1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (C) 2018 Joe Lawrence <joe.lawrence@redhat.com>
3 
4 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
5 
6 #include <linux/module.h>
7 #include <linux/kernel.h>
8 #include <linux/sched.h>
9 #include <linux/workqueue.h>
10 #include <linux/delay.h>
11 
12 /* load/run-time control from sysfs writer  */
13 static bool block_transition;
14 module_param(block_transition, bool, 0644);
15 MODULE_PARM_DESC(block_transition, "block_transition (default=false)");
16 
17 static void busymod_work_func(struct work_struct *work);
18 static DECLARE_WORK(work, busymod_work_func);
19 
20 static void busymod_work_func(struct work_struct *work)
21 {
22 	pr_info("%s enter\n", __func__);
23 
24 	while (READ_ONCE(block_transition)) {
25 		/*
26 		 * Busy-wait until the sysfs writer has acknowledged a
27 		 * blocked transition and clears the flag.
28 		 */
29 		msleep(20);
30 	}
31 
32 	pr_info("%s exit\n", __func__);
33 }
34 
35 static int test_klp_callbacks_busy_init(void)
36 {
37 	pr_info("%s\n", __func__);
38 	schedule_work(&work);
39 
40 	if (!block_transition) {
41 		/*
42 		 * Serialize output: print all messages from the work
43 		 * function before returning from init().
44 		 */
45 		flush_work(&work);
46 	}
47 
48 	return 0;
49 }
50 
51 static void test_klp_callbacks_busy_exit(void)
52 {
53 	WRITE_ONCE(block_transition, false);
54 	flush_work(&work);
55 	pr_info("%s\n", __func__);
56 }
57 
58 module_init(test_klp_callbacks_busy_init);
59 module_exit(test_klp_callbacks_busy_exit);
60 MODULE_LICENSE("GPL");
61 MODULE_AUTHOR("Joe Lawrence <joe.lawrence@redhat.com>");
62 MODULE_DESCRIPTION("Livepatch test: busy target module");
63