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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 94727CD4840 for ; Mon, 11 May 2026 16:27:36 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 032A010E82D; Mon, 11 May 2026 16:27:36 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=arm.com header.i=@arm.com header.b="JxYED0L5"; dkim-atps=neutral Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by gabe.freedesktop.org (Postfix) with ESMTP id 8C30410E828 for ; Mon, 11 May 2026 16:27:34 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D0CF416F2 for ; Mon, 11 May 2026 09:27:28 -0700 (PDT) Received: from [192.168.0.1] (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id E4CEA3F85F for ; Mon, 11 May 2026 09:27:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1778516854; bh=YonN8VL2BLEr4Q2OyxUKcgv3XivnvGDz2zoMI7+3kf0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JxYED0L5hD5f7S39vURTwe1p9M2Q3bGEayeu1Qa2P0mPELsUCPOi0xz58TkqdsYCO fo7Tna5AlR+Z1Q+coP6OmtTt14O/djiMCfeX86vcppVIZxWZv7G2G6XyfsJ5xEWQs6 zJz2neF3KadJKzkjRKU1+8JyWgXDI2+JnncybbDI= Date: Mon, 11 May 2026 17:27:13 +0100 From: Liviu Dudau To: Rob Clark Cc: Boris Brezillon , Steven Price , Dmitry Osipenko , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Akash Goel , Chia-I Wu , Dmitry Baryshkov , Abhinav Kumar , Jessica Zhang , Sean Paul , Marijn Suijten , linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 4/4] drm/gem: Make the GEM LRU lock part of drm_device Message-ID: References: <20260508-panthor-shrinker-fixes-v2-0-39cdb7d577c9@collabora.com> <20260508-panthor-shrinker-fixes-v2-4-39cdb7d577c9@collabora.com> <20260511174429.35afcdee@fedora> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Mon, May 11, 2026 at 09:16:49AM -0700, Rob Clark wrote: > On Mon, May 11, 2026 at 8:44 AM Boris Brezillon > wrote: > > > > On Mon, 11 May 2026 06:18:44 -0700 > > Rob Clark wrote: > > > > > On Fri, May 8, 2026 at 3:41 AM Boris Brezillon > > > wrote: > > > > > > > > Recently, a few races have been discovered in the GEM LRU logic, all > > > > of them caused by the fact the LRU lock is accessed through > > > > gem->lru->lock, and that lock itself also protects changes to > > > > gem->lru, leading to situations where gem->lru needs to first be > > > > accessed without the lock held, to then get the lru to access the lock > > > > through and finally take the lock and do the expected operation. > > > > > > > > Currently, the two drivers making use of this API declare device-wide > > > > locks, and there's no clue that we will ever have a driver that wants > > > > different pools of LRUs protected by different locks under the same > > > > drm_device. So we're better off moving this lock to drm_device and > > > > always locking it through obj->dev->gem_lru_mutex, or directly through > > > > dev->gem_lru_mutex. > > > > > > > > If anyone ever needs more fine-grained locking, this can be revisited > > > > to pass some drm_gem_lru_pool object represent the pool of LRUs under > > > > a specific lock, but for now, the per-device lock seems to be enough. > > > > > > > > Signed-off-by: Boris Brezillon > > > > > > Reviewed-by: Rob Clark > > > > If every one is happy with patch 4, I'm tempted to drop patch 1 and 3, > > since they are irrelevant if the locking is fixed the way it is in this > > patch. Question is, do we care about patch 2 being backported to stable > > kernels then? > > Or backport patch 4? It's a bit bigger, but mostly mechanical.. with > only issue being backporting across addition of panthor shrinker, I > guess? I'm agreeing with Rob here, but it makes a mess of the backport. Maybe split patch 4 into the drm_gem.c and msm changes and make another one for panthor, as that is still in linux-next? Best regards, Liviu > > BR, > -R -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯