lib/livepatch/test_klp_callbacks_busy.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (C) 2018 Joe Lawrence <joe.lawrence@redhat.com>
   3
   4 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   5
   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  */
  13 static bool block_transition;
  14 module_param(block_transition, bool, 0644);
  15 MODULE_PARM_DESC(block_transition, "block_transition (default=false)");
  16
  17 static void busymod_work_func(struct work_struct *work);
  18 static DECLARE_WORK(work, busymod_work_func);
  19
  20 static void busymod_work_func(struct work_struct *work)
  21 {
  22         pr_info("%s enter\n", __func__);
  23
  24         while (READ_ONCE(block_transition)) {
  25                 /*
  26                  * Busy-wait until the sysfs writer has acknowledged a
  27                  * blocked transition and clears the flag.
  28                  */
  29                 msleep(20);
  30         }
  31
  32         pr_info("%s exit\n", __func__);
  33 }
  34
  35 static int test_klp_callbacks_busy_init(void)
  36 {
  37         pr_info("%s\n", __func__);
  38         schedule_work(&work);
  39
  40         if (!block_transition) {
  41                 /*
  42                  * Serialize output: print all messages from the work
  43                  * function before returning from init().
  44                  */
  45                 flush_work(&work);
  46         }
  47
  48         return 0;
  49 }
  50
  51 static void test_klp_callbacks_busy_exit(void)
  52 {
  53         WRITE_ONCE(block_transition, false);
  54         flush_work(&work);
  55         pr_info("%s\n", __func__);
  56 }
  57
  58 module_init(test_klp_callbacks_busy_init);
  59 module_exit(test_klp_callbacks_busy_exit);
  60 MODULE_LICENSE("GPL");
  61 MODULE_AUTHOR("Joe Lawrence <joe.lawrence@redhat.com>");
  62 MODULE_DESCRIPTION("Livepatch test: busy target module");