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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,T_DKIMWL_WL_HIGH autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by aws-us-west-2-korg-lkml-1.web.codeaurora.org (Postfix) with ESMTP id 8A071C433EF for ; Wed, 13 Jun 2018 07:54:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4067D208AF for ; Wed, 13 Jun 2018 07:54:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="XWPjWc7i" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4067D208AF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.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 S934709AbeFMHyn (ORCPT ); Wed, 13 Jun 2018 03:54:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:48028 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754472AbeFMHyg (ORCPT ); Wed, 13 Jun 2018 03:54:36 -0400 Received: from localhost (unknown [37.169.25.123]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6DA37208AF; Wed, 13 Jun 2018 07:54:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1528876476; bh=CD76DzcJmC48fDQlYq2aHQQ83LWuYBs9Nw4JTShz4B4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XWPjWc7ipM5oKZsy3fMh5HJxV59kVn6Q3s5Kj+jyxWuJXrrKPsUH3yqlTqHjMJZEH QfOLAWSUiFp0eEYfabaEqN2ZuLO6T9gofLV0b1+fHff99ULbygFXMPeJK7ubPdj5b/ dgaoe2WZBBIoIVKzIsuj3sRDLS+VcOTN2Z4udDa4= Date: Wed, 13 Jun 2018 09:54:11 +0200 From: Greg Kroah-Hartman To: Thomas Hellstrom Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Jonathan Corbet , Gustavo Padovan , Maarten Lankhorst , Sean Paul , David Airlie , Davidlohr Bueso , "Paul E. McKenney" , Josh Triplett , Thomas Gleixner , Kate Stewart , Philippe Ombredanne , linux-doc@vger.kernel.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org Subject: Re: [PATCH 1/2] locking: Implement an algorithm choice for Wound-Wait mutexes Message-ID: <20180613075411.GA17681@kroah.com> References: <20180613074745.14750-1-thellstrom@vmware.com> <20180613074745.14750-2-thellstrom@vmware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180613074745.14750-2-thellstrom@vmware.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 13, 2018 at 09:47:44AM +0200, Thomas Hellstrom wrote: > ----- > > +The algorithm (Wait-Die vs Wound-Wait) is chosen using the _is_wait_die > +argument to DEFINE_WW_CLASS(). As a rough rule of thumb, use Wound-Wait iff you > +typically expect the number of simultaneous competing transactions to be small, > +and the rollback cost can be substantial. > + > Three different ways to acquire locks within the same w/w class. Common > definitions for methods #1 and #2: > > -static DEFINE_WW_CLASS(ww_class); > +static DEFINE_WW_CLASS(ww_class, false); Minor nit on the api here. Having a "flag" is a royal pain. You have to go and look up exactly what that "true/false" means every time you run across it in code to figure out what it means. Don't do that if at all possible. Make a new api: DEFINE_WW_CLASS_DIE(ww_class); instead that then wraps that boolean internally to switch between the different types. That way the api is "self-documenting" and we all know what is going on without having to dig through a header file. thanks, greg k-h