kernel/trace/trace_stat.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Infrastructure for statistic tracing (histogram output).
   4  *
   5  * Copyright (C) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
   6  *
   7  * Based on the code from trace_branch.c which is
   8  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
   9  *
  10  */
  11
  12
  13 #include <linux/list.h>
  14 #include <linux/slab.h>
  15 #include <linux/rbtree.h>
  16 #include <linux/tracefs.h>
  17 #include "trace_stat.h"
  18 #include "trace.h"
  19
  20
  21 /*
  22  * List of stat red-black nodes from a tracer
  23  * We use a such tree to sort quickly the stat
  24  * entries from the tracer.
  25  */
  26 struct stat_node {
  27         struct rb_node          node;
  28         void                    *stat;
  29 };
  30
  31 /* A stat session is the stats output in one file */
  32 struct stat_session {
  33         struct list_head        session_list;
  34         struct tracer_stat      *ts;
  35         struct rb_root          stat_root;
  36         struct mutex            stat_mutex;
  37         struct dentry           *file;
  38 };
  39
  40 /* All of the sessions currently in use. Each stat file embed one session */
  41 static LIST_HEAD(all_stat_sessions);
  42 static DEFINE_MUTEX(all_stat_sessions_mutex);
  43
  44 /* The root directory for all stat files */
  45 static struct dentry            *stat_dir;
  46
  47 static void __reset_stat_session(struct stat_session *session)
  48 {
  49         struct stat_node *snode, *n;
  50
  51         rbtree_postorder_for_each_entry_safe(snode, n, &session->stat_root, node) {
  52                 if (session->ts->stat_release)
  53                         session->ts->stat_release(snode->stat);
  54                 kfree(snode);
  55         }
  56
  57         session->stat_root = RB_ROOT;
  58 }
  59
  60 static void reset_stat_session(struct stat_session *session)
  61 {
  62         mutex_lock(&session->stat_mutex);
  63         __reset_stat_session(session);
  64         mutex_unlock(&session->stat_mutex);
  65 }
  66
  67 static void destroy_session(struct stat_session *session)
  68 {
  69         tracefs_remove(session->file);
  70         __reset_stat_session(session);
  71         mutex_destroy(&session->stat_mutex);
  72         kfree(session);
  73 }
  74
  75 typedef int (*cmp_stat_t)(void *, void *);
  76
  77 static int insert_stat(struct rb_root *root, void *stat, cmp_stat_t cmp)
  78 {
  79         struct rb_node **new = &(root->rb_node), *parent = NULL;
  80         struct stat_node *data;
  81
  82         data = kzalloc(sizeof(*data), GFP_KERNEL);
  83         if (!data)
  84                 return -ENOMEM;
  85         data->stat = stat;
  86
  87         /*
  88          * Figure out where to put new node
  89          * This is a descendent sorting
  90          */
  91         while (*new) {
  92                 struct stat_node *this;
  93                 int result;
  94
  95                 this = container_of(*new, struct stat_node, node);
  96                 result = cmp(data->stat, this->stat);
  97
  98                 parent = *new;
  99                 if (result >= 0)
 100                         new = &((*new)->rb_left);
 101                 else
 102                         new = &((*new)->rb_right);
 103         }
 104
 105         rb_link_node(&data->node, parent, new);
 106         rb_insert_color(&data->node, root);
 107         return 0;
 108 }
 109
 110 /*
 111  * For tracers that don't provide a stat_cmp callback.
 112  * This one will force an insertion as right-most node
 113  * in the rbtree.
 114  */
 115 static int dummy_cmp(void *p1, void *p2)
 116 {
 117         return -1;
 118 }
 119
 120 /*
 121  * Initialize the stat rbtree at each trace_stat file opening.
 122  * All of these copies and sorting are required on all opening
 123  * since the stats could have changed between two file sessions.
 124  */
 125 static int stat_seq_init(struct stat_session *session)
 126 {
 127         struct tracer_stat *ts = session->ts;
 128         struct rb_root *root = &session->stat_root;
 129         void *stat;
 130         int ret = 0;
 131         int i;
 132
 133         mutex_lock(&session->stat_mutex);
 134         __reset_stat_session(session);
 135
 136         if (!ts->stat_cmp)
 137                 ts->stat_cmp = dummy_cmp;
 138
 139         stat = ts->stat_start(ts);
 140         if (!stat)
 141                 goto exit;
 142
 143         ret = insert_stat(root, stat, ts->stat_cmp);
 144         if (ret)
 145                 goto exit;
 146
 147         /*
 148          * Iterate over the tracer stat entries and store them in an rbtree.
 149          */
 150         for (i = 1; ; i++) {
 151                 stat = ts->stat_next(stat, i);
 152
 153                 /* End of insertion */
 154                 if (!stat)
 155                         break;
 156
 157                 ret = insert_stat(root, stat, ts->stat_cmp);
 158                 if (ret)
 159                         goto exit_free_rbtree;
 160         }
 161
 162 exit:
 163         mutex_unlock(&session->stat_mutex);
 164         return ret;
 165
 166 exit_free_rbtree:
 167         __reset_stat_session(session);
 168         mutex_unlock(&session->stat_mutex);
 169         return ret;
 170 }
 171
 172
 173 static void *stat_seq_start(struct seq_file *s, loff_t *pos)
 174 {
 175         struct stat_session *session = s->private;
 176         struct rb_node *node;
 177         int n = *pos;
 178         int i;
 179
 180         /* Prevent from tracer switch or rbtree modification */
 181         mutex_lock(&session->stat_mutex);
 182
 183         /* If we are in the beginning of the file, print the headers */
 184         if (session->ts->stat_headers) {
 185                 if (n == 0)
 186                         return SEQ_START_TOKEN;
 187                 n--;
 188         }
 189
 190         node = rb_first(&session->stat_root);
 191         for (i = 0; node && i < n; i++)
 192                 node = rb_next(node);
 193
 194         return node;
 195 }
 196
 197 static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
 198 {
 199         struct stat_session *session = s->private;
 200         struct rb_node *node = p;
 201
 202         (*pos)++;
 203
 204         if (p == SEQ_START_TOKEN)
 205                 return rb_first(&session->stat_root);
 206
 207         return rb_next(node);
 208 }
 209
 210 static void stat_seq_stop(struct seq_file *s, void *p)
 211 {
 212         struct stat_session *session = s->private;
 213         mutex_unlock(&session->stat_mutex);
 214 }
 215
 216 static int stat_seq_show(struct seq_file *s, void *v)
 217 {
 218         struct stat_session *session = s->private;
 219         struct stat_node *l = container_of(v, struct stat_node, node);
 220
 221         if (v == SEQ_START_TOKEN)
 222                 return session->ts->stat_headers(s);
 223
 224         return session->ts->stat_show(s, l->stat);
 225 }
 226
 227 static const struct seq_operations trace_stat_seq_ops = {
 228         .start          = stat_seq_start,
 229         .next           = stat_seq_next,
 230         .stop           = stat_seq_stop,
 231         .show           = stat_seq_show
 232 };
 233
 234 /* The session stat is refilled and resorted at each stat file opening */
 235 static int tracing_stat_open(struct inode *inode, struct file *file)
 236 {
 237         int ret;
 238         struct seq_file *m;
 239         struct stat_session *session = inode->i_private;
 240
 241         ret = stat_seq_init(session);
 242         if (ret)
 243                 return ret;
 244
 245         ret = seq_open(file, &trace_stat_seq_ops);
 246         if (ret) {
 247                 reset_stat_session(session);
 248                 return ret;
 249         }
 250
 251         m = file->private_data;
 252         m->private = session;
 253         return ret;
 254 }
 255
 256 /*
 257  * Avoid consuming memory with our now useless rbtree.
 258  */
 259 static int tracing_stat_release(struct inode *i, struct file *f)
 260 {
 261         struct stat_session *session = i->i_private;
 262
 263         reset_stat_session(session);
 264
 265         return seq_release(i, f);
 266 }
 267
 268 static const struct file_operations tracing_stat_fops = {
 269         .open           = tracing_stat_open,
 270         .read           = seq_read,
 271         .llseek         = seq_lseek,
 272         .release        = tracing_stat_release
 273 };
 274
 275 static int tracing_stat_init(void)
 276 {
 277         struct dentry *d_tracing;
 278
 279         d_tracing = tracing_init_dentry();
 280         if (IS_ERR(d_tracing))
 281                 return 0;
 282
 283         stat_dir = tracefs_create_dir("trace_stat", d_tracing);
 284         if (!stat_dir)
 285                 pr_warn("Could not create tracefs 'trace_stat' entry\n");
 286         return 0;
 287 }
 288
 289 static int init_stat_file(struct stat_session *session)
 290 {
 291         if (!stat_dir && tracing_stat_init())
 292                 return -ENODEV;
 293
 294         session->file = tracefs_create_file(session->ts->name, 0644,
 295                                             stat_dir,
 296                                             session, &tracing_stat_fops);
 297         if (!session->file)
 298                 return -ENOMEM;
 299         return 0;
 300 }
 301
 302 int register_stat_tracer(struct tracer_stat *trace)
 303 {
 304         struct stat_session *session, *node;
 305         int ret;
 306
 307         if (!trace)
 308                 return -EINVAL;
 309
 310         if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
 311                 return -EINVAL;
 312
 313         /* Already registered? */
 314         mutex_lock(&all_stat_sessions_mutex);
 315         list_for_each_entry(node, &all_stat_sessions, session_list) {
 316                 if (node->ts == trace) {
 317                         mutex_unlock(&all_stat_sessions_mutex);
 318                         return -EINVAL;
 319                 }
 320         }
 321         mutex_unlock(&all_stat_sessions_mutex);
 322
 323         /* Init the session */
 324         session = kzalloc(sizeof(*session), GFP_KERNEL);
 325         if (!session)
 326                 return -ENOMEM;
 327
 328         session->ts = trace;
 329         INIT_LIST_HEAD(&session->session_list);
 330         mutex_init(&session->stat_mutex);
 331
 332         ret = init_stat_file(session);
 333         if (ret) {
 334                 destroy_session(session);
 335                 return ret;
 336         }
 337
 338         /* Register */
 339         mutex_lock(&all_stat_sessions_mutex);
 340         list_add_tail(&session->session_list, &all_stat_sessions);
 341         mutex_unlock(&all_stat_sessions_mutex);
 342
 343         return 0;
 344 }
 345
 346 void unregister_stat_tracer(struct tracer_stat *trace)
 347 {
 348         struct stat_session *node, *tmp;
 349
 350         mutex_lock(&all_stat_sessions_mutex);
 351         list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
 352                 if (node->ts == trace) {
 353                         list_del(&node->session_list);
 354                         destroy_session(node);
 355                         break;
 356                 }
 357         }
 358         mutex_unlock(&all_stat_sessions_mutex);
 359 }