Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751149AbdFAMNf (ORCPT ); Thu, 1 Jun 2017 08:13:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37304 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751054AbdFAMNe (ORCPT ); Thu, 1 Jun 2017 08:13:34 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 765FDC01CB71 Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=hdegoede@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 765FDC01CB71 Subject: Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8) To: jeffy , Chris Wilson , Sean Paul , linux-kernel@vger.kernel.org, briannorris@chromium.org, dianders@chromium.org, tfiga@chromium.org, zyw@rock-chips.com, marcheu@chromium.org, mark.yao@rock-chips.com, hshi@chromium.org, Daniel Vetter , Jani Nikula , dri-devel@lists.freedesktop.org, David Airlie , Tom Gundersen , =?UTF-8?Q?Marco_Diego_Aur=c3=a9lio_Mesquita?= , Patrik Jakobsson , Dave Airlie References: <1492068764-24353-1-git-send-email-jeffy.chen@rock-chips.com> <20170414151503.lmpp3udfuycavfki@art_vandelay> <20170529202512.GF23936@nuc-i3427.alporthouse.com> <47c5eca2-3624-edbc-bb2d-453645b6bf3b@redhat.com> <592E2CD1.8080206@rock-chips.com> From: Hans de Goede Message-ID: <7941eb36-725e-72b5-67c7-1e3a9ae8f422@redhat.com> Date: Thu, 1 Jun 2017 14:13:28 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 MIME-Version: 1.0 In-Reply-To: <592E2CD1.8080206@rock-chips.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Thu, 01 Jun 2017 12:13:33 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7045 Lines: 199 Hi, On 31-05-17 04:39, jeffy wrote: > Hi Hans, > > thanx for investigating :) > > On 05/30/2017 03:06 PM, Hans de Goede wrote: >> Hi, >> >> On 29-05-17 22:25, Chris Wilson wrote: >>> On Fri, Apr 14, 2017 at 11:15:04AM -0400, Sean Paul wrote: >>>> On Thu, Apr 13, 2017 at 03:32:44PM +0800, Jeffy Chen wrote: >>>>> After unbinding drm, the user space may still owns the drm dev fd, and >>>>> may still be able to call drm ioctl. >>>>> >>>>> We're using an unplugged state to prevent something like that, so let's >>>>> reuse it here. >>>>> >>>>> Also drop drm_unplug_dev, because it would be unused after other >>>>> changes. >>>>> >>>>> Verified on rk3399 chromebook kevin(with cros 4.4 kernel), no more >>>>> crashes >>>>> when unbinding drm with ui service still running. >>>>> >>>>> v2: Fix some commit messages. >>>>> v3: Reuse unplug status. >>>>> v4: Add drm_device_set_plug_state helper. >>>>> v5: Fix hang when unregistering drm dev with open_count 0. >>>>> v6: Move drm_device_set_plug_state into drm_drv. >>>>> v7: Add missing drm_dev_unref in udl_drv. >>>>> v8: Fix compiler errors after enable udl. >>>>> >>>>> Signed-off-by: Jeffy Chen >>>>> >>>>> --- >>>> >>>> Hi Jeffy, >>>> Given the trouble we've had with this patch already, coupled with the >>>> fact that >>>> unbinding while userspace is active is a contrived/pathological case, >>>> I don't >>>> think it's worth picking this patch upstream. >>>> >>>> If it's really causing issues downstream, you can add my Reviewed-by >>>> for a CHROMIUM >>>> patch, but I'd rather not carry patches in the CrOS repo if we don't >>>> need to. >>> >>> Would a >>> >>> Fixes: a39be606f99d ("drm: Do a full device unregister when unplugging") >>> Reported-by: Marco Diego Aurélio Mesquita >>> Cc: Hans de Goede >>> >>> convince us to look into this patch again? >> >> The problem is this patch is wrong, see below. >> >>>>> drivers/gpu/drm/drm_drv.c | 26 ++++++++++---------------- >>>>> drivers/gpu/drm/udl/udl_drv.c | 3 ++- >>>>> include/drm/drmP.h | 6 ------ >>>>> include/drm/drm_drv.h | 1 - >>>>> 4 files changed, 12 insertions(+), 24 deletions(-) >>>>> >>>>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c >>>>> index b5c6bb4..e1da4d1 100644 >>>>> --- a/drivers/gpu/drm/drm_drv.c >>>>> +++ b/drivers/gpu/drm/drm_drv.c >>>>> @@ -355,22 +355,6 @@ void drm_put_dev(struct drm_device *dev) >>>>> } >>>>> EXPORT_SYMBOL(drm_put_dev); >>>>> -void drm_unplug_dev(struct drm_device *dev) >>>>> -{ >>>>> - /* for a USB device */ >>>>> - drm_dev_unregister(dev); >>>>> - >>>>> - mutex_lock(&drm_global_mutex); >>>>> - >>>>> - drm_device_set_unplugged(dev); >>>>> - >>>>> - if (dev->open_count == 0) { >>>>> - drm_put_dev(dev); >>>>> - } >>>>> - mutex_unlock(&drm_global_mutex); >>>>> -} >>>>> -EXPORT_SYMBOL(drm_unplug_dev); >>>>> - >>>>> /* >>>>> * DRM internal mount >>>>> * We want to be able to allocate our own "struct address_space" >>>>> to control >>>>> @@ -733,6 +717,13 @@ static void remove_compat_control_link(struct >>>>> drm_device *dev) >>>>> kfree(name); >>>>> } >>>>> +static inline void drm_device_set_plug_state(struct drm_device *dev, >>>>> + bool plugged) >>>>> +{ >>>>> + smp_wmb(); >>>>> + atomic_set(&dev->unplugged, !plugged); >>>>> +} >>>>> + >>>>> /** >>>>> * drm_dev_register - Register DRM device >>>>> * @dev: Device to register >>>>> @@ -787,6 +778,8 @@ int drm_dev_register(struct drm_device *dev, >>>>> unsigned long flags) >>>>> if (drm_core_check_feature(dev, DRIVER_MODESET)) >>>>> drm_modeset_register_all(dev); >>>>> + drm_device_set_plug_state(dev, true); >>>>> + >>>>> ret = 0; >>>>> DRM_INFO("Initialized %s %d.%d.%d %s for %s on minor %d\n", >>>>> @@ -826,6 +819,7 @@ void drm_dev_unregister(struct drm_device *dev) >>>>> drm_lastclose(dev); >>>>> dev->registered = false; >>>>> + drm_device_set_plug_state(dev, false); >>>>> if (drm_core_check_feature(dev, DRIVER_MODESET)) >>>>> drm_modeset_unregister_all(dev); >>>>> diff --git a/drivers/gpu/drm/udl/udl_drv.c >>>>> b/drivers/gpu/drm/udl/udl_drv.c >>>>> index cd8b017..fc73e24 100644 >>>>> --- a/drivers/gpu/drm/udl/udl_drv.c >>>>> +++ b/drivers/gpu/drm/udl/udl_drv.c >>>>> @@ -108,7 +108,8 @@ static void udl_usb_disconnect(struct >>>>> usb_interface *interface) >>>>> drm_kms_helper_poll_disable(dev); >>>>> udl_fbdev_unplug(dev); >>>>> udl_drop_usb(dev); >>>>> - drm_unplug_dev(dev); >>>>> + drm_dev_unregister(dev); >>>>> + drm_dev_unref(dev); >> >> The unref here will cause the device struct to get free-ed even if >> userspace still holds references to it through the drm_dev. To fix >> this we would need to call drm_dev_ref on a open from userspace and >> drm_dev_unref from drm_release. > > right, but i think we are already did the ref/unref in the open/release through drm_minor_acquire/drm_minor_release. Ah yes, I see. Still calling drm_dev_unregister() directly from udl_usb_disconnect() is not going to work, see the patch titled "drm: Fix oops + Xserver hang when unplugging USB drm devices" The problem is that drm_dev_unregister() probably should be split into a drm_dev_unregister() and drm_dev_cleanup() function with the cleanup part getting called by the last unref, and at least calling drm_lastclose and the driver->unload call needs to be moved to the new drm_dev_cleanup. However splitting drm_dev_unregister() into drm_dev_unregister() and drm_dev_cleanup() is easier said then done because that would change the teardown order (e.g. calling driver->unload later) which may very well cause problems in various places and drivers. Regards, Hans >>>>> } >>>>> /* >>>>> diff --git a/include/drm/drmP.h b/include/drm/drmP.h >>>>> index 3bfafcd..980a204 100644 >>>>> --- a/include/drm/drmP.h >>>>> +++ b/include/drm/drmP.h >>>>> @@ -488,12 +488,6 @@ static __inline__ int >>>>> drm_core_check_feature(struct drm_device *dev, >>>>> return ((dev->driver->driver_features & feature) ? 1 : 0); >>>>> } >>>>> -static inline void drm_device_set_unplugged(struct drm_device *dev) >>>>> -{ >>>>> - smp_wmb(); >>>>> - atomic_set(&dev->unplugged, 1); >>>>> -} >>>>> - >>>>> static inline int drm_device_is_unplugged(struct drm_device *dev) >>>>> { >>>>> int ret = atomic_read(&dev->unplugged); >>>>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h >>>>> index 0fefc3f..eb63078 100644 >>>>> --- a/include/drm/drm_drv.h >>>>> +++ b/include/drm/drm_drv.h >>>>> @@ -544,7 +544,6 @@ void drm_dev_unregister(struct drm_device *dev); >>>>> void drm_dev_ref(struct drm_device *dev); >>>>> void drm_dev_unref(struct drm_device *dev); >>>>> void drm_put_dev(struct drm_device *dev); >>>>> -void drm_unplug_dev(struct drm_device *dev); >>>>> int drm_dev_set_unique(struct drm_device *dev, const char *name); >>> >> >> >> > >