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Subject: Re: [PATCH v2 2/2] drm/qxl: add drm_driver.release callback.
To:     Gerd Hoffmann <kraxel@redhat.com>, dri-devel@lists.freedesktop.org,
        Dave Airlie <airlied@redhat.com>,
        David Airlie <airlied@linux.ie>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <virtualization@lists.linux-foundation.org>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <spice-devel@lists.freedesktop.org>,
        open list <linux-kernel@vger.kernel.org>
References: <20200210113753.5614-1-kraxel@redhat.com>
 <20200210113753.5614-3-kraxel@redhat.com>
 <20200210150633.GS43062@phenom.ffwll.local>
From:   =?UTF-8?Q?Noralf_Tr=c3=b8nnes?= <noralf@tronnes.org>
Message-ID: <f83001ab-8017-0576-69fd-d5f62bda84fd@tronnes.org>
Date:   Mon, 10 Feb 2020 17:57:41 +0100
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Den 10.02.2020 16.06, skrev Daniel Vetter:
> On Mon, Feb 10, 2020 at 12:37:52PM +0100, Gerd Hoffmann wrote:
>> Move final cleanups to qxl_drm_release() callback.
>> Add drm_atomic_helper_shutdown() call to qxl_pci_remove().
>>
>> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
>> ---
>>  drivers/gpu/drm/qxl/qxl_drv.c | 26 +++++++++++++++++++-------
>>  1 file changed, 19 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/qxl/qxl_drv.c b/drivers/gpu/drm/qxl/qxl_drv.c
>> index 1d601f57a6ba..4fda3f9b29f4 100644
>> --- a/drivers/gpu/drm/qxl/qxl_drv.c
>> +++ b/drivers/gpu/drm/qxl/qxl_drv.c
>> @@ -34,6 +34,7 @@
>>  #include <linux/pci.h>
>>  
>>  #include <drm/drm.h>
>> +#include <drm/drm_atomic_helper.h>
>>  #include <drm/drm_drv.h>
>>  #include <drm/drm_file.h>
>>  #include <drm/drm_modeset_helper.h>
>> @@ -132,21 +133,30 @@ qxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>>  	return ret;
>>  }
>>  
>> +static void qxl_drm_release(struct drm_device *dev)
>> +{
>> +	struct qxl_device *qdev = dev->dev_private;
>> +
>> +	/*
>> +	 * TODO: qxl_device_fini() call should be in qxl_pci_remove(),
>> +	 * reodering qxl_modeset_fini() + qxl_device_fini() calls is
>> +	 * non-trivial though.
>> +	 */
>> +	qxl_modeset_fini(qdev);
> 
> So the drm_mode_config_cleanup call in here belongs in ->release, but the
> qxl_destroy_monitors_object feels like should be perfectly fine in the
> remove hook. You might need to sprinkle a few drm_dev_enter/exit around to
> protect code paths thought.
> 
> Aside from this lgtm, for the series
> 
> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> 
> And up to you whether you want to fix this or not really.
> 
> Btw for testing all these patches that add a ->release hook I think it'd
> be good if the drm core checks that drm_device->dev is set to NULL, and
> that we do this in the remove hook. Since that's guaranteed to be gone at
> that point, so anything in ->release that still needs the device is
> broken. Ofc maybe do that check only for drivers which have a ->release
> hook, and we might need a few fixups.
> 

We take a ref on the parent device in drm_dev_init() and release it in
drm_dev_fini(). I added this because of the DRM_DEV_* macros we have, to
protect access to the device struct after it was unregistered. Setting
drm_device->dev to NULL in drm_dev_unregister() instead will provide the
same protection I think.

commit 56be6503aab2
drm/drv: Hold ref on parent device during drm_device lifetime

Noralf.

> Cheers, Daniel
> 
>> +	qxl_device_fini(qdev);
>> +	dev->dev_private = NULL;
>> +	kfree(qdev);
>> +}
>> +
>>  static void
>>  qxl_pci_remove(struct pci_dev *pdev)
>>  {
>>  	struct drm_device *dev = pci_get_drvdata(pdev);
>> -	struct qxl_device *qdev = dev->dev_private;
>>  
>>  	drm_dev_unregister(dev);
>> -
>> -	qxl_modeset_fini(qdev);
>> -	qxl_device_fini(qdev);
>> +	drm_atomic_helper_shutdown(dev);
>>  	if (is_vga(pdev))
>>  		vga_put(pdev, VGA_RSRC_LEGACY_IO);
>> -
>> -	dev->dev_private = NULL;
>> -	kfree(qdev);
>>  	drm_dev_put(dev);
>>  }
>>  
>> @@ -279,6 +289,8 @@ static struct drm_driver qxl_driver = {
>>  	.major = 0,
>>  	.minor = 1,
>>  	.patchlevel = 0,
>> +
>> +	.release = qxl_drm_release,
>>  };
>>  
>>  static int __init qxl_init(void)
>> -- 
>> 2.18.1
>>
>