Fix T91518: crash when recalculating looptris after clearing geometry.

When clearing geometry the runtime mutexes of a mesh were freed. This
resulted in crashes afterwards. The clear geometry is an RNA function so
would only effect when using from scripts.

This patch separates init/freeing of the mutexes from other code so they
can be used when needed.

Reviewed By: mont29

Maniphest Tasks: T91518

Differential Revision: https://developer.blender.org/D13142

3 files changed, 53 insertions, 22 deletions

diff --git a/source/blender/blenkernel/BKE_mesh_runtime.h b/source/blender/blenkernel/BKE_mesh_runtime.h
index 3efbef94081..df111360bcd 100644
--- a/source/blender/blenkernel/BKE_mesh_runtime.h
+++ b/source/blender/blenkernel/BKE_mesh_runtime.h
@@ -41,7 +41,8 @@ struct Mesh;
 struct Object;
 struct Scene;
 
-void BKE_mesh_runtime_reset(struct Mesh *mesh);
+void BKE_mesh_runtime_init_data(struct Mesh *mesh);
+void BKE_mesh_runtime_free_data(struct Mesh *mesh);
 void BKE_mesh_runtime_reset_on_copy(struct Mesh *mesh, const int flag);
 int BKE_mesh_runtime_looptri_len(const struct Mesh *mesh);
 void BKE_mesh_runtime_looptri_recalc(struct Mesh *mesh);
diff --git a/source/blender/blenkernel/intern/mesh.c b/source/blender/blenkernel/intern/mesh.c
index 7277f7ad209..f0ba83b396b 100644
--- a/source/blender/blenkernel/intern/mesh.c
+++ b/source/blender/blenkernel/intern/mesh.c
@@ -88,7 +88,7 @@ static void mesh_init_data(ID *id)
   CustomData_reset(&mesh->pdata);
   CustomData_reset(&mesh->ldata);
 
-  BKE_mesh_runtime_reset(mesh);
+  BKE_mesh_runtime_init_data(mesh);
 
   mesh->face_sets_color_seed = BLI_hash_int(PIL_check_seconds_timer_i() & UINT_MAX);
 }
@@ -168,7 +168,7 @@ static void mesh_free_data(ID *id)
     mesh->edit_mesh = NULL;
   }
 
-  BKE_mesh_runtime_clear_cache(mesh);
+  BKE_mesh_runtime_free_data(mesh);
   mesh_clear_geometry(mesh);
   MEM_SAFE_FREE(mesh->mat);
 }
@@ -308,7 +308,9 @@ static void mesh_blend_read_data(BlendDataReader *reader, ID *id)
 
   mesh->texflag &= ~ME_AUTOSPACE_EVALUATED;
   mesh->edit_mesh = NULL;
-  BKE_mesh_runtime_reset(mesh);
+
+  memset(&mesh->runtime, 0, sizeof(mesh->runtime));
+  BKE_mesh_runtime_init_data(mesh);
 
   /* happens with old files */
   if (mesh->mselect == NULL) {
diff --git a/source/blender/blenkernel/intern/mesh_runtime.c b/source/blender/blenkernel/intern/mesh_runtime.c
index 1c8646a4bdd..ce89c723a61 100644
--- a/source/blender/blenkernel/intern/mesh_runtime.c
+++ b/source/blender/blenkernel/intern/mesh_runtime.c
@@ -45,17 +45,54 @@
  * \{ */
 
 /**
- * Default values defined at read time.
+ * \brief Initialize the runtime mutexes of the given mesh.
+ *
+ * Any existing mutexes will be overridden.
  */
-void BKE_mesh_runtime_reset(Mesh *mesh)
+static void mesh_runtime_init_mutexes(Mesh *mesh)
 {
-  memset(&mesh->runtime, 0, sizeof(mesh->runtime));
   mesh->runtime.eval_mutex = MEM_mallocN(sizeof(ThreadMutex), "mesh runtime eval_mutex");
   BLI_mutex_init(mesh->runtime.eval_mutex);
   mesh->runtime.render_mutex = MEM_mallocN(sizeof(ThreadMutex), "mesh runtime render_mutex");
   BLI_mutex_init(mesh->runtime.render_mutex);
 }
 
+/**
+ * \brief free the mutexes of the given mesh runtime.
+ */
+static void mesh_runtime_free_mutexes(Mesh *mesh)
+{
+  if (mesh->runtime.eval_mutex != NULL) {
+    BLI_mutex_end(mesh->runtime.eval_mutex);
+    MEM_freeN(mesh->runtime.eval_mutex);
+    mesh->runtime.eval_mutex = NULL;
+  }
+  if (mesh->runtime.render_mutex != NULL) {
+    BLI_mutex_end(mesh->runtime.render_mutex);
+    MEM_freeN(mesh->runtime.render_mutex);
+    mesh->runtime.render_mutex = NULL;
+  }
+}
+
+/**
+ * \brief Initialize the runtime of the given mesh.
+ *
+ * Function expects that the runtime is already cleared.
+ */
+void BKE_mesh_runtime_init_data(Mesh *mesh)
+{
+  mesh_runtime_init_mutexes(mesh);
+}
+
+/**
+ * \brief Free all data (and mutexes) inside the runtime of the given mesh.
+ */
+void BKE_mesh_runtime_free_data(Mesh *mesh)
+{
+  BKE_mesh_runtime_clear_cache(mesh);
+  mesh_runtime_free_mutexes(mesh);
+}
+
 /* Clear all pointers which we don't want to be shared on copying the datablock.
  * However, keep all the flags which defines what the mesh is (for example, that
  * it's deformed only, or that its custom data layers are out of date.) */
@@ -71,25 +108,16 @@ void BKE_mesh_runtime_reset_on_copy(Mesh *mesh, const int UNUSED(flag))
   runtime->bvh_cache = NULL;
   runtime->shrinkwrap_data = NULL;
 
-  mesh->runtime.eval_mutex = MEM_mallocN(sizeof(ThreadMutex), "mesh runtime eval_mutex");
-  BLI_mutex_init(mesh->runtime.eval_mutex);
-
-  mesh->runtime.render_mutex = MEM_mallocN(sizeof(ThreadMutex), "mesh runtime render_mutex");
-  BLI_mutex_init(mesh->runtime.render_mutex);
+  mesh_runtime_init_mutexes(mesh);
 }
 
+/**
+ * \brief This function clears runtime cache of the given mesh.
+ * 
+ * Call this function to recalculate runtime data when used.
+ */
 void BKE_mesh_runtime_clear_cache(Mesh *mesh)
 {
-  if (mesh->runtime.eval_mutex != NULL) {
-    BLI_mutex_end(mesh->runtime.eval_mutex);
-    MEM_freeN(mesh->runtime.eval_mutex);
-    mesh->runtime.eval_mutex = NULL;
-  }
-  if (mesh->runtime.render_mutex != NULL) {
-    BLI_mutex_end(mesh->runtime.render_mutex);
-    MEM_freeN(mesh->runtime.render_mutex);
-    mesh->runtime.render_mutex = NULL;
-  }
   if (mesh->runtime.mesh_eval != NULL) {
     mesh->runtime.mesh_eval->edit_mesh = NULL;
     BKE_id_free(NULL, mesh->runtime.mesh_eval);