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/seq_file.h>
14 #include <linux/debugfs.h>
18 /* List of stat entries from a tracer */
19 struct trace_stat_list {
20 struct list_head list;
24 static LIST_HEAD(stat_list);
27 * This is a copy of the current tracer to avoid racy
28 * and dangerous output while the current tracer is
31 static struct tracer current_tracer;
34 * Protect both the current tracer and the global
37 static DEFINE_MUTEX(stat_list_mutex);
40 static void reset_stat_list(void)
42 struct trace_stat_list *node, *next;
44 list_for_each_entry_safe(node, next, &stat_list, list)
47 INIT_LIST_HEAD(&stat_list);
50 void init_tracer_stat(struct tracer *trace)
52 mutex_lock(&stat_list_mutex);
53 current_tracer = *trace;
54 mutex_unlock(&stat_list_mutex);
58 * For tracers that don't provide a stat_cmp callback.
59 * This one will force an immediate insertion on tail of
62 static int dummy_cmp(void *p1, void *p2)
68 * Initialize the stat list at each trace_stat file opening.
69 * All of these copies and sorting are required on all opening
70 * since the stats could have changed between two file sessions.
72 static int stat_seq_init(void)
74 struct trace_stat_list *iter_entry, *new_entry;
79 mutex_lock(&stat_list_mutex);
82 if (!current_tracer.stat_start || !current_tracer.stat_next ||
83 !current_tracer.stat_show)
86 if (!current_tracer.stat_cmp)
87 current_tracer.stat_cmp = dummy_cmp;
90 * The first entry. Actually this is the second, but the first
91 * one (the stat_list head) is pointless.
93 new_entry = kmalloc(sizeof(struct trace_stat_list), GFP_KERNEL);
99 INIT_LIST_HEAD(&new_entry->list);
100 list_add(&new_entry->list, &stat_list);
101 new_entry->stat = current_tracer.stat_start();
103 prev_stat = new_entry->stat;
106 * Iterate over the tracer stat entries and store them in a sorted
110 new_entry = kmalloc(sizeof(struct trace_stat_list), GFP_KERNEL);
116 INIT_LIST_HEAD(&new_entry->list);
117 new_entry->stat = current_tracer.stat_next(prev_stat, i);
119 /* End of insertion */
120 if (!new_entry->stat)
123 list_for_each_entry(iter_entry, &stat_list, list) {
124 /* Insertion with a descendent sorting */
125 if (current_tracer.stat_cmp(new_entry->stat,
126 iter_entry->stat) > 0) {
128 list_add_tail(&new_entry->list,
132 /* The current smaller value */
133 } else if (list_is_last(&iter_entry->list,
135 list_add(&new_entry->list, &iter_entry->list);
140 prev_stat = new_entry->stat;
143 mutex_unlock(&stat_list_mutex);
148 mutex_unlock(&stat_list_mutex);
153 static void *stat_seq_start(struct seq_file *s, loff_t *pos)
155 struct list_head *l = (struct list_head *)s->private;
157 /* Prevent from tracer switch or stat_list modification */
158 mutex_lock(&stat_list_mutex);
160 /* If we are in the beginning of the file, print the headers */
161 if (!*pos && current_tracer.stat_headers)
162 current_tracer.stat_headers(s);
164 return seq_list_start(l, *pos);
167 static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
169 struct list_head *l = (struct list_head *)s->private;
171 return seq_list_next(p, l, pos);
174 static void stat_seq_stop(struct seq_file *m, void *p)
176 mutex_unlock(&stat_list_mutex);
179 static int stat_seq_show(struct seq_file *s, void *v)
181 struct trace_stat_list *entry =
182 list_entry(v, struct trace_stat_list, list);
184 return current_tracer.stat_show(s, entry->stat);
187 static const struct seq_operations trace_stat_seq_ops = {
188 .start = stat_seq_start,
189 .next = stat_seq_next,
190 .stop = stat_seq_stop,
191 .show = stat_seq_show
194 static int tracing_stat_open(struct inode *inode, struct file *file)
198 ret = seq_open(file, &trace_stat_seq_ops);
200 struct seq_file *m = file->private_data;
201 m->private = &stat_list;
202 ret = stat_seq_init();
210 * Avoid consuming memory with our now useless list.
212 static int tracing_stat_release(struct inode *i, struct file *f)
214 mutex_lock(&stat_list_mutex);
216 mutex_unlock(&stat_list_mutex);
220 static const struct file_operations tracing_stat_fops = {
221 .open = tracing_stat_open,
224 .release = tracing_stat_release
227 static int __init tracing_stat_init(void)
229 struct dentry *d_tracing;
230 struct dentry *entry;
232 d_tracing = tracing_init_dentry();
234 entry = debugfs_create_file("trace_stat", 0444, d_tracing,
238 pr_warning("Could not create debugfs "
239 "'trace_stat' entry\n");
242 fs_initcall(tracing_stat_init);