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rculist.h: introduce list_entry_rcu() and list_first_entry_rcu()

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I've run into the situation where I need to use list_first_entry with
rcu-guarded list. This patch introduces this.

Also simplify list_for_each_entry_rcu() to use new list_entry_rcu()
instead of list_entry().

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: dipankar@in.ibm.com
LKML-Reference: <20090414153356.GC3999@psychotron.englab.brq.redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jiri Pirko 2009-04-14 17:33:57 +02:00 • committed by Ingo Molnar
commit 72c6a9870f
1 changed files with 28 additions and 2 deletions
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30
include/linux/rculist.h
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@ -198,6 +198,32 @@ static inline void list_splice_init_rcu(struct list_head *list,
at->prev = last; at->prev = last;
} }
/**
* list_entry_rcu - get the struct for this entry
* @ptr: the &struct list_head pointer.
* @type: the type of the struct this is embedded in.
* @member: the name of the list_struct within the struct.
*
* This primitive may safely run concurrently with the _rcu list-mutation
* primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
*/
#define list_entry_rcu(ptr, type, member) \
container_of(rcu_dereference(ptr), type, member)
/**
* list_first_entry_rcu - get the first element from a list
* @ptr: the list head to take the element from.
* @type: the type of the struct this is embedded in.
* @member: the name of the list_struct within the struct.
*
* Note, that list is expected to be not empty.
*
* This primitive may safely run concurrently with the _rcu list-mutation
* primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
*/
#define list_first_entry_rcu(ptr, type, member) \
list_entry_rcu((ptr)->next, type, member)
#define __list_for_each_rcu(pos, head) \ #define __list_for_each_rcu(pos, head) \
for (pos = rcu_dereference((head)->next); \ for (pos = rcu_dereference((head)->next); \
pos != (head); \ pos != (head); \
@ -214,9 +240,9 @@ static inline void list_splice_init_rcu(struct list_head *list,
* as long as the traversal is guarded by rcu_read_lock(). * as long as the traversal is guarded by rcu_read_lock().
*/ */
#define list_for_each_entry_rcu(pos, head, member) \ #define list_for_each_entry_rcu(pos, head, member) \
for (pos = list_entry(rcu_dereference((head)->next), typeof(*pos), member); \ for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \
prefetch(pos->member.next), &pos->member != (head); \ prefetch(pos->member.next), &pos->member != (head); \
pos = list_entry(rcu_dereference(pos->member.next), typeof(*pos), member)) pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
/** /**