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 */
26struct stat_node {
27 struct rb_node node;
28 void *stat;
29};
30
31/* A stat session is the stats output in one file */
32struct 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 */
41static LIST_HEAD(all_stat_sessions);
42static DEFINE_MUTEX(all_stat_sessions_mutex);
43
44/* The root directory for all stat files */
45static struct dentry *stat_dir;
46
47static 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
60static 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
67static 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
75typedef int (*cmp_stat_t)(void *, void *);
76
77static 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 */
115static 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 */
125static 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
162exit:
163 mutex_unlock(&session->stat_mutex);
164 return ret;
165
166exit_free_rbtree:
167 __reset_stat_session(session);
168 mutex_unlock(&session->stat_mutex);
169 return ret;
170}
171
172
173static 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
197static 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
210static 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
216static 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
227static 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 */
235static 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 */
259static 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
268static 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
275static 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
289static 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
302int 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
346void 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