xref: /linux/kernel/trace/trace_stat.c (revision ca55b2fef3a9373fcfc30f82fd26bc7fccbda732) 
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/tracefs.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 static void __reset_stat_session(struct stat_session *session)
47 {
48 	struct stat_node *snode, *n;
49 
50 	rbtree_postorder_for_each_entry_safe(snode, n, &session->stat_root, node) {
51 		if (session->ts->stat_release)
52 			session->ts->stat_release(snode->stat);
53 		kfree(snode);
54 	}
55 
56 	session->stat_root = RB_ROOT;
57 }
58 
59 static void reset_stat_session(struct stat_session *session)
60 {
61 	mutex_lock(&session->stat_mutex);
62 	__reset_stat_session(session);
63 	mutex_unlock(&session->stat_mutex);
64 }
65 
66 static void destroy_session(struct stat_session *session)
67 {
68 	tracefs_remove(session->file);
69 	__reset_stat_session(session);
70 	mutex_destroy(&session->stat_mutex);
71 	kfree(session);
72 }
73 
74 typedef int (*cmp_stat_t)(void *, void *);
75 
76 static int insert_stat(struct rb_root *root, void *stat, cmp_stat_t cmp)
77 {
78 	struct rb_node **new = &(root->rb_node), *parent = NULL;
79 	struct stat_node *data;
80 
81 	data = kzalloc(sizeof(*data), GFP_KERNEL);
82 	if (!data)
83 		return -ENOMEM;
84 	data->stat = stat;
85 
86 	/*
87 	 * Figure out where to put new node
88 	 * This is a descendent sorting
89 	 */
90 	while (*new) {
91 		struct stat_node *this;
92 		int result;
93 
94 		this = container_of(*new, struct stat_node, node);
95 		result = cmp(data->stat, this->stat);
96 
97 		parent = *new;
98 		if (result >= 0)
99 			new = &((*new)->rb_left);
100 		else
101 			new = &((*new)->rb_right);
102 	}
103 
104 	rb_link_node(&data->node, parent, new);
105 	rb_insert_color(&data->node, root);
106 	return 0;
107 }
108 
109 /*
110  * For tracers that don't provide a stat_cmp callback.
111  * This one will force an insertion as right-most node
112  * in the rbtree.
113  */
114 static int dummy_cmp(void *p1, void *p2)
115 {
116 	return -1;
117 }
118 
119 /*
120  * Initialize the stat rbtree at each trace_stat file opening.
121  * All of these copies and sorting are required on all opening
122  * since the stats could have changed between two file sessions.
123  */
124 static int stat_seq_init(struct stat_session *session)
125 {
126 	struct tracer_stat *ts = session->ts;
127 	struct rb_root *root = &session->stat_root;
128 	void *stat;
129 	int ret = 0;
130 	int i;
131 
132 	mutex_lock(&session->stat_mutex);
133 	__reset_stat_session(session);
134 
135 	if (!ts->stat_cmp)
136 		ts->stat_cmp = dummy_cmp;
137 
138 	stat = ts->stat_start(ts);
139 	if (!stat)
140 		goto exit;
141 
142 	ret = insert_stat(root, stat, ts->stat_cmp);
143 	if (ret)
144 		goto exit;
145 
146 	/*
147 	 * Iterate over the tracer stat entries and store them in an rbtree.
148 	 */
149 	for (i = 1; ; i++) {
150 		stat = ts->stat_next(stat, i);
151 
152 		/* End of insertion */
153 		if (!stat)
154 			break;
155 
156 		ret = insert_stat(root, stat, ts->stat_cmp);
157 		if (ret)
158 			goto exit_free_rbtree;
159 	}
160 
161 exit:
162 	mutex_unlock(&session->stat_mutex);
163 	return ret;
164 
165 exit_free_rbtree:
166 	__reset_stat_session(session);
167 	mutex_unlock(&session->stat_mutex);
168 	return ret;
169 }
170 
171 
172 static void *stat_seq_start(struct seq_file *s, loff_t *pos)
173 {
174 	struct stat_session *session = s->private;
175 	struct rb_node *node;
176 	int n = *pos;
177 	int i;
178 
179 	/* Prevent from tracer switch or rbtree modification */
180 	mutex_lock(&session->stat_mutex);
181 
182 	/* If we are in the beginning of the file, print the headers */
183 	if (session->ts->stat_headers) {
184 		if (n == 0)
185 			return SEQ_START_TOKEN;
186 		n--;
187 	}
188 
189 	node = rb_first(&session->stat_root);
190 	for (i = 0; node && i < n; i++)
191 		node = rb_next(node);
192 
193 	return node;
194 }
195 
196 static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
197 {
198 	struct stat_session *session = s->private;
199 	struct rb_node *node = p;
200 
201 	(*pos)++;
202 
203 	if (p == SEQ_START_TOKEN)
204 		return rb_first(&session->stat_root);
205 
206 	return rb_next(node);
207 }
208 
209 static void stat_seq_stop(struct seq_file *s, void *p)
210 {
211 	struct stat_session *session = s->private;
212 	mutex_unlock(&session->stat_mutex);
213 }
214 
215 static int stat_seq_show(struct seq_file *s, void *v)
216 {
217 	struct stat_session *session = s->private;
218 	struct stat_node *l = container_of(v, struct stat_node, node);
219 
220 	if (v == SEQ_START_TOKEN)
221 		return session->ts->stat_headers(s);
222 
223 	return session->ts->stat_show(s, l->stat);
224 }
225 
226 static const struct seq_operations trace_stat_seq_ops = {
227 	.start		= stat_seq_start,
228 	.next		= stat_seq_next,
229 	.stop		= stat_seq_stop,
230 	.show		= stat_seq_show
231 };
232 
233 /* The session stat is refilled and resorted at each stat file opening */
234 static int tracing_stat_open(struct inode *inode, struct file *file)
235 {
236 	int ret;
237 	struct seq_file *m;
238 	struct stat_session *session = inode->i_private;
239 
240 	ret = stat_seq_init(session);
241 	if (ret)
242 		return ret;
243 
244 	ret = seq_open(file, &trace_stat_seq_ops);
245 	if (ret) {
246 		reset_stat_session(session);
247 		return ret;
248 	}
249 
250 	m = file->private_data;
251 	m->private = session;
252 	return ret;
253 }
254 
255 /*
256  * Avoid consuming memory with our now useless rbtree.
257  */
258 static int tracing_stat_release(struct inode *i, struct file *f)
259 {
260 	struct stat_session *session = i->i_private;
261 
262 	reset_stat_session(session);
263 
264 	return seq_release(i, f);
265 }
266 
267 static const struct file_operations tracing_stat_fops = {
268 	.open		= tracing_stat_open,
269 	.read		= seq_read,
270 	.llseek		= seq_lseek,
271 	.release	= tracing_stat_release
272 };
273 
274 static int tracing_stat_init(void)
275 {
276 	struct dentry *d_tracing;
277 
278 	d_tracing = tracing_init_dentry();
279 	if (IS_ERR(d_tracing))
280 		return 0;
281 
282 	stat_dir = tracefs_create_dir("trace_stat", d_tracing);
283 	if (!stat_dir)
284 		pr_warning("Could not create tracefs "
285 			   "'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 }
360