[Intel-gfx] [PATCH] drm: simplify the locking in the GETCRTC ioctl

[Harry Wentland]

Reviewed-by: Harry Wentland <harry.wentland at amd.com>

Harry

On 2017-03-28 03:01 AM, Daniel Vetter wrote:
> No need to grab both plane and crtc locks at the same time, we can do
> them one after the other. If userspace races it'll get what it
> deserves either way.
>
> This removes another user of drm_modeset_lock_crtc. There's only one
> left.
>
> v2: Make sure all access to primary->state is properly protected
> (Harry).
>
> Cc: Harry Wentland <harry.wentland at amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
>  drivers/gpu/drm/drm_crtc.c           | 11 ++++++++---
>  drivers/gpu/drm/i915/intel_display.c |  5 +++++
>  2 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 660b4c8715de..55b3da2e2a82 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -406,9 +406,9 @@ int drm_mode_getcrtc(struct drm_device *dev,
>  	if (!crtc)
>  		return -ENOENT;
>
> -	drm_modeset_lock_crtc(crtc, crtc->primary);
>  	crtc_resp->gamma_size = crtc->gamma_size;
>
> +	drm_modeset_lock(&crtc->primary->mutex, NULL);
>  	if (crtc->primary->state && crtc->primary->state->fb)
>  		crtc_resp->fb_id = crtc->primary->state->fb->base.id;
>  	else if (!crtc->primary->state && crtc->primary->fb)
> @@ -416,9 +416,14 @@ int drm_mode_getcrtc(struct drm_device *dev,
>  	else
>  		crtc_resp->fb_id = 0;
>
> -	if (crtc->state) {
> +	if (crtc->primary->state) {
>  		crtc_resp->x = crtc->primary->state->src_x >> 16;
>  		crtc_resp->y = crtc->primary->state->src_y >> 16;
> +	}
> +	drm_modeset_unlock(&crtc->primary->mutex);
> +
> +	drm_modeset_lock(&crtc->mutex, NULL);
> +	if (crtc->state) {
>  		if (crtc->state->enable) {
>  			drm_mode_convert_to_umode(&crtc_resp->mode, &crtc->state->mode);
>  			crtc_resp->mode_valid = 1;
> @@ -437,7 +442,7 @@ int drm_mode_getcrtc(struct drm_device *dev,
>  			crtc_resp->mode_valid = 0;
>  		}
>  	}
> -	drm_modeset_unlock_crtc(crtc);
> +	drm_modeset_unlock(&crtc->mutex);
>
>  	return 0;
>  }
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 68cded453882..43dbad62786e 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -12463,6 +12463,11 @@ static int intel_atomic_check(struct drm_device *dev,
>  	ret = drm_atomic_helper_check_modeset(dev, state);
>  	if (ret)
>  		return ret;
> +	/* enocder->atomic_check might upgrade some crtc to a full modeset */
> +	ret = drm_atomic_helper_check_modeset(dev, state);
> +	if (ret)
> +		return ret;
> +
>
>  	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, crtc_state, i) {
>  		struct intel_crtc_state *pipe_config =
>