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 }
381
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