xref: /linux/kernel/trace/trace_stat.c (revision 5bdef865eb358b6f3760e25e591ae115e9eeddef) 
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 destroy_session(struct stat_session *session)
87 {
88 	debugfs_remove(session->file);
89 	reset_stat_session(session);
90 	mutex_destroy(&session->stat_mutex);
91 	kfree(session);
92 }
93 
94 typedef int (*cmp_stat_t)(void *, void *);
95 
96 static int insert_stat(struct rb_root *root, void *stat, cmp_stat_t cmp)
97 {
98 	struct rb_node **new = &(root->rb_node), *parent = NULL;
99 	struct stat_node *data;
100 
101 	data = kzalloc(sizeof(*data), GFP_KERNEL);
102 	if (!data)
103 		return -ENOMEM;
104 	data->stat = stat;
105 
106 	/*
107 	 * Figure out where to put new node
108 	 * This is a descendent sorting
109 	 */
110 	while (*new) {
111 		struct stat_node *this;
112 		int result;
113 
114 		this = container_of(*new, struct stat_node, node);
115 		result = cmp(data->stat, this->stat);
116 
117 		parent = *new;
118 		if (result >= 0)
119 			new = &((*new)->rb_left);
120 		else
121 			new = &((*new)->rb_right);
122 	}
123 
124 	rb_link_node(&data->node, parent, new);
125 	rb_insert_color(&data->node, root);
126 	return 0;
127 }
128 
129 /*
130  * For tracers that don't provide a stat_cmp callback.
131  * This one will force an insertion as right-most node
132  * in the rbtree.
133  */
134 static int dummy_cmp(void *p1, void *p2)
135 {
136 	return -1;
137 }
138 
139 /*
140  * Initialize the stat rbtree at each trace_stat file opening.
141  * All of these copies and sorting are required on all opening
142  * since the stats could have changed between two file sessions.
143  */
144 static int stat_seq_init(struct stat_session *session)
145 {
146 	struct tracer_stat *ts = session->ts;
147 	struct rb_root *root = &session->stat_root;
148 	void *stat;
149 	int ret = 0;
150 	int i;
151 
152 	mutex_lock(&session->stat_mutex);
153 	reset_stat_session(session);
154 
155 	if (!ts->stat_cmp)
156 		ts->stat_cmp = dummy_cmp;
157 
158 	stat = ts->stat_start(ts);
159 	if (!stat)
160 		goto exit;
161 
162 	ret = insert_stat(root, stat, ts->stat_cmp);
163 	if (ret)
164 		goto exit;
165 
166 	/*
167 	 * Iterate over the tracer stat entries and store them in an rbtree.
168 	 */
169 	for (i = 1; ; i++) {
170 		stat = ts->stat_next(stat, i);
171 
172 		/* End of insertion */
173 		if (!stat)
174 			break;
175 
176 		ret = insert_stat(root, stat, ts->stat_cmp);
177 		if (ret)
178 			goto exit_free_rbtree;
179 	}
180 
181 exit:
182 	mutex_unlock(&session->stat_mutex);
183 	return ret;
184 
185 exit_free_rbtree:
186 	reset_stat_session(session);
187 	mutex_unlock(&session->stat_mutex);
188 	return ret;
189 }
190 
191 
192 static void *stat_seq_start(struct seq_file *s, loff_t *pos)
193 {
194 	struct stat_session *session = s->private;
195 	struct rb_node *node;
196 	int i;
197 
198 	/* Prevent from tracer switch or rbtree modification */
199 	mutex_lock(&session->stat_mutex);
200 
201 	/* If we are in the beginning of the file, print the headers */
202 	if (!*pos && session->ts->stat_headers)
203 		return SEQ_START_TOKEN;
204 
205 	node = rb_first(&session->stat_root);
206 	for (i = 0; node && i < *pos; i++)
207 		node = rb_next(node);
208 
209 	return node;
210 }
211 
212 static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
213 {
214 	struct stat_session *session = s->private;
215 	struct rb_node *node = p;
216 
217 	(*pos)++;
218 
219 	if (p == SEQ_START_TOKEN)
220 		return rb_first(&session->stat_root);
221 
222 	return rb_next(node);
223 }
224 
225 static void stat_seq_stop(struct seq_file *s, void *p)
226 {
227 	struct stat_session *session = s->private;
228 	mutex_unlock(&session->stat_mutex);
229 }
230 
231 static int stat_seq_show(struct seq_file *s, void *v)
232 {
233 	struct stat_session *session = s->private;
234 	struct stat_node *l = container_of(v, struct stat_node, node);
235 
236 	if (v == SEQ_START_TOKEN)
237 		return session->ts->stat_headers(s);
238 
239 	return session->ts->stat_show(s, l->stat);
240 }
241 
242 static const struct seq_operations trace_stat_seq_ops = {
243 	.start		= stat_seq_start,
244 	.next		= stat_seq_next,
245 	.stop		= stat_seq_stop,
246 	.show		= stat_seq_show
247 };
248 
249 /* The session stat is refilled and resorted at each stat file opening */
250 static int tracing_stat_open(struct inode *inode, struct file *file)
251 {
252 	int ret;
253 
254 	struct stat_session *session = inode->i_private;
255 
256 	ret = seq_open(file, &trace_stat_seq_ops);
257 	if (!ret) {
258 		struct seq_file *m = file->private_data;
259 		m->private = session;
260 		ret = stat_seq_init(session);
261 	}
262 
263 	return ret;
264 }
265 
266 /*
267  * Avoid consuming memory with our now useless rbtree.
268  */
269 static int tracing_stat_release(struct inode *i, struct file *f)
270 {
271 	struct stat_session *session = i->i_private;
272 
273 	mutex_lock(&session->stat_mutex);
274 	reset_stat_session(session);
275 	mutex_unlock(&session->stat_mutex);
276 
277 	return 0;
278 }
279 
280 static const struct file_operations tracing_stat_fops = {
281 	.open		= tracing_stat_open,
282 	.read		= seq_read,
283 	.llseek		= seq_lseek,
284 	.release	= tracing_stat_release
285 };
286 
287 static int tracing_stat_init(void)
288 {
289 	struct dentry *d_tracing;
290 
291 	d_tracing = tracing_init_dentry();
292 
293 	stat_dir = debugfs_create_dir("trace_stat", d_tracing);
294 	if (!stat_dir)
295 		pr_warning("Could not create debugfs "
296 			   "'trace_stat' entry\n");
297 	return 0;
298 }
299 
300 static int init_stat_file(struct stat_session *session)
301 {
302 	if (!stat_dir && tracing_stat_init())
303 		return -ENODEV;
304 
305 	session->file = debugfs_create_file(session->ts->name, 0644,
306 					    stat_dir,
307 					    session, &tracing_stat_fops);
308 	if (!session->file)
309 		return -ENOMEM;
310 	return 0;
311 }
312 
313 int register_stat_tracer(struct tracer_stat *trace)
314 {
315 	struct stat_session *session, *node;
316 	int ret;
317 
318 	if (!trace)
319 		return -EINVAL;
320 
321 	if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
322 		return -EINVAL;
323 
324 	/* Already registered? */
325 	mutex_lock(&all_stat_sessions_mutex);
326 	list_for_each_entry(node, &all_stat_sessions, session_list) {
327 		if (node->ts == trace) {
328 			mutex_unlock(&all_stat_sessions_mutex);
329 			return -EINVAL;
330 		}
331 	}
332 	mutex_unlock(&all_stat_sessions_mutex);
333 
334 	/* Init the session */
335 	session = kzalloc(sizeof(*session), GFP_KERNEL);
336 	if (!session)
337 		return -ENOMEM;
338 
339 	session->ts = trace;
340 	INIT_LIST_HEAD(&session->session_list);
341 	mutex_init(&session->stat_mutex);
342 
343 	ret = init_stat_file(session);
344 	if (ret) {
345 		destroy_session(session);
346 		return ret;
347 	}
348 
349 	/* Register */
350 	mutex_lock(&all_stat_sessions_mutex);
351 	list_add_tail(&session->session_list, &all_stat_sessions);
352 	mutex_unlock(&all_stat_sessions_mutex);
353 
354 	return 0;
355 }
356 
357 void unregister_stat_tracer(struct tracer_stat *trace)
358 {
359 	struct stat_session *node, *tmp;
360 
361 	mutex_lock(&all_stat_sessions_mutex);
362 	list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
363 		if (node->ts == trace) {
364 			list_del(&node->session_list);
365 			destroy_session(node);
366 			break;
367 		}
368 	}
369 	mutex_unlock(&all_stat_sessions_mutex);
370 }
371