include/linux/rculist_nulls.h

Source file repositories/reference/linux-study-clean/include/linux/rculist_nulls.h

File Facts

System
Linux kernel
Corpus path
include/linux/rculist_nulls.h
Extension
.h
Size
8949 bytes
Lines
249
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

#ifndef _LINUX_RCULIST_NULLS_H
#define _LINUX_RCULIST_NULLS_H

#ifdef __KERNEL__

/*
 * RCU-protected list version
 */
#include <linux/list_nulls.h>
#include <linux/rcupdate.h>

/**
 * hlist_nulls_del_init_rcu - deletes entry from hash list with re-initialization
 * @n: the element to delete from the hash list.
 *
 * Note: hlist_nulls_unhashed() on the node return true after this. It is
 * useful for RCU based read lockfree traversal if the writer side
 * must know if the list entry is still hashed or already unhashed.
 *
 * In particular, it means that we can not poison the forward pointers
 * that may still be used for walking the hash list and we can only
 * zero the pprev pointer so list_unhashed() will return true after
 * this.
 *
 * The caller must take whatever precautions are necessary (such as
 * holding appropriate locks) to avoid racing with another
 * list-mutation primitive, such as hlist_nulls_add_head_rcu() or
 * hlist_nulls_del_rcu(), running on this same list.  However, it is
 * perfectly legal to run concurrently with the _rcu list-traversal
 * primitives, such as hlist_nulls_for_each_entry_rcu().
 */
static inline void hlist_nulls_del_init_rcu(struct hlist_nulls_node *n)
{
	if (!hlist_nulls_unhashed(n)) {
		__hlist_nulls_del(n);
		WRITE_ONCE(n->pprev, NULL);
	}
}

/**
 * hlist_nulls_first_rcu - returns the first element of the hash list.
 * @head: the head of the list.
 */
#define hlist_nulls_first_rcu(head) \
	(*((struct hlist_nulls_node __rcu __force **)&(head)->first))

/**
 * hlist_nulls_next_rcu - returns the element of the list after @node.
 * @node: element of the list.
 */
#define hlist_nulls_next_rcu(node) \
	(*((struct hlist_nulls_node __rcu __force **)&(node)->next))

/**
 * hlist_nulls_pprev_rcu - returns the dereferenced pprev of @node.
 * @node: element of the list.
 */
#define hlist_nulls_pprev_rcu(node) \
	(*((struct hlist_nulls_node __rcu __force **)(node)->pprev))

/**
 * hlist_nulls_del_rcu - deletes entry from hash list without re-initialization
 * @n: the element to delete from the hash list.
 *
 * Note: hlist_nulls_unhashed() on entry does not return true after this,
 * the entry is in an undefined state. It is useful for RCU based
 * lockfree traversal.
 *
 * In particular, it means that we can not poison the forward
 * pointers that may still be used for walking the hash list.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as hlist_nulls_add_head_rcu()
 * or hlist_nulls_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * hlist_nulls_for_each_entry().
 */
static inline void hlist_nulls_del_rcu(struct hlist_nulls_node *n)
{
	__hlist_nulls_del(n);
	WRITE_ONCE(n->pprev, LIST_POISON2);
}

/**
 * hlist_nulls_add_head_rcu
 * @n: the element to add to the hash list.
 * @h: the list to add to.
 *

Annotation

Implementation Notes