From patchwork Tue May 1 03:11:29 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 10373141 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id ADC296038F for ; Tue, 1 May 2018 03:11:47 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 90A6028AAF for ; Tue, 1 May 2018 03:11:47 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 83D7328AE0; Tue, 1 May 2018 03:11:47 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,T_TVD_MIME_EPI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E0A4428AAF for ; Tue, 1 May 2018 03:11:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751871AbeEADLp (ORCPT ); Mon, 30 Apr 2018 23:11:45 -0400 Received: from mx2.suse.de ([195.135.220.15]:56826 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751558AbeEADLp (ORCPT ); Mon, 30 Apr 2018 23:11:45 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id B1E1FAD02; Tue, 1 May 2018 03:11:43 +0000 (UTC) From: NeilBrown To: paulmck@linux.vnet.ibm.com, Steven Rostedt Date: Tue, 01 May 2018 13:11:29 +1000 Cc: Josh Triplett , Trond Myklebust , Mathieu Desnoyers , Anna Schumaker , linux-nfs@vger.kernel.org, Lai Jiangshan , linux-kernel@vger.kernel.org Subject: [PATCH 3/4 v2] rculist: add list_for_each_entry_from_rcu() In-Reply-To: <20180430153505.GW26088@linux.vnet.ibm.com> References: <152506256513.7246.13171564155614823841.stgit@noble> <152506269061.7246.13075216914692813995.stgit@noble> <20180430052032.GA16963@localhost> <20180430134308.GT26088@linux.vnet.ibm.com> <20180430111454.722c2aa8@gandalf.local.home> <20180430153505.GW26088@linux.vnet.ibm.com> Message-ID: <87y3h4gjdq.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 Reviewed-by: Paul E. McKenney --- 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.