Re: [PATCH v3 1/9] llist: Provide a safe version for llist_for_each
From: Huang\, Ying
Date: Tue Feb 14 2017 - 02:46:05 EST
Byungchul Park <byungchul.park@xxxxxxx> writes:
> Sometimes we have to dereference next field of llist node before entering
> loop becasue the node might be deleted or the next field might be
> modified within the loop. So this adds the safe version of llist_for_each,
> that is, llist_for_each_safe.
> Signed-off-by: Byungchul Park <byungchul.park@xxxxxxx>
Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
> include/linux/llist.h | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
> diff --git a/include/linux/llist.h b/include/linux/llist.h
> index fd4ca0b..b90c9f2 100644
> --- a/include/linux/llist.h
> +++ b/include/linux/llist.h
> @@ -105,6 +105,25 @@ static inline void init_llist_head(struct llist_head *list)
> for ((pos) = (node); pos; (pos) = (pos)->next)
> + * llist_for_each_safe - iterate over some deleted entries of a lock-less list
> + * safe against removal of list entry
> + * @pos: the &struct llist_node to use as a loop cursor
> + * @n: another &struct llist_node to use as temporary storage
> + * @node: the first entry of deleted list entries
> + *
> + * In general, some entries of the lock-less list can be traversed
> + * safely only after being deleted from list, so start with an entry
> + * instead of list head.
> + *
> + * If being used on entries deleted from lock-less list directly, the
> + * traverse order is from the newest to the oldest added entry. If
> + * you want to traverse from the oldest to the newest, you must
> + * reverse the order by yourself before traversing.
> + */
> +#define llist_for_each_safe(pos, n, node) \
> + for ((pos) = (node); (pos) && ((n) = (pos)->next, true); (pos) = (n))
> * llist_for_each_entry - iterate over some deleted entries of lock-less list of given type
> * @pos: the type * to use as a loop cursor.
> * @node: the fist entry of deleted list entries.