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 X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C514C63797 for ; Thu, 22 Jul 2021 10:36:01 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 7945660FED for ; Thu, 22 Jul 2021 10:35:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7945660FED Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0C8846ECC2; Thu, 22 Jul 2021 10:35:59 +0000 (UTC) Received: from mail-ej1-x62a.google.com (mail-ej1-x62a.google.com [IPv6:2a00:1450:4864:20::62a]) by gabe.freedesktop.org (Postfix) with ESMTPS id CED7A6ECC3 for ; Thu, 22 Jul 2021 10:35:57 +0000 (UTC) Received: by mail-ej1-x62a.google.com with SMTP id hr1so7711425ejc.1 for ; Thu, 22 Jul 2021 03:35:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=date:from:to:cc:subject:message-id:mail-followup-to:references :mime-version:content-disposition:in-reply-to; bh=GrVJiLCQ2td0LvFK6G+f6bTrOT7qBQ9CowikA35mI6k=; b=MPLRAuRMQscjJ1bRSPG4VJjStt0rZUgJLQkjV8Ee74n4JK+gKsZ7E7GbremKpAbXEa 5RSfjjBngX0otVhG9sMSkQLeikaSoPGMoGGqC4NPQ/xZwSIJGc3C3qKQAjXJzoqHtrnc PPUUoOevWpVg4MQ3t0pqVrvjBRHgXApPIqqX0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id :mail-followup-to:references:mime-version:content-disposition :in-reply-to; bh=GrVJiLCQ2td0LvFK6G+f6bTrOT7qBQ9CowikA35mI6k=; b=ryCWSQJcjrGQb3m8gRVH6ybvTPqenko0aF1K+P3aGDcEjWycgC49w0K8X1J3B1aho9 KuUgFGOR7h+PagPgPuETakAhe2xXhHH4+TOBMyaEKRv2dQvsTBSnn2wt5ZUj7bcu3h/+ kSj/kmCMTi1U4MqDrchY/yssfqHocyaEz7VECjGYePAlS9INlMHO+JPaylzjogwa0mT4 VmpmFSt1H4dyX9cpJxF3JjcDi0SviBtBbRseP60AaRaKugRrpbBHN3wwb4WjTFWeT/tf HxloIWAbDXJifMg9ToAqZ43mdtfZ7UfkGFrBJp7dt2F/gfwDKIwz6f8AsHxfYBvPx2CO s6UA== X-Gm-Message-State: AOAM5328PxKNbYcAJlFwC57WGDFbKpzYdtsh+D6DOJ4CXNNFN0S9s3+7 MWTGCREd/PCx4tdOn8do5cKPRA== X-Google-Smtp-Source: ABdhPJzNq6lAT9fVXCqbmiOVhh6CzSJjtq8+tM+DSHEpE5WiLhtvjojRagf8CYVO6eOi+rS6ouALzA== X-Received: by 2002:a17:906:990f:: with SMTP id zl15mr43047702ejb.34.1626950156329; Thu, 22 Jul 2021 03:35:56 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id i6sm9257113ejr.68.2021.07.22.03.35.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Jul 2021 03:35:55 -0700 (PDT) Date: Thu, 22 Jul 2021 12:35:53 +0200 From: Daniel Vetter To: Desmond Cheong Zhi Xi Subject: Re: [PATCH 2/3] drm: clarify lifetime/locking for drm_master's lease fields Message-ID: Mail-Followup-To: Desmond Cheong Zhi Xi , linux-graphics-maintainer@vmware.com, zackr@vmware.com, airlied@linux.ie, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, skhan@linuxfoundation.org, gregkh@linuxfoundation.org, linux-kernel-mentees@lists.linuxfoundation.org References: <20210722092929.244629-1-desmondcheongzx@gmail.com> <20210722092929.244629-3-desmondcheongzx@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210722092929.244629-3-desmondcheongzx@gmail.com> X-Operating-System: Linux phenom 5.10.0-7-amd64 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: , Cc: tzimmermann@suse.de, airlied@linux.ie, gregkh@linuxfoundation.org, intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-graphics-maintainer@vmware.com, dri-devel@lists.freedesktop.org, skhan@linuxfoundation.org, linux-kernel-mentees@lists.linuxfoundation.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Thu, Jul 22, 2021 at 05:29:28PM +0800, Desmond Cheong Zhi Xi wrote: > In particular, we make it clear that &drm_device.mode_config.idr_mutex > protects the lease idr and list structures for drm_master. The lessor > field itself doesn't need to be protected as it doesn't change after > it's set in drm_lease_create. > > Additionally, we add descriptions for the lifetime of lessors and > leases to make it easier to reason about them. > > Signed-off-by: Desmond Cheong Zhi Xi > --- > include/drm/drm_auth.h | 62 ++++++++++++++++++++++++++++++++++-------- > 1 file changed, 51 insertions(+), 11 deletions(-) > > diff --git a/include/drm/drm_auth.h b/include/drm/drm_auth.h > index f99d3417f304..c978c85464fa 100644 > --- a/include/drm/drm_auth.h > +++ b/include/drm/drm_auth.h > @@ -58,12 +58,6 @@ struct drm_lock_data { > * @refcount: Refcount for this master object. > * @dev: Link back to the DRM device > * @driver_priv: Pointer to driver-private information. > - * @lessor: Lease holder > - * @lessee_id: id for lessees. Owners always have id 0 > - * @lessee_list: other lessees of the same master > - * @lessees: drm_masters leasing from this one > - * @leases: Objects leased to this drm_master. > - * @lessee_idr: All lessees under this owner (only used where lessor == NULL) > * > * Note that master structures are only relevant for the legacy/primary device > * nodes, hence there can only be one per device, not one per drm_minor. > @@ -88,17 +82,63 @@ struct drm_master { > struct idr magic_map; > void *driver_priv; > > - /* Tree of display resource leases, each of which is a drm_master struct > - * All of these get activated simultaneously, so drm_device master points > - * at the top of the tree (for which lessor is NULL). Protected by > - * &drm_device.mode_config.idr_mutex. > + /** > + * @lessor: > + * > + * Lease holder. The lessor does not change once it's set in Lessor is the lease grantor, lessee is the one receiving the lease. Maybe clarify this with "Lease grantor, only set if this struct drm_master represents a lessee holding a lease of objects from @lessor. Full owners of the device have this set to NULL." > + * drm_lease_create(). Each lessee holds a reference to its lessor that I also figured it'd be a good idea to link to the drm_lease docs here to explain the concepts, but alas we don't have those :-( Hence at least define what we mean with lessor, lessee, lease and owner. > + * it releases upon being destroyed in drm_lease_destroy(). > + * > + * Display resource leases form a tree of &struct drm_master. All of For now we've limited the tree to a depth of 1, you can't create another lease if yourself are a lease. I guess another reason to update the drm_lease.c docs. So maybe add "Currently the lease tree depth is limited to 1." > + * these get activated simultaneously, so &drm_device.master > + * points at the top of the tree (for which lessor is NULL). > */ > - > struct drm_master *lessor; > + > + /** > + * @lessee_id: > + * > + * ID for lessees. Owners always have ID 0. Protected by Maybe clarify to "Owners (i.e. @lessor is NULL) ..." > + * &drm_device.mode_config's &drm_mode_config.idr_mutex. > + */ > int lessee_id; > + > + /** > + * @lessee_list: > + * > + * List of lessees of the same master. Protected by We try to distinguis between list entries and the list, even though it's the same struct. So maybe "List entry of lessees of @lessor, where they are linked to @lessee. Not use for owners." > + * &drm_device.mode_config's &drm_mode_config.idr_mutex. > + */ > struct list_head lessee_list; > + > + /** > + * @lessees: > + * > + * List of drm_masters leasing from this one. Protected by > + * &drm_device.mode_config's &drm_mode_config.idr_mutex. > + * > + * This master cannot be destroyed unless this list is empty as lessors > + * are referenced by all their lessees. Maybe add "this list is empty of no leases have been granted." > + */ > struct list_head lessees; > + > + /** > + * @leases: > + * > + * Objects leased to this drm_master. Protected by > + * &drm_device.mode_config's &drm_mode_config.idr_mutex. > + * > + * Objects are leased all together in drm_lease_create(), and are > + * removed all together when the lease is revoked. > + */ > struct idr leases; > + > + /** > + * @lessee_idr: > + * > + * All lessees under this owner (only used where lessor is NULL). @lessor so it's highlighted correctly > + * Protected by &drm_device.mode_config's &drm_mode_config.idr_mutex. > + */ > struct idr lessee_idr; > /* private: */ With the nits addressed: Reviewed-by: Daniel Vetter Thanks for updating the docs! -Daniel > #if IS_ENABLED(CONFIG_DRM_LEGACY) > -- > 2.25.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch