From 2c153f5d504ce063a71745128af36db7c18ecd43 Mon Sep 17 00:00:00 2001
From: Imbris <imbrisf@gmail.com>
Date: Sun, 28 Feb 2021 00:56:17 -0500
Subject: [PATCH] Fix issue with multiple queued mappings where the last one is
 not cancelled

---
 wgpu-core/src/device/life.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/wgpu-core/src/device/life.rs b/wgpu-core/src/device/life.rs
index c4694b2c3b..c903781e13 100644
--- a/wgpu-core/src/device/life.rs
+++ b/wgpu-core/src/device/life.rs
@@ -700,6 +700,12 @@ impl<B: GfxBackend> LifetimeTracker<B> {
                     resource::BufferMapState::Waiting(pending_mapping) => pending_mapping,
                     // Mapping cancelled
                     resource::BufferMapState::Idle => continue,
+                    // Mapping queued at least twice by map -> unmap -> map
+                    // and was already successfully mapped below
+                    active @ resource::BufferMapState::Active { .. } => {
+                        buffer.map_state = active;
+                        continue;
+                    }
                     _ => panic!("No pending mapping."),
                 };
                 let status = if mapping.range.start != mapping.range.end {