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, 10 insertions, 41 deletions

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index c7380ad3c51b..0d58c40aa440 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -3128,23 +3128,13 @@ void drm_atomic_helper_shutdown(struct drm_device *dev)
 	struct drm_modeset_acquire_ctx ctx;
 	int ret;
 
-	drm_modeset_acquire_init(&ctx, 0);
-	while (1) {
-		ret = drm_modeset_lock_all_ctx(dev, &ctx);
-		if (!ret)
-			ret = __drm_atomic_helper_disable_all(dev, &ctx, true);
-
-		if (ret != -EDEADLK)
-			break;
-
-		drm_modeset_backoff(&ctx);
-	}
+	DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, 0, ret);
 
+	ret = __drm_atomic_helper_disable_all(dev, &ctx, true);
 	if (ret)
 		DRM_ERROR("Disabling all crtc's during unload failed with %i\n", ret);
 
-	drm_modeset_drop_locks(&ctx);
-	drm_modeset_acquire_fini(&ctx);
+	DRM_MODESET_LOCK_ALL_END(ctx, ret);
 }
 EXPORT_SYMBOL(drm_atomic_helper_shutdown);
 
@@ -3179,14 +3169,7 @@ struct drm_atomic_state *drm_atomic_helper_suspend(struct drm_device *dev)
 	struct drm_atomic_state *state;
 	int err;
 
-	drm_modeset_acquire_init(&ctx, 0);
-
-retry:
-	err = drm_modeset_lock_all_ctx(dev, &ctx);
-	if (err < 0) {
-		state = ERR_PTR(err);
-		goto unlock;
-	}
+	DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, 0, err);
 
 	state = drm_atomic_helper_duplicate_state(dev, &ctx);
 	if (IS_ERR(state))
@@ -3200,13 +3183,10 @@ retry:
 	}
 
 unlock:
-	if (PTR_ERR(state) == -EDEADLK) {
-		drm_modeset_backoff(&ctx);
-		goto retry;
-	}
+	DRM_MODESET_LOCK_ALL_END(ctx, err);
+	if (err)
+		return ERR_PTR(err);
 
-	drm_modeset_drop_locks(&ctx);
-	drm_modeset_acquire_fini(&ctx);
 	return state;
 }
 EXPORT_SYMBOL(drm_atomic_helper_suspend);
@@ -3280,22 +3260,11 @@ int drm_atomic_helper_resume(struct drm_device *dev,
 
 	drm_mode_config_reset(dev);
 
-	drm_modeset_acquire_init(&ctx, 0);
-	while (1) {
-		err = drm_modeset_lock_all_ctx(dev, &ctx);
-		if (err)
-			goto out;
+	DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, 0, err);
 
-		err = drm_atomic_helper_commit_duplicated_state(state, &ctx);
-out:
-		if (err != -EDEADLK)
-			break;
-
-		drm_modeset_backoff(&ctx);
-	}
+	err = drm_atomic_helper_commit_duplicated_state(state, &ctx);
 
-	drm_modeset_drop_locks(&ctx);
-	drm_modeset_acquire_fini(&ctx);
+	DRM_MODESET_LOCK_ALL_END(ctx, err);
 	drm_atomic_state_put(state);
 
 	return err;