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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 931A6EB64DC for ; Wed, 21 Jun 2023 18:16:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230269AbjFUSQh (ORCPT ); Wed, 21 Jun 2023 14:16:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44686 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229570AbjFUSQg (ORCPT ); Wed, 21 Jun 2023 14:16:36 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CAA1AFE; Wed, 21 Jun 2023 11:16:35 -0700 (PDT) Received: from [192.168.2.254] (109-252-154-132.dynamic.spd-mgts.ru [109.252.154.132]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: dmitry.osipenko) by madras.collabora.co.uk (Postfix) with ESMTPSA id 61D736606FAC; Wed, 21 Jun 2023 19:16:32 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1687371394; bh=PQA2rc/Gs+XDzpOTYaQqwgwiDRANnpvkFuiUXn6B45A=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=a6uFWwMGM2Wn9oqIqY7w7ZXRsmW9BSZjBsI4Ir5fTcMPux5toiFC6wlyILN77QVfb 0L+ZFaptUWmBOJZm2yvNv0eh15H4wUN+1EiHsUsv63mFz6hu/moMeG3T4oQV6i35F0 sHKIlQJA6GxprALI1nuPl+VQIhbWRMZVczzPnrUz21ntwNTap1H/IueLMyT7eRukEz N3GdhDZdinRaXuMBSFTeA1MUT7KUhYwb+koIItqlM5t/HFmZVenSeMDvjEPNqpSvPr WnQ/f7ngy10rNR4q+TxKWqOltsVMxB7/UwzmOPEST6X3Ell8COhkS5FvW3+wJ2ZV00 b/tPSDkrH1Jtg== Message-ID: <106bc72b-9358-de06-6f3f-06fdfa3859cd@collabora.com> Date: Wed, 21 Jun 2023 21:16:29 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.1 Subject: Re: [PATCH v4 2/6] dma-buf/heaps: Don't assert held reservation lock for dma-buf mmapping Content-Language: en-US To: "T.J. Mercier" Cc: Sumit Semwal , =?UTF-8?Q?Christian_K=c3=b6nig?= , Benjamin Gaignard , Brian Starkey , John Stultz , Gerd Hoffmann , Daniel Vetter , Jani Nikula , Arnd Bergmann , Thomas Zimmermann , Tomi Valkeinen , Thierry Reding , Tomasz Figa , Marek Szyprowski , Mauro Carvalho Chehab , Emil Velikov , intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org, kernel@collabora.com, linux-media@vger.kernel.org References: <20230529223935.2672495-1-dmitry.osipenko@collabora.com> <20230529223935.2672495-3-dmitry.osipenko@collabora.com> From: Dmitry Osipenko In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Hi, On 6/21/23 20:21, T.J. Mercier wrote: > On Mon, May 29, 2023 at 3:46 PM Dmitry Osipenko > wrote: >> >> Don't assert held dma-buf reservation lock on memory mapping of exported >> buffer. >> >> We're going to change dma-buf mmap() locking policy such that exporters >> will have to handle the lock. The previous locking policy caused deadlock >> problem for DRM drivers in a case of self-imported dma-bufs once these >> drivers are moved to use reservation lock universally. The problem >> solved by moving the lock down to exporters. This patch prepares dma-buf >> heaps for the locking policy update. >> > Hi Dmitry, > > I see that in patch 6 of this series calls to > dma_resv_lock/dma_resv_unlock have been added to the > drm_gem_shmem_helper functions and some exporters. But I'm curious why > no dma_resv_lock/dma_resv_unlock calls were added to these two dma-buf > heap exporters for mmap? DMA-buf heaps are exporters, drm_gem_shmem_helper is importer. Locking rules are different for importers and exporters. DMA-heaps use own locking, they can be moved to resv lock in the future. DMA-heaps don't protect internal data in theirs mmap() implementations, nothing to protect there. -- Best regards, Dmitry