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 
82 int foo_bar_reg(void)
83 {
84 	pr_info("Starting thread for foo_bar_fn\n");
85 	/*
86 	 * We shouldn't be able to start a trace when the module is
87 	 * unloading (there's other locks to prevent that). But
88 	 * for consistency sake, we still take the thread_mutex.
89 	 */
90 	mutex_lock(&thread_mutex);
91 	simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
92 	mutex_unlock(&thread_mutex);
93 	return 0;
94 }
95 
96 void foo_bar_unreg(void)
97 {
98 	pr_info("Killing thread for foo_bar_fn\n");
99 	/* protect against module unloading */
100 	mutex_lock(&thread_mutex);
101 	if (simple_tsk_fn)
102 		kthread_stop(simple_tsk_fn);
103 	simple_tsk_fn = NULL;
104 	mutex_unlock(&thread_mutex);
105 }
106 
107 static int __init trace_event_init(void)
108 {
109 	simple_tsk = kthread_run(simple_thread, NULL, "event-sample");
110 	if (IS_ERR(simple_tsk))
111 		return -1;
112 
113 	return 0;
114 }
115 
116 static void __exit trace_event_exit(void)
117 {
118 	kthread_stop(simple_tsk);
119 	mutex_lock(&thread_mutex);
120 	if (simple_tsk_fn)
121 		kthread_stop(simple_tsk_fn);
122 	simple_tsk_fn = NULL;
123 	mutex_unlock(&thread_mutex);
124 }
125 
126 module_init(trace_event_init);
127 module_exit(trace_event_exit);
128 
129 MODULE_AUTHOR("Steven Rostedt");
130 MODULE_DESCRIPTION("trace-events-sample");
131 MODULE_LICENSE("GPL");
132