Re: [PATCH RFC 05/24] Revert "drm: Nerf the preclose callback for modern drivers"

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Well NAK, that brings back a callback we worked quite hard on getting 
rid of.

It looks like the problem isn't that you need the preclose callback, but 
you rather seem to misunderstood how TTM works.

All you need to do is to cleanup your command submission path so that 
the caller of lima_sched_context_queue_task() adds the resulting 
scheduler fence to TTMs buffer objects.

Regards,
Christian.

Am 18.05.2018 um 11:27 schrieb Qiang Yu:
> This reverts commit 45c3d213a400c952ab7119f394c5293bb6877e6b.
>
> lima driver need preclose to wait all task in the context
> created within closing file to finish before free all the
> buffer object. Otherwise pending tesk may fail and get
> noisy MMU fault message.
>
> Move this wait to each buffer object free function can
> achieve the same result but some buffer object is shared
> with other file context, but we only want to wait the
> closing file context's tasks. So the implementation is
> not that straight forword compared to the preclose one.
>
> Signed-off-by: Qiang Yu <yuq825@gmail.com>
> ---
>   drivers/gpu/drm/drm_file.c |  8 ++++----
>   include/drm/drm_drv.h      | 23 +++++++++++++++++++++--
>   2 files changed, 25 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> index e394799979a6..0a43107396b9 100644
> --- a/drivers/gpu/drm/drm_file.c
> +++ b/drivers/gpu/drm/drm_file.c
> @@ -361,8 +361,9 @@ void drm_lastclose(struct drm_device * dev)
>    *
>    * This function must be used by drivers as their &file_operations.release
>    * method. It frees any resources associated with the open file, and calls the
> - * &drm_driver.postclose driver callback. If this is the last open file for the
> - * DRM device also proceeds to call the &drm_driver.lastclose driver callback.
> + * &drm_driver.preclose and &drm_driver.lastclose driver callbacks. If this is
> + * the last open file for the DRM device also proceeds to call the
> + * &drm_driver.lastclose driver callback.
>    *
>    * RETURNS:
>    *
> @@ -382,8 +383,7 @@ int drm_release(struct inode *inode, struct file *filp)
>   	list_del(&file_priv->lhead);
>   	mutex_unlock(&dev->filelist_mutex);
>   
> -	if (drm_core_check_feature(dev, DRIVER_LEGACY) &&
> -	    dev->driver->preclose)
> +	if (dev->driver->preclose)
>   		dev->driver->preclose(dev, file_priv);
>   
>   	/* ========================================================
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index d23dcdd1bd95..8d6080f97ed4 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -107,6 +107,23 @@ struct drm_driver {
>   	 */
>   	int (*open) (struct drm_device *, struct drm_file *);
>   
> +	/**
> +	 * @preclose:
> +	 *
> +	 * One of the driver callbacks when a new &struct drm_file is closed.
> +	 * Useful for tearing down driver-private data structures allocated in
> +	 * @open like buffer allocators, execution contexts or similar things.
> +	 *
> +	 * Since the display/modeset side of DRM can only be owned by exactly
> +	 * one &struct drm_file (see &drm_file.is_master and &drm_device.master)
> +	 * there should never be a need to tear down any modeset related
> +	 * resources in this callback. Doing so would be a driver design bug.
> +	 *
> +	 * FIXME: It is not really clear why there's both @preclose and
> +	 * @postclose. Without a really good reason, use @postclose only.
> +	 */
> +	void (*preclose) (struct drm_device *, struct drm_file *file_priv);
> +
>   	/**
>   	 * @postclose:
>   	 *
> @@ -118,6 +135,9 @@ struct drm_driver {
>   	 * one &struct drm_file (see &drm_file.is_master and &drm_device.master)
>   	 * there should never be a need to tear down any modeset related
>   	 * resources in this callback. Doing so would be a driver design bug.
> +	 *
> +	 * FIXME: It is not really clear why there's both @preclose and
> +	 * @postclose. Without a really good reason, use @postclose only.
>   	 */
>   	void (*postclose) (struct drm_device *, struct drm_file *);
>   
> @@ -134,7 +154,7 @@ struct drm_driver {
>   	 * state changes, e.g. in conjunction with the :ref:`vga_switcheroo`
>   	 * infrastructure.
>   	 *
> -	 * This is called after @postclose hook has been called.
> +	 * This is called after @preclose and @postclose have been called.
>   	 *
>   	 * NOTE:
>   	 *
> @@ -601,7 +621,6 @@ struct drm_driver {
>   	/* List of devices hanging off this driver with stealth attach. */
>   	struct list_head legacy_dev_list;
>   	int (*firstopen) (struct drm_device *);
> -	void (*preclose) (struct drm_device *, struct drm_file *file_priv);
>   	int (*dma_ioctl) (struct drm_device *dev, void *data, struct drm_file *file_priv);
>   	int (*dma_quiescent) (struct drm_device *);
>   	int (*context_dtor) (struct drm_device *dev, int context);

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