Re: [PATCH v2] drm/radeon: Track the status of a page flip more explicitly

["Christian König" <deathsimple@vodafone.de>]

Am 30.06.2014 11:12, schrieb Michel Dänzer:
> From: Michel Dänzer <michel.daenzer@amd.com>
>
> This prevents a panic: radeon_crtc_handle_page_flip() could run before
> radeon_flip_work_func(), triggering the BUG_ON() in drm_vblank_put().
>
> Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>
> Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>

Reviewed-by: Christian König <christian.koenig@amd.com>

> ---
>
> v2: Update log message
>
>   drivers/gpu/drm/radeon/radeon_display.c | 19 ++++++++++++++-----
>   drivers/gpu/drm/radeon/radeon_mode.h    |  7 +++++++
>   2 files changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
> index 8b575a4..65882cd 100644
> --- a/drivers/gpu/drm/radeon/radeon_display.c
> +++ b/drivers/gpu/drm/radeon/radeon_display.c
> @@ -284,7 +284,6 @@ static void radeon_unpin_work_func(struct work_struct *__work)
>   void radeon_crtc_handle_vblank(struct radeon_device *rdev, int crtc_id)
>   {
>   	struct radeon_crtc *radeon_crtc = rdev->mode_info.crtcs[crtc_id];
> -	struct radeon_flip_work *work;
>   	unsigned long flags;
>   	u32 update_pending;
>   	int vpos, hpos;
> @@ -294,8 +293,11 @@ void radeon_crtc_handle_vblank(struct radeon_device *rdev, int crtc_id)
>   		return;
>   
>   	spin_lock_irqsave(&rdev->ddev->event_lock, flags);
> -	work = radeon_crtc->flip_work;
> -	if (work == NULL) {
> +	if (radeon_crtc->flip_status != RADEON_FLIP_SUBMITTED) {
> +		DRM_DEBUG_DRIVER("radeon_crtc->flip_status = %d != "
> +				 "RADEON_FLIP_SUBMITTED(%d)\n",
> +				 radeon_crtc->flip_status,
> +				 RADEON_FLIP_SUBMITTED);
>   		spin_unlock_irqrestore(&rdev->ddev->event_lock, flags);
>   		return;
>   	}
> @@ -343,12 +345,17 @@ void radeon_crtc_handle_flip(struct radeon_device *rdev, int crtc_id)
>   
>   	spin_lock_irqsave(&rdev->ddev->event_lock, flags);
>   	work = radeon_crtc->flip_work;
> -	if (work == NULL) {
> +	if (radeon_crtc->flip_status != RADEON_FLIP_SUBMITTED) {
> +		DRM_DEBUG_DRIVER("radeon_crtc->flip_status = %d != "
> +				 "RADEON_FLIP_SUBMITTED(%d)\n",
> +				 radeon_crtc->flip_status,
> +				 RADEON_FLIP_SUBMITTED);
>   		spin_unlock_irqrestore(&rdev->ddev->event_lock, flags);
>   		return;
>   	}
>   
>   	/* Pageflip completed. Clean up. */
> +	radeon_crtc->flip_status = RADEON_FLIP_NONE;
>   	radeon_crtc->flip_work = NULL;
>   
>   	/* wakeup userspace */
> @@ -475,6 +482,7 @@ static void radeon_flip_work_func(struct work_struct *__work)
>   	/* do the flip (mmio) */
>   	radeon_page_flip(rdev, radeon_crtc->crtc_id, base);
>   
> +	radeon_crtc->flip_status = RADEON_FLIP_SUBMITTED;
>   	spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
>   	up_read(&rdev->exclusive_lock);
>   
> @@ -543,7 +551,7 @@ static int radeon_crtc_page_flip(struct drm_crtc *crtc,
>   	/* We borrow the event spin lock for protecting flip_work */
>   	spin_lock_irqsave(&crtc->dev->event_lock, flags);
>   
> -	if (radeon_crtc->flip_work) {
> +	if (radeon_crtc->flip_status != RADEON_FLIP_NONE) {
>   		DRM_DEBUG_DRIVER("flip queue: crtc already busy\n");
>   		spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
>   		drm_gem_object_unreference_unlocked(&work->old_rbo->gem_base);
> @@ -551,6 +559,7 @@ static int radeon_crtc_page_flip(struct drm_crtc *crtc,
>   		kfree(work);
>   		return -EBUSY;
>   	}
> +	radeon_crtc->flip_status = RADEON_FLIP_PENDING;
>   	radeon_crtc->flip_work = work;
>   
>   	/* update crtc fb */
> diff --git a/drivers/gpu/drm/radeon/radeon_mode.h b/drivers/gpu/drm/radeon/radeon_mode.h
> index b59096f..ed6b6e0 100644
> --- a/drivers/gpu/drm/radeon/radeon_mode.h
> +++ b/drivers/gpu/drm/radeon/radeon_mode.h
> @@ -301,6 +301,12 @@ struct radeon_atom_ss {
>   	uint16_t amount;
>   };
>   
> +enum radeon_flip_status {
> +	RADEON_FLIP_NONE,
> +	RADEON_FLIP_PENDING,
> +	RADEON_FLIP_SUBMITTED
> +};
> +
>   struct radeon_crtc {
>   	struct drm_crtc base;
>   	int crtc_id;
> @@ -326,6 +332,7 @@ struct radeon_crtc {
>   	/* page flipping */
>   	struct workqueue_struct *flip_queue;
>   	struct radeon_flip_work *flip_work;
> +	enum radeon_flip_status flip_status;
>   	/* pll sharing */
>   	struct radeon_atom_ss ss;
>   	bool ss_enabled;

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