Messages in this thread | | | Date | Mon, 28 Feb 2011 11:33:54 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] list: add list_last_entry macros |
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On Sun, Feb 27, 2011 at 11:46:21AM +0100, Jiri Pirko wrote: > Handy to get last item in a list. Also corrected parameter name for > list_first_entry. > > Signed-off-by: Jiri Pirko <jpirko@redhat.com> > > diff --git a/include/linux/list.h b/include/linux/list.h > index 3a54266..e10862e 100644 > --- a/include/linux/list.h > +++ b/include/linux/list.h > @@ -352,14 +352,25 @@ static inline void list_splice_tail_init(struct list_head *list, > > /** > * list_first_entry - get the first element from a list > - * @ptr: the list head to take the element from. > + * @head: 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. > */ > -#define list_first_entry(ptr, type, member) \ > - list_entry((ptr)->next, type, member) > +#define list_first_entry(head, type, member) \ > + list_entry((head)->next, type, member) > + > +/** > + * list_last_entry - get the last element from a list > + * @head: 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. > + */ > +#define list_last_entry(head, type, member) \ > + list_entry((head)->prev, type, member) > > /** > * list_for_each - iterate over a list > diff --git a/include/linux/rculist.h b/include/linux/rculist.h > index 2dea94f..2cfa99f 100644 > --- a/include/linux/rculist.h > +++ b/include/linux/rculist.h > @@ -229,7 +229,7 @@ static inline void list_splice_init_rcu(struct list_head *list, > > /** > * list_first_entry_rcu - get the first element from a list > - * @ptr: the list head to take the element from. > + * @head: 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. > * > @@ -238,8 +238,23 @@ static inline void list_splice_init_rcu(struct list_head *list, > * 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_first_entry_rcu(head, type, member) \ > + list_entry_rcu((head)->next, type, member) > + > +/** > + * list_last_entry_rcu - get the last element from a list > + * @head: 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_last_entry_rcu(head, type, member) \ > + list_entry_rcu((head)->prev, type, member)
But won't a concurrent list_del_rcu() on head, which removes the full list, poison the ->prev pointer?
Do you have a definite use case for list_last_entry_rcu()?
Thanx, Paul
> /** > * list_for_each_entry_rcu - iterate over rcu list of given type > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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