aboutsummaryrefslogtreecommitdiff
path: root/samples/ftrace/sample-trace-array.c
blob: 6aba02a31c96c52d24804aad834b9a169c8c318f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
// SPDX-License-Identifier: GPL-2.0-only
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/trace.h>
#include <linux/trace_events.h>
#include <linux/timer.h>
#include <linux/err.h>
#include <linux/jiffies.h>
#include <linux/workqueue.h>

/*
 * Any file that uses trace points, must include the header.
 * But only one file, must include the header by defining
 * CREATE_TRACE_POINTS first.  This will make the C code that
 * creates the handles for the trace points.
 */
#define CREATE_TRACE_POINTS
#include "sample-trace-array.h"

struct trace_array *tr;
static void mytimer_handler(struct timer_list *unused);
static struct task_struct *simple_tsk;

static void trace_work_fn(struct work_struct *work)
{
	/*
	 * Disable tracing for event "sample_event".
	 */
	trace_array_set_clr_event(tr, "sample-subsystem", "sample_event",
			false);
}
static DECLARE_WORK(trace_work, trace_work_fn);

/*
 * mytimer: Timer setup to disable tracing for event "sample_event". This
 * timer is only for the purposes of the sample module to demonstrate access of
 * Ftrace instances from within kernel.
 */
static DEFINE_TIMER(mytimer, mytimer_handler);

static void mytimer_handler(struct timer_list *unused)
{
	schedule_work(&trace_work);
}

static void simple_thread_func(int count)
{
	set_current_state(TASK_INTERRUPTIBLE);
	schedule_timeout(HZ);

	/*
	 * Printing count value using trace_array_printk() - trace_printk()
	 * equivalent for the instance buffers.
	 */
	trace_array_printk(tr, _THIS_IP_, "trace_array_printk: count=%d\n",
			count);
	/*
	 * Tracepoint for event "sample_event". This will print the
	 * current value of count and current jiffies.
	 */
	trace_sample_event(count, jiffies);
}

static int simple_thread(void *arg)
{
	int count = 0;
	unsigned long delay = msecs_to_jiffies(5000);

	/*
	 * Enable tracing for "sample_event".
	 */
	trace_array_set_clr_event(tr, "sample-subsystem", "sample_event", true);

	/*
	 * Adding timer - mytimer. This timer will disable tracing after
	 * delay seconds.
	 *
	 */
	add_timer(&mytimer);
	mod_timer(&mytimer, jiffies+delay);

	while (!kthread_should_stop())
		simple_thread_func(count++);

	del_timer(&mytimer);
	cancel_work_sync(&trace_work);

	/*
	 * trace_array_put() decrements the reference counter associated with
	 * the trace array - "tr". We are done using the trace array, hence
	 * decrement the reference counter so that it can be destroyed using
	 * trace_array_destroy().
	 */
	trace_array_put(tr);

	return 0;
}

static int __init sample_trace_array_init(void)
{
	/*
	 * Return a pointer to the trace array with name "sample-instance" if it
	 * exists, else create a new trace array.
	 *
	 * NOTE: This function increments the reference counter
	 * associated with the trace array - "tr".
	 */
	tr = trace_array_get_by_name("sample-instance");

	if (!tr)
		return -1;
	/*
	 * If context specific per-cpu buffers havent already been allocated.
	 */
	trace_printk_init_buffers();

	simple_tsk = kthread_run(simple_thread, NULL, "sample-instance");
	if (IS_ERR(simple_tsk)) {
		trace_array_put(tr);
		trace_array_destroy(tr);
		return -1;
	}

	return 0;
}

static void __exit sample_trace_array_exit(void)
{
	kthread_stop(simple_tsk);

	/*
	 * We are unloading our module and no longer require the trace array.
	 * Remove/destroy "tr" using trace_array_destroy()
	 */
	trace_array_destroy(tr);
}

module_init(sample_trace_array_init);
module_exit(sample_trace_array_exit);

MODULE_AUTHOR("Divya Indi");
MODULE_DESCRIPTION("Sample module for kernel access to Ftrace instances");
MODULE_LICENSE("GPL");