xref: /linux/kernel/trace/trace_stat.c (revision ac6a0cf6716bb46813d0161024c66c2af66e53d1) 
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