[PATCH v2 01/10] drm/exec: Add helper to bypass IGNORE_DUPLICATES flag

[Natalie Vock <nat@pixelcluster.dev>]

TTM is about to switch to drm_exec for locking objects
in the LRU list. When we're done processing the object, we want to
unlock it only if the caller doesn't already hold that lock. If
DRM_EXEC_IGNORE_DUPLICATES is set on the exec object (which callers may
require for unrelated reasons), we have no way of knowing whether the
lock is already held.

To remedy this, add a separate helper that forcefully bypasses the
IGNORE_DUPLICATES flag for only a single locking operation.

Signed-off-by: Natalie Vock <nat@pixelcluster.dev>
---
 drivers/gpu/drm/drm_exec.c | 54 ++++++++++++++++++++++++++++++++++------------
 include/drm/drm_exec.h     |  2 ++
 2 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/drm_exec.c b/drivers/gpu/drm/drm_exec.c
index 7988f5e7d56a3..ec33ed4a523cc 100644
--- a/drivers/gpu/drm/drm_exec.c
+++ b/drivers/gpu/drm/drm_exec.c
@@ -190,18 +190,9 @@ static int drm_exec_lock_contended(struct drm_exec *exec)
 	return ret;
 }
 
-/**
- * drm_exec_lock_obj - lock a GEM object for use
- * @exec: the drm_exec object with the state
- * @obj: the GEM object to lock
- *
- * Lock a GEM object for use and grab a reference to it.
- *
- * Returns: -EDEADLK if a contention is detected, -EALREADY when object is
- * already locked (can be suppressed by setting the DRM_EXEC_IGNORE_DUPLICATES
- * flag), -ENOMEM when memory allocation failed and zero for success.
- */
-int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj)
+static int __drm_exec_lock_obj(struct drm_exec *exec,
+			       struct drm_gem_object *obj,
+			       bool ignore_duplicates)
 {
 	int ret;
 
@@ -226,8 +217,7 @@ int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj)
 		return -EDEADLK;
 	}
 
-	if (unlikely(ret == -EALREADY) &&
-	    exec->flags & DRM_EXEC_IGNORE_DUPLICATES)
+	if (unlikely(ret == -EALREADY) && ignore_duplicates)
 		return 0;
 
 	if (unlikely(ret))
@@ -243,8 +233,44 @@ int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj)
 	dma_resv_unlock(obj->resv);
 	return ret;
 }
+
+/**
+ * drm_exec_lock_obj - lock a GEM object for use
+ * @exec: the drm_exec object with the state
+ * @obj: the GEM object to lock
+ *
+ * Lock a GEM object for use and grab a reference to it.
+ *
+ * Returns: -EDEADLK if a contention is detected, -EALREADY when object is
+ * already locked (can be suppressed by setting the DRM_EXEC_IGNORE_DUPLICATES
+ * flag), -ENOMEM when memory allocation failed and zero for success.
+ */
+int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj)
+{
+	return __drm_exec_lock_obj(exec, obj,
+				   exec->flags & DRM_EXEC_IGNORE_DUPLICATES);
+}
 EXPORT_SYMBOL(drm_exec_lock_obj);
 
+/**
+ * drm_exec_lock_obj_report_dup - lock a GEM object for use, but always report duplicates
+ * @exec: the drm_exec object with the state
+ * @obj: the GEM object to lock
+ *
+ * Like drm_exec_lock_obj, lock a GEM object for use and grab a reference to it.
+ * Unlike drm_exec_lock_obj, DRM_EXEC_IGNORE_DUPLICATES is ignored and duplicates are
+ * always reported.
+ *
+ * Returns: -EDEADLK if a contention is detected, -EALREADY when object is
+ * already locked, -ENOMEM when memory allocation failed and zero for success.
+ */
+int drm_exec_lock_obj_report_dup(struct drm_exec *exec,
+				 struct drm_gem_object *obj)
+{
+	return __drm_exec_lock_obj(exec, obj, false);
+}
+EXPORT_SYMBOL(drm_exec_lock_obj_report_dup);
+
 /**
  * drm_exec_unlock_obj - unlock a GEM object in this exec context
  * @exec: the drm_exec object with the state
diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h
index 8725ba92ff916..ff80dd2b72240 100644
--- a/include/drm/drm_exec.h
+++ b/include/drm/drm_exec.h
@@ -176,6 +176,8 @@ void drm_exec_init(struct drm_exec *exec, u32 flags, unsigned nr);
 void drm_exec_fini(struct drm_exec *exec);
 bool drm_exec_cleanup(struct drm_exec *exec);
 int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj);
+int drm_exec_lock_obj_report_dup(struct drm_exec *exec,
+				 struct drm_gem_object *obj);
 void drm_exec_unlock_obj(struct drm_exec *exec, struct drm_gem_object *obj);
 int drm_exec_prepare_obj(struct drm_exec *exec, struct drm_gem_object *obj,
 			 unsigned int num_fences);

-- 
2.55.0