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