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 
do_simple_thread_func(int cnt,const char * fmt,...)22 static void do_simple_thread_func(int cnt, const char *fmt, ...)
23 {
24 	unsigned long bitmask[1] = {0xdeadbeefUL};
25 	va_list va;
26 	int array[6];
27 	int len = cnt % 5;
28 	int i;
29 
30 	set_current_state(TASK_INTERRUPTIBLE);
31 	schedule_timeout(HZ);
32 
33 	for (i = 0; i < len; i++)
34 		array[i] = i + 1;
35 	array[i] = 0;
36 
37 	va_start(va, fmt);
38 
39 	/* Silly tracepoints */
40 	trace_foo_bar("hello", cnt, array, random_strings[len],
41 		      current->cpus_ptr, fmt, &va);
42 
43 	va_end(va);
44 
45 	trace_foo_with_template_simple("HELLO", cnt);
46 
47 	trace_foo_bar_with_cond("Some times print", cnt);
48 
49 	trace_foo_with_template_cond("prints other times", cnt);
50 
51 	trace_foo_with_template_print("I have to be different", cnt);
52 
53 	trace_foo_rel_loc("Hello __rel_loc", cnt, bitmask, current->cpus_ptr);
54 }
55 
simple_thread_func(int cnt)56 static void simple_thread_func(int cnt)
57 {
58 	do_simple_thread_func(cnt, "iter=%d", cnt);
59 }
60 
simple_thread(void * arg)61 static int simple_thread(void *arg)
62 {
63 	int cnt = 0;
64 
65 	while (!kthread_should_stop())
66 		simple_thread_func(cnt++);
67 
68 	return 0;
69 }
70 
71 static struct task_struct *simple_tsk;
72 static struct task_struct *simple_tsk_fn;
73 
simple_thread_func_fn(int cnt)74 static void simple_thread_func_fn(int cnt)
75 {
76 	set_current_state(TASK_INTERRUPTIBLE);
77 	schedule_timeout(HZ);
78 
79 	/* More silly tracepoints */
80 	trace_foo_bar_with_fn("Look at me", cnt);
81 	trace_foo_with_template_fn("Look at me too", cnt);
82 }
83 
simple_thread_fn(void * arg)84 static int simple_thread_fn(void *arg)
85 {
86 	int cnt = 0;
87 
88 	while (!kthread_should_stop())
89 		simple_thread_func_fn(cnt++);
90 
91 	return 0;
92 }
93 
94 static DEFINE_MUTEX(thread_mutex);
95 static int simple_thread_cnt;
96 
foo_bar_reg(void)97 int foo_bar_reg(void)
98 {
99 	mutex_lock(&thread_mutex);
100 	if (simple_thread_cnt++)
101 		goto out;
102 
103 	pr_info("Starting thread for foo_bar_fn\n");
104 	/*
105 	 * We shouldn't be able to start a trace when the module is
106 	 * unloading (there's other locks to prevent that). But
107 	 * for consistency sake, we still take the thread_mutex.
108 	 */
109 	simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
110  out:
111 	mutex_unlock(&thread_mutex);
112 	return 0;
113 }
114 
foo_bar_unreg(void)115 void foo_bar_unreg(void)
116 {
117 	mutex_lock(&thread_mutex);
118 	if (--simple_thread_cnt)
119 		goto out;
120 
121 	pr_info("Killing thread for foo_bar_fn\n");
122 	if (simple_tsk_fn)
123 		kthread_stop(simple_tsk_fn);
124 	simple_tsk_fn = NULL;
125  out:
126 	mutex_unlock(&thread_mutex);
127 }
128 
trace_event_init(void)129 static int __init trace_event_init(void)
130 {
131 	simple_tsk = kthread_run(simple_thread, NULL, "event-sample");
132 	if (IS_ERR(simple_tsk))
133 		return -1;
134 
135 	return 0;
136 }
137 
trace_event_exit(void)138 static void __exit trace_event_exit(void)
139 {
140 	kthread_stop(simple_tsk);
141 	mutex_lock(&thread_mutex);
142 	if (simple_tsk_fn)
143 		kthread_stop(simple_tsk_fn);
144 	simple_tsk_fn = NULL;
145 	mutex_unlock(&thread_mutex);
146 }
147 
148 module_init(trace_event_init);
149 module_exit(trace_event_exit);
150 
151 MODULE_AUTHOR("Steven Rostedt");
152 MODULE_DESCRIPTION("trace-events-sample");
153 MODULE_LICENSE("GPL");
154