1 #include <linux/module.h>
2 #include <linux/kthread.h>
3 
4 /*
5  * Any file that uses trace points, must include the header.
6  * But only one file, must include the header by defining
7  * CREATE_TRACE_POINTS first.  This will make the C code that
8  * creates the handles for the trace points.
9  */
10 #define CREATE_TRACE_POINTS
11 #include "trace-events-sample.h"
12 
13 static const char *random_strings[] = {
14 	"Mother Goose",
15 	"Snoopy",
16 	"Gandalf",
17 	"Frodo",
18 	"One ring to rule them all"
19 };
20 
21 static void simple_thread_func(int cnt)
22 {
23 	int array[6];
24 	int len = cnt % 5;
25 	int i;
26 
27 	set_current_state(TASK_INTERRUPTIBLE);
28 	schedule_timeout(HZ);
29 
30 	for (i = 0; i < len; i++)
31 		array[i] = i + 1;
32 	array[i] = 0;
33 
34 	/* Silly tracepoints */
35 	trace_foo_bar("hello", cnt, array, random_strings[len],
36 		      &current->cpus_allowed);
37 
38 	trace_foo_with_template_simple("HELLO", cnt);
39 
40 	trace_foo_bar_with_cond("Some times print", cnt);
41 
42 	trace_foo_with_template_cond("prints other times", cnt);
43 
44 	trace_foo_with_template_print("I have to be different", cnt);
45 }
46 
47 static int simple_thread(void *arg)
48 {
49 	int cnt = 0;
50 
51 	while (!kthread_should_stop())
52 		simple_thread_func(cnt++);
53 
54 	return 0;
55 }
56 
57 static struct task_struct *simple_tsk;
58 static struct task_struct *simple_tsk_fn;
59 
60 static void simple_thread_func_fn(int cnt)
61 {
62 	set_current_state(TASK_INTERRUPTIBLE);
63 	schedule_timeout(HZ);
64 
65 	/* More silly tracepoints */
66 	trace_foo_bar_with_fn("Look at me", cnt);
67 	trace_foo_with_template_fn("Look at me too", cnt);
68 }
69 
70 static int simple_thread_fn(void *arg)
71 {
72 	int cnt = 0;
73 
74 	while (!kthread_should_stop())
75 		simple_thread_func_fn(cnt++);
76 
77 	return 0;
78 }
79 
80 static DEFINE_MUTEX(thread_mutex);
81 static int simple_thread_cnt;
82 
83 int foo_bar_reg(void)
84 {
85 	mutex_lock(&thread_mutex);
86 	if (simple_thread_cnt++)
87 		goto out;
88 
89 	pr_info("Starting thread for foo_bar_fn\n");
90 	/*
91 	 * We shouldn't be able to start a trace when the module is
92 	 * unloading (there's other locks to prevent that). But
93 	 * for consistency sake, we still take the thread_mutex.
94 	 */
95 	simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
96  out:
97 	mutex_unlock(&thread_mutex);
98 	return 0;
99 }
100 
101 void foo_bar_unreg(void)
102 {
103 	mutex_lock(&thread_mutex);
104 	if (--simple_thread_cnt)
105 		goto out;
106 
107 	pr_info("Killing thread for foo_bar_fn\n");
108 	if (simple_tsk_fn)
109 		kthread_stop(simple_tsk_fn);
110 	simple_tsk_fn = NULL;
111  out:
112 	mutex_unlock(&thread_mutex);
113 }
114 
115 static int __init trace_event_init(void)
116 {
117 	simple_tsk = kthread_run(simple_thread, NULL, "event-sample");
118 	if (IS_ERR(simple_tsk))
119 		return -1;
120 
121 	return 0;
122 }
123 
124 static void __exit trace_event_exit(void)
125 {
126 	kthread_stop(simple_tsk);
127 	mutex_lock(&thread_mutex);
128 	if (simple_tsk_fn)
129 		kthread_stop(simple_tsk_fn);
130 	simple_tsk_fn = NULL;
131 	mutex_unlock(&thread_mutex);
132 }
133 
134 module_init(trace_event_init);
135 module_exit(trace_event_exit);
136 
137 MODULE_AUTHOR("Steven Rostedt");
138 MODULE_DESCRIPTION("trace-events-sample");
139 MODULE_LICENSE("GPL");
140