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