[PATCH] drm: Implement drm_modeset_{,un}lock_all_ctx()

[Thierry Reding]

From: Thierry Reding <treding at nvidia.com>

These functions are like drm_modeset_{,un}lock_all(), but they take the
lock acquisition context as a parameter rather than storing it in the
DRM device's drm_mode_config structure.

Implement drm_modeset_{,un}lock_all() in terms of the new function for
better code reuse, and add a note to the kerneldoc that new code should
use the new functions.

Signed-off-by: Thierry Reding <treding at nvidia.com>
---
 drivers/gpu/drm/drm_modeset_lock.c | 87 +++++++++++++++++++++++++++++---------
 include/drm/drm_modeset_lock.h     |  4 ++
 2 files changed, 70 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/drm_modeset_lock.c b/drivers/gpu/drm/drm_modeset_lock.c
index fba321ca4344..eddbc3676d5d 100644
--- a/drivers/gpu/drm/drm_modeset_lock.c
+++ b/drivers/gpu/drm/drm_modeset_lock.c
@@ -56,42 +56,31 @@
  */
 
 /**
- * drm_modeset_lock_all - take all modeset locks
+ * drm_modeset_lock_all_ctx - take all modeset locks
  * @dev: drm device
+ * @ctx: lock acquisition context
  *
  * This function takes all modeset locks, suitable where a more fine-grained
  * scheme isn't (yet) implemented. Locks must be dropped with
  * drm_modeset_unlock_all.
  */
-void drm_modeset_lock_all(struct drm_device *dev)
+void drm_modeset_lock_all_ctx(struct drm_device *dev,
+			      struct drm_modeset_acquire_ctx *ctx)
 {
 	struct drm_mode_config *config = &dev->mode_config;
-	struct drm_modeset_acquire_ctx *ctx;
 	int ret;
 
-	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
-	if (WARN_ON(!ctx))
-		return;
-
 	mutex_lock(&config->mutex);
 
-	drm_modeset_acquire_init(ctx, 0);
-
 retry:
 	ret = drm_modeset_lock(&config->connection_mutex, ctx);
 	if (ret)
 		goto fail;
+
 	ret = drm_modeset_lock_all_crtcs(dev, ctx);
 	if (ret)
 		goto fail;
 
-	WARN_ON(config->acquire_ctx);
-
-	/* now we hold the locks, so now that it is safe, stash the
-	 * ctx for drm_modeset_unlock_all():
-	 */
-	config->acquire_ctx = ctx;
-
 	drm_warn_on_modeset_not_all_locked(dev);
 
 	return;
@@ -101,8 +90,60 @@ fail:
 		drm_modeset_backoff(ctx);
 		goto retry;
 	}
+}
+EXPORT_SYMBOL(drm_modeset_lock_all_ctx);
 
-	kfree(ctx);
+/**
+ * drm_modeset_unlock_all_ctx - drop all modeset locks
+ * @dev: device
+ * @ctx: lock acquisition context
+ *
+ * This function drop all modeset locks taken by drm_modeset_lock_all.
+ */
+void drm_modeset_unlock_all_ctx(struct drm_device *dev,
+				struct drm_modeset_acquire_ctx *ctx)
+{
+	struct drm_mode_config *config = &dev->mode_config;
+
+	drm_modeset_drop_locks(ctx);
+	mutex_unlock(&config->mutex);
+}
+EXPORT_SYMBOL(drm_modeset_unlock_all_ctx);
+
+/**
+ * drm_modeset_lock_all - take all modeset locks
+ * @dev: drm device
+ *
+ * This function takes all modeset locks, suitable where a more fine-grained
+ * scheme isn't (yet) implemented. Locks must be dropped with
+ * drm_modeset_unlock_all.
+ *
+ * This function is deprecated. It allocates a lock acquisition context and
+ * stores it in drm_mode_config. This facilitate conversion of existing code
+ * because it removes the need to manually deal with the acquisition context,
+ * but it is also brittle because the context is global and care must be
+ * taken not to nest calls. New code should use drm_modeset_lock_all_ctx()
+ * and pass in the context explicitly.
+ */
+void drm_modeset_lock_all(struct drm_device *dev)
+{
+	struct drm_mode_config *config = &dev->mode_config;
+	struct drm_modeset_acquire_ctx *ctx;
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	if (WARN_ON(!ctx))
+		return;
+
+	drm_modeset_acquire_init(ctx, 0);
+	drm_modeset_lock_all_ctx(dev, ctx);
+
+	WARN_ON(config->acquire_ctx);
+
+	/*
+	 * We hold the locks now, so it is safe to stash the acquisition
+	 * context for drm_modeset_unlock_all().
+	 */
+	config->acquire_ctx = ctx;
 }
 EXPORT_SYMBOL(drm_modeset_lock_all);
 
@@ -111,6 +152,13 @@ EXPORT_SYMBOL(drm_modeset_lock_all);
  * @dev: device
  *
  * This function drop all modeset locks taken by drm_modeset_lock_all.
+ *
+ * This function is deprecated. It uses the lock acquisition context stored
+ * in drm_mode_config. This facilitate conversion of existing code because it
+ * removes the need to manually deal with the acquisition context, but it is
+ * also brittle because the context is global and care must be taken not to
+ * nest calls. New code should use drm_modeset_unlock_all_ctx() and pass in
+ * the context explicitly.
  */
 void drm_modeset_unlock_all(struct drm_device *dev)
 {
@@ -121,12 +169,9 @@ void drm_modeset_unlock_all(struct drm_device *dev)
 		return;
 
 	config->acquire_ctx = NULL;
-	drm_modeset_drop_locks(ctx);
+	drm_modeset_unlock_all_ctx(dev, ctx);
 	drm_modeset_acquire_fini(ctx);
-
 	kfree(ctx);
-
-	mutex_unlock(&dev->mode_config.mutex);
 }
 EXPORT_SYMBOL(drm_modeset_unlock_all);
 
diff --git a/include/drm/drm_modeset_lock.h b/include/drm/drm_modeset_lock.h
index 94938d89347c..2a42a66098cb 100644
--- a/include/drm/drm_modeset_lock.h
+++ b/include/drm/drm_modeset_lock.h
@@ -129,6 +129,10 @@ struct drm_device;
 struct drm_crtc;
 struct drm_plane;
 
+void drm_modeset_lock_all_ctx(struct drm_device *dev,
+			      struct drm_modeset_acquire_ctx *ctx);
+void drm_modeset_unlock_all_ctx(struct drm_device *dev,
+				struct drm_modeset_acquire_ctx *ctx);
 void drm_modeset_lock_all(struct drm_device *dev);
 void drm_modeset_unlock_all(struct drm_device *dev);
 void drm_modeset_lock_crtc(struct drm_crtc *crtc,
-- 
2.5.0