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Linux/kernel/trace/trace_stat.c

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  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 }
391 

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