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/slab.h>
  14 #include <linux/rbtree.h>
  15 #include <linux/debugfs.h>
  16 #include "trace_stat.h"
  17 #include "trace.h"
  18
  19
  20 /*
  21  * List of stat red-black nodes from a tracer
  22  * We use a such tree to sort quickly the stat
  23  * entries from the tracer.
  24  */
  25 struct stat_node {
  26         struct rb_node          node;
  27         void                    *stat;
  28 };
  29
  30 /* A stat session is the stats output in one file */
  31 struct stat_session {
  32         struct list_head        session_list;
  33         struct tracer_stat      *ts;
  34         struct rb_root          stat_root;
  35         struct mutex            stat_mutex;
  36         struct dentry           *file;
  37 };
  38
  39 /* All of the sessions currently in use. Each stat file embed one session */
  40 static LIST_HEAD(all_stat_sessions);
  41 static DEFINE_MUTEX(all_stat_sessions_mutex);
  42
  43 /* The root directory for all stat files */
  44 static struct dentry            *stat_dir;
  45
  46 /*
  47  * Iterate through the rbtree using a post order traversal path
  48  * to release the next node.
  49  * It won't necessary release one at each iteration
  50  * but it will at least advance closer to the next one
  51  * to be released.
  52  */
  53 static struct rb_node *release_next(struct tracer_stat *ts,
  54                                     struct rb_node *node)
  55 {
  56         struct stat_node *snode;
  57         struct rb_node *parent = rb_parent(node);
  58
  59         if (node->rb_left)
  60                 return node->rb_left;
  61         else if (node->rb_right)
  62                 return node->rb_right;
  63         else {
  64                 if (!parent)
  65                         ;
  66                 else if (parent->rb_left == node)
  67                         parent->rb_left = NULL;
  68                 else
  69                         parent->rb_right = NULL;
  70
  71                 snode = container_of(node, struct stat_node, node);
  72                 if (ts->stat_release)
  73                         ts->stat_release(snode->stat);
  74                 kfree(snode);
  75
  76                 return parent;
  77         }
  78 }
  79
  80 static void __reset_stat_session(struct stat_session *session)
  81 {
  82         struct rb_node *node = session->stat_root.rb_node;
  83
  84         while (node)
  85                 node = release_next(session->ts, node);
  86
  87         session->stat_root = RB_ROOT;
  88 }
  89
  90 static void reset_stat_session(struct stat_session *session)
  91 {
  92         mutex_lock(&session->stat_mutex);
  93         __reset_stat_session(session);
  94         mutex_unlock(&session->stat_mutex);
  95 }
  96
  97 static void destroy_session(struct stat_session *session)
  98 {
  99         debugfs_remove(session->file);
 100         __reset_stat_session(session);
 101         mutex_destroy(&session->stat_mutex);
 102         kfree(session);
 103 }
 104
 105 typedef int (*cmp_stat_t)(void *, void *);
 106
 107 static int insert_stat(struct rb_root *root, void *stat, cmp_stat_t cmp)
 108 {
 109         struct rb_node **new = &(root->rb_node), *parent = NULL;
 110         struct stat_node *data;
 111
 112         data = kzalloc(sizeof(*data), GFP_KERNEL);
 113         if (!data)
 114                 return -ENOMEM;
 115         data->stat = stat;
 116
 117         /*
 118          * Figure out where to put new node
 119          * This is a descendent sorting
 120          */
 121         while (*new) {
 122                 struct stat_node *this;
 123                 int result;
 124
 125                 this = container_of(*new, struct stat_node, node);
 126                 result = cmp(data->stat, this->stat);
 127
 128                 parent = *new;
 129                 if (result >= 0)
 130                         new = &((*new)->rb_left);
 131                 else
 132                         new = &((*new)->rb_right);
 133         }
 134
 135         rb_link_node(&data->node, parent, new);
 136         rb_insert_color(&data->node, root);
 137         return 0;
 138 }
 139
 140 /*
 141  * For tracers that don't provide a stat_cmp callback.
 142  * This one will force an insertion as right-most node
 143  * in the rbtree.
 144  */
 145 static int dummy_cmp(void *p1, void *p2)
 146 {
 147         return -1;
 148 }
 149
 150 /*
 151  * Initialize the stat rbtree at each trace_stat file opening.
 152  * All of these copies and sorting are required on all opening
 153  * since the stats could have changed between two file sessions.
 154  */
 155 static int stat_seq_init(struct stat_session *session)
 156 {
 157         struct tracer_stat *ts = session->ts;
 158         struct rb_root *root = &session->stat_root;
 159         void *stat;
 160         int ret = 0;
 161         int i;
 162
 163         mutex_lock(&session->stat_mutex);
 164         __reset_stat_session(session);
 165
 166         if (!ts->stat_cmp)
 167                 ts->stat_cmp = dummy_cmp;
 168
 169         stat = ts->stat_start(ts);
 170         if (!stat)
 171                 goto exit;
 172
 173         ret = insert_stat(root, stat, ts->stat_cmp);
 174         if (ret)
 175                 goto exit;
 176
 177         /*
 178          * Iterate over the tracer stat entries and store them in an rbtree.
 179          */
 180         for (i = 1; ; i++) {
 181                 stat = ts->stat_next(stat, i);
 182
 183                 /* End of insertion */
 184                 if (!stat)
 185                         break;
 186
 187                 ret = insert_stat(root, stat, ts->stat_cmp);
 188                 if (ret)
 189                         goto exit_free_rbtree;
 190         }
 191
 192 exit:
 193         mutex_unlock(&session->stat_mutex);
 194         return ret;
 195
 196 exit_free_rbtree:
 197         __reset_stat_session(session);
 198         mutex_unlock(&session->stat_mutex);
 199         return ret;
 200 }
 201
 202
 203 static void *stat_seq_start(struct seq_file *s, loff_t *pos)
 204 {
 205         struct stat_session *session = s->private;
 206         struct rb_node *node;
 207         int n = *pos;
 208         int i;
 209
 210         /* Prevent from tracer switch or rbtree modification */
 211         mutex_lock(&session->stat_mutex);
 212
 213         /* If we are in the beginning of the file, print the headers */
 214         if (session->ts->stat_headers) {
 215                 if (n == 0)
 216                         return SEQ_START_TOKEN;
 217                 n--;
 218         }
 219
 220         node = rb_first(&session->stat_root);
 221         for (i = 0; node && i < n; i++)
 222                 node = rb_next(node);
 223
 224         return node;
 225 }
 226
 227 static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
 228 {
 229         struct stat_session *session = s->private;
 230         struct rb_node *node = p;
 231
 232         (*pos)++;
 233
 234         if (p == SEQ_START_TOKEN)
 235                 return rb_first(&session->stat_root);
 236
 237         return rb_next(node);
 238 }
 239
 240 static void stat_seq_stop(struct seq_file *s, void *p)
 241 {
 242         struct stat_session *session = s->private;
 243         mutex_unlock(&session->stat_mutex);
 244 }
 245
 246 static int stat_seq_show(struct seq_file *s, void *v)
 247 {
 248         struct stat_session *session = s->private;
 249         struct stat_node *l = container_of(v, struct stat_node, node);
 250
 251         if (v == SEQ_START_TOKEN)
 252                 return session->ts->stat_headers(s);
 253
 254         return session->ts->stat_show(s, l->stat);
 255 }
 256
 257 static const struct seq_operations trace_stat_seq_ops = {
 258         .start          = stat_seq_start,
 259         .next           = stat_seq_next,
 260         .stop           = stat_seq_stop,
 261         .show           = stat_seq_show
 262 };
 263
 264 /* The session stat is refilled and resorted at each stat file opening */
 265 static int tracing_stat_open(struct inode *inode, struct file *file)
 266 {
 267         int ret;
 268         struct seq_file *m;
 269         struct stat_session *session = inode->i_private;
 270
 271         ret = stat_seq_init(session);
 272         if (ret)
 273                 return ret;
 274
 275         ret = seq_open(file, &trace_stat_seq_ops);
 276         if (ret) {
 277                 reset_stat_session(session);
 278                 return ret;
 279         }
 280
 281         m = file->private_data;
 282         m->private = session;
 283         return ret;
 284 }
 285
 286 /*
 287  * Avoid consuming memory with our now useless rbtree.
 288  */
 289 static int tracing_stat_release(struct inode *i, struct file *f)
 290 {
 291         struct stat_session *session = i->i_private;
 292
 293         reset_stat_session(session);
 294
 295         return seq_release(i, f);
 296 }
 297
 298 static const struct file_operations tracing_stat_fops = {
 299         .open           = tracing_stat_open,
 300         .read           = seq_read,
 301         .llseek         = seq_lseek,
 302         .release        = tracing_stat_release
 303 };
 304
 305 static int tracing_stat_init(void)
 306 {
 307         struct dentry *d_tracing;
 308
 309         d_tracing = tracing_init_dentry();
 310         if (!d_tracing)
 311                 return 0;
 312
 313         stat_dir = debugfs_create_dir("trace_stat", d_tracing);
 314         if (!stat_dir)
 315                 pr_warning("Could not create debugfs "
 316                            "'trace_stat' entry\n");
 317         return 0;
 318 }
 319
 320 static int init_stat_file(struct stat_session *session)
 321 {
 322         if (!stat_dir && tracing_stat_init())
 323                 return -ENODEV;
 324
 325         session->file = debugfs_create_file(session->ts->name, 0644,
 326                                             stat_dir,
 327                                             session, &tracing_stat_fops);
 328         if (!session->file)
 329                 return -ENOMEM;
 330         return 0;
 331 }
 332
 333 int register_stat_tracer(struct tracer_stat *trace)
 334 {
 335         struct stat_session *session, *node;
 336         int ret;
 337
 338         if (!trace)
 339                 return -EINVAL;
 340
 341         if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
 342                 return -EINVAL;
 343
 344         /* Already registered? */
 345         mutex_lock(&all_stat_sessions_mutex);
 346         list_for_each_entry(node, &all_stat_sessions, session_list) {
 347                 if (node->ts == trace) {
 348                         mutex_unlock(&all_stat_sessions_mutex);
 349                         return -EINVAL;
 350                 }
 351         }
 352         mutex_unlock(&all_stat_sessions_mutex);
 353
 354         /* Init the session */
 355         session = kzalloc(sizeof(*session), GFP_KERNEL);
 356         if (!session)
 357                 return -ENOMEM;
 358
 359         session->ts = trace;
 360         INIT_LIST_HEAD(&session->session_list);
 361         mutex_init(&session->stat_mutex);
 362
 363         ret = init_stat_file(session);
 364         if (ret) {
 365                 destroy_session(session);
 366                 return ret;
 367         }
 368
 369         /* Register */
 370         mutex_lock(&all_stat_sessions_mutex);
 371         list_add_tail(&session->session_list, &all_stat_sessions);
 372         mutex_unlock(&all_stat_sessions_mutex);
 373
 374         return 0;
 375 }
 376
 377 void unregister_stat_tracer(struct tracer_stat *trace)
 378 {
 379         struct stat_session *node, *tmp;
 380
 381         mutex_lock(&all_stat_sessions_mutex);
 382         list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
 383                 if (node->ts == trace) {
 384                         list_del(&node->session_list);
 385                         destroy_session(node);
 386                         break;
 387                 }
 388         }
 389         mutex_unlock(&all_stat_sessions_mutex);
 390 }