lib/list_debug.c

   1 /*
   2  * Copyright 2006, Red Hat, Inc., Dave Jones
   3  * Released under the General Public License (GPL).
   4  *
   5  * This file contains the linked list implementations for
   6  * DEBUG_LIST.
   7  */
   8
   9 #include <linux/export.h>
  10 #include <linux/list.h>
  11 #include <linux/bug.h>
  12 #include <linux/kernel.h>
  13 #include <linux/rculist.h>
  14
  15 static struct list_head force_poison;
  16 void list_force_poison(struct list_head *entry)
  17 {
  18         entry->next = &force_poison;
  19         entry->prev = &force_poison;
  20 }
  21
  22 /*
  23  * Insert a new entry between two known consecutive entries.
  24  *
  25  * This is only for internal list manipulation where we know
  26  * the prev/next entries already!
  27  */
  28
  29 void __list_add(struct list_head *new,
  30                               struct list_head *prev,
  31                               struct list_head *next)
  32 {
  33         WARN(new->next == &force_poison || new->prev == &force_poison,
  34                 "list_add attempted on force-poisoned entry\n");
  35         WARN(next->prev != prev,
  36                 "list_add corruption. next->prev should be "
  37                 "prev (%p), but was %p. (next=%p).\n",
  38                 prev, next->prev, next);
  39         WARN(prev->next != next,
  40                 "list_add corruption. prev->next should be "
  41                 "next (%p), but was %p. (prev=%p).\n",
  42                 next, prev->next, prev);
  43         WARN(new == prev || new == next,
  44              "list_add double add: new=%p, prev=%p, next=%p.\n",
  45              new, prev, next);
  46         next->prev = new;
  47         new->next = next;
  48         new->prev = prev;
  49         WRITE_ONCE(prev->next, new);
  50 }
  51 EXPORT_SYMBOL(__list_add);
  52
  53 void __list_del_entry(struct list_head *entry)
  54 {
  55         struct list_head *prev, *next;
  56
  57         prev = entry->prev;
  58         next = entry->next;
  59
  60         if (WARN(next == LIST_POISON1,
  61                 "list_del corruption, %p->next is LIST_POISON1 (%p)\n",
  62                 entry, LIST_POISON1) ||
  63             WARN(prev == LIST_POISON2,
  64                 "list_del corruption, %p->prev is LIST_POISON2 (%p)\n",
  65                 entry, LIST_POISON2) ||
  66             WARN(prev->next != entry,
  67                 "list_del corruption. prev->next should be %p, "
  68                 "but was %p\n", entry, prev->next) ||
  69             WARN(next->prev != entry,
  70                 "list_del corruption. next->prev should be %p, "
  71                 "but was %p\n", entry, next->prev))
  72                 return;
  73
  74         __list_del(prev, next);
  75 }
  76 EXPORT_SYMBOL(__list_del_entry);
  77
  78 /**
  79  * list_del - deletes entry from list.
  80  * @entry: the element to delete from the list.
  81  * Note: list_empty on entry does not return true after this, the entry is
  82  * in an undefined state.
  83  */
  84 void list_del(struct list_head *entry)
  85 {
  86         __list_del_entry(entry);
  87         entry->next = LIST_POISON1;
  88         entry->prev = LIST_POISON2;
  89 }
  90 EXPORT_SYMBOL(list_del);
  91
  92 /*
  93  * RCU variants.
  94  */
  95 void __list_add_rcu(struct list_head *new,
  96                     struct list_head *prev, struct list_head *next)
  97 {
  98         WARN(next->prev != prev,
  99                 "list_add_rcu corruption. next->prev should be prev (%p), but was %p. (next=%p).\n",
 100                 prev, next->prev, next);
 101         WARN(prev->next != next,
 102                 "list_add_rcu corruption. prev->next should be next (%p), but was %p. (prev=%p).\n",
 103                 next, prev->next, prev);
 104         new->next = next;
 105         new->prev = prev;
 106         rcu_assign_pointer(list_next_rcu(prev), new);
 107         next->prev = new;
 108 }
 109 EXPORT_SYMBOL(__list_add_rcu);