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