From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E8F8C43382 for ; Fri, 28 Sep 2018 17:54:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D7040204FD for ; Fri, 28 Sep 2018 17:53:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D7040204FD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727273AbeI2ASf (ORCPT ); Fri, 28 Sep 2018 20:18:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33532 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726100AbeI2ASf (ORCPT ); Fri, 28 Sep 2018 20:18:35 -0400 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.25]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C9E9A3002738; Fri, 28 Sep 2018 17:53:41 +0000 (UTC) Received: from llong.com (dhcp-17-8.bos.redhat.com [10.18.17.8]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2CAAF2010D95; Fri, 28 Sep 2018 17:53:41 +0000 (UTC) From: Waiman Long To: Peter Zijlstra , Ingo Molnar , Will Deacon Cc: linux-kernel@vger.kernel.org, Waiman Long Subject: [PATCH 3/5] locking/lockdep: Add a faster path in __lock_release() Date: Fri, 28 Sep 2018 13:53:19 -0400 Message-Id: <1538157201-29173-4-git-send-email-longman@redhat.com> In-Reply-To: <1538157201-29173-1-git-send-email-longman@redhat.com> References: <1538157201-29173-1-git-send-email-longman@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.25 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Fri, 28 Sep 2018 17:53:41 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When __lock_release() is called, the most likely unlock scenario is on the innermost lock in the chain. In this case, we can skip some of the checks and provide a faster path to completion. Signed-off-by: Waiman Long --- kernel/locking/lockdep.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index add0468..ca002c0 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3625,6 +3625,13 @@ static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip) curr->lockdep_depth = i; curr->curr_chain_key = hlock->prev_chain_key; + /* + * The most likely case is when the unlock is on the innermost + * lock. In this case, we are done! + */ + if (i == depth - 1) + return 1; + if (reacquire_held_locks(curr, depth, i + 1)) return 0; @@ -3632,10 +3639,14 @@ static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip) * We had N bottles of beer on the wall, we drank one, but now * there's not N-1 bottles of beer left on the wall... */ - if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1)) - return 0; + DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1); - return 1; + /* + * Since reacquire_held_locks() would have called check_chain_key() + * indirectly via __lock_acquire(), we don't need to do it again + * on return. + */ + return 0; } static int __lock_is_held(const struct lockdep_map *lock, int read) -- 1.8.3.1