xref: /openbmc/linux/kernel/trace/trace_stat.c (revision 78c99ba1) 
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 		(*pos)++;
204 		return SEQ_START_TOKEN;
205 	}
206 
207 	node = rb_first(&session->stat_root);
208 	for (i = 0; node && i < *pos; i++)
209 		node = rb_next(node);
210 
211 	(*pos)++;
212 
213 	return node;
214 }
215 
216 static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
217 {
218 	struct stat_session *session = s->private;
219 	struct rb_node *node = p;
220 
221 	(*pos)++;
222 
223 	if (p == SEQ_START_TOKEN)
224 		return rb_first(&session->stat_root);
225 
226 	return rb_next(node);
227 }
228 
229 static void stat_seq_stop(struct seq_file *s, void *p)
230 {
231 	struct stat_session *session = s->private;
232 	mutex_unlock(&session->stat_mutex);
233 }
234 
235 static int stat_seq_show(struct seq_file *s, void *v)
236 {
237 	struct stat_session *session = s->private;
238 	struct stat_node *l = container_of(v, struct stat_node, node);
239 
240 	if (v == SEQ_START_TOKEN)
241 		return session->ts->stat_headers(s);
242 
243 	return session->ts->stat_show(s, l->stat);
244 }
245 
246 static const struct seq_operations trace_stat_seq_ops = {
247 	.start		= stat_seq_start,
248 	.next		= stat_seq_next,
249 	.stop		= stat_seq_stop,
250 	.show		= stat_seq_show
251 };
252 
253 /* The session stat is refilled and resorted at each stat file opening */
254 static int tracing_stat_open(struct inode *inode, struct file *file)
255 {
256 	int ret;
257 
258 	struct stat_session *session = inode->i_private;
259 
260 	ret = seq_open(file, &trace_stat_seq_ops);
261 	if (!ret) {
262 		struct seq_file *m = file->private_data;
263 		m->private = session;
264 		ret = stat_seq_init(session);
265 	}
266 
267 	return ret;
268 }
269 
270 /*
271  * Avoid consuming memory with our now useless rbtree.
272  */
273 static int tracing_stat_release(struct inode *i, struct file *f)
274 {
275 	struct stat_session *session = i->i_private;
276 
277 	mutex_lock(&session->stat_mutex);
278 	reset_stat_session(session);
279 	mutex_unlock(&session->stat_mutex);
280 
281 	return 0;
282 }
283 
284 static const struct file_operations tracing_stat_fops = {
285 	.open		= tracing_stat_open,
286 	.read		= seq_read,
287 	.llseek		= seq_lseek,
288 	.release	= tracing_stat_release
289 };
290 
291 static int tracing_stat_init(void)
292 {
293 	struct dentry *d_tracing;
294 
295 	d_tracing = tracing_init_dentry();
296 
297 	stat_dir = debugfs_create_dir("trace_stat", d_tracing);
298 	if (!stat_dir)
299 		pr_warning("Could not create debugfs "
300 			   "'trace_stat' entry\n");
301 	return 0;
302 }
303 
304 static int init_stat_file(struct stat_session *session)
305 {
306 	if (!stat_dir && tracing_stat_init())
307 		return -ENODEV;
308 
309 	session->file = debugfs_create_file(session->ts->name, 0644,
310 					    stat_dir,
311 					    session, &tracing_stat_fops);
312 	if (!session->file)
313 		return -ENOMEM;
314 	return 0;
315 }
316 
317 int register_stat_tracer(struct tracer_stat *trace)
318 {
319 	struct stat_session *session, *node;
320 	int ret;
321 
322 	if (!trace)
323 		return -EINVAL;
324 
325 	if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
326 		return -EINVAL;
327 
328 	/* Already registered? */
329 	mutex_lock(&all_stat_sessions_mutex);
330 	list_for_each_entry(node, &all_stat_sessions, session_list) {
331 		if (node->ts == trace) {
332 			mutex_unlock(&all_stat_sessions_mutex);
333 			return -EINVAL;
334 		}
335 	}
336 	mutex_unlock(&all_stat_sessions_mutex);
337 
338 	/* Init the session */
339 	session = kzalloc(sizeof(*session), GFP_KERNEL);
340 	if (!session)
341 		return -ENOMEM;
342 
343 	session->ts = trace;
344 	INIT_LIST_HEAD(&session->session_list);
345 	mutex_init(&session->stat_mutex);
346 
347 	ret = init_stat_file(session);
348 	if (ret) {
349 		destroy_session(session);
350 		return ret;
351 	}
352 
353 	/* Register */
354 	mutex_lock(&all_stat_sessions_mutex);
355 	list_add_tail(&session->session_list, &all_stat_sessions);
356 	mutex_unlock(&all_stat_sessions_mutex);
357 
358 	return 0;
359 }
360 
361 void unregister_stat_tracer(struct tracer_stat *trace)
362 {
363 	struct stat_session *node, *tmp;
364 
365 	mutex_lock(&all_stat_sessions_mutex);
366 	list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
367 		if (node->ts == trace) {
368 			list_del(&node->session_list);
369 			destroy_session(node);
370 			break;
371 		}
372 	}
373 	mutex_unlock(&all_stat_sessions_mutex);
374 }
375