include/linux/rculist_bl.h

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

File Facts

System
Linux kernel
Corpus path
include/linux/rculist_bl.h
Extension
.h
Size
4726 bytes
Lines
133
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_BL_H
#define _LINUX_RCULIST_BL_H

/*
 * RCU-protected bl list version. See include/linux/list_bl.h.
 */
#include <linux/list_bl.h>
#include <linux/rcupdate.h>

/* return the first ptr or next element in an RCU protected list */
#define hlist_bl_first_rcu(head)	\
	(*((struct hlist_bl_node __rcu **)(&(head)->first)))
#define hlist_bl_next_rcu(node)	\
	(*((struct hlist_bl_node __rcu **)(&(node)->next)))

static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
					struct hlist_bl_node *n)
{
	LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
	LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
							LIST_BL_LOCKMASK);
	rcu_assign_pointer(hlist_bl_first_rcu(h),
		(struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
}

#define hlist_bl_first_rcu_dereference(head)				\
({									\
	struct hlist_bl_head *__head = (head);				\
									\
	(struct hlist_bl_node *)					\
	((unsigned long)rcu_dereference_check(hlist_bl_first_rcu(__head), \
					      hlist_bl_is_locked(__head)) & \
					      ~LIST_BL_LOCKMASK);	\
})

/**
 * hlist_bl_del_rcu - deletes entry from hash list without re-initialization
 * @n: the element to delete from the hash list.
 *
 * Note: hlist_bl_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_bl_add_head_rcu()
 * or hlist_bl_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * hlist_bl_for_each_entry().
 */
static inline void hlist_bl_del_rcu(struct hlist_bl_node *n)
{
	__hlist_bl_del(n);
	n->pprev = LIST_POISON2;
}

/**
 * hlist_bl_add_head_rcu
 * @n: the element to add to the hash list.
 * @h: the list to add to.
 *
 * Description:
 * Adds the specified element to the specified hlist_bl,
 * while permitting racing traversals.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
 * or hlist_bl_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency
 * problems on Alpha CPUs.  Regardless of the type of CPU, the
 * list-traversal primitive must be guarded by rcu_read_lock().
 */
static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n,
					struct hlist_bl_head *h)
{
	struct hlist_bl_node *first;

	/* don't need hlist_bl_first_rcu* because we're under lock */
	first = hlist_bl_first(h);

	n->next = first;
	if (first)
		first->pprev = &n->next;

Annotation

Implementation Notes