xref: /openbmc/linux/kernel/trace/trace_stat.c (revision e23feb16) 
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