Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751196AbdFAMXJ (ORCPT ); Thu, 1 Jun 2017 08:23:09 -0400 Received: from mail.fireflyinternet.com ([109.228.58.192]:65103 "EHLO fireflyinternet.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751134AbdFAMXF (ORCPT ); Thu, 1 Jun 2017 08:23:05 -0400 X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Date: Thu, 1 Jun 2017 13:22:29 +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: <20170601122229.GP11742@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> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7941eb36-725e-72b5-67c7-1e3a9ae8f422@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: 6029 Lines: 160 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. -Chris -- Chris Wilson, Intel Open Source Technology Centre