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=-1.2 required=3.0 tests=DATE_IN_PAST_06_12, DKIM_INVALID,DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,USER_AGENT_MUTT 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 425BCC43441 for ; Sat, 10 Nov 2018 22:43:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0BA1320892 for ; Sat, 10 Nov 2018 22:43:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="VDEJdPwx" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0BA1320892 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S1726665AbeKKI3z (ORCPT ); Sun, 11 Nov 2018 03:29:55 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:36086 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725859AbeKKI3z (ORCPT ); Sun, 11 Nov 2018 03:29:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=kWfHLnXC8cbME/mYsBEh7YwvLGQFj/efe+ilZ0JVN+Y=; b=VDEJdPwxLQpoLwDGJ8FH+xtQ1 3sf2Uy1rYvB5oMopdUHkJXbQcJH+KOQBdGo6abr4lxIiFTTqKIsDestYhXLBhbpSXVuprTeh07u8B 7FT+2yZJmyysm24XNMR6i3DLzfEjTuDgdOOJ+bIurZ16Sj0Z6KKNQ2S4mpKj+4BSPaaWhaxYOddDG ernwGtOMc7ArO3hiFbD3yGW/wbzM5x5fDqJIm5zenSuaNwPPmD/pAbKCf7Z7tRf7/ms4RtknJRhOz j2MHN3Nuynti3EKw/66JNh2i//6dyrtaq9soDEUyVk1zifD+ylF2/Q3u/cKM7TZG/ZLyRCwhSKUKF GWwmWqp5A==; Received: from [64.114.255.114] (helo=worktop) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gLbyE-0001jh-6e; Sat, 10 Nov 2018 22:43:14 +0000 Received: by worktop (Postfix, from userid 1000) id 2B3126E08A0; Sat, 10 Nov 2018 15:17:34 +0100 (CET) Date: Sat, 10 Nov 2018 15:17:34 +0100 From: Peter Zijlstra To: Waiman Long Cc: Ingo Molnar , Will Deacon , Thomas Gleixner , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, Petr Mladek , Sergey Senozhatsky , Andrey Ryabinin , Tejun Heo , Andrew Morton Subject: Re: [RFC PATCH 02/12] locking/lockdep: Add a new terminal lock type Message-ID: <20181110141734.GF3339@worktop.programming.kicks-ass.net> References: <1541709268-3766-1-git-send-email-longman@redhat.com> <1541709268-3766-3-git-send-email-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1541709268-3766-3-git-send-email-longman@redhat.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 08, 2018 at 03:34:18PM -0500, Waiman Long wrote: > A terminal lock is a lock where further locking or unlocking on another > lock is not allowed. IOW, no forward dependency is permitted. > > With such a restriction in place, we don't really need to do a full > validation of the lock chain involving a terminal lock. Instead, > we just check if there is any further locking or unlocking on another > lock when a terminal lock is being held. > @@ -263,6 +270,7 @@ struct held_lock { > unsigned int hardirqs_off:1; > unsigned int references:12; /* 32 bits */ > unsigned int pin_count; > + unsigned int flags; > }; I'm thinking we can easily steal some bits off of the pin_count field if we have to.