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 40661CD37BE for ; Mon, 11 May 2026 15:44:39 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 9C52A10E7D2; Mon, 11 May 2026 15:44:38 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=collabora.com header.i=@collabora.com header.b="TrS8d6pH"; dkim-atps=neutral Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) by gabe.freedesktop.org (Postfix) with ESMTPS id 46DF210E1D4; Mon, 11 May 2026 15:44:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1778514275; bh=BClQxIrtlJf+uCt+8eJy+vplQxwI6Of0OhdL/r5XqzU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=TrS8d6pHgxpSLEgsPlarE4gNM42EVGOv7vtZLRXVrIada9O3gxDC1tkqeoBXPtazN ZGRAksNZzqICJIH8tGS7QuvXIVnOQ6vSjgU3Z4EKTO7tUlTXVNZ6aagzoe7PplZbS7 v+HrXnoMTAIFZBmuL7hyGzsBE87sZ6ANY0tDJ/W3nsx5wDYNC/VZXw16nj1qtjQ8Sk rQ7HWmr1Q5TIq+21pRNyRCNMgD6mCPMBqZcdB58B8CH+TuXeWoqfKfAHSl9HmFemvG BkmKxynFDbCdEnV+27KrAeeKlWQsN4eBzhj+pfrCcVM71u93La85AKnLoj1jWiisfZ V68JclhfmeR9A== Received: from fedora (unknown [100.64.0.11]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by bali.collaboradmins.com (Postfix) with ESMTPSA id 3216717E0615; Mon, 11 May 2026 17:44:35 +0200 (CEST) Date: Mon, 11 May 2026 17:44:29 +0200 From: Boris Brezillon To: Rob Clark Cc: Steven Price , Liviu Dudau , 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: <20260511174429.35afcdee@fedora> In-Reply-To: References: <20260508-panthor-shrinker-fixes-v2-0-39cdb7d577c9@collabora.com> <20260508-panthor-shrinker-fixes-v2-4-39cdb7d577c9@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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, 11 May 2026 06:18:44 -0700 Rob Clark wrote: > On Fri, May 8, 2026 at 3:41=E2=80=AFAM 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 =20 >=20 > 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?