BLI: use explicit task isolation, no longer part of parallel operations

After looking into task isolation issues with Sergey, we couldn't find the
reason behind the deadlocks that we are getting in T87938 and a Sprite Fright
file involving motion blur renders.

There is no apparent place where we adding or waiting on tasks in a task group
from different isolation regions, which is what is known to cause problems. Yet
it still hangs. Either we do not understand some limitation of TBB isolation,
or there is a bug in TBB, but we could not figure it out.

Instead the idea is to use isolation only where we know we need it: when
holding a mutex lock and then doing some multithreaded operation within that
locked region. Three places where we do this now:
* Generated images
* Cached BVH tree building
* OpenVDB lazy grid loading

Compared to the more automatic approach previously used, there is the downside
that it is easy to miss places where we need isolation. Yet doing it more
automatically is also causing unexpected issue and bugs that we found no
solution for, so this seems better.

Patch implemented by Sergey and me.

Differential Revision: https://developer.blender.org/D11603

source/blender/blenkernel/intern/bvhutils.c

@@ -31,6 +31,7 @@
 
 #include "BLI_linklist.h"
 #include "BLI_math.h"
+#include "BLI_task.h"
 #include "BLI_threads.h"
 #include "BLI_utildefines.h"
 
@@ -160,6 +161,26 @@ void bvhcache_free(BVHCache *bvh_cache)
   MEM_freeN(bvh_cache);
 }
 
+/* BVH tree balancing inside a mutex lock must be run in isolation. Balancing
+ * is multithreaded, and we do not want the current thread to start another task
+ * that may involve acquiring the same mutex lock that it is waiting for. */
+static void bvhtree_balance_isolated(void *userdata)
+{
+  BLI_bvhtree_balance((BVHTree *)userdata);
+}
+
+static void bvhtree_balance(BVHTree *tree, const bool isolate)
+{
+  if (tree) {
+    if (isolate) {
+      BLI_task_isolate(bvhtree_balance_isolated, tree);
+    }
+    else {
+      BLI_bvhtree_balance(tree);
+    }
+  }
+}
+
 /** \} */
 /* -------------------------------------------------------------------- */
 /** \name Local Callbacks
@@ -566,7 +587,6 @@ static BVHTree *bvhtree_from_editmesh_verts_create_tree(float epsilon,
       BLI_bvhtree_insert(tree, i, eve->co, 1);
     }
     BLI_assert(BLI_bvhtree_get_len(tree) == verts_num_active);
-    BLI_bvhtree_balance(tree);
   }
 
   return tree;
@@ -600,7 +620,6 @@ static BVHTree *bvhtree_from_mesh_verts_create_tree(float epsilon,
         BLI_bvhtree_insert(tree, i, vert[i].co, 1);
       }
       BLI_assert(BLI_bvhtree_get_len(tree) == verts_num_active);
-      BLI_bvhtree_balance(tree);
     }
   }
 
@@ -649,6 +668,7 @@ BVHTree *bvhtree_from_editmesh_verts_ex(BVHTreeFromEditMesh *data,
     if (data->cached == false) {
       tree = bvhtree_from_editmesh_verts_create_tree(
           epsilon, tree_type, axis, em, verts_mask, verts_num_active);
+      bvhtree_balance(tree, true);
 
       /* Save on cache for later use */
       /* printf("BVHTree built and saved on cache\n"); */
@@ -660,6 +680,7 @@ BVHTree *bvhtree_from_editmesh_verts_ex(BVHTreeFromEditMesh *data,
   else {
     tree = bvhtree_from_editmesh_verts_create_tree(
         epsilon, tree_type, axis, em, verts_mask, verts_num_active);
+    bvhtree_balance(tree, false);
   }
 
   if (tree) {
@@ -711,6 +732,7 @@ BVHTree *bvhtree_from_mesh_verts_ex(BVHTreeFromMesh *data,
   if (in_cache == false) {
     tree = bvhtree_from_mesh_verts_create_tree(
         epsilon, tree_type, axis, vert, verts_num, verts_mask, verts_num_active);
+    bvhtree_balance(tree, bvh_cache_p != NULL);
 
     if (bvh_cache_p) {
       /* Save on cache for later use */
@@ -771,7 +793,6 @@ static BVHTree *bvhtree_from_editmesh_edges_create_tree(float epsilon,
       BLI_bvhtree_insert(tree, i, co[0], 2);
     }
     BLI_assert(BLI_bvhtree_get_len(tree) == edges_num_active);
-    BLI_bvhtree_balance(tree);
   }
 
   return tree;
@@ -809,7 +830,6 @@ static BVHTree *bvhtree_from_mesh_edges_create_tree(const MVert *vert,
 
         BLI_bvhtree_insert(tree, i, co[0], 2);
       }
-      BLI_bvhtree_balance(tree);
     }
   }
 
@@ -861,7 +881,7 @@ BVHTree *bvhtree_from_editmesh_edges_ex(BVHTreeFromEditMesh *data,
     if (data->cached == false) {
       tree = bvhtree_from_editmesh_edges_create_tree(
           epsilon, tree_type, axis, em, edges_mask, edges_num_active);
-
+      bvhtree_balance(tree, true);
       /* Save on cache for later use */
       /* printf("BVHTree built and saved on cache\n"); */
       bvhcache_insert(bvh_cache, tree, bvh_cache_type);
@@ -872,6 +892,7 @@ BVHTree *bvhtree_from_editmesh_edges_ex(BVHTreeFromEditMesh *data,
   else {
     tree = bvhtree_from_editmesh_edges_create_tree(
         epsilon, tree_type, axis, em, edges_mask, edges_num_active);
+    bvhtree_balance(tree, false);
   }
 
   if (tree) {
@@ -928,12 +949,17 @@ BVHTree *bvhtree_from_mesh_edges_ex(BVHTreeFromMesh *data,
         vert, edge, edges_num, edges_mask, edges_num_active, epsilon, tree_type, axis);
 
     if (bvh_cache_p) {
+      bvhtree_balance(tree, true);
+
       BVHCache *bvh_cache = *bvh_cache_p;
       /* Save on cache for later use */
       /* printf("BVHTree built and saved on cache\n"); */
       bvhcache_insert(bvh_cache, tree, bvh_cache_type);
       in_cache = true;
     }
+    else {
+      bvhtree_balance(tree, false);
+    }
   }
 
   if (bvh_cache_p) {
@@ -994,7 +1020,6 @@ static BVHTree *bvhtree_from_mesh_faces_create_tree(float epsilon,
         }
       }
       BLI_assert(BLI_bvhtree_get_len(tree) == faces_num_active);
-      BLI_bvhtree_balance(tree);
     }
   }
 
@@ -1057,6 +1082,7 @@ BVHTree *bvhtree_from_mesh_faces_ex(BVHTreeFromMesh *data,
   if (in_cache == false) {
     tree = bvhtree_from_mesh_faces_create_tree(
         epsilon, tree_type, axis, vert, face, numFaces, faces_mask, faces_num_active);
+    bvhtree_balance(tree, bvh_cache_p != NULL);
 
     if (bvh_cache_p) {
       /* Save on cache for later use */
@@ -1127,7 +1153,6 @@ static BVHTree *bvhtree_from_editmesh_looptri_create_tree(float epsilon,
         }
       }
       BLI_assert(BLI_bvhtree_get_len(tree) == looptri_num_active);
-      BLI_bvhtree_balance(tree);
     }
   }
 
@@ -1173,7 +1198,6 @@ static BVHTree *bvhtree_from_mesh_looptri_create_tree(float epsilon,
         }
       }
       BLI_assert(BLI_bvhtree_get_len(tree) == looptri_num_active);
-      BLI_bvhtree_balance(tree);
     }
   }
 
@@ -1229,6 +1253,7 @@ BVHTree *bvhtree_from_editmesh_looptri_ex(BVHTreeFromEditMesh *data,
     bool in_cache = bvhcache_find(
         bvh_cache_p, bvh_cache_type, &tree, &lock_started, mesh_eval_mutex);
     BVHCache *bvh_cache = *bvh_cache_p;
+    bvhtree_balance(tree, true);
 
     if (in_cache == false) {
       tree = bvhtree_from_editmesh_looptri_create_tree(
@@ -1243,6 +1268,7 @@ BVHTree *bvhtree_from_editmesh_looptri_ex(BVHTreeFromEditMesh *data,
   else {
     tree = bvhtree_from_editmesh_looptri_create_tree(
         epsilon, tree_type, axis, em, looptri_mask, looptri_num_active);
+    bvhtree_balance(tree, false);
   }
 
   if (tree) {
@@ -1303,6 +1329,8 @@ BVHTree *bvhtree_from_mesh_looptri_ex(BVHTreeFromMesh *data,
                                                  looptri_mask,
                                                  looptri_num_active);
 
+    bvhtree_balance(tree, bvh_cache_p != NULL);
+
     if (bvh_cache_p) {
       BVHCache *bvh_cache = *bvh_cache_p;
       bvhcache_insert(bvh_cache, tree, bvh_cache_type);
@@ -1742,7 +1770,7 @@ BVHTree *BKE_bvhtree_from_pointcloud_get(BVHTreeFromPointCloud *data,
     BLI_bvhtree_insert(tree, i, pointcloud->co[i], 1);
   }
   BLI_assert(BLI_bvhtree_get_len(tree) == pointcloud->totpoint);
-  BLI_bvhtree_balance(tree);
+  bvhtree_balance(tree, false);
 
   data->coords = pointcloud->co;
   data->tree = tree;

source/blender/blenkernel/intern/editmesh_tangent.c

@@ -362,7 +362,7 @@ void BKE_editmesh_loop_tangent_calc(BMEditMesh *em,
     /* Calculation */
     if (em->tottri != 0) {
       TaskPool *task_pool;
-      task_pool = BLI_task_pool_create(NULL, TASK_PRIORITY_LOW, TASK_ISOLATION_ON);
+      task_pool = BLI_task_pool_create(NULL, TASK_PRIORITY_LOW);
 
       tangent_mask_curr = 0;
       /* Calculate tangent layers */

source/blender/blenkernel/intern/image.c

@@ -68,6 +68,7 @@
 #include "BLI_math_vector.h"
 #include "BLI_mempool.h"
 #include "BLI_system.h"
+#include "BLI_task.h"
 #include "BLI_threads.h"
 #include "BLI_timecode.h" /* For stamp time-code format. */
 #include "BLI_utildefines.h"
@@ -882,6 +883,39 @@ Image *BKE_image_load_exists(Main *bmain, const char *filepath)
   return BKE_image_load_exists_ex(bmain, filepath, NULL);
 }
 
+typedef struct ImageFillData {
+  short gen_type;
+  uint width;
+  uint height;
+  unsigned char *rect;
+  float *rect_float;
+  float fill_color[4];
+} ImageFillData;
+
+static void image_buf_fill_isolated(void *usersata_v)
+{
+  ImageFillData *usersata = usersata_v;
+
+  const short gen_type = usersata->gen_type;
+  const uint width = usersata->width;
+  const uint height = usersata->height;
+
+  unsigned char *rect = usersata->rect;
+  float *rect_float = usersata->rect_float;
+
+  switch (gen_type) {
+    case IMA_GENTYPE_GRID:
+      BKE_image_buf_fill_checker(rect, rect_float, width, height);
+      break;
+    case IMA_GENTYPE_GRID_COLOR:
+      BKE_image_buf_fill_checker_color(rect, rect_float, width, height);
+      break;
+    default:
+      BKE_image_buf_fill_color(rect, rect_float, width, height, usersata->fill_color);
+      break;
+  }
+}
+
 static ImBuf *add_ibuf_size(unsigned int width,
                             unsigned int height,
                             const char *name,
@@ -944,17 +978,16 @@ static ImBuf *add_ibuf_size(unsigned int width,
 
   STRNCPY(ibuf->name, name);
 
-  switch (gen_type) {
-    case IMA_GENTYPE_GRID:
-      BKE_image_buf_fill_checker(rect, rect_float, width, height);
-      break;
-    case IMA_GENTYPE_GRID_COLOR:
-      BKE_image_buf_fill_checker_color(rect, rect_float, width, height);
-      break;
-    default:
-      BKE_image_buf_fill_color(rect, rect_float, width, height, fill_color);
-      break;
-  }
+  ImageFillData data;
+
+  data.gen_type = gen_type;
+  data.width = width;
+  data.height = height;
+  data.rect = rect;
+  data.rect_float = rect_float;
+  copy_v4_v4(data.fill_color, fill_color);
+
+  BLI_task_isolate(image_buf_fill_isolated, &data);
 
   return ibuf;
 }

source/blender/blenkernel/intern/lib_override.c

@@ -2335,8 +2335,7 @@ bool BKE_lib_override_library_main_operations_create(Main *bmain, const bool for
   }
 
   struct LibOverrideOpCreateData create_pool_data = {.bmain = bmain, .changed = false};
-  TaskPool *task_pool = BLI_task_pool_create(
-      &create_pool_data, TASK_PRIORITY_HIGH, TASK_ISOLATION_ON);
+  TaskPool *task_pool = BLI_task_pool_create(&create_pool_data, TASK_PRIORITY_HIGH);
 
   FOREACH_MAIN_ID_BEGIN (bmain, id) {
     if (!ID_IS_LINKED(id) && ID_IS_OVERRIDE_LIBRARY_REAL(id) &&

source/blender/blenkernel/intern/mesh_evaluate.c

@@ -1715,8 +1715,7 @@ void BKE_mesh_normals_loop_split(const MVert *mverts,
     loop_split_generator(NULL, &common_data);
   }
   else {
-    TaskPool *task_pool = BLI_task_pool_create(
-        &common_data, TASK_PRIORITY_HIGH, TASK_ISOLATION_ON);
+    TaskPool *task_pool = BLI_task_pool_create(&common_data, TASK_PRIORITY_HIGH);
 
     loop_split_generator(task_pool, &common_data);
 

source/blender/blenkernel/intern/mesh_tangent.c

@@ -656,7 +656,7 @@ void BKE_mesh_calc_loop_tangent_ex(const MVert *mvert,
 
     /* Calculation */
     if (looptri_len != 0) {
-      TaskPool *task_pool = BLI_task_pool_create(NULL, TASK_PRIORITY_LOW, TASK_ISOLATION_ON);
+      TaskPool *task_pool = BLI_task_pool_create(NULL, TASK_PRIORITY_LOW);
 
       tangent_mask_curr = 0;
       /* Calculate tangent layers */

source/blender/blenkernel/intern/ocean.c

@@ -663,7 +663,7 @@ void BKE_ocean_simulate(struct Ocean *o, float t, float scale, float chop_amount
   osd.scale = scale;
   osd.chop_amount = chop_amount;
 
-  pool = BLI_task_pool_create(&osd, TASK_PRIORITY_HIGH, TASK_ISOLATION_ON);
+  pool = BLI_task_pool_create(&osd, TASK_PRIORITY_HIGH);
 
   BLI_rw_mutex_lock(&o->oceanmutex, THREAD_LOCK_WRITE);
 

source/blender/blenkernel/intern/particle.c

@@ -3179,7 +3179,7 @@ void psys_cache_child_paths(ParticleSimulationData *sim,
     return;
   }
 
-  task_pool = BLI_task_pool_create(&ctx, TASK_PRIORITY_LOW, TASK_ISOLATION_ON);
+  task_pool = BLI_task_pool_create(&ctx, TASK_PRIORITY_LOW);
   totchild = ctx.totchild;
   totparent = ctx.totparent;
 

source/blender/blenkernel/intern/particle_distribute.c

@@ -1330,7 +1330,7 @@ static void distribute_particles_on_dm(ParticleSimulationData *sim, int from)
     return;
   }
 
-  task_pool = BLI_task_pool_create(&ctx, TASK_PRIORITY_LOW, TASK_ISOLATION_ON);
+  task_pool = BLI_task_pool_create(&ctx, TASK_PRIORITY_LOW);
 
   totpart = (from == PART_FROM_CHILD ? sim->psys->totchild : sim->psys->totpart);
   psys_tasks_create(&ctx, 0, totpart, &tasks, &numtasks);

source/blender/blenkernel/intern/volume.cc

@@ -324,15 +324,20 @@ struct VolumeGrid {
 
     openvdb::io::File file(filepath);
 
-    try {
-      file.setCopyMaxBytes(0);
-      file.open();
-      openvdb::GridBase::Ptr vdb_grid = file.readGrid(name());
-      entry->grid->setTree(vdb_grid->baseTreePtr());
-    }
-    catch (const openvdb::IoError &e) {
-      entry->error_msg = e.what();
-    }
+    /* Isolate file loading since that's potentially multithreaded and we are
+     * holding a mutex lock. See BLI_task_isolate. Note OpenVDB already uses
+     * TBB, so it's fine to use here without a wrapper. */
+    tbb::this_task_arena::isolate([&] {
+      try {
+        file.setCopyMaxBytes(0);
+        file.open();
+        openvdb::GridBase::Ptr vdb_grid = file.readGrid(name());
+        entry->grid->setTree(vdb_grid->baseTreePtr());
+      }
+      catch (const openvdb::IoError &e) {
+        entry->error_msg = e.what();
+      }
+    });
 
     std::atomic_thread_fence(std::memory_order_release);
     entry->is_loaded = true;