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=-12.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 DD57FC43461 for ; Thu, 29 Apr 2021 12:33:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA82C61400 for ; Thu, 29 Apr 2021 12:33:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231708AbhD2MeL (ORCPT ); Thu, 29 Apr 2021 08:34:11 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:39231 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237075AbhD2MeJ (ORCPT ); Thu, 29 Apr 2021 08:34:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619699602; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GrKq3UC4OJTuxJrBqTBTU6T4d2IlYMcI0WkWfsWdexI=; b=BY3NK6K/lBjsl+5wAtZE5UH0yVWILhLEY8T2wWmRz7tI0j7z7iCdmU03ZJVdtK8vBFKmBJ jxzgoC+9AF7gDePK0z2VfxxUtWAD0wvpDThZphwwaAeYOFhalu4YfD19r9d5k2Eq6yrB40 xDQkUgZyG0kYSFnykS4L8/7Skb5IWuI= Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-317-iQBCQezlOxCHpWxFLd5fOw-1; Thu, 29 Apr 2021 08:33:20 -0400 X-MC-Unique: iQBCQezlOxCHpWxFLd5fOw-1 Received: by mail-ed1-f71.google.com with SMTP id o4-20020a0564024384b0290378d45ecf57so28873098edc.12 for ; Thu, 29 Apr 2021 05:33:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=GrKq3UC4OJTuxJrBqTBTU6T4d2IlYMcI0WkWfsWdexI=; b=aPv/jU7bMrmJOOApZlL0RQyMEETXH07lAyCgt9uWRvD+SqvEjSVFSgVU2YuOY52gnE twawxb4O7sUF1wuF4nRox9bCfOoT0YlUIRgKF3dbEm7hTVPeHYi5NAwQMzI1zC4Fqn5e Z4LZZ9Vst/zn5hlM7vT3fSqX55NFyhbiFI+qRnAhZg/aiF2obrbMGF+y8h7z2//027Qv g5lUq6dlSPDCk+buxwiS2r0EyuUZnJjdDyzCvRs6+BcN/Uh/exw3KNVI0jUChsoJXJyZ B5a49V7OlJDHUiaVinCIMmowo13e5ORLhPzNjT0S8HGZqPwy/2SeTKRR4oRu1KbjZ5q3 o+Dg== X-Gm-Message-State: AOAM53360iGwFUfAWyK3newWNXlG41XMZFQAnGrDIC4SOgaqnciodlZ/ WJ4s5G6iPwECFZiaFSlQGJ4eGfGHgVCilTanTMt+epEz/HQSY5F3ABSzdSnGGXHTNLn+bh/RNrX HvVUJjgTHpyhOWgpREm1Z4H7wtbrJc/D4cg== X-Received: by 2002:a17:907:75f6:: with SMTP id jz22mr24635651ejc.504.1619699599298; Thu, 29 Apr 2021 05:33:19 -0700 (PDT) X-Google-Smtp-Source: ABdhPJy6XSSTtlaPBL2Al2wSDZ5kLm8eA5zhcM5X1CoKpafjS9IMvkP05RefygrrVGfqccP4YWJw7A== X-Received: by 2002:a17:907:75f6:: with SMTP id jz22mr24635628ejc.504.1619699599119; Thu, 29 Apr 2021 05:33:19 -0700 (PDT) Received: from x1.localdomain (2001-1c00-0c1e-bf00-1054-9d19-e0f0-8214.cable.dynamic.v6.ziggo.nl. [2001:1c00:c1e:bf00:1054:9d19:e0f0:8214]) by smtp.gmail.com with ESMTPSA id t15sm2296998edr.55.2021.04.29.05.33.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Apr 2021 05:33:18 -0700 (PDT) Subject: Re: [PATCH 1/9] drm/connector: Make the drm_sysfs connector->kdev device hold a reference to the connector To: Daniel Vetter , Greg Kroah-Hartman Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Guenter Roeck , Heikki Krogerus , intel-gfx , dri-devel@lists.freedesktop.org, platform-driver-x86@vger.kernel.org, linux-usb@vger.kernel.org References: <20210428215257.500088-1-hdegoede@redhat.com> <20210428215257.500088-2-hdegoede@redhat.com> From: Hans de Goede Message-ID: <4e78d188-f257-ad33-e703-bcbc54a30c31@redhat.com> Date: Thu, 29 Apr 2021 14:33:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: platform-driver-x86@vger.kernel.org Hi, On 4/29/21 2:04 PM, Daniel Vetter wrote: > On Thu, Apr 29, 2021 at 01:54:46PM +0200, Greg Kroah-Hartman wrote: >> On Thu, Apr 29, 2021 at 01:40:28PM +0200, Daniel Vetter wrote: >>> On Wed, Apr 28, 2021 at 11:52:49PM +0200, Hans de Goede wrote: >>>> Userspace could hold open a reference to the connector->kdev device, >>>> through e.g. holding a sysfs-atrtribute open after >>>> drm_sysfs_connector_remove() has been called. In this case the connector >>>> could be free-ed while the connector->kdev device's drvdata is still >>>> pointing to it. >>>> >>>> Give drm_connector devices there own device type, which allows >>>> us to specify our own release function and make drm_sysfs_connector_add() >>>> take a reference on the connector object, and have the new release >>>> function put the reference when the device is released. >>>> >>>> Giving drm_connector devices there own device type, will also allow >>>> checking if a device is a drm_connector device with a >>>> "if (device->type == &drm_sysfs_device_connector)" check. >>>> >>>> Note that the setting of the name member of the device_type struct will >>>> cause udev events for drm_connector-s to now contain DEVTYPE=drm_connector >>>> as extra info. So this extends the uevent part of the userspace API. >>>> >>>> Signed-off-by: Hans de Goede >>> >>> Are you sure? I thought sysfs is supposed to flush out any pending >>> operations (they complete fast) and handle open fd internally? >> >> Yes, it "should" :) > > Thanks for confirming my vague memories :-) > > Hans, pls drop this one. Please see my earlier reply to your review of this patch, it is still needed but for a different reason: """ We still need this change though to make sure that the "drm/connector: Add drm_connector_find_by_fwnode() function" does not end up following a dangling drvdat pointer from one if the drm_connector kdev-s. The class_dev_iter_init() in drm_connector_find_by_fwnode() gets a reference on all devices and between getting that reference and it calling drm_connector_get() - drm_connector_unregister() may run and drop the possibly last reference to the drm_connector object, freeing it and leaving the kdev's drvdata as a dangling pointer. """ This is actually why I added it initially, and while adding it I came up with this wrong theory of why it was necessary independently of the drm_connector_find_by_fwnode() addition, sorry about that. Regards, Hans 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=-10.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 AE36DC433ED for ; Thu, 29 Apr 2021 12:33:25 +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 4431F6101C for ; Thu, 29 Apr 2021 12:33:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4431F6101C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 77DA16EE8D; Thu, 29 Apr 2021 12:33:24 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id E8CF26EE8D for ; Thu, 29 Apr 2021 12:33:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619699602; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GrKq3UC4OJTuxJrBqTBTU6T4d2IlYMcI0WkWfsWdexI=; b=BY3NK6K/lBjsl+5wAtZE5UH0yVWILhLEY8T2wWmRz7tI0j7z7iCdmU03ZJVdtK8vBFKmBJ jxzgoC+9AF7gDePK0z2VfxxUtWAD0wvpDThZphwwaAeYOFhalu4YfD19r9d5k2Eq6yrB40 xDQkUgZyG0kYSFnykS4L8/7Skb5IWuI= Received: from mail-ej1-f69.google.com (mail-ej1-f69.google.com [209.85.218.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-570-a3Rpx9Z6OQaSEFLityI7Wg-1; Thu, 29 Apr 2021 08:33:20 -0400 X-MC-Unique: a3Rpx9Z6OQaSEFLityI7Wg-1 Received: by mail-ej1-f69.google.com with SMTP id h9-20020a1709063c09b0290393e97fec0fso1673031ejg.13 for ; Thu, 29 Apr 2021 05:33:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=GrKq3UC4OJTuxJrBqTBTU6T4d2IlYMcI0WkWfsWdexI=; b=Wx+yDTttuhFghb21piz3iBsKTHInxMZacelmFJ6ywZUzWG7MtjDfMMngxxheHf15YI COrBhsJzn0m92f6tBFYNqWbGQ+F+ozUjhslKg5Xrvvcj7LQeM6Ne7WLM58D11pyRt+rE lOUUEiI5NmOL41ORPPDI+HtY+UMjAq5NVnJsZcPZVZBaB5otNmVz9zcJTGYOJNyPfWdZ DkRyffCSAReeX00bY69Amd08CXZPYVV0Sd2ZYfiCA1SoGq6BV5Op9jBBYqRt7f4vA6+B q/crB2ASq4PTwBJ7c4uYJGTa3Ej1C4iEcKQvwThOPYMnlXzrCyLQnLSTWqqUoLg+7i0z e0+Q== X-Gm-Message-State: AOAM531vI9uM8pqz606VVP3CmSlsqcZWcNrH1cgsOd9J8hT6WwgPALdx wYv5MAAh/Ciw0oqCIblTchStyIgM3VXrCdqRGqoNJGu72nEcXXdJWYRW6lAPCDL1iEvsHbzVWoD hLjZ1oTGf56xRrvlRW1UI0w3cr1Dn X-Received: by 2002:a17:907:75f6:: with SMTP id jz22mr24635653ejc.504.1619699599321; Thu, 29 Apr 2021 05:33:19 -0700 (PDT) X-Google-Smtp-Source: ABdhPJy6XSSTtlaPBL2Al2wSDZ5kLm8eA5zhcM5X1CoKpafjS9IMvkP05RefygrrVGfqccP4YWJw7A== X-Received: by 2002:a17:907:75f6:: with SMTP id jz22mr24635628ejc.504.1619699599119; Thu, 29 Apr 2021 05:33:19 -0700 (PDT) Received: from x1.localdomain (2001-1c00-0c1e-bf00-1054-9d19-e0f0-8214.cable.dynamic.v6.ziggo.nl. [2001:1c00:c1e:bf00:1054:9d19:e0f0:8214]) by smtp.gmail.com with ESMTPSA id t15sm2296998edr.55.2021.04.29.05.33.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Apr 2021 05:33:18 -0700 (PDT) Subject: Re: [PATCH 1/9] drm/connector: Make the drm_sysfs connector->kdev device hold a reference to the connector To: Daniel Vetter , Greg Kroah-Hartman References: <20210428215257.500088-1-hdegoede@redhat.com> <20210428215257.500088-2-hdegoede@redhat.com> From: Hans de Goede Message-ID: <4e78d188-f257-ad33-e703-bcbc54a30c31@redhat.com> Date: Thu, 29 Apr 2021 14:33:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=hdegoede@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US 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: Heikki Krogerus , dri-devel@lists.freedesktop.org, David Airlie , intel-gfx , platform-driver-x86@vger.kernel.org, linux-usb@vger.kernel.org, Thomas Zimmermann , Rodrigo Vivi , Guenter Roeck Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi, On 4/29/21 2:04 PM, Daniel Vetter wrote: > On Thu, Apr 29, 2021 at 01:54:46PM +0200, Greg Kroah-Hartman wrote: >> On Thu, Apr 29, 2021 at 01:40:28PM +0200, Daniel Vetter wrote: >>> On Wed, Apr 28, 2021 at 11:52:49PM +0200, Hans de Goede wrote: >>>> Userspace could hold open a reference to the connector->kdev device, >>>> through e.g. holding a sysfs-atrtribute open after >>>> drm_sysfs_connector_remove() has been called. In this case the connector >>>> could be free-ed while the connector->kdev device's drvdata is still >>>> pointing to it. >>>> >>>> Give drm_connector devices there own device type, which allows >>>> us to specify our own release function and make drm_sysfs_connector_add() >>>> take a reference on the connector object, and have the new release >>>> function put the reference when the device is released. >>>> >>>> Giving drm_connector devices there own device type, will also allow >>>> checking if a device is a drm_connector device with a >>>> "if (device->type == &drm_sysfs_device_connector)" check. >>>> >>>> Note that the setting of the name member of the device_type struct will >>>> cause udev events for drm_connector-s to now contain DEVTYPE=drm_connector >>>> as extra info. So this extends the uevent part of the userspace API. >>>> >>>> Signed-off-by: Hans de Goede >>> >>> Are you sure? I thought sysfs is supposed to flush out any pending >>> operations (they complete fast) and handle open fd internally? >> >> Yes, it "should" :) > > Thanks for confirming my vague memories :-) > > Hans, pls drop this one. Please see my earlier reply to your review of this patch, it is still needed but for a different reason: """ We still need this change though to make sure that the "drm/connector: Add drm_connector_find_by_fwnode() function" does not end up following a dangling drvdat pointer from one if the drm_connector kdev-s. The class_dev_iter_init() in drm_connector_find_by_fwnode() gets a reference on all devices and between getting that reference and it calling drm_connector_get() - drm_connector_unregister() may run and drop the possibly last reference to the drm_connector object, freeing it and leaving the kdev's drvdata as a dangling pointer. """ This is actually why I added it initially, and while adding it I came up with this wrong theory of why it was necessary independently of the drm_connector_find_by_fwnode() addition, sorry about that. Regards, Hans _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel 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=-10.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 D485DC433B4 for ; Thu, 29 Apr 2021 12:33:26 +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 7671E613F4 for ; Thu, 29 Apr 2021 12:33:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7671E613F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E77B56EE8E; Thu, 29 Apr 2021 12:33:24 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id 88B4A6EE8D for ; Thu, 29 Apr 2021 12:33:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619699602; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GrKq3UC4OJTuxJrBqTBTU6T4d2IlYMcI0WkWfsWdexI=; b=BY3NK6K/lBjsl+5wAtZE5UH0yVWILhLEY8T2wWmRz7tI0j7z7iCdmU03ZJVdtK8vBFKmBJ jxzgoC+9AF7gDePK0z2VfxxUtWAD0wvpDThZphwwaAeYOFhalu4YfD19r9d5k2Eq6yrB40 xDQkUgZyG0kYSFnykS4L8/7Skb5IWuI= Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-423-dsDSaCsJMXeFl31mZGqpNg-1; Thu, 29 Apr 2021 08:33:20 -0400 X-MC-Unique: dsDSaCsJMXeFl31mZGqpNg-1 Received: by mail-ed1-f72.google.com with SMTP id c15-20020a056402100fb029038518e5afc5so21214929edu.18 for ; Thu, 29 Apr 2021 05:33:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=GrKq3UC4OJTuxJrBqTBTU6T4d2IlYMcI0WkWfsWdexI=; b=i/HNyO79JouQSeHVlsqULba93XBr9g0Nu4aQVXCTTDcC18DrpYKLtVrMZZqeLJWsbS twyJETBOipTAXkFKSccUUtcRJVntAAT1MJoAMUWO0QoftLY0Z9oVC5rpqBakedZK1GgN BrYKDA4oJeeI8x5ZtsBp4KmMnNeKQxRqQXt74ckvSJZ5mH2Lik8jwtoY6sS/ziv5R9i3 Rz63skH0z2+5kRhArE3uSeoNSvDOwexa+YgTjUb7UjNLkDe4pNRrglNAxTO6urRgf34H Jw9cPe/JFSsQ1Pij/bGXxkdXhi5OINhceH5XKZC6S0FEmNfYTk7+tQRVDzj/RilKWp00 epig== X-Gm-Message-State: AOAM530q/+2zigrlI3W25r375dcPokIlxoleF7/tPWkLeXrijhSBHQ4c pXsuOOSq+CeC0CMtYC/fatvLS5q0wIZ2VceN2IgG2yl0zKb2eh/b58k8p3cH3l/pfKwbToKZrmv WG908r8bKb4dWwiVWmD3FtNQlxWxy X-Received: by 2002:a17:907:75f6:: with SMTP id jz22mr24635660ejc.504.1619699599405; Thu, 29 Apr 2021 05:33:19 -0700 (PDT) X-Google-Smtp-Source: ABdhPJy6XSSTtlaPBL2Al2wSDZ5kLm8eA5zhcM5X1CoKpafjS9IMvkP05RefygrrVGfqccP4YWJw7A== X-Received: by 2002:a17:907:75f6:: with SMTP id jz22mr24635628ejc.504.1619699599119; Thu, 29 Apr 2021 05:33:19 -0700 (PDT) Received: from x1.localdomain (2001-1c00-0c1e-bf00-1054-9d19-e0f0-8214.cable.dynamic.v6.ziggo.nl. [2001:1c00:c1e:bf00:1054:9d19:e0f0:8214]) by smtp.gmail.com with ESMTPSA id t15sm2296998edr.55.2021.04.29.05.33.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Apr 2021 05:33:18 -0700 (PDT) To: Daniel Vetter , Greg Kroah-Hartman References: <20210428215257.500088-1-hdegoede@redhat.com> <20210428215257.500088-2-hdegoede@redhat.com> From: Hans de Goede Message-ID: <4e78d188-f257-ad33-e703-bcbc54a30c31@redhat.com> Date: Thu, 29 Apr 2021 14:33:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=hdegoede@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Subject: Re: [Intel-gfx] [PATCH 1/9] drm/connector: Make the drm_sysfs connector->kdev device hold a reference to the connector X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Heikki Krogerus , dri-devel@lists.freedesktop.org, David Airlie , intel-gfx , platform-driver-x86@vger.kernel.org, linux-usb@vger.kernel.org, Maxime Ripard , Thomas Zimmermann , Guenter Roeck Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Hi, On 4/29/21 2:04 PM, Daniel Vetter wrote: > On Thu, Apr 29, 2021 at 01:54:46PM +0200, Greg Kroah-Hartman wrote: >> On Thu, Apr 29, 2021 at 01:40:28PM +0200, Daniel Vetter wrote: >>> On Wed, Apr 28, 2021 at 11:52:49PM +0200, Hans de Goede wrote: >>>> Userspace could hold open a reference to the connector->kdev device, >>>> through e.g. holding a sysfs-atrtribute open after >>>> drm_sysfs_connector_remove() has been called. In this case the connector >>>> could be free-ed while the connector->kdev device's drvdata is still >>>> pointing to it. >>>> >>>> Give drm_connector devices there own device type, which allows >>>> us to specify our own release function and make drm_sysfs_connector_add() >>>> take a reference on the connector object, and have the new release >>>> function put the reference when the device is released. >>>> >>>> Giving drm_connector devices there own device type, will also allow >>>> checking if a device is a drm_connector device with a >>>> "if (device->type == &drm_sysfs_device_connector)" check. >>>> >>>> Note that the setting of the name member of the device_type struct will >>>> cause udev events for drm_connector-s to now contain DEVTYPE=drm_connector >>>> as extra info. So this extends the uevent part of the userspace API. >>>> >>>> Signed-off-by: Hans de Goede >>> >>> Are you sure? I thought sysfs is supposed to flush out any pending >>> operations (they complete fast) and handle open fd internally? >> >> Yes, it "should" :) > > Thanks for confirming my vague memories :-) > > Hans, pls drop this one. Please see my earlier reply to your review of this patch, it is still needed but for a different reason: """ We still need this change though to make sure that the "drm/connector: Add drm_connector_find_by_fwnode() function" does not end up following a dangling drvdat pointer from one if the drm_connector kdev-s. The class_dev_iter_init() in drm_connector_find_by_fwnode() gets a reference on all devices and between getting that reference and it calling drm_connector_get() - drm_connector_unregister() may run and drop the possibly last reference to the drm_connector object, freeing it and leaving the kdev's drvdata as a dangling pointer. """ This is actually why I added it initially, and while adding it I came up with this wrong theory of why it was necessary independently of the drm_connector_find_by_fwnode() addition, sorry about that. Regards, Hans _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx