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/*
* Copyright 2006, Red Hat, Inc., Dave Jones
* Released under the General Public License (GPL).
*
* This file contains the linked list implementations for
* DEBUG_LIST.
*/
#include <linux/export.h>
#include <linux/list.h>
#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/rculist.h>
#ifdef CONFIG_X86_64
static unsigned long count_bits(unsigned long value)
{
value = value - ((value >> 1) & 0x5555555555555555);
value = (value & 0x3333333333333333) + ((value >> 2) & 0x3333333333333333);
return (((value + (value >> 4)) & 0xF0F0F0F0F0F0F0F) * 0x101010101010101) >> 56;
}
#else
static unsigned long count_bits(unsigned long value)
{
value = value - ((value >> 1) & 0x55555555);
value = (value & 0x33333333) + ((value >> 2) & 0x33333333);
return (((value + (value >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24;
}
#endif
inline int check_list_corruption(void *ptr1, void *ptr2, void *ptr3, const char *func_name,
const char *ptr1_name, const char *ptr2_name, const char *ptr3_name) {
unsigned long delta_bits = (unsigned long)ptr1 ^ (unsigned long)ptr2;
if (!delta_bits)
return 0;
if (count_bits(delta_bits) < 3) {
/* less than 3 bits differ; probably a bit flip...*/
panic("Bit flip in %s: value %p should be %p\n", func_name, ptr2, ptr1);
}
return WARN(1,
"%s corruption. %s should be "
"%s (%p), but was %p. (%s=%p).\n",
func_name, ptr1_name, ptr2_name, ptr2, ptr1, ptr3_name, ptr3);
}
/*
* Insert a new entry between two known consecutive entries.
*
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
int panic_on_list_corruption;
EXPORT_SYMBOL_GPL(panic_on_list_corruption);
static int __init panic_on_list_corruption_setup(char *str)
{
unsigned long enabled;
int ret;
ret = kstrtoul(str, 10, &enabled);
if (ret)
return ret;
if (enabled == 1)
panic_on_list_corruption = 1;
return 0;
}
early_param("panic_on_list_corruption", panic_on_list_corruption_setup);
void __list_add(struct list_head *new,
struct list_head *prev,
struct list_head *next)
{
int warn = 0;
warn |= check_list_corruption(next->prev, prev, next, __func__, "next->prev", "prev", "next");
warn |= check_list_corruption(prev->next, next, prev, __func__, "prev->next", "next", "prev");
warn |= WARN(new == prev || new == next,
"list_add double add: new=%p, prev=%p, next=%p.\n",
new, prev, next);
if ((warn) && (panic_on_list_corruption))
panic("List corruption");
next->prev = new;
new->next = next;
new->prev = prev;
prev->next = new;
}
EXPORT_SYMBOL(__list_add);
void __list_del_entry(struct list_head *entry)
{
struct list_head *prev, *next;
prev = entry->prev;
next = entry->next;
if (WARN(next == LIST_POISON1,
"list_del corruption, %p->next is LIST_POISON1 (%p)\n",
entry, LIST_POISON1) ||
WARN(prev == LIST_POISON2,
"list_del corruption, %p->prev is LIST_POISON2 (%p)\n",
entry, LIST_POISON2) ||
check_list_corruption(next->prev, entry, next,
__func__, "next->prev", "entry", "next") ||
check_list_corruption(prev->next, entry, prev,
__func__, "prev->next", "entry", "prev")) {
if (panic_on_list_corruption)
panic("List corruption");
return;
}
__list_del(prev, next);
}
EXPORT_SYMBOL(__list_del_entry);
/**
* list_del - deletes entry from list.
* @entry: the element to delete from the list.
* Note: list_empty on entry does not return true after this, the entry is
* in an undefined state.
*/
void list_del(struct list_head *entry)
{
__list_del_entry(entry);
entry->next = LIST_POISON1;
entry->prev = LIST_POISON2;
}
EXPORT_SYMBOL(list_del);
/*
* RCU variants.
*/
void __list_add_rcu(struct list_head *new,
struct list_head *prev, struct list_head *next)
{
int warn = 0;
warn |= check_list_corruption(next->prev, prev, next, __func__, "next->prev", "prev", "next");
warn |= check_list_corruption(prev->next, next, prev, __func__, "prev->next", "next", "prev");
if ((warn) && (panic_on_list_corruption))
panic("List corruption");
new->next = next;
new->prev = prev;
rcu_assign_pointer(list_next_rcu(prev), new);
next->prev = new;
}
EXPORT_SYMBOL(__list_add_rcu);
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