1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/module.h>
3 #include <linux/kthread.h>
4 
5 /*
6  * Any file that uses trace points, must include the header.
7  * But only one file, must include the header by defining
8  * CREATE_TRACE_POINTS first.  This will make the C code that
9  * creates the handles for the trace points.
10  */
11 #define CREATE_TRACE_POINTS
12 #include "trace-events-sample.h"
13 
14 static const char *random_strings[] = {
15 	"Mother Goose",
16 	"Snoopy",
17 	"Gandalf",
18 	"Frodo",
19 	"One ring to rule them all"
20 };
21 
22 static void simple_thread_func(int cnt)
23 {
24 	int array[6];
25 	int len = cnt % 5;
26 	int i;
27 
28 	set_current_state(TASK_INTERRUPTIBLE);
29 	schedule_timeout(HZ);
30 
31 	for (i = 0; i < len; i++)
32 		array[i] = i + 1;
33 	array[i] = 0;
34 
35 	/* Silly tracepoints */
36 	trace_foo_bar("hello", cnt, array, random_strings[len],
37 		      current->cpus_ptr);
38 
39 	trace_foo_with_template_simple("HELLO", cnt);
40 
41 	trace_foo_bar_with_cond("Some times print", cnt);
42 
43 	trace_foo_with_template_cond("prints other times", cnt);
44 
45 	trace_foo_with_template_print("I have to be different", cnt);
46 }
47 
48 static int simple_thread(void *arg)
49 {
50 	int cnt = 0;
51 
52 	while (!kthread_should_stop())
53 		simple_thread_func(cnt++);
54 
55 	return 0;
56 }
57 
58 static struct task_struct *simple_tsk;
59 static struct task_struct *simple_tsk_fn;
60 
61 static void simple_thread_func_fn(int cnt)
62 {
63 	set_current_state(TASK_INTERRUPTIBLE);
64 	schedule_timeout(HZ);
65 
66 	/* More silly tracepoints */
67 	trace_foo_bar_with_fn("Look at me", cnt);
68 	trace_foo_with_template_fn("Look at me too", cnt);
69 }
70 
71 static int simple_thread_fn(void *arg)
72 {
73 	int cnt = 0;
74 
75 	while (!kthread_should_stop())
76 		simple_thread_func_fn(cnt++);
77 
78 	return 0;
79 }
80 
81 static DEFINE_MUTEX(thread_mutex);
82 static int simple_thread_cnt;
83 
84 int foo_bar_reg(void)
85 {
86 	mutex_lock(&thread_mutex);
87 	if (simple_thread_cnt++)
88 		goto out;
89 
90 	pr_info("Starting thread for foo_bar_fn\n");
91 	/*
92 	 * We shouldn't be able to start a trace when the module is
93 	 * unloading (there's other locks to prevent that). But
94 	 * for consistency sake, we still take the thread_mutex.
95 	 */
96 	simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
97  out:
98 	mutex_unlock(&thread_mutex);
99 	return 0;
100 }
101 
102 void foo_bar_unreg(void)
103 {
104 	mutex_lock(&thread_mutex);
105 	if (--simple_thread_cnt)
106 		goto out;
107 
108 	pr_info("Killing thread for foo_bar_fn\n");
109 	if (simple_tsk_fn)
110 		kthread_stop(simple_tsk_fn);
111 	simple_tsk_fn = NULL;
112  out:
113 	mutex_unlock(&thread_mutex);
114 }
115 
116 static int __init trace_event_init(void)
117 {
118 	simple_tsk = kthread_run(simple_thread, NULL, "event-sample");
119 	if (IS_ERR(simple_tsk))
120 		return -1;
121 
122 	return 0;
123 }
124 
125 static void __exit trace_event_exit(void)
126 {
127 	kthread_stop(simple_tsk);
128 	mutex_lock(&thread_mutex);
129 	if (simple_tsk_fn)
130 		kthread_stop(simple_tsk_fn);
131 	simple_tsk_fn = NULL;
132 	mutex_unlock(&thread_mutex);
133 }
134 
135 module_init(trace_event_init);
136 module_exit(trace_event_exit);
137 
138 MODULE_AUTHOR("Steven Rostedt");
139 MODULE_DESCRIPTION("trace-events-sample");
140 MODULE_LICENSE("GPL");
141