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 */
13static bool block_transition;
14module_param(block_transition, bool, 0644);
15MODULE_PARM_DESC(block_transition, "block_transition (default=false)");
16
17static void busymod_work_func(struct work_struct *work);
18static DECLARE_WORK(work, busymod_work_func);
19static DECLARE_COMPLETION(busymod_work_started);
20
21static void busymod_work_func(struct work_struct *work)
22{
23 pr_info("%s enter\n", __func__);
24 complete(&busymod_work_started);
25
26 while (READ_ONCE(block_transition)) {
27 /*
28 * Busy-wait until the sysfs writer has acknowledged a
29 * blocked transition and clears the flag.
30 */
31 msleep(msecs: 20);
32 }
33
34 pr_info("%s exit\n", __func__);
35}
36
37static int test_klp_callbacks_busy_init(void)
38{
39 pr_info("%s\n", __func__);
40 schedule_work(work: &work);
41
42 /*
43 * To synchronize kernel messages, hold the init function from
44 * exiting until the work function's entry message has printed.
45 */
46 wait_for_completion(&busymod_work_started);
47
48 if (!block_transition) {
49 /*
50 * Serialize output: print all messages from the work
51 * function before returning from init().
52 */
53 flush_work(work: &work);
54 }
55
56 return 0;
57}
58
59static void test_klp_callbacks_busy_exit(void)
60{
61 WRITE_ONCE(block_transition, false);
62 flush_work(work: &work);
63 pr_info("%s\n", __func__);
64}
65
66module_init(test_klp_callbacks_busy_init);
67module_exit(test_klp_callbacks_busy_exit);
68MODULE_LICENSE("GPL");
69MODULE_AUTHOR("Joe Lawrence <joe.lawrence@redhat.com>");
70MODULE_DESCRIPTION("Livepatch test: busy target module");
71

source code of linux/lib/livepatch/test_klp_callbacks_busy.c