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                 return SEQ_START_TOKEN;
 204
 205         node = rb_first(&session->stat_root);
 206         for (i = 0; node && i < *pos; i++)
 207                 node = rb_next(node);
 208
 209         return node;
 210 }
 211
 212 static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
 213 {
 214         struct stat_session *session = s->private;
 215         struct rb_node *node = p;
 216
 217         (*pos)++;
 218
 219         if (p == SEQ_START_TOKEN)
 220                 return rb_first(&session->stat_root);
 221
 222         return rb_next(node);
 223 }
 224
 225 static void stat_seq_stop(struct seq_file *s, void *p)
 226 {
 227         struct stat_session *session = s->private;
 228         mutex_unlock(&session->stat_mutex);
 229 }
 230
 231 static int stat_seq_show(struct seq_file *s, void *v)
 232 {
 233         struct stat_session *session = s->private;
 234         struct stat_node *l = container_of(v, struct stat_node, node);
 235
 236         if (v == SEQ_START_TOKEN)
 237                 return session->ts->stat_headers(s);
 238
 239         return session->ts->stat_show(s, l->stat);
 240 }
 241
 242 static const struct seq_operations trace_stat_seq_ops = {
 243         .start          = stat_seq_start,
 244         .next           = stat_seq_next,
 245         .stop           = stat_seq_stop,
 246         .show           = stat_seq_show
 247 };
 248
 249 /* The session stat is refilled and resorted at each stat file opening */
 250 static int tracing_stat_open(struct inode *inode, struct file *file)
 251 {
 252         int ret;
 253
 254         struct stat_session *session = inode->i_private;
 255
 256         ret = seq_open(file, &trace_stat_seq_ops);
 257         if (!ret) {
 258                 struct seq_file *m = file->private_data;
 259                 m->private = session;
 260                 ret = stat_seq_init(session);
 261         }
 262
 263         return ret;
 264 }
 265
 266 /*
 267  * Avoid consuming memory with our now useless rbtree.
 268  */
 269 static int tracing_stat_release(struct inode *i, struct file *f)
 270 {
 271         struct stat_session *session = i->i_private;
 272
 273         mutex_lock(&session->stat_mutex);
 274         reset_stat_session(session);
 275         mutex_unlock(&session->stat_mutex);
 276
 277         return 0;
 278 }
 279
 280 static const struct file_operations tracing_stat_fops = {
 281         .open           = tracing_stat_open,
 282         .read           = seq_read,
 283         .llseek         = seq_lseek,
 284         .release        = tracing_stat_release
 285 };
 286
 287 static int tracing_stat_init(void)
 288 {
 289         struct dentry *d_tracing;
 290
 291         d_tracing = tracing_init_dentry();
 292
 293         stat_dir = debugfs_create_dir("trace_stat", d_tracing);
 294         if (!stat_dir)
 295                 pr_warning("Could not create debugfs "
 296                            "'trace_stat' entry\n");
 297         return 0;
 298 }
 299
 300 static int init_stat_file(struct stat_session *session)
 301 {
 302         if (!stat_dir && tracing_stat_init())
 303                 return -ENODEV;
 304
 305         session->file = debugfs_create_file(session->ts->name, 0644,
 306                                             stat_dir,
 307                                             session, &tracing_stat_fops);
 308         if (!session->file)
 309                 return -ENOMEM;
 310         return 0;
 311 }
 312
 313 int register_stat_tracer(struct tracer_stat *trace)
 314 {
 315         struct stat_session *session, *node;
 316         int ret;
 317
 318         if (!trace)
 319                 return -EINVAL;
 320
 321         if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
 322                 return -EINVAL;
 323
 324         /* Already registered? */
 325         mutex_lock(&all_stat_sessions_mutex);
 326         list_for_each_entry(node, &all_stat_sessions, session_list) {
 327                 if (node->ts == trace) {
 328                         mutex_unlock(&all_stat_sessions_mutex);
 329                         return -EINVAL;
 330                 }
 331         }
 332         mutex_unlock(&all_stat_sessions_mutex);
 333
 334         /* Init the session */
 335         session = kzalloc(sizeof(*session), GFP_KERNEL);
 336         if (!session)
 337                 return -ENOMEM;
 338
 339         session->ts = trace;
 340         INIT_LIST_HEAD(&session->session_list);
 341         mutex_init(&session->stat_mutex);
 342
 343         ret = init_stat_file(session);
 344         if (ret) {
 345                 destroy_session(session);
 346                 return ret;
 347         }
 348
 349         /* Register */
 350         mutex_lock(&all_stat_sessions_mutex);
 351         list_add_tail(&session->session_list, &all_stat_sessions);
 352         mutex_unlock(&all_stat_sessions_mutex);
 353
 354         return 0;
 355 }
 356
 357 void unregister_stat_tracer(struct tracer_stat *trace)
 358 {
 359         struct stat_session *node, *tmp;
 360
 361         mutex_lock(&all_stat_sessions_mutex);
 362         list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
 363                 if (node->ts == trace) {
 364                         list_del(&node->session_list);
 365                         destroy_session(node);
 366                         break;
 367                 }
 368         }
 369         mutex_unlock(&all_stat_sessions_mutex);
 370 }