1 files changed, 251 insertions, 0 deletions
diff --git a/kernel/trace/trace_stat.c b/kernel/trace/trace_stat.c
new file mode 100644
index 00000000000..6f194a33a64
--- /dev/null
+++ b/kernel/trace/trace_stat.c
@@ -0,0 +1,251 @@
+/*
+ * Infrastructure for statistic tracing (histogram output).
+ *
+ * Copyright (C) 2008 Frederic Weisbecker <fweisbec@gmail.com>
+ *
+ * Based on the code from trace_branch.c which is
+ * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
+ *
+ */
+
+
+#include <linux/list.h>
+#include <linux/seq_file.h>
+#include <linux/debugfs.h>
+#include "trace.h"
+
+
+/* List of stat entries from a tracer */
+struct trace_stat_list {
+	struct list_head list;
+	void *stat;
+};
+
+static struct trace_stat_list stat_list;
+
+/*
+ * This is a copy of the current tracer to avoid racy
+ * and dangerous output while the current tracer is
+ * switched.
+ */
+static struct tracer current_tracer;
+
+/*
+ * Protect both the current tracer and the global
+ * stat list.
+ */
+static DEFINE_MUTEX(stat_list_mutex);
+
+
+static void reset_stat_list(void)
+{
+	struct trace_stat_list *node;
+	struct list_head *next;
+
+	if (list_empty(&stat_list.list))
+		return;
+
+	node = list_entry(stat_list.list.next, struct trace_stat_list, list);
+	next = node->list.next;
+
+	while (&node->list != next) {
+		kfree(node);
+		node = list_entry(next, struct trace_stat_list, list);
+	}
+	kfree(node);
+
+	INIT_LIST_HEAD(&stat_list.list);
+}
+
+void init_tracer_stat(struct tracer *trace)
+{
+	mutex_lock(&stat_list_mutex);
+	current_tracer = *trace;
+	mutex_unlock(&stat_list_mutex);
+}
+
+/*
+ * For tracers that don't provide a stat_cmp callback.
+ * This one will force an immediate insertion on tail of
+ * the list.
+ */
+static int dummy_cmp(void *p1, void *p2)
+{
+	return 1;
+}
+
+/*
+ * Initialize the stat list at each trace_stat file opening.
+ * All of these copies and sorting are required on all opening
+ * since the stats could have changed between two file sessions.
+ */
+static int stat_seq_init(void)
+{
+	struct trace_stat_list *iter_entry, *new_entry;
+	void *prev_stat;
+	int ret = 0;
+	int i;
+
+	mutex_lock(&stat_list_mutex);
+	reset_stat_list();
+
+	if (!current_tracer.stat_start || !current_tracer.stat_next ||
+					!current_tracer.stat_show)
+		goto exit;
+
+	if (!current_tracer.stat_cmp)
+		current_tracer.stat_cmp = dummy_cmp;
+
+	/*
+	 * The first entry. Actually this is the second, but the first
+	 * one (the stat_list head) is pointless.
+	 */
+	new_entry = kmalloc(sizeof(struct trace_stat_list), GFP_KERNEL);
+	if (!new_entry) {
+		ret = -ENOMEM;
+		goto exit;
+	}
+
+	INIT_LIST_HEAD(&new_entry->list);
+	list_add(&new_entry->list, &stat_list.list);
+	new_entry->stat = current_tracer.stat_start();
+
+	prev_stat = new_entry->stat;
+
+	/*
+	 * Iterate over the tracer stat entries and store them in a sorted
+	 * list.
+	 */
+	for (i = 1; ; i++) {
+		new_entry = kmalloc(sizeof(struct trace_stat_list), GFP_KERNEL);
+		if (!new_entry) {
+			ret = -ENOMEM;
+			goto exit_free_list;
+		}
+
+		INIT_LIST_HEAD(&new_entry->list);
+		new_entry->stat = current_tracer.stat_next(prev_stat, i);
+
+		/* End of insertion */
+		if (!new_entry->stat)
+			break;
+
+		list_for_each_entry(iter_entry, &stat_list.list, list) {
+			/* Insertion with a descendent sorting */
+			if (current_tracer.stat_cmp(new_entry->stat,
+						iter_entry->stat) > 0) {
+
+				list_add_tail(&new_entry->list,
+						&iter_entry->list);
+				break;
+
+			/* The current smaller value */
+			} else if (list_is_last(&iter_entry->list,
+						&stat_list.list)) {
+				list_add(&new_entry->list, &iter_entry->list);
+				break;
+			}
+		}
+
+		prev_stat = new_entry->stat;
+	}
+exit:
+	mutex_unlock(&stat_list_mutex);
+	return ret;
+
+exit_free_list:
+	reset_stat_list();
+	mutex_unlock(&stat_list_mutex);
+	return ret;
+}
+
+
+static void *stat_seq_start(struct seq_file *s, loff_t *pos)
+{
+	struct trace_stat_list *l = (struct trace_stat_list *)s->private;
+
+	/* Prevent from tracer switch or stat_list modification */
+	mutex_lock(&stat_list_mutex);
+
+	/* If we are in the beginning of the file, print the headers */
+	if (!*pos && current_tracer.stat_headers)
+		current_tracer.stat_headers(s);
+
+	return seq_list_start(&l->list, *pos);
+}
+
+static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
+{
+	struct trace_stat_list *l = (struct trace_stat_list *)s->private;
+
+	return seq_list_next(p, &l->list, pos);
+}
+
+static void stat_seq_stop(struct seq_file *m, void *p)
+{
+	mutex_unlock(&stat_list_mutex);
+}
+
+static int stat_seq_show(struct seq_file *s, void *v)
+{
+	struct trace_stat_list *l = list_entry(v, struct trace_stat_list, list);
+	return current_tracer.stat_show(s, l->stat);
+}
+
+static const struct seq_operations trace_stat_seq_ops = {
+	.start = stat_seq_start,
+	.next = stat_seq_next,
+	.stop = stat_seq_stop,
+	.show = stat_seq_show
+};
+
+static int tracing_stat_open(struct inode *inode, struct file *file)
+{
+	int ret;
+
+	ret = seq_open(file, &trace_stat_seq_ops);
+	if (!ret) {
+		struct seq_file *m = file->private_data;
+		m->private = &stat_list;
+		ret = stat_seq_init();
+	}
+
+	return ret;
+}
+
+
+/*
+ * Avoid consuming memory with our now useless list.
+ */
+static int tracing_stat_release(struct inode *i, struct file *f)
+{
+	mutex_lock(&stat_list_mutex);
+	reset_stat_list();
+	mutex_unlock(&stat_list_mutex);
+	return 0;
+}
+
+static const struct file_operations tracing_stat_fops = {
+	.open		= tracing_stat_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= tracing_stat_release
+};
+
+static int __init tracing_stat_init(void)
+{
+	struct dentry *d_tracing;
+	struct dentry *entry;
+
+	INIT_LIST_HEAD(&stat_list.list);
+	d_tracing = tracing_init_dentry();
+
+	entry = debugfs_create_file("trace_stat", 0444, d_tracing,
+					NULL,
+				    &tracing_stat_fops);
+	if (!entry)
+		pr_warning("Could not create debugfs "
+			   "'trace_stat' entry\n");
+	return 0;
+}
+fs_initcall(tracing_stat_init);