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);
19
20static 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
35static 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
51static 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
58module_init(test_klp_callbacks_busy_init);
59module_exit(test_klp_callbacks_busy_exit);
60MODULE_LICENSE("GPL");
61MODULE_AUTHOR("Joe Lawrence <joe.lawrence@redhat.com>");
62MODULE_DESCRIPTION("Livepatch test: busy target module");