Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751151AbdFANEh (ORCPT ); Thu, 1 Jun 2017 09:04:37 -0400 Received: from mail.fireflyinternet.com ([109.228.58.192]:55364 "EHLO fireflyinternet.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751097AbdFANEf (ORCPT ); Thu, 1 Jun 2017 09:04:35 -0400 X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Date: Thu, 1 Jun 2017 14:03:57 +0100 From: Chris Wilson To: Hans de Goede Cc: jeffy , 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 , Marco Diego =?iso-8859-1?Q?Aur=E9lio?= Mesquita , Patrik Jakobsson , Dave Airlie Subject: Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8) Message-ID: <20170601130357.GQ11742@nuc-i3427.alporthouse.com> Mail-Followup-To: Chris Wilson , Hans de Goede , jeffy , 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 , Marco Diego =?iso-8859-1?Q?Aur=E9lio?= 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> <7941eb36-725e-72b5-67c7-1e3a9ae8f422@redhat.com> <20170601122229.GP11742@nuc-i3427.alporthouse.com> <81db9974-e666-1d04-e18c-776e17296a6f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <81db9974-e666-1d04-e18c-776e17296a6f@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7306 Lines: 184 On Thu, Jun 01, 2017 at 02:26:01PM +0200, Hans de Goede wrote: > Hi, > > On 01-06-17 14:22, Chris Wilson wrote: > >On Thu, Jun 01, 2017 at 02:13:28PM +0200, Hans de Goede wrote: > >>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 Aur?lio 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. > > > >It already is. driver->unload() has been deprecated for a while, in > >spirit at least, we probably should add a warning to it, and is > >not meant to be used anymore. > > Ok, what about drm_lastclose ? Calling that while userspace still > has fds open seems wrong too. Same for this part of drm_dev_unregister(): lastclose should not be a part of unregister, or it is spectacularly misnamed. > list_for_each_entry_safe(r_list, list_temp, &dev->maplist, head) > drm_legacy_rmmap(dev, r_list->map); Just give Daniel some more fuel for killing legacy, he'll be thankful. > > Removing mmapping backing data (if I understand correctly) while > it may still be used seems like a bad idea too, so I do believe that > drm_dev_unregister needs some love / some bits moved to the last > drm_dev_put call before it will be safe to call it directly > on usb-disconnect. True, it needs more love, and the usb devices are the best test cases for this unless we write some hw independent selftests. -Chris -- Chris Wilson, Intel Open Source Technology Centre