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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 1E660C433DB for ; Mon, 15 Mar 2021 07:52:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 87E1D64E6B for ; Mon, 15 Mar 2021 07:52:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 87E1D64E6B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C20A26B0072; Mon, 15 Mar 2021 03:52:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BAA096B0073; Mon, 15 Mar 2021 03:52:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9FDB46B0074; Mon, 15 Mar 2021 03:52:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0096.hostedemail.com [216.40.44.96]) by kanga.kvack.org (Postfix) with ESMTP id 7FA906B0072 for ; Mon, 15 Mar 2021 03:52:44 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 3D93C4857 for ; Mon, 15 Mar 2021 07:52:44 +0000 (UTC) X-FDA: 77921341848.05.280352C Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf15.hostedemail.com (Postfix) with ESMTP id CF4A1A0009CA for ; Mon, 15 Mar 2021 07:52:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=FCQj5B5Zp1rCBgedoXr3WWrEwlMWhZUzdqOcxosJGQw=; b=wRkw1cfr0IC8CR6t82z+HYxHFv VwF/tmGGdg4KPiwHX84XlVhB70vI4qKVPJb4zq2X0u72shDpS3zQnjEPkkVBEQyLoYdu7hZMdOQXM UIdFcYK8CUjNIvi3bzvpYQfQefNFXErUWa8P0ORjcvxmtaUgR3L2QHe8JipBS3IXKTRAUYM8zt3CL PlSQnfmpbv68kjqm6E5FTHerLPsTO1lDnQtEl+KweBJyzyuRjrj/f7i47X3awojHqCazrDuXVvNnJ B+BCGRiX8eIBhxPucslU4zDrXnmg9fLIfS7pNLD8peWWGhHmwlVcDfaGAn229P3hdRo0y0OsXuxsA QWr2l9bw==; Received: from hch by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lLi0P-00HOOO-B9; Mon, 15 Mar 2021 07:51:24 +0000 Date: Mon, 15 Mar 2021 07:51:13 +0000 From: Christoph Hellwig To: Alistair Popple Cc: linux-mm@kvack.org, nouveau@lists.freedesktop.org, bskeggs@redhat.com, akpm@linux-foundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, dri-devel@lists.freedesktop.org, jhubbard@nvidia.com, rcampbell@nvidia.com, jglisse@redhat.com, jgg@nvidia.com, hch@infradead.org, daniel@ffwll.ch, willy@infradead.org Subject: Re: [PATCH v6 8/8] nouveau/svm: Implement atomic SVM access Message-ID: <20210315075113.GD4136862@infradead.org> References: <20210312083851.15981-1-apopple@nvidia.com> <20210312083851.15981-9-apopple@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210312083851.15981-9-apopple@nvidia.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html X-Stat-Signature: 4f8bfq664jpr188b43z8qrf7kto3shfe X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: CF4A1A0009CA Received-SPF: none (casper.srs.infradead.org>: No applicable sender policy available) receiver=imf15; identity=mailfrom; envelope-from=""; helo=casper.infradead.org; client-ip=90.155.50.34 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615794763-522050 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > - /*XXX: atomic? */ > - return (fa->access == 0 || fa->access == 3) - > - (fb->access == 0 || fb->access == 3); > + /* Atomic access (2) has highest priority */ > + return (-1*(fa->access == 2) + (fa->access == 0 || fa->access == 3)) - > + (-1*(fb->access == 2) + (fb->access == 0 || fb->access == 3)); This looks really unreabable. If the magic values 0, 2 and 3 had names it might become a little more understadable, then factor the duplicated calculation of the priority value into a helper and we'll have code that mere humans can understand.. > + mutex_lock(&svmm->mutex); > + if (mmu_interval_read_retry(¬ifier->notifier, > + notifier_seq)) { > + mutex_unlock(&svmm->mutex); > + continue; > + } > + break; > + } This looks good, why not: mutex_lock(&svmm->mutex); if (!mmu_interval_read_retry(¬ifier->notifier, notifier_seq)) break; mutex_unlock(&svmm->mutex); }