From 14d44c2d84f3a67171a8376ef7aa862e6786e2aa Mon Sep 17 00:00:00 2001
From: Dzmitry Malyshau <dmalyshau@mozilla.com>
Date: Sun, 3 May 2020 23:39:05 -0400
Subject: [PATCH] Wait for idle before destroying swapchains

---
 wgpu-core/src/device/mod.rs | 15 +++++++++------
 wgpu-core/src/hub.rs        |  3 +++
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/wgpu-core/src/device/mod.rs b/wgpu-core/src/device/mod.rs
index 062f072b30..eacc4e8fd3 100644
--- a/wgpu-core/src/device/mod.rs
+++ b/wgpu-core/src/device/mod.rs
@@ -460,11 +460,14 @@ impl<B: hal::Backend> Device<B> {
         }
     }
 
+    /// Wait for idle and remove resources that we can, before we die.
+    pub(crate) fn prepare_to_die(&mut self) {
+        let mut life_tracker = self.life_tracker.lock();
+        life_tracker.triage_submissions(&self.raw, true);
+        life_tracker.cleanup(&self.raw, &self.mem_allocator, &self.desc_allocator);
+    }
+
     pub(crate) fn dispose(self) {
-        self.life_tracker.lock().triage_submissions(&self.raw, true);
-        self.life_tracker
-            .lock()
-            .cleanup(&self.raw, &self.mem_allocator, &self.desc_allocator);
         self.com_allocator.destroy(&self.raw);
         let mut desc_alloc = self.desc_allocator.into_inner();
         let mut mem_alloc = self.mem_allocator.into_inner();
@@ -2104,8 +2107,8 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
         let hub = B::hub(self);
         let mut token = Token::root();
         let device = {
-            let (device, mut token) = hub.devices.unregister(device_id, &mut token);
-            device.maintain(self, true, &mut token);
+            let (mut device, _) = hub.devices.unregister(device_id, &mut token);
+            device.prepare_to_die();
             device
         };
 
diff --git a/wgpu-core/src/hub.rs b/wgpu-core/src/hub.rs
index 0d38931803..fd0f5e6530 100644
--- a/wgpu-core/src/hub.rs
+++ b/wgpu-core/src/hub.rs
@@ -418,6 +418,9 @@ impl<B: GfxBackend, F: GlobalIdentityHandlerFactory> Hub<B, F> {
         use hal::{device::Device as _, window::PresentationSurface as _};
 
         let mut devices = self.devices.data.write();
+        for (device, _) in devices.map.values_mut() {
+            device.prepare_to_die();
+        }
 
         for (_, (sampler, _)) in self.samplers.data.write().map.drain() {
             unsafe {