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 CED6ECA1009 for ; Tue, 5 Sep 2023 17:08:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351410AbjIERFW (ORCPT ); Tue, 5 Sep 2023 13:05:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50034 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353724AbjIEHd2 (ORCPT ); Tue, 5 Sep 2023 03:33:28 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e5ab]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F1DF918C for ; Tue, 5 Sep 2023 00:33:24 -0700 (PDT) Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by madras.collabora.co.uk (Postfix) with ESMTPSA id EB205660716C; Tue, 5 Sep 2023 08:33:22 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1693899203; bh=77PTdlmF0OU78SUMZuNK96mglFtntqL2JeT8yn02ajs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=EqvzcgU5VH/pSuVHsNn6GF+WxvkX4Z61bGfgcsACjQrW0qnZAXPPKBS8On4o/nw2K CiJfsgpszqWOeWdGwBrh7VD3lYAr+FUUMyAEdrKP0DHVdAg4i+EXvSCBeDDvILsxnY 7ouEn1J/6n+bh5XqV9K6CUfTivk1MaXtP+WTMQe8+TcvXa2tt0WZRjuJcBNIkhghxR B4boyww+atN/8YZ0AFwC4EUqDLr8w/G89wYpgp04T4+DcialHK2eHXKGeM5l8OdlFo bUjvinVuakOuI56VfQ5c85rd2RLVvHRck5CyDYHk/4TbmBrkFmPhP3woHm5s+3TWSY EW+a/t02HPIvw== Date: Tue, 5 Sep 2023 09:33:19 +0200 From: Boris Brezillon To: Dmitry Osipenko Cc: David Airlie , Gerd Hoffmann , Gurchetan Singh , Chia-I Wu , Daniel Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Christian =?UTF-8?B?S8O2bmln?= , Qiang Yu , Steven Price , Emma Anholt , Melissa Wen , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v16 05/20] drm/v3d: Replace open-coded drm_gem_shmem_free() with drm_gem_object_put() Message-ID: <20230905093319.25300fa4@collabora.com> In-Reply-To: <20230903170736.513347-6-dmitry.osipenko@collabora.com> References: <20230903170736.513347-1-dmitry.osipenko@collabora.com> <20230903170736.513347-6-dmitry.osipenko@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 3 Sep 2023 20:07:21 +0300 Dmitry Osipenko wrote: > The drm_gem_shmem_free() doesn't put GEM's kref to zero, which becomes > important with addition of the shrinker support to drm-shmem that will > use kref=0 in order to prevent taking lock during special GEM-freeing > time in order to avoid spurious lockdep warning about locking ordering > vs fs_reclaim code paths. As for patch 4, I don't mind the change (I actually think it's better to have a single error path with a free function handling partially initialized GEM objects, which is exactly what your patch is doing), but I disagree with the explanation, especially after you dropped "drm/shmem-helper: Add and use drm_gem_shmem_resv_assert_held() helper" and went for a drm_gem_shmem_do_release_pages_locked() helper called in drm_gem_shmem_free(). > > Replace open-coded drm_gem_shmem_free() with drm_gem_object_put() that > drops kref to zero before freeing GEM. > > Signed-off-by: Dmitry Osipenko > --- > drivers/gpu/drm/v3d/v3d_bo.c | 22 ++++++++++++---------- > 1 file changed, 12 insertions(+), 10 deletions(-) > > diff --git a/drivers/gpu/drm/v3d/v3d_bo.c b/drivers/gpu/drm/v3d/v3d_bo.c > index 8b3229a37c6d..70c1095d6eec 100644 > --- a/drivers/gpu/drm/v3d/v3d_bo.c > +++ b/drivers/gpu/drm/v3d/v3d_bo.c > @@ -33,16 +33,18 @@ void v3d_free_object(struct drm_gem_object *obj) > struct v3d_dev *v3d = to_v3d_dev(obj->dev); > struct v3d_bo *bo = to_v3d_bo(obj); > > - v3d_mmu_remove_ptes(bo); > + if (drm_mm_node_allocated(&bo->node)) { > + v3d_mmu_remove_ptes(bo); > > - mutex_lock(&v3d->bo_lock); > - v3d->bo_stats.num_allocated--; > - v3d->bo_stats.pages_allocated -= obj->size >> PAGE_SHIFT; > - mutex_unlock(&v3d->bo_lock); > + mutex_lock(&v3d->bo_lock); > + v3d->bo_stats.num_allocated--; > + v3d->bo_stats.pages_allocated -= obj->size >> PAGE_SHIFT; > + mutex_unlock(&v3d->bo_lock); > > - spin_lock(&v3d->mm_lock); > - drm_mm_remove_node(&bo->node); > - spin_unlock(&v3d->mm_lock); > + spin_lock(&v3d->mm_lock); > + drm_mm_remove_node(&bo->node); > + spin_unlock(&v3d->mm_lock); > + } > > /* GPU execution may have dirtied any pages in the BO. */ > bo->base.pages_mark_dirty_on_put = true; > @@ -142,7 +144,7 @@ struct v3d_bo *v3d_bo_create(struct drm_device *dev, struct drm_file *file_priv, > return bo; > > free_obj: > - drm_gem_shmem_free(shmem_obj); > + drm_gem_object_put(&shmem_obj->base); > return ERR_PTR(ret); > } > > @@ -160,7 +162,7 @@ v3d_prime_import_sg_table(struct drm_device *dev, > > ret = v3d_bo_create_finish(obj); > if (ret) { > - drm_gem_shmem_free(&to_v3d_bo(obj)->base); > + drm_gem_object_put(obj); > return ERR_PTR(ret); > } >