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=-10.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 78230C4338F for ; Fri, 23 Jul 2021 08:04:22 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EFD7160E91 for ; Fri, 23 Jul 2021 08:04:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org EFD7160E91 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=daenzer.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7CE6D6EAC1; Fri, 23 Jul 2021 08:04:21 +0000 (UTC) Received: from netline-mail3.netline.ch (mail.netline.ch [148.251.143.180]) by gabe.freedesktop.org (Postfix) with ESMTP id 0EBAA6EAC1 for ; Fri, 23 Jul 2021 08:04:20 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by netline-mail3.netline.ch (Postfix) with ESMTP id 7136920201C; Fri, 23 Jul 2021 10:04:19 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at netline-mail3.netline.ch Received: from netline-mail3.netline.ch ([127.0.0.1]) by localhost (netline-mail3.netline.ch [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 0r4-p7gQVT_L; Fri, 23 Jul 2021 10:04:19 +0200 (CEST) Received: from thor (24.99.2.85.dynamic.wline.res.cust.swisscom.ch [85.2.99.24]) by netline-mail3.netline.ch (Postfix) with ESMTPA id E142C20201A; Fri, 23 Jul 2021 10:04:18 +0200 (CEST) Received: from [::1] by thor with esmtp (Exim 4.94.2) (envelope-from ) id 1m6qAL-000B1T-SD; Fri, 23 Jul 2021 10:04:17 +0200 To: =?UTF-8?Q?Christian_K=c3=b6nig?= References: <20210720131110.88512-1-christian.koenig@amd.com> From: =?UTF-8?Q?Michel_D=c3=a4nzer?= Subject: Re: [PATCH] dma-buf: fix and rework dma_buf_poll v7 Message-ID: <97ea61fb-aa20-5220-8304-e71145cc7587@daenzer.net> Date: Fri, 23 Jul 2021 10:04:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210720131110.88512-1-christian.koenig@amd.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-CA Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: daniel.vetter@ffwll.ch, dri-devel@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 2021-07-20 3:11 p.m., Christian König wrote: > Daniel pointed me towards this function and there are multiple obvious problems > in the implementation. > > First of all the retry loop is not working as intended. In general the retry > makes only sense if you grab the reference first and then check the sequence > values. > > Then we should always also wait for the exclusive fence. > > It's also good practice to keep the reference around when installing callbacks > to fences you don't own. > > And last the whole implementation was unnecessary complex and rather hard to > understand which could lead to probably unexpected behavior of the IOCTL. > > Fix all this by reworking the implementation from scratch. Dropping the > whole RCU approach and taking the lock instead. > > Only mildly tested and needs a thoughtful review of the code. > > v2: fix the reference counting as well > v3: keep the excl fence handling as is for stable > v4: back to testing all fences, drop RCU > v5: handle in and out separately > v6: add missing clear of events > v7: change coding style as suggested by Michel, drop unused variables > > Signed-off-by: Christian König > CC: stable@vger.kernel.org Working fine with https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880 Tested-by: Michel Dänzer -- Earthling Michel Dänzer | https://redhat.com Libre software enthusiast | Mesa and X developer