2 * Infrastructure for statistic tracing (histogram output).
4 * Copyright (C) 2008 Frederic Weisbecker <fweisbec@gmail.com>
6 * Based on the code from trace_branch.c which is
7 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
12 #include <linux/list.h>
13 #include <linux/debugfs.h>
14 #include "trace_stat.h"
18 /* List of stat entries from a tracer */
19 struct trace_stat_list {
20 struct list_head list;
24 /* A stat session is the stats output in one file */
25 struct tracer_stat_session {
26 struct list_head session_list;
27 struct tracer_stat *ts;
28 struct list_head stat_list;
29 struct mutex stat_mutex;
33 /* All of the sessions currently in use. Each stat file embeed one session */
34 static LIST_HEAD(all_stat_sessions);
35 static DEFINE_MUTEX(all_stat_sessions_mutex);
37 /* The root directory for all stat files */
38 static struct dentry *stat_dir;
41 static void reset_stat_session(struct tracer_stat_session *session)
43 struct trace_stat_list *node, *next;
45 list_for_each_entry_safe(node, next, &session->stat_list, list)
48 INIT_LIST_HEAD(&session->stat_list);
51 static void destroy_session(struct tracer_stat_session *session)
53 debugfs_remove(session->file);
54 reset_stat_session(session);
55 mutex_destroy(&session->stat_mutex);
60 static int init_stat_file(struct tracer_stat_session *session);
62 int register_stat_tracer(struct tracer_stat *trace)
64 struct tracer_stat_session *session, *node, *tmp;
70 if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
73 /* Already registered? */
74 mutex_lock(&all_stat_sessions_mutex);
75 list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
76 if (node->ts == trace)
79 mutex_unlock(&all_stat_sessions_mutex);
81 /* Init the session */
82 session = kmalloc(sizeof(struct tracer_stat_session), GFP_KERNEL);
87 INIT_LIST_HEAD(&session->session_list);
88 INIT_LIST_HEAD(&session->stat_list);
89 mutex_init(&session->stat_mutex);
92 ret = init_stat_file(session);
94 destroy_session(session);
99 mutex_lock(&all_stat_sessions_mutex);
100 list_add_tail(&session->session_list, &all_stat_sessions);
101 mutex_unlock(&all_stat_sessions_mutex);
106 void unregister_stat_tracer(struct tracer_stat *trace)
108 struct tracer_stat_session *node, *tmp;
110 mutex_lock(&all_stat_sessions_mutex);
111 list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
112 if (node->ts == trace) {
113 list_del(&node->session_list);
114 destroy_session(node);
118 mutex_unlock(&all_stat_sessions_mutex);
123 * For tracers that don't provide a stat_cmp callback.
124 * This one will force an immediate insertion on tail of
127 static int dummy_cmp(void *p1, void *p2)
133 * Initialize the stat list at each trace_stat file opening.
134 * All of these copies and sorting are required on all opening
135 * since the stats could have changed between two file sessions.
137 static int stat_seq_init(struct tracer_stat_session *session)
139 struct trace_stat_list *iter_entry, *new_entry;
140 struct tracer_stat *ts = session->ts;
145 mutex_lock(&session->stat_mutex);
146 reset_stat_session(session);
149 ts->stat_cmp = dummy_cmp;
152 * The first entry. Actually this is the second, but the first
153 * one (the stat_list head) is pointless.
155 new_entry = kmalloc(sizeof(struct trace_stat_list), GFP_KERNEL);
161 INIT_LIST_HEAD(&new_entry->list);
163 list_add(&new_entry->list, &session->stat_list);
165 new_entry->stat = ts->stat_start();
166 prev_stat = new_entry->stat;
169 * Iterate over the tracer stat entries and store them in a sorted
173 new_entry = kmalloc(sizeof(struct trace_stat_list), GFP_KERNEL);
179 INIT_LIST_HEAD(&new_entry->list);
180 new_entry->stat = ts->stat_next(prev_stat, i);
182 /* End of insertion */
183 if (!new_entry->stat)
186 list_for_each_entry(iter_entry, &session->stat_list, list) {
188 /* Insertion with a descendent sorting */
189 if (ts->stat_cmp(new_entry->stat,
190 iter_entry->stat) > 0) {
192 list_add_tail(&new_entry->list,
196 /* The current smaller value */
197 } else if (list_is_last(&iter_entry->list,
198 &session->stat_list)) {
199 list_add(&new_entry->list, &iter_entry->list);
204 prev_stat = new_entry->stat;
207 mutex_unlock(&session->stat_mutex);
211 reset_stat_session(session);
212 mutex_unlock(&session->stat_mutex);
217 static void *stat_seq_start(struct seq_file *s, loff_t *pos)
219 struct tracer_stat_session *session = s->private;
221 /* Prevent from tracer switch or stat_list modification */
222 mutex_lock(&session->stat_mutex);
224 /* If we are in the beginning of the file, print the headers */
225 if (!*pos && session->ts->stat_headers)
226 session->ts->stat_headers(s);
228 return seq_list_start(&session->stat_list, *pos);
231 static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
233 struct tracer_stat_session *session = s->private;
235 return seq_list_next(p, &session->stat_list, pos);
238 static void stat_seq_stop(struct seq_file *s, void *p)
240 struct tracer_stat_session *session = s->private;
241 mutex_unlock(&session->stat_mutex);
244 static int stat_seq_show(struct seq_file *s, void *v)
246 struct tracer_stat_session *session = s->private;
247 struct trace_stat_list *l = list_entry(v, struct trace_stat_list, list);
249 return session->ts->stat_show(s, l->stat);
252 static const struct seq_operations trace_stat_seq_ops = {
253 .start = stat_seq_start,
254 .next = stat_seq_next,
255 .stop = stat_seq_stop,
256 .show = stat_seq_show
259 /* The session stat is refilled and resorted at each stat file opening */
260 static int tracing_stat_open(struct inode *inode, struct file *file)
264 struct tracer_stat_session *session = inode->i_private;
266 ret = seq_open(file, &trace_stat_seq_ops);
268 struct seq_file *m = file->private_data;
269 m->private = session;
270 ret = stat_seq_init(session);
278 * Avoid consuming memory with our now useless list.
280 static int tracing_stat_release(struct inode *i, struct file *f)
282 struct tracer_stat_session *session = i->i_private;
284 mutex_lock(&session->stat_mutex);
285 reset_stat_session(session);
286 mutex_unlock(&session->stat_mutex);
291 static const struct file_operations tracing_stat_fops = {
292 .open = tracing_stat_open,
295 .release = tracing_stat_release
298 static int tracing_stat_init(void)
300 struct dentry *d_tracing;
302 d_tracing = tracing_init_dentry();
304 stat_dir = debugfs_create_dir("trace_stat", d_tracing);
306 pr_warning("Could not create debugfs "
307 "'trace_stat' entry\n");
311 static int init_stat_file(struct tracer_stat_session *session)
313 if (!stat_dir && tracing_stat_init())
316 session->file = debugfs_create_file(session->ts->name, 0644,
318 session, &tracing_stat_fops);