1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun // Copyright (C) 2018 Joe Lawrence <joe.lawrence@redhat.com>
3*4882a593Smuzhiyun
4*4882a593Smuzhiyun #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
5*4882a593Smuzhiyun
6*4882a593Smuzhiyun #include <linux/module.h>
7*4882a593Smuzhiyun #include <linux/kernel.h>
8*4882a593Smuzhiyun #include <linux/sched.h>
9*4882a593Smuzhiyun #include <linux/workqueue.h>
10*4882a593Smuzhiyun #include <linux/delay.h>
11*4882a593Smuzhiyun
12*4882a593Smuzhiyun /* load/run-time control from sysfs writer */
13*4882a593Smuzhiyun static bool block_transition;
14*4882a593Smuzhiyun module_param(block_transition, bool, 0644);
15*4882a593Smuzhiyun MODULE_PARM_DESC(block_transition, "block_transition (default=false)");
16*4882a593Smuzhiyun
17*4882a593Smuzhiyun static void busymod_work_func(struct work_struct *work);
18*4882a593Smuzhiyun static DECLARE_WORK(work, busymod_work_func);
19*4882a593Smuzhiyun static DECLARE_COMPLETION(busymod_work_started);
20*4882a593Smuzhiyun
busymod_work_func(struct work_struct * work)21*4882a593Smuzhiyun static void busymod_work_func(struct work_struct *work)
22*4882a593Smuzhiyun {
23*4882a593Smuzhiyun pr_info("%s enter\n", __func__);
24*4882a593Smuzhiyun complete(&busymod_work_started);
25*4882a593Smuzhiyun
26*4882a593Smuzhiyun while (READ_ONCE(block_transition)) {
27*4882a593Smuzhiyun /*
28*4882a593Smuzhiyun * Busy-wait until the sysfs writer has acknowledged a
29*4882a593Smuzhiyun * blocked transition and clears the flag.
30*4882a593Smuzhiyun */
31*4882a593Smuzhiyun msleep(20);
32*4882a593Smuzhiyun }
33*4882a593Smuzhiyun
34*4882a593Smuzhiyun pr_info("%s exit\n", __func__);
35*4882a593Smuzhiyun }
36*4882a593Smuzhiyun
test_klp_callbacks_busy_init(void)37*4882a593Smuzhiyun static int test_klp_callbacks_busy_init(void)
38*4882a593Smuzhiyun {
39*4882a593Smuzhiyun pr_info("%s\n", __func__);
40*4882a593Smuzhiyun schedule_work(&work);
41*4882a593Smuzhiyun
42*4882a593Smuzhiyun /*
43*4882a593Smuzhiyun * To synchronize kernel messages, hold the init function from
44*4882a593Smuzhiyun * exiting until the work function's entry message has printed.
45*4882a593Smuzhiyun */
46*4882a593Smuzhiyun wait_for_completion(&busymod_work_started);
47*4882a593Smuzhiyun
48*4882a593Smuzhiyun if (!block_transition) {
49*4882a593Smuzhiyun /*
50*4882a593Smuzhiyun * Serialize output: print all messages from the work
51*4882a593Smuzhiyun * function before returning from init().
52*4882a593Smuzhiyun */
53*4882a593Smuzhiyun flush_work(&work);
54*4882a593Smuzhiyun }
55*4882a593Smuzhiyun
56*4882a593Smuzhiyun return 0;
57*4882a593Smuzhiyun }
58*4882a593Smuzhiyun
test_klp_callbacks_busy_exit(void)59*4882a593Smuzhiyun static void test_klp_callbacks_busy_exit(void)
60*4882a593Smuzhiyun {
61*4882a593Smuzhiyun WRITE_ONCE(block_transition, false);
62*4882a593Smuzhiyun flush_work(&work);
63*4882a593Smuzhiyun pr_info("%s\n", __func__);
64*4882a593Smuzhiyun }
65*4882a593Smuzhiyun
66*4882a593Smuzhiyun module_init(test_klp_callbacks_busy_init);
67*4882a593Smuzhiyun module_exit(test_klp_callbacks_busy_exit);
68*4882a593Smuzhiyun MODULE_LICENSE("GPL");
69*4882a593Smuzhiyun MODULE_AUTHOR("Joe Lawrence <joe.lawrence@redhat.com>");
70*4882a593Smuzhiyun MODULE_DESCRIPTION("Livepatch test: busy target module");
71