From patchwork Mon Jun 1 14:47:58 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andy Shevchenko X-Patchwork-Id: 6522741 Return-Path: X-Original-To: patchwork-dmaengine@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 6EDA3C0433 for ; Mon, 1 Jun 2015 14:49:57 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8B5CF2043C for ; Mon, 1 Jun 2015 14:49:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 916FC2044C for ; Mon, 1 Jun 2015 14:49:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752387AbbFAOtz (ORCPT ); Mon, 1 Jun 2015 10:49:55 -0400 Received: from mga03.intel.com ([134.134.136.65]:57136 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753502AbbFAOsm (ORCPT ); Mon, 1 Jun 2015 10:48:42 -0400 Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga103.jf.intel.com with ESMTP; 01 Jun 2015 07:48:41 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,533,1427785200"; d="scan'208";a="718719718" Received: from black.fi.intel.com ([10.237.72.86]) by fmsmga001.fm.intel.com with ESMTP; 01 Jun 2015 07:48:36 -0700 Received: by black.fi.intel.com (Postfix, from userid 1003) id A9A3A57C; Mon, 1 Jun 2015 17:48:05 +0300 (EEST) From: Andy Shevchenko To: "Rafael J . Wysocki" , linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, Greg Kroah-Hartman , Vinod Koul , Lee Jones , Andrew Morton , Mika Westerberg , linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org, Heikki Krogerus , Jarkko Nikula , "Wysocki, Rafael J" , Mike Turquette Cc: Andy Shevchenko Subject: [PATCH v3 4/8] klist: implement klist_prev() Date: Mon, 1 Jun 2015 17:47:58 +0300 Message-Id: <1433170082-117462-5-git-send-email-andriy.shevchenko@linux.intel.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1433170082-117462-1-git-send-email-andriy.shevchenko@linux.intel.com> References: <1433170082-117462-1-git-send-email-andriy.shevchenko@linux.intel.com> Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP klist_prev() gets the previous element in the list. It is useful to traverse through the list in reverse order, for example, to provide LIFO (last in first out) variant of access. Signed-off-by: Andy Shevchenko Acked-by: Greg Kroah-Hartman --- include/linux/klist.h | 1 + lib/klist.c | 41 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 42 insertions(+) diff --git a/include/linux/klist.h b/include/linux/klist.h index 61e5b72..953f283 100644 --- a/include/linux/klist.h +++ b/include/linux/klist.h @@ -63,6 +63,7 @@ extern void klist_iter_init(struct klist *k, struct klist_iter *i); extern void klist_iter_init_node(struct klist *k, struct klist_iter *i, struct klist_node *n); extern void klist_iter_exit(struct klist_iter *i); +extern struct klist_node *klist_prev(struct klist_iter *i); extern struct klist_node *klist_next(struct klist_iter *i); #endif diff --git a/lib/klist.c b/lib/klist.c index 89b485a..d74cf7a 100644 --- a/lib/klist.c +++ b/lib/klist.c @@ -324,6 +324,47 @@ static struct klist_node *to_klist_node(struct list_head *n) } /** + * klist_prev - Ante up prev node in list. + * @i: Iterator structure. + * + * First grab list lock. Decrement the reference count of the previous + * node, if there was one. Grab the prev node, increment its reference + * count, drop the lock, and return that prev node. + */ +struct klist_node *klist_prev(struct klist_iter *i) +{ + void (*put)(struct klist_node *) = i->i_klist->put; + struct klist_node *last = i->i_cur; + struct klist_node *prev; + + spin_lock(&i->i_klist->k_lock); + + if (last) { + prev = to_klist_node(last->n_node.prev); + if (!klist_dec_and_del(last)) + put = NULL; + } else + prev = to_klist_node(i->i_klist->k_list.prev); + + i->i_cur = NULL; + while (prev != to_klist_node(&i->i_klist->k_list)) { + if (likely(!knode_dead(prev))) { + kref_get(&prev->n_ref); + i->i_cur = prev; + break; + } + prev = to_klist_node(prev->n_node.prev); + } + + spin_unlock(&i->i_klist->k_lock); + + if (put && last) + put(last); + return i->i_cur; +} +EXPORT_SYMBOL_GPL(klist_prev); + +/** * klist_next - Ante up next node in list. * @i: Iterator structure. *