Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754851Ab1B1Td6 (ORCPT ); Mon, 28 Feb 2011 14:33:58 -0500 Received: from e4.ny.us.ibm.com ([32.97.182.144]:56305 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753180Ab1B1Td5 (ORCPT ); Mon, 28 Feb 2011 14:33:57 -0500 Date: Mon, 28 Feb 2011 11:33:54 -0800 From: "Paul E. McKenney" To: Jiri Pirko Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] list: add list_last_entry macros Message-ID: <20110228193354.GW2331@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20110227104620.GA2814@psychotron.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110227104620.GA2814@psychotron.redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) X-Content-Scanned: Fidelis XPS MAILER Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3814 Lines: 95 On Sun, Feb 27, 2011 at 11:46:21AM +0100, Jiri Pirko wrote: > Handy to get last item in a list. Also corrected parameter name for > list_first_entry. > > Signed-off-by: Jiri Pirko > > diff --git a/include/linux/list.h b/include/linux/list.h > index 3a54266..e10862e 100644 > --- a/include/linux/list.h > +++ b/include/linux/list.h > @@ -352,14 +352,25 @@ static inline void list_splice_tail_init(struct list_head *list, > > /** > * list_first_entry - get the first element from a list > - * @ptr: the list head to take the element from. > + * @head: the list head to take the element from. > * @type: the type of the struct this is embedded in. > * @member: the name of the list_struct within the struct. > * > * Note, that list is expected to be not empty. > */ > -#define list_first_entry(ptr, type, member) \ > - list_entry((ptr)->next, type, member) > +#define list_first_entry(head, type, member) \ > + list_entry((head)->next, type, member) > + > +/** > + * list_last_entry - get the last element from a list > + * @head: the list head to take the element from. > + * @type: the type of the struct this is embedded in. > + * @member: the name of the list_struct within the struct. > + * > + * Note, that list is expected to be not empty. > + */ > +#define list_last_entry(head, type, member) \ > + list_entry((head)->prev, type, member) > > /** > * list_for_each - iterate over a list > diff --git a/include/linux/rculist.h b/include/linux/rculist.h > index 2dea94f..2cfa99f 100644 > --- a/include/linux/rculist.h > +++ b/include/linux/rculist.h > @@ -229,7 +229,7 @@ static inline void list_splice_init_rcu(struct list_head *list, > > /** > * list_first_entry_rcu - get the first element from a list > - * @ptr: the list head to take the element from. > + * @head: the list head to take the element from. > * @type: the type of the struct this is embedded in. > * @member: the name of the list_struct within the struct. > * > @@ -238,8 +238,23 @@ static inline void list_splice_init_rcu(struct list_head *list, > * This primitive may safely run concurrently with the _rcu list-mutation > * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). > */ > -#define list_first_entry_rcu(ptr, type, member) \ > - list_entry_rcu((ptr)->next, type, member) > +#define list_first_entry_rcu(head, type, member) \ > + list_entry_rcu((head)->next, type, member) > + > +/** > + * list_last_entry_rcu - get the last element from a list > + * @head: the list head to take the element from. > + * @type: the type of the struct this is embedded in. > + * @member: the name of the list_struct within the struct. > + * > + * Note, that list is expected to be not empty. > + * > + * This primitive may safely run concurrently with the _rcu list-mutation > + * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). > + */ > + > +#define list_last_entry_rcu(head, type, member) \ > + list_entry_rcu((head)->prev, type, member) But won't a concurrent list_del_rcu() on head, which removes the full list, poison the ->prev pointer? Do you have a definite use case for list_last_entry_rcu()? Thanx, Paul > /** > * list_for_each_entry_rcu - iterate over rcu list of given type > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/