From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752105AbdBMHgh (ORCPT ); Mon, 13 Feb 2017 02:36:37 -0500 Received: from mga11.intel.com ([192.55.52.93]:50818 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751730AbdBMHgg (ORCPT ); Mon, 13 Feb 2017 02:36:36 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.35,155,1484035200"; d="scan'208";a="1094074334" From: "Huang\, Ying" To: Byungchul Park Cc: , , , , , , , , Subject: Re: [PATCH v2 1/9] llist: Provide a safe version for llist_for_each References: <1486970469-30917-1-git-send-email-byungchul.park@lge.com> <1486970469-30917-2-git-send-email-byungchul.park@lge.com> Date: Mon, 13 Feb 2017 15:36:33 +0800 In-Reply-To: <1486970469-30917-2-git-send-email-byungchul.park@lge.com> (Byungchul Park's message of "Mon, 13 Feb 2017 16:21:01 +0900") Message-ID: <87efz2pmny.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Byungchul Park 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 > --- > include/linux/llist.h | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/include/linux/llist.h b/include/linux/llist.h > index fd4ca0b..4c508a5 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 type * to use as temporary storage s/type */&struct llist_node/ > + * @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)) > + Following the style of other xxx_for_each_safe, #define llist_for_each_safe(pos, n, node) \ for (pos = (node), (pos && (n = pos->next)); pos; pos = n, n = pos->next) Best Regards, Huang, Ying > +/** > * 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.