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lib/llist.c
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f49f23abf
lib, Add lock-les...
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/*
* Lock-less NULL terminated single linked list
*
* The basic atomic operation of this list is cmpxchg on long. On
* architectures that don't have NMI-safe cmpxchg implementation, the
* list can NOT be used in NMI handler. So code uses the list in NMI
* handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
*
* Copyright 2010,2011 Intel Corp.
* Author: Huang Ying <ying.huang@intel.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version
* 2 as published by the Free Software Foundation;
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/llist.h>
#include <asm/system.h>
/**
* llist_add - add a new entry
* @new: new entry to be added
* @head: the head for your lock-less list
*/
void llist_add(struct llist_node *new, struct llist_head *head)
{
struct llist_node *entry, *old_entry;
#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
BUG_ON(in_nmi());
#endif
entry = head->first;
do {
old_entry = entry;
new->next = entry;
cpu_relax();
} while ((entry = cmpxchg(&head->first, old_entry, new)) != old_entry);
}
EXPORT_SYMBOL_GPL(llist_add);
/**
* llist_add_batch - add several linked entries in batch
* @new_first: first entry in batch to be added
* @new_last: last entry in batch to be added
* @head: the head for your lock-less list
*/
void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
struct llist_head *head)
{
struct llist_node *entry, *old_entry;
#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
BUG_ON(in_nmi());
#endif
entry = head->first;
do {
old_entry = entry;
new_last->next = entry;
cpu_relax();
} while ((entry = cmpxchg(&head->first, old_entry, new_first)) != old_entry);
}
EXPORT_SYMBOL_GPL(llist_add_batch);
/**
* llist_del_first - delete the first entry of lock-less list
* @head: the head for your lock-less list
*
* If list is empty, return NULL, otherwise, return the first entry
* deleted, this is the newest added one.
*
* Only one llist_del_first user can be used simultaneously with
* multiple llist_add users without lock. Because otherwise
* llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
* llist_add) sequence in another user may change @head->first->next,
* but keep @head->first. If multiple consumers are needed, please
* use llist_del_all or use lock between consumers.
*/
struct llist_node *llist_del_first(struct llist_head *head)
{
struct llist_node *entry, *old_entry, *next;
#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
BUG_ON(in_nmi());
#endif
entry = head->first;
do {
if (entry == NULL)
return NULL;
old_entry = entry;
next = entry->next;
cpu_relax();
} while ((entry = cmpxchg(&head->first, old_entry, next)) != old_entry);
return entry;
}
EXPORT_SYMBOL_GPL(llist_del_first);
/**
* llist_del_all - delete all entries from lock-less list
* @head: the head of lock-less list to delete all entries
*
* If list is empty, return NULL, otherwise, delete all entries and
* return the pointer to the first entry. The order of entries
* deleted is from the newest to the oldest added one.
*/
struct llist_node *llist_del_all(struct llist_head *head)
{
#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
BUG_ON(in_nmi());
#endif
return xchg(&head->first, NULL);
}
EXPORT_SYMBOL_GPL(llist_del_all);
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