Commit 1cc52327 authored by stephen hemminger's avatar stephen hemminger Committed by David S. Miller
Browse files

seq_file: add RCU versions of new hlist/list iterators (v3) 



Many usages of seq_file use RCU protected lists, so non RCU
iterators will not work safely.

Signed-off-by: default avatarStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 35e2da46

fs/seq_file.c

+71 −0
Original line number Diff line number Diff line
@@ -750,3 +750,74 @@ struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head, 
		return node->next;

}

EXPORT_SYMBOL(seq_hlist_next);



/**

 * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU

 * @head: the head of the hlist

 * @pos:  the start position of the sequence

 *

 * Called at seq_file->op->start().

 *

 * This list-traversal primitive may safely run concurrently with

 * the _rcu list-mutation primitives such as hlist_add_head_rcu()

 * as long as the traversal is guarded by rcu_read_lock().

 */

struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,

				       loff_t pos)

{

	struct hlist_node *node;



	__hlist_for_each_rcu(node, head)

		if (pos-- == 0)

			return node;

	return NULL;

}

EXPORT_SYMBOL(seq_hlist_start_rcu);



/**

 * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU

 * @head: the head of the hlist

 * @pos:  the start position of the sequence

 *

 * Called at seq_file->op->start(). Call this function if you want to

 * print a header at the top of the output.

 *

 * This list-traversal primitive may safely run concurrently with

 * the _rcu list-mutation primitives such as hlist_add_head_rcu()

 * as long as the traversal is guarded by rcu_read_lock().

 */

struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,

					    loff_t pos)

{

	if (!pos)

		return SEQ_START_TOKEN;



	return seq_hlist_start_rcu(head, pos - 1);

}

EXPORT_SYMBOL(seq_hlist_start_head_rcu);



/**

 * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU

 * @v:    the current iterator

 * @head: the head of the hlist

 * @pos:  the current posision

 *

 * Called at seq_file->op->next().

 *

 * This list-traversal primitive may safely run concurrently with

 * the _rcu list-mutation primitives such as hlist_add_head_rcu()

 * as long as the traversal is guarded by rcu_read_lock().

 */

struct hlist_node *seq_hlist_next_rcu(void *v,

				      struct hlist_head *head,

				      loff_t *ppos)

{

	struct hlist_node *node = v;



	++*ppos;

	if (v == SEQ_START_TOKEN)

		return rcu_dereference(head->first);

	else

		return rcu_dereference(node->next);

}

EXPORT_SYMBOL(seq_hlist_next_rcu);

include/linux/rculist.h

+5 −0
Original line number Diff line number Diff line
@@ -406,6 +406,11 @@ static inline void hlist_add_after_rcu(struct hlist_node *prev, 
		n->next->pprev = &n->next;

}



#define __hlist_for_each_rcu(pos, head)			\

	for (pos = rcu_dereference((head)->first);	\

	     pos && ({ prefetch(pos->next); 1; });	\

	     pos = rcu_dereference(pos->next))



/**

 * hlist_for_each_entry_rcu - iterate over rcu list of given type

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

include/linux/seq_file.h

+11 −4
Original line number Diff line number Diff line
@@ -146,4 +146,11 @@ extern struct hlist_node *seq_hlist_start_head(struct hlist_head *head, 
extern struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,

					 loff_t *ppos);



extern struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,

					      loff_t pos);

extern struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,

						   loff_t pos);

extern struct hlist_node *seq_hlist_next_rcu(void *v,

						   struct hlist_head *head,

						   loff_t *ppos);

#endif