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