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// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2018 Joe Lawrence <joe.lawrence@redhat.com>
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/workqueue.h>
#include <linux/delay.h>
/* load/run-time control from sysfs writer */
static bool block_transition;
module_param(block_transition, bool, 0644);
MODULE_PARM_DESC(block_transition, "block_transition (default=false)");
static void busymod_work_func(struct work_struct *work);
static DECLARE_WORK(work, busymod_work_func);
static DECLARE_COMPLETION(busymod_work_started);
static void busymod_work_func(struct work_struct *work)
{
pr_info("%s enter\n", __func__);
complete(&busymod_work_started);
while (READ_ONCE(block_transition)) {
/*
* Busy-wait until the sysfs writer has acknowledged a
* blocked transition and clears the flag.
*/
msleep(20);
}
pr_info("%s exit\n", __func__);
}
static int test_klp_callbacks_busy_init(void)
{
pr_info("%s\n", __func__);
schedule_work(&work);
/*
* To synchronize kernel messages, hold the init function from
* exiting until the work function's entry message has printed.
*/
wait_for_completion(&busymod_work_started);
if (!block_transition) {
/*
* Serialize output: print all messages from the work
* function before returning from init().
*/
flush_work(&work);
}
return 0;
}
static void test_klp_callbacks_busy_exit(void)
{
WRITE_ONCE(block_transition, false);
flush_work(&work);
pr_info("%s\n", __func__);
}
module_init(test_klp_callbacks_busy_init);
module_exit(test_klp_callbacks_busy_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Joe Lawrence <joe.lawrence@redhat.com>");
MODULE_DESCRIPTION("Livepatch test: busy target module");
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