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1// SPDX-License-Identifier: GPL-2.02// Copyright (C) 2018 Joe Lawrence <joe.lawrence@redhat.com>3 4#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt5 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 a29 * blocked transition and clears the flag.30 */31 msleep(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);41 42 /*43 * To synchronize kernel messages, hold the init function from44 * 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 work51 * function before returning from init().52 */53 flush_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);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