Hold BGL alive by BG (#2075)

wgpu-core/src/binding_model.rs

@@ -421,6 +421,14 @@ pub struct BindGroupLayoutDescriptor<'a> {
 
 pub(crate) type BindEntryMap = FastHashMap<u32, wgt::BindGroupLayoutEntry>;
 
+/// Bind group layout.
+///
+/// The lifetime of BGLs is a bit special. They are only referenced on CPU
+/// without considering GPU operations. And on CPU they get manual
+/// inc-refs and dec-refs. In particular, the following objects depend on them:
+///  - produced bind groups
+///  - produced pipeline layouts
+///  - pipelines with implicit layouts
 #[derive(Debug)]
 pub struct BindGroupLayout<A: hal::Api> {
     pub(crate) raw: A::BindGroupLayout,

wgpu-core/src/device/life.rs

@@ -397,6 +397,10 @@ impl<A: HalApi> LifetimeTracker<A> {
                     if let Some(res) = hub.bind_groups.unregister_locked(id.0, &mut *guard) {
                         self.suspected_resources.add_trackers(&res.used);
 
+                        self.suspected_resources
+                            .bind_group_layouts
+                            .push(res.layout_id);
+
                         let submit_index = res.life_guard.life_count();
                         self.active
                             .iter_mut()

wgpu-core/src/device/mod.rs

@@ -1606,6 +1606,9 @@ impl<A: HalApi> Device<A> {
                 .map_err(DeviceError::from)?
         };
 
+        // manually add a dependency on BGL
+        layout.multi_ref_count.inc();
+
         Ok(binding_model::BindGroup {
             raw,
             device_id: Stored {
@@ -1874,6 +1877,7 @@ impl<A: HalApi> Device<A> {
                 .bind_group_layouts
                 .iter()
                 .map(|&id| {
+                    // manually add a dependency to BGL
                     bgl_guard.get(id).unwrap().multi_ref_count.inc();
                     id::Valid(id)
                 })