From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0CB17423A8A; Mon, 11 May 2026 16:27:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.251.105.195 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778516823; cv=none; b=t7y8xi7L8DivVC40KKmk7ewJ/Gx3x6VDbpnRgiBkW+VjHOg5R/tQ5XeNitYOZGZvikPPXokHMQkS3Hjg9EYb64biT44j4kluUhTg2OucXDLACapOc/TrVRx5ZdLn02ZC5Xl9x1zN1k6gDgxHqiyQ/BRTbz8D0KIE3Rq6sTwF9H8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778516823; c=relaxed/simple; bh=o/nruX8ocP49ocj+MJGaWE8H3U7n4bIxuduRAQlimDk=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=jvAKhLSjEomh1Suf53wUnXKQIu5wUS38h63T5iJuZRzE8hLUZNn5hnS099sHqNXUpeuYKV3BhQBUWfuGk0amvklSk7Mb9ZtyClc3Eh0r6VSbpPUIRts4VH2C/ON3IJfPtTKgtn/te/VGjR/uQjgy4sJ53NlOISZrWfr9QP/HTkg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b=hBTFhxz6; arc=none smtp.client-ip=148.251.105.195 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="hBTFhxz6" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1778516820; bh=o/nruX8ocP49ocj+MJGaWE8H3U7n4bIxuduRAQlimDk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=hBTFhxz64qsvOcHN7XP5q5gZ6kjAVpZ5UHS95KbcsH58nbl3Gcqeq/IkpL6tg0xVO LnZtqAzfErhoKjegNRaiRlUAHt3QI693n0x3AgEf+nxWTtWP/K9/zU/lhjHkmAmTow dm9xwHEeZKlZ4kGEGAhhxbXOpLnkpyIcISPr1zhyBEHk/HuZ39sPtj6OV+LvpvE6gS KKICNIZCMgUuO4qHkc2uRMxv8H+wzDGTWl2GuB6QxtZq6z9wynQfW6/iBdejMSdxIe eLwm8stfaOqpotqGytkJjG/8/3sUaaA406c3PkIpaZdr/Z69rNq1gc8wqV6m5uYHLS xMKpXapI5FClw== 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 72DB817E1004; Mon, 11 May 2026 18:26:59 +0200 (CEST) Date: Mon, 11 May 2026 18:26:53 +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: <20260511182653.5a9c99fb@fedora> In-Reply-To: References: <20260508-panthor-shrinker-fixes-v2-0-39cdb7d577c9@collabora.com> <20260508-panthor-shrinker-fixes-v2-4-39cdb7d577c9@collabora.com> <20260511174429.35afcdee@fedora> Organization: Collabora X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Mon, 11 May 2026 09:16:49 -0700 Rob Clark wrote: > On Mon, May 11, 2026 at 8:44=E2=80=AFAM Boris Brezillon > wrote: > > > > On Mon, 11 May 2026 06:18:44 -0700 > > Rob Clark wrote: > > =20 > > > On Fri, May 8, 2026 at 3:41=E2=80=AFAM Boris Brezillon > > > wrote: =20 > > > > > > > > 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 l= ock > > > > through and finally take the lock and do the expected operation. > > > > > > > > Currently, the two drivers making use of this API declare device-wi= de > > > > locks, and there's no clue that we will ever have a driver that wan= ts > > > > 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 thro= ugh > > > > dev->gem_lru_mutex. > > > > > > > > If anyone ever needs more fine-grained locking, this can be revisit= ed > > > > to pass some drm_gem_lru_pool object represent the pool of LRUs und= er > > > > a specific lock, but for now, the per-device lock seems to be enoug= h. > > > > > > > > Signed-off-by: Boris Brezillon =20 > > > > > > Reviewed-by: Rob Clark =20 > > > > 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? =20 >=20 > 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 fine with that too (the panthor resolution should be fairly straightforward anyway). I'll post a v3 with just patch 4 then.