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Commit 7d86dccf authored by Petko Manolov's avatar Petko Manolov Committed by Paul E. McKenney
Browse files

list: Introduces generic list_splice_tail_init_rcu() 



The list_splice_init_rcu() can be used as a stack onto which full lists
are pushed, but queue-like behavior is now needed by some security
policies.  This requires a list_splice_tail_init_rcu().

This commit therefore supplies a list_splice_tail_init_rcu() by
pulling code common it and to list_splice_init_rcu() into a new
__list_splice_init_rcu() function.  This new function is based on the
existing list_splice_init_rcu() implementation.

Signed-off-by: default avatarPetko Manolov <petkan@mip-labs.com>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 1658d35e

include/linux/rculist.h

+49 −20
Original line number Diff line number Diff line
@@ -179,32 +179,31 @@ static inline void list_replace_rcu(struct list_head *old, 
}



/**

 * list_splice_init_rcu - splice an RCU-protected list into an existing list.

 * __list_splice_init_rcu - join an RCU-protected list into an existing list.

 * @list:	the RCU-protected list to splice

 * @head:	the place in the list to splice the first list into

 * @prev:	points to the last element of the existing list

 * @next:	points to the first element of the existing list

 * @sync:	function to sync: synchronize_rcu(), synchronize_sched(), ...

 *

 * @head can be RCU-read traversed concurrently with this function.

 * The list pointed to by @prev and @next can be RCU-read traversed

 * concurrently with this function.

 *

 * Note that this function blocks.

 *

 * Important note: the caller must take whatever action is necessary to

 *	prevent any other updates to @head.  In principle, it is possible

 *	to modify the list as soon as sync() begins execution.

 *	If this sort of thing becomes necessary, an alternative version

 *	based on call_rcu() could be created.  But only if -really-

 *	needed -- there is no shortage of RCU API members.

 * Important note: the caller must take whatever action is necessary to prevent

 * any other updates to the existing list.  In principle, it is possible to

 * modify the list as soon as sync() begins execution. If this sort of thing

 * becomes necessary, an alternative version based on call_rcu() could be

 * created.  But only if -really- needed -- there is no shortage of RCU API

 * members.

 */

static inline void list_splice_init_rcu(struct list_head *list,

					struct list_head *head,

static inline void __list_splice_init_rcu(struct list_head *list,

					  struct list_head *prev,

					  struct list_head *next,

					  void (*sync)(void))

{

	struct list_head *first = list->next;

	struct list_head *last = list->prev;

	struct list_head *at = head->next;



	if (list_empty(list))

		return;



	/*

	 * "first" and "last" tracking list, so initialize it.  RCU readers
@@ -231,10 +230,40 @@ static inline void list_splice_init_rcu(struct list_head *list, 
	 * this function.

	 */



	last->next = at;

	rcu_assign_pointer(list_next_rcu(head), first);

	first->prev = head;

	at->prev = last;

	last->next = next;

	rcu_assign_pointer(list_next_rcu(prev), first);

	first->prev = prev;

	next->prev = last;

}



/**

 * list_splice_init_rcu - splice an RCU-protected list into an existing list,

 *                        designed for stacks.

 * @list:	the RCU-protected list to splice

 * @head:	the place in the existing list to splice the first list into

 * @sync:	function to sync: synchronize_rcu(), synchronize_sched(), ...

 */

static inline void list_splice_init_rcu(struct list_head *list,

					struct list_head *head,

					void (*sync)(void))

{

	if (!list_empty(list))

		__list_splice_init_rcu(list, head, head->next, sync);

}



/**

 * list_splice_tail_init_rcu - splice an RCU-protected list into an existing

 *                             list, designed for queues.

 * @list:	the RCU-protected list to splice

 * @head:	the place in the existing list to splice the first list into

 * @sync:	function to sync: synchronize_rcu(), synchronize_sched(), ...

 */

static inline void list_splice_tail_init_rcu(struct list_head *list,

					     struct list_head *head,

					     void (*sync)(void))

{

	if (!list_empty(list))

		__list_splice_init_rcu(list, head->prev, head, sync);

}



/**