drm: Add DRM_MODESET_LOCK_BEGIN/END helpers

This patch adds a couple of helpers to remove the boilerplate involved
in grabbing all of the modeset locks.

I've also converted the obvious cases in drm core to use the helpers.

The only remaining instance of drm_modeset_lock_all_ctx() is in
drm_framebuffer. It's complicated by the state clear that occurs on
deadlock. ATM, there's no way to inject code in the deadlock path with
the helpers, so it's unfit for conversion.

Changes in v2:
- Relocate ret argument to the end of the list (Daniel)
- Incorporate Daniel's doc suggestions (Daniel)

Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Reviewed-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20181129150423.239081-4-sean@poorly.run

1 files changed, 2 insertions, 12 deletions

diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c
index 581cc3788223..07dcf47daafe 100644
--- a/drivers/gpu/drm/drm_color_mgmt.c
+++ b/drivers/gpu/drm/drm_color_mgmt.c
@@ -255,11 +255,7 @@ int drm_mode_gamma_set_ioctl(struct drm_device *dev,
 	if (crtc_lut->gamma_size != crtc->gamma_size)
 		return -EINVAL;
 
-	drm_modeset_acquire_init(&ctx, 0);
-retry:
-	ret = drm_modeset_lock_all_ctx(dev, &ctx);
-	if (ret)
-		goto out;
+	DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, 0, ret);
 
 	size = crtc_lut->gamma_size * (sizeof(uint16_t));
 	r_base = crtc->gamma_store;
@@ -284,13 +280,7 @@ retry:
 				     crtc->gamma_size, &ctx);
 
 out:
-	if (ret == -EDEADLK) {
-		drm_modeset_backoff(&ctx);
-		goto retry;
-	}
-	drm_modeset_drop_locks(&ctx);
-	drm_modeset_acquire_fini(&ctx);
-
+	DRM_MODESET_LOCK_ALL_END(ctx, ret);
 	return ret;
 
 }