317 int register_stat_tracer(struct tracer_stat *trace)
 318 {
 319         struct stat_session *session, *node;
 320         int ret;
 321
 322         if (!trace)
 323                 return -EINVAL;
 324
 325         if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
 326                 return -EINVAL;
 327
 328         /* Already registered? */
 329         mutex_lock(&all_stat_sessions_mutex);
 330         list_for_each_entry(node, &all_stat_sessions, session_list) {
 331                 if (node->ts == trace) {
 332                         mutex_unlock(&all_stat_sessions_mutex);
 333                         return -EINVAL;
 334                 }
 335         }
 336         mutex_unlock(&all_stat_sessions_mutex);
 337
 338         /* Init the session */
 339         session = kzalloc(sizeof(*session), GFP_KERNEL);
 340         if (!session)
 341                 return -ENOMEM;
 342
 343         session->ts = trace;
 344         INIT_LIST_HEAD(&session->session_list);
 345         mutex_init(&session->stat_mutex);
 346
 347         ret = init_stat_file(session);
 348         if (ret) {
 349                 destroy_session(session);
 350                 return ret;
 351         }
 352
 353         /* Register */
 354         mutex_lock(&all_stat_sessions_mutex);
 355         list_add_tail(&session->session_list, &all_stat_sessions);
 356         mutex_unlock(&all_stat_sessions_mutex);
 357
 358         return 0;
 359 }
 360
 361 void unregister_stat_tracer(struct tracer_stat *trace)
 362 {
 363         struct stat_session *node, *tmp;
 364
 365         mutex_lock(&all_stat_sessions_mutex);
 366         list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
 367                 if (node->ts == trace) {
 368                         list_del(&node->session_list);
 369                         destroy_session(node);
 370                         break;
 371                 }
 372         }
 373         mutex_unlock(&all_stat_sessions_mutex);
 374 }