lib, Add lock-less NULL terminated single list

#ifndef LLIST_H

#define LLIST_H

/*

 * Lock-less NULL terminated single linked list

 *

 * If there are multiple producers and multiple consumers, llist_add

 * can be used in producers and llist_del_all can be used in

 * consumers.  They can work simultaneously without lock.  But

 * llist_del_first can not be used here.  Because llist_del_first

 * depends on list->first->next does not changed if list->first is not

 * changed during its operation, but llist_del_first, llist_add,

 * llist_add (or llist_del_all, llist_add, llist_add) sequence in

 * another consumer may violate that.

 *

 * If there are multiple producers and one consumer, llist_add can be

 * used in producers and llist_del_all or llist_del_first can be used

 * in the consumer.

 *

 * This can be summarized as follow:

 *

 *           |   add    | del_first |  del_all

 * add       |    -     |     -     |     -

 * del_first |          |     L     |     L

 * del_all   |          |           |     -

 *

 * Where "-" stands for no lock is needed, while "L" stands for lock

 * is needed.

 *

 * The list entries deleted via llist_del_all can be traversed with

 * traversing function such as llist_for_each etc.  But the list

 * entries can not be traversed safely before deleted from the list.

 * The order of deleted entries is from the newest to the oldest added

 * one.  If you want to traverse from the oldest to the newest, you

 * must reverse the order by yourself before traversing.

 *

 * 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.

 */

struct llist_head {

	struct llist_node *first;

};

struct llist_node {

	struct llist_node *next;

};

#define LLIST_HEAD_INIT(name)	{ NULL }

#define LLIST_HEAD(name)	struct llist_head name = LLIST_HEAD_INIT(name)

/**

 * init_llist_head - initialize lock-less list head

 * @head:	the head for your lock-less list

 */

static inline void init_llist_head(struct llist_head *list)

{

	list->first = NULL;

}

/**

 * llist_entry - get the struct of this entry

 * @ptr:	the &struct llist_node pointer.

 * @type:	the type of the struct this is embedded in.

 * @member:	the name of the llist_node within the struct.

 */

#define llist_entry(ptr, type, member)		\

	container_of(ptr, type, member)

/**

 * llist_for_each - iterate over some deleted entries of a lock-less list

 * @pos:	the &struct llist_node to use as a loop cursor

 * @node:	the first entry of deleted list entries

 *

 * In general, some entries of the lock-less list can be traversed

 * safely only after being deleted from list, so start with an entry

 * instead of list head.

 *

 * If being used on entries deleted from lock-less list directly, the

 * traverse order is from the newest to the oldest added entry.  If

 * you want to traverse from the oldest to the newest, you must

 * reverse the order by yourself before traversing.

 */

#define llist_for_each(pos, node)			\

	for ((pos) = (node); pos; (pos) = (pos)->next)

/**

 * llist_for_each_entry - iterate over some deleted entries of lock-less list of given type

 * @pos:	the type * to use as a loop cursor.

 * @node:	the fist entry of deleted list entries.

 * @member:	the name of the llist_node with the struct.

 *

 * In general, some entries of the lock-less list can be traversed

 * safely only after being removed from list, so start with an entry

 * instead of list head.

 *

 * If being used on entries deleted from lock-less list directly, the

 * traverse order is from the newest to the oldest added entry.  If

 * you want to traverse from the oldest to the newest, you must

 * reverse the order by yourself before traversing.

 */

#define llist_for_each_entry(pos, node, member)				\

	for ((pos) = llist_entry((node), typeof(*(pos)), member);	\

	     &(pos)->member != NULL;					\

	     (pos) = llist_entry((pos)->member.next, typeof(*(pos)), member))

/**

 * llist_empty - tests whether a lock-less list is empty

 * @head:	the list to test

 *

 * Not guaranteed to be accurate or up to date.  Just a quick way to

 * test whether the list is empty without deleting something from the

 * list.

 */

static inline int llist_empty(const struct llist_head *head)

{

	return ACCESS_ONCE(head->first) == NULL;

}

void llist_add(struct llist_node *new, struct llist_head *head);

void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,

		     struct llist_head *head);

struct llist_node *llist_del_first(struct llist_head *head);

struct llist_node *llist_del_all(struct llist_head *head);

#endif /* LLIST_H */

	  If unsure, say N.

config LLIST

	bool

endmenu

obj-$(CONFIG_CPU_RMAP) += cpu_rmap.o

obj-$(CONFIG_LLIST) += llist.o

hostprogs-y	:= gen_crc32table

clean-files	:= crc32table.h

/*

 * 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);