Hello folks, I'm careful in saying.. and curious about..
In restrictive cases like only addtions happen but never deletion, can't we safely traverse a llist? I believe llist can be more useful if we can release the restriction. Can't we? If yes, we may add another function traversing starting from a head. Or just use existing funtion with head->first. Thank a lot for your answers in advance :) ----->8----- >From 1e73882799b269cd86e7a7c955021e3a18d1e6cf Mon Sep 17 00:00:00 2001 From: Byungchul Park <byungchul.p...@lge.com> Date: Tue, 31 Jul 2018 09:31:57 +0900 Subject: [QUESTION] llist: Comment releasing 'must delete' restriction before traversing llist traversing can run without deletion in restrictive cases all items are added but never deleted like a rculist traversing such as list_for_each_entry_lockless. So add the comment. Signed-off-by: Byungchul Park <byungchul.p...@lge.com> --- include/linux/llist.h | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/include/linux/llist.h b/include/linux/llist.h index 85abc29..d012d3e 100644 --- a/include/linux/llist.h +++ b/include/linux/llist.h @@ -32,8 +32,12 @@ * operation, with "-" being no lock needed, while "L" being lock is needed. * * The list entries deleted via llist_del_all can be traversed with - * traversing function such as llist_for_each etc. But the list - * entries can not be traversed safely before deleted from the list. + * traversing function such as llist_for_each etc. Normally the list + * entries cannot be traversed safely before deleted from the list + * except the cases items are added to the list but never deleted. In + * that restrictive cases the list may be safely traversed concurrently + * with llist_add. + * * The order of deleted entries is from the newest to the oldest added * one. If you want to traverse from the oldest to the newest, you * must reverse the order by yourself before traversing. @@ -116,7 +120,9 @@ static inline void init_llist_head(struct llist_head *list) * * 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. + * instead of list head. But in restrictive cases items are added to + * the list but never deleted, the list may be safely traversed + * concurrently with llist_add. * * If being used on entries deleted from lock-less list directly, the * traverse order is from the newest to the oldest added entry. If @@ -135,7 +141,9 @@ static inline void init_llist_head(struct llist_head *list) * * 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. + * instead of list head. But in restrictive cases items are added to + * the list but never deleted, the list may be safely traversed + * concurrently with llist_add. * * If being used on entries deleted from lock-less list directly, the * traverse order is from the newest to the oldest added entry. If @@ -153,7 +161,9 @@ static inline void init_llist_head(struct llist_head *list) * * In general, some entries of the lock-less list can be traversed * safely only after being removed from list, so start with an entry - * instead of list head. + * instead of list head. But in restrictive cases items are added to + * the list but never deleted, the list may be safely traversed + * concurrently with llist_add. * * If being used on entries deleted from lock-less list directly, the * traverse order is from the newest to the oldest added entry. If @@ -175,7 +185,9 @@ static inline void init_llist_head(struct llist_head *list) * * In general, some entries of the lock-less list can be traversed * safely only after being removed from list, so start with an entry - * instead of list head. + * instead of list head. But in restrictive cases items are added to + * the list but never deleted, the list may be safely traversed + * concurrently with llist_add. * * If being used on entries deleted from lock-less list directly, the * traverse order is from the newest to the oldest added entry. If -- 1.9.1
