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Message-ID: <20170414151503.lmpp3udfuycavfki@art_vandelay>
Date: Fri, 14 Apr 2017 11:15:04 -0400
From: Sean Paul <seanpaul@...omium.org>
To: Jeffy Chen <jeffy.chen@...k-chips.com>
Cc: linux-kernel@...r.kernel.org, briannorris@...omium.org,
dianders@...omium.org, tfiga@...omium.org, seanpaul@...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,
Chris Wilson <chris@...is-wilson.co.uk>,
David Airlie <airlied@...ux.ie>, Tom Gundersen <teg@...m.no>,
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 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.
Sean
>
> 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);
>
> --
> 2.1.4
>
--
Sean Paul, Software Engineer, Google / Chromium OS
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