drivers/md/dm-vdo/thread-registry.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright 2023 Red Hat
   4  */
   5
   6 #include "thread-registry.h"
   7
   8 #include <linux/rculist.h>
   9
  10 #include "permassert.h"
  11
  12 /*
  13  * We need to be careful when using other facilities that may use thread registry functions in
  14  * their normal operation. For example, we do not want to invoke the logger while holding a lock.
  15  */
  16
  17 void vdo_initialize_thread_registry(struct thread_registry *registry)
  18 {
  19         INIT_LIST_HEAD(&registry->links);
  20         spin_lock_init(&registry->lock);
  21 }
  22
  23 /* Register the current thread and associate it with a data pointer. */
  24 void vdo_register_thread(struct thread_registry *registry,
  25                          struct registered_thread *new_thread, const void *pointer)
  26 {
  27         struct registered_thread *thread;
  28         bool found_it = false;
  29
  30         INIT_LIST_HEAD(&new_thread->links);
  31         new_thread->pointer = pointer;
  32         new_thread->task = current;
  33
  34         spin_lock(&registry->lock);
  35         list_for_each_entry(thread, &registry->links, links) {
  36                 if (thread->task == current) {
  37                         /* There should be no existing entry. */
  38                         list_del_rcu(&thread->links);
  39                         found_it = true;
  40                         break;
  41                 }
  42         }
  43         list_add_tail_rcu(&new_thread->links, &registry->links);
  44         spin_unlock(&registry->lock);
  45
  46         ASSERT_LOG_ONLY(!found_it, "new thread not already in registry");
  47         if (found_it) {
  48                 /* Ensure no RCU iterators see it before re-initializing. */
  49                 synchronize_rcu();
  50                 INIT_LIST_HEAD(&thread->links);
  51         }
  52 }
  53
  54 void vdo_unregister_thread(struct thread_registry *registry)
  55 {
  56         struct registered_thread *thread;
  57         bool found_it = false;
  58
  59         spin_lock(&registry->lock);
  60         list_for_each_entry(thread, &registry->links, links) {
  61                 if (thread->task == current) {
  62                         list_del_rcu(&thread->links);
  63                         found_it = true;
  64                         break;
  65                 }
  66         }
  67         spin_unlock(&registry->lock);
  68
  69         ASSERT_LOG_ONLY(found_it, "thread found in registry");
  70         if (found_it) {
  71                 /* Ensure no RCU iterators see it before re-initializing. */
  72                 synchronize_rcu();
  73                 INIT_LIST_HEAD(&thread->links);
  74         }
  75 }
  76
  77 const void *vdo_lookup_thread(struct thread_registry *registry)
  78 {
  79         struct registered_thread *thread;
  80         const void *result = NULL;
  81
  82         rcu_read_lock();
  83         list_for_each_entry_rcu(thread, &registry->links, links) {
  84                 if (thread->task == current) {
  85                         result = thread->pointer;
  86                         break;
  87                 }
  88         }
  89         rcu_read_unlock();
  90
  91         return result;
  92 }