Return-Path: 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 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 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" Sender: linux-nfs-owner@vger.kernel.org List-ID: --=-=-= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable 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 =2D-- 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 =2D-- 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 =2D-- a/include/linux/rculist.h +++ b/include/linux/rculist.h @@ -396,13 +396,43 @@ static inline void list_splice_tail_init_rcu(struct l= ist_head *list, * @member: the name of the list_head within the struct. * * Continue to iterate over list of given type, continuing after =2D * 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 =3D list_entry_rcu(pos->member.next, typeof(*pos), member); \ &pos->member !=3D (head); \ pos =3D list_entry_rcu(pos->member.next, typeof(*pos), member)) =20 +/** + * 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 positi= on + * after the given position. + */ +#define list_for_each_entry_from_rcu(pos, head, member) \ + for (; &(pos)->member !=3D (head); \ + pos =3D 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. =2D-=20 2.14.0.rc0.dirty --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEG8Yp69OQ2HB7X0l6Oeye3VZigbkFAlrn2uMACgkQOeye3VZi gbl7bA//W3TjUzSU4+ja3D9oxTbNDhIv2f1bnpDn/vnltpEe4pHlc65X9ldm8Xyz y4PmifQozWFUjYJwHyLasWgHGJrVD/Ij9bEv7bj94DJEOkF4S611XcLEM+Ke6R8t rf9lYzJQINcdbJcgubC2FKa11aMmBn78pqUQPUSfYomo/kaDdyQaReUJ2p4cujr9 vewOHFdFp6nksvFLU7AAWgj77jyDQ40CVJC4RnS7c6V72I+kcK+r1+dWv2K05onA 4HZGA5Hr8mamdgAT4QCr2azG93Vyp3HROug50rszEpk4JnYex0nN1e9YH4d9/9zl aHOK2RsS+hd/S8gkRcsgStMNVnyqE+DKIDBXdHejaTPtY6M9JrfrihFMhLhzrjhe YqNFngoZ3l9D7F+cI6gmacGoiEKvLDrl7l9TDu2Np01p1eFc4tgG6qJ5nCV4ikcL y/tw4OBK2/WVrkZbPPfd7pKmkzUzP/KKyd53PchQfpK/OhjOBVwSCE7hW1Lrs4iI vyiuOaexLfYYaFhAvzTdJNd4wz0pxiEKN1U9e1v624Zys+mDMxQs7F+v+vf/WF7F WaPDG60kvO16G6GGWMYAdePfXJ4xPyYKxzSelR56MvaByIDWiAh2Qr7f14RjZL3F YeOnr7SOndaNM5/R6zsEshnbCM3tvFFuOAEHHyvIlfa7SRFtRow= =UjZC -----END PGP SIGNATURE----- --=-=-=--