Fix AnyDevice drop implementation dropping the wrong thing

[Wumpf]

Connections

• SIGSEGV on demo_app quit after wgpu 22.0.0 update emilk/egui#4874
• AnyDevice can hopefully go away soon as part of my ongoing generification work
  • wgpu-hal dynamic dispatch, towards fewer generics in wgpu-core #6002

Post-merge edit:

• Corrected fix of Cast ptr to Device not Surface #5640
  • Making this the actual fix for STATUS_ACCESS_VIOLATION on exit #5637

Description
There is a crash report in egui after wgpu update. Quickly realized that this happens only when the surface is destroyed after the all other resources are dropped. Which leads to this simple repro in hello_triangle (cc: @cwfitzgerald any idea how I can unit-testify this? :/)

diff --git a/examples/src/hello_triangle/mod.rs b/examples/src/hello_triangle/mod.rs
index 7c82d49cf..418bf5c66 100644
--- a/examples/src/hello_triangle/mod.rs
+++ b/examples/src/hello_triangle/mod.rs
@@ -1,4 +1,4 @@
-use std::borrow::Cow;
+use std::{borrow::Cow, sync::Arc};
 use winit::{
     event::{Event, WindowEvent},
     event_loop::EventLoop,
@@ -80,6 +80,8 @@ async fn run(event_loop: EventLoop<()>, window: Window) {
         .get_default_config(&adapter, size.width, size.height)
         .unwrap();
     surface.configure(&device, &config);
+    let surface = Arc::new(surface);
+    let surface_b = surface.clone();
 
     let window = &window;
     event_loop
@@ -143,6 +145,8 @@ async fn run(event_loop: EventLoop<()>, window: Window) {
             }
         })
         .unwrap();
+
+    drop(surface_b);
 }
 
 pub fn main() {

Unknown why this happened after wgpu 22.0.0 update, I strongly suspect the error is older and just surfaces (hah!) now because of improving ownership hygiene in the project.

A shining case of "How did this ever work?"
(A: this still drops the right ref count, so this is ONLY an issue if the last droping of Arc<Device<A>> happens through AnyDevice which is surprisingly rare)

Testing
Above manual test works now

Checklist

• Run cargo fmt.
• Run cargo clippy. If applicable, add:
  • --target wasm32-unknown-unknown
  • --target wasm32-unknown-emscripten
• Run cargo xtask test to run tests.
• Add change to CHANGELOG.md. See simple instructions inside file.

[Wumpf]

(force push to fill in the changelog pr numbers, no other change)

[sagudev]

any idea how I can unit-testify this?

Simple test that inits every possible resource (device, buffer, texture, ...) and then runs all permutations of drops.

[Wumpf]

that would be a good unit test to have regardless indeed! The main problem specifically here though is that we need to create a Surface and we're still having issues to do so on CI afaik

[sagudev]

Maybe xvfb-run can help (for linux), that's what we use in servo.