// 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");