On Tue, Aug 15, 2023 at 08:30:18PM +0300, Julian Anastasov wrote:
> Add hlist_bl_for_each_entry_continue_rcu and hlist_bl_next_rcu
>
> Signed-off-by: Julian Anastasov <ja@xxxxxx>
> ---
> include/linux/rculist_bl.h | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/include/linux/rculist_bl.h b/include/linux/rculist_bl.h
> index 0b952d06eb0b..93a757793d83 100644
> --- a/include/linux/rculist_bl.h
> +++ b/include/linux/rculist_bl.h
> @@ -24,6 +24,10 @@ static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
> ((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK);
> }
>
> +/* return the next element in an RCU protected list */
> +#define hlist_bl_next_rcu(node) \
> + (*((struct hlist_bl_node __rcu **)(&(node)->next)))
> +
> /**
> * hlist_bl_del_rcu - deletes entry from hash list without re-initialization
> * @n: the element to delete from the hash list.
> @@ -98,4 +102,17 @@ static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n,
> ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
> pos = rcu_dereference_raw(pos->next))
>
> +/**
> + * hlist_bl_for_each_entry_continue_rcu - iterate over a list continuing after
> + * current point
Please add a comment to the effect that the element continued from
must have been either: (1) Iterated to within the same RCU read-side
critical section or (2) Nailed down using some lock, reference count,
or whatever suffices to keep the continued-from element from being freed
in the meantime.
Thanx, Paul
> + * @tpos: the type * to use as a loop cursor.
> + * @pos: the &struct hlist_bl_node to use as a loop cursor.
> + * @member: the name of the hlist_bl_node within the struct.
> + */
> +#define hlist_bl_for_each_entry_continue_rcu(tpos, pos, member) \
> + for (pos = rcu_dereference_raw(hlist_bl_next_rcu(&(tpos)->member)); \
> + pos && \
> + ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
> + pos = rcu_dereference_raw(hlist_bl_next_rcu(pos)))
> +
> #endif
> --
> 2.41.0
>
>
