cregit-Linux how code gets into the kernel

Release 4.12 include/linux/llist.h

Directory: include/linux
#ifndef LLIST_H

#define LLIST_H
/*
 * Lock-less NULL terminated single linked list
 *
 * Cases where locking is not needed:
 * If there are multiple producers and multiple consumers, llist_add can be
 * used in producers and llist_del_all can be used in consumers simultaneously
 * without locking. Also a single consumer can use llist_del_first while
 * multiple producers simultaneously use llist_add, without any locking.
 *
 * Cases where locking is needed:
 * If we have multiple consumers with llist_del_first used in one consumer, and
 * llist_del_first or llist_del_all used in other consumers, then a lock is
 * needed.  This is because llist_del_first depends on list->first->next not
 * changing, but without lock protection, there's no way to be sure about that
 * if a preemption happens in the middle of the delete operation and on being
 * preempted back, the list->first is the same as before causing the cmpxchg in
 * llist_del_first to succeed. For example, while a llist_del_first operation
 * is in progress in one consumer, then a llist_del_first, llist_add,
 * llist_add (or llist_del_all, llist_add, llist_add) sequence in another
 * consumer may cause violations.
 *
 * This can be summarized as follows:
 *
 *           |   add    | del_first |  del_all
 * add       |    -     |     -     |     -
 * del_first |          |     L     |     L
 * del_all   |          |           |     -
 *
 * Where, a particular row's operation can happen concurrently with a column's
 * operation, with "-" being no lock needed, while "L" being 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 handlers.  So code that uses the list in
 * an 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/atomic.h>
#include <linux/kernel.h>


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; }

Contributors

PersonTokensPropCommitsCommitProp
Huang Ying18100.00%1100.00%
Total18100.00%1100.00%

/** * 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_for_each_entry_safe - iterate over some deleted entries of lock-less list of given type * safe against removal of list entry * @pos: the type * to use as a loop cursor. * @n: another type * to use as temporary storage * @node: the first 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_safe(pos, n, node, member) \ for (pos = llist_entry((node), typeof(*pos), member); \ &pos->member != NULL && \ (n = llist_entry(pos->member.next, typeof(*n), member), true); \ pos = n) /** * 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 bool llist_empty(const struct llist_head *head) { return ACCESS_ONCE(head->first) == NULL; }

Contributors

PersonTokensPropCommitsCommitProp
Huang Ying2295.65%266.67%
Peter Zijlstra14.35%133.33%
Total23100.00%3100.00%


static inline struct llist_node *llist_next(struct llist_node *node) { return node->next; }

Contributors

PersonTokensPropCommitsCommitProp
Peter Zijlstra1894.74%150.00%
Huang Ying15.26%150.00%
Total19100.00%2100.00%

extern bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last, struct llist_head *head); /** * llist_add - add a new entry * @new: new entry to be added * @head: the head for your lock-less list * * Returns true if the list was empty prior to adding this entry. */
static inline bool llist_add(struct llist_node *new, struct llist_head *head) { return llist_add_batch(new, new, head); }

Contributors

PersonTokensPropCommitsCommitProp
Huang Ying2281.48%375.00%
Oleg Nesterov518.52%125.00%
Total27100.00%4100.00%

/** * 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. */
static inline struct llist_node *llist_del_all(struct llist_head *head) { return xchg(&head->first, NULL); }

Contributors

PersonTokensPropCommitsCommitProp
Huang Ying25100.00%2100.00%
Total25100.00%2100.00%

extern struct llist_node *llist_del_first(struct llist_head *head); struct llist_node *llist_reverse_order(struct llist_node *head); #endif /* LLIST_H */

Overall Contributors

PersonTokensPropCommitsCommitProp
Huang Ying17567.05%327.27%
Oleg Nesterov259.58%19.09%
Peter Zijlstra197.28%19.09%
Peter Hurley155.75%19.09%
Stephen Rothwell124.60%19.09%
Christoph Hellwig114.21%19.09%
Will Deacon20.77%19.09%
Andrew Morton10.38%19.09%
Joel Fernandes10.38%19.09%
Total261100.00%11100.00%
Directory: include/linux
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