On Tue, May 01, 2018 at 01:11:29PM +1000, NeilBrown wrote:
>
> list_for_each_entry_from_rcu() is an RCU version of
> list_for_each_entry_from(). It walks a linked list under rcu
> protection, from a given start point.
>
> It is similar to list_for_each_entry_continue_rcu() but starts *at*
> the given position rather than *after* it.
>
> Naturally, the start point must be known to be in the list.
>
> Also update the documentation for list_for_each_entry_continue_rcu()
> to match the documentation for the new list_for_each_entry_from_rcu(),
> and add list_for_each_entry_from_rcu() and the already existing
> hlist_for_each_entry_from_rcu() to section 7 of whatisRCU.txt.
>
> Signed-off-by: NeilBrown <ne...@suse.com>
I am guessing that it would be more convenient for you to carry this
with the patches using it, so:
Reviewed-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
If not, please let me know.
Thanx, Paul
> ---
> Documentation/RCU/whatisRCU.txt | 2 ++
> include/linux/rculist.h | 32 +++++++++++++++++++++++++++++++-
> 2 files changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
> index a27fbfb0efb8..b7d38bd212d2 100644
> --- a/Documentation/RCU/whatisRCU.txt
> +++ b/Documentation/RCU/whatisRCU.txt
> @@ -814,11 +814,13 @@ RCU list traversal:
> list_next_rcu
> list_for_each_entry_rcu
> list_for_each_entry_continue_rcu
> + list_for_each_entry_from_rcu
> hlist_first_rcu
> hlist_next_rcu
> hlist_pprev_rcu
> hlist_for_each_entry_rcu
> hlist_for_each_entry_rcu_bh
> + hlist_for_each_entry_from_rcu
> hlist_for_each_entry_continue_rcu
> hlist_for_each_entry_continue_rcu_bh
> hlist_nulls_first_rcu
> diff --git a/include/linux/rculist.h b/include/linux/rculist.h
> index 127f534fec94..4786c2235b98 100644
> --- a/include/linux/rculist.h
> +++ b/include/linux/rculist.h
> @@ -396,13 +396,43 @@ static inline void list_splice_tail_init_rcu(struct
> list_head *list,
> * @member: the name of the list_head within the struct.
> *
> * Continue to iterate over list of given type, continuing after
> - * the current position.
> + * the current position which must have been in the list when the RCU read
> + * lock was taken.
> + * This would typically require either that you obtained the node from a
> + * previous walk of the list in the same RCU read-side critical section, or
> + * that you held some sort of non-RCU reference (such as a reference count)
> + * to keep the node alive *and* in the list.
> + *
> + * This iterator is similar to list_for_each_entry_from_rcu() except
> + * this starts after the given position and that one starts at the given
> + * position.
> */
> #define list_for_each_entry_continue_rcu(pos, head, member) \
> for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \
> &pos->member != (head); \
> pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
>
> +/**
> + * list_for_each_entry_from_rcu - iterate over a list from current point
> + * @pos: the type * to use as a loop cursor.
> + * @head: the head for your list.
> + * @member: the name of the list_node within the struct.
> + *
> + * Iterate over the tail of a list starting from a given position,
> + * which must have been in the list when the RCU read lock was taken.
> + * This would typically require either that you obtained the node from a
> + * previous walk of the list in the same RCU read-side critical section, or
> + * that you held some sort of non-RCU reference (such as a reference count)
> + * to keep the node alive *and* in the list.
> + *
> + * This iterator is similar to list_for_each_entry_continue_rcu() except
> + * this starts from the given position and that one starts from the position
> + * after the given position.
> + */
> +#define list_for_each_entry_from_rcu(pos, head, member)
> \
> + for (; &(pos)->member != (head);
> \
> + pos = list_entry_rcu(pos->member.next, typeof(*(pos)), member))
> +
> /**
> * hlist_del_rcu - deletes entry from hash list without re-initialization
> * @n: the element to delete from the hash list.
> --
> 2.14.0.rc0.dirty
>
