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Message-ID: <20170529202512.GF23936@nuc-i3427.alporthouse.com>
Date: Mon, 29 May 2017 21:25:12 +0100
From: Chris Wilson <chris@...is-wilson.co.uk>
To: Sean Paul <seanpaul@...omium.org>
Cc: Jeffy Chen <jeffy.chen@...k-chips.com>,
linux-kernel@...r.kernel.org, briannorris@...omium.org,
dianders@...omium.org, tfiga@...omium.org, zyw@...k-chips.com,
marcheu@...omium.org, mark.yao@...k-chips.com, hshi@...omium.org,
Daniel Vetter <daniel.vetter@...el.com>,
Jani Nikula <jani.nikula@...ux.intel.com>,
dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
Tom Gundersen <teg@...m.no>,
Hans de Goede <hdegoede@...hat.com>,
Marco Diego Aurélio Mesquita
<marcodiegomesquita@...il.com>,
Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
Dave Airlie <airlied@...hat.com>
Subject: Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8)
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 <jeffy.chen@...k-chips.com>
> >
> > ---
>
> 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 <marcodiegomesquita@...il.com>
Cc: Hans de Goede <hdegoede@...hat.com>
convince us to look into this patch again?
-Chris
> >
> > 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);
> > }
> >
> > /*
> > 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);
--
Chris Wilson, Intel Open Source Technology Centre
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