xref: /openbmc/linux/kernel/trace/trace_stat.c (revision 2462bca0) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Infrastructure for statistic tracing (histogram output).
4  *
5  * Copyright (C) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
6  *
7  * Based on the code from trace_branch.c which is
8  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
9  *
10  */
11 
12 
13 #include <linux/list.h>
14 #include <linux/slab.h>
15 #include <linux/rbtree.h>
16 #include <linux/tracefs.h>
17 #include "trace_stat.h"
18 #include "trace.h"
19 
20 
21 /*
22  * List of stat red-black nodes from a tracer
23  * We use a such tree to sort quickly the stat
24  * entries from the tracer.
25  */
26 struct stat_node {
27 	struct rb_node		node;
28 	void			*stat;
29 };
30 
31 /* A stat session is the stats output in one file */
32 struct stat_session {
33 	struct list_head	session_list;
34 	struct tracer_stat	*ts;
35 	struct rb_root		stat_root;
36 	struct mutex		stat_mutex;
37 	struct dentry		*file;
38 };
39 
40 /* All of the sessions currently in use. Each stat file embed one session */
41 static LIST_HEAD(all_stat_sessions);
42 static DEFINE_MUTEX(all_stat_sessions_mutex);
43 
44 /* The root directory for all stat files */
45 static struct dentry		*stat_dir;
46 
47 static void __reset_stat_session(struct stat_session *session)
48 {
49 	struct stat_node *snode, *n;
50 
51 	rbtree_postorder_for_each_entry_safe(snode, n, &session->stat_root, node) {
52 		if (session->ts->stat_release)
53 			session->ts->stat_release(snode->stat);
54 		kfree(snode);
55 	}
56 
57 	session->stat_root = RB_ROOT;
58 }
59 
60 static void reset_stat_session(struct stat_session *session)
61 {
62 	mutex_lock(&session->stat_mutex);
63 	__reset_stat_session(session);
64 	mutex_unlock(&session->stat_mutex);
65 }
66 
67 static void destroy_session(struct stat_session *session)
68 {
69 	tracefs_remove(session->file);
70 	__reset_stat_session(session);
71 	mutex_destroy(&session->stat_mutex);
72 	kfree(session);
73 }
74 
75 typedef int (*cmp_stat_t)(void *, void *);
76 
77 static int insert_stat(struct rb_root *root, void *stat, cmp_stat_t cmp)
78 {
79 	struct rb_node **new = &(root->rb_node), *parent = NULL;
80 	struct stat_node *data;
81 
82 	data = kzalloc(sizeof(*data), GFP_KERNEL);
83 	if (!data)
84 		return -ENOMEM;
85 	data->stat = stat;
86 
87 	/*
88 	 * Figure out where to put new node
89 	 * This is a descendent sorting
90 	 */
91 	while (*new) {
92 		struct stat_node *this;
93 		int result;
94 
95 		this = container_of(*new, struct stat_node, node);
96 		result = cmp(data->stat, this->stat);
97 
98 		parent = *new;
99 		if (result >= 0)
100 			new = &((*new)->rb_left);
101 		else
102 			new = &((*new)->rb_right);
103 	}
104 
105 	rb_link_node(&data->node, parent, new);
106 	rb_insert_color(&data->node, root);
107 	return 0;
108 }
109 
110 /*
111  * For tracers that don't provide a stat_cmp callback.
112  * This one will force an insertion as right-most node
113  * in the rbtree.
114  */
115 static int dummy_cmp(void *p1, void *p2)
116 {
117 	return -1;
118 }
119 
120 /*
121  * Initialize the stat rbtree at each trace_stat file opening.
122  * All of these copies and sorting are required on all opening
123  * since the stats could have changed between two file sessions.
124  */
125 static int stat_seq_init(struct stat_session *session)
126 {
127 	struct tracer_stat *ts = session->ts;
128 	struct rb_root *root = &session->stat_root;
129 	void *stat;
130 	int ret = 0;
131 	int i;
132 
133 	mutex_lock(&session->stat_mutex);
134 	__reset_stat_session(session);
135 
136 	if (!ts->stat_cmp)
137 		ts->stat_cmp = dummy_cmp;
138 
139 	stat = ts->stat_start(ts);
140 	if (!stat)
141 		goto exit;
142 
143 	ret = insert_stat(root, stat, ts->stat_cmp);
144 	if (ret)
145 		goto exit;
146 
147 	/*
148 	 * Iterate over the tracer stat entries and store them in an rbtree.
149 	 */
150 	for (i = 1; ; i++) {
151 		stat = ts->stat_next(stat, i);
152 
153 		/* End of insertion */
154 		if (!stat)
155 			break;
156 
157 		ret = insert_stat(root, stat, ts->stat_cmp);
158 		if (ret)
159 			goto exit_free_rbtree;
160 	}
161 
162 exit:
163 	mutex_unlock(&session->stat_mutex);
164 	return ret;
165 
166 exit_free_rbtree:
167 	__reset_stat_session(session);
168 	mutex_unlock(&session->stat_mutex);
169 	return ret;
170 }
171 
172 
173 static void *stat_seq_start(struct seq_file *s, loff_t *pos)
174 {
175 	struct stat_session *session = s->private;
176 	struct rb_node *node;
177 	int n = *pos;
178 	int i;
179 
180 	/* Prevent from tracer switch or rbtree modification */
181 	mutex_lock(&session->stat_mutex);
182 
183 	/* If we are in the beginning of the file, print the headers */
184 	if (session->ts->stat_headers) {
185 		if (n == 0)
186 			return SEQ_START_TOKEN;
187 		n--;
188 	}
189 
190 	node = rb_first(&session->stat_root);
191 	for (i = 0; node && i < n; i++)
192 		node = rb_next(node);
193 
194 	return node;
195 }
196 
197 static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
198 {
199 	struct stat_session *session = s->private;
200 	struct rb_node *node = p;
201 
202 	(*pos)++;
203 
204 	if (p == SEQ_START_TOKEN)
205 		return rb_first(&session->stat_root);
206 
207 	return rb_next(node);
208 }
209 
210 static void stat_seq_stop(struct seq_file *s, void *p)
211 {
212 	struct stat_session *session = s->private;
213 	mutex_unlock(&session->stat_mutex);
214 }
215 
216 static int stat_seq_show(struct seq_file *s, void *v)
217 {
218 	struct stat_session *session = s->private;
219 	struct stat_node *l = container_of(v, struct stat_node, node);
220 
221 	if (v == SEQ_START_TOKEN)
222 		return session->ts->stat_headers(s);
223 
224 	return session->ts->stat_show(s, l->stat);
225 }
226 
227 static const struct seq_operations trace_stat_seq_ops = {
228 	.start		= stat_seq_start,
229 	.next		= stat_seq_next,
230 	.stop		= stat_seq_stop,
231 	.show		= stat_seq_show
232 };
233 
234 /* The session stat is refilled and resorted at each stat file opening */
235 static int tracing_stat_open(struct inode *inode, struct file *file)
236 {
237 	int ret;
238 	struct seq_file *m;
239 	struct stat_session *session = inode->i_private;
240 
241 	ret = stat_seq_init(session);
242 	if (ret)
243 		return ret;
244 
245 	ret = seq_open(file, &trace_stat_seq_ops);
246 	if (ret) {
247 		reset_stat_session(session);
248 		return ret;
249 	}
250 
251 	m = file->private_data;
252 	m->private = session;
253 	return ret;
254 }
255 
256 /*
257  * Avoid consuming memory with our now useless rbtree.
258  */
259 static int tracing_stat_release(struct inode *i, struct file *f)
260 {
261 	struct stat_session *session = i->i_private;
262 
263 	reset_stat_session(session);
264 
265 	return seq_release(i, f);
266 }
267 
268 static const struct file_operations tracing_stat_fops = {
269 	.open		= tracing_stat_open,
270 	.read		= seq_read,
271 	.llseek		= seq_lseek,
272 	.release	= tracing_stat_release
273 };
274 
275 static int tracing_stat_init(void)
276 {
277 	struct dentry *d_tracing;
278 
279 	d_tracing = tracing_init_dentry();
280 	if (IS_ERR(d_tracing))
281 		return 0;
282 
283 	stat_dir = tracefs_create_dir("trace_stat", d_tracing);
284 	if (!stat_dir)
285 		pr_warn("Could not create tracefs '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