From 368ca941ebeef81b9b7c317418c4eaa6ac1fd732 Mon Sep 17 00:00:00 2001
From: Jonah Williams <jonahwilliams@google.com>
Date: Fri, 25 Oct 2024 13:30:17 -0700
Subject: [PATCH] [Impeller] Lock access to descriptor pool map.
 (flutter/engine#56113)

Speculative fix for https://github.com/flutter/flutter/issues/157565
which looks like the kind of error that might happen if we concurrently
mutate this hashmap.
---
 .../renderer/backend/vulkan/context_vk.cc     | 24 ++++++++++++-------
 .../renderer/backend/vulkan/context_vk.h      |  4 +++-
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/engine/src/flutter/impeller/renderer/backend/vulkan/context_vk.cc b/engine/src/flutter/impeller/renderer/backend/vulkan/context_vk.cc
index eaef668e474..82f3091e61c 100644
--- a/engine/src/flutter/impeller/renderer/backend/vulkan/context_vk.cc
+++ b/engine/src/flutter/impeller/renderer/backend/vulkan/context_vk.cc
@@ -503,15 +503,18 @@ std::shared_ptr<CommandBuffer> ContextVK::CreateCommandBuffer() const {
 
   // look up a cached descriptor pool for the current frame and reuse it
   // if it exists, otherwise create a new pool.
-  DescriptorPoolMap::iterator current_pool =
-      cached_descriptor_pool_.find(std::this_thread::get_id());
   std::shared_ptr<DescriptorPoolVK> descriptor_pool;
-  if (current_pool == cached_descriptor_pool_.end()) {
-    descriptor_pool =
-        (cached_descriptor_pool_[std::this_thread::get_id()] =
-             std::make_shared<DescriptorPoolVK>(weak_from_this()));
-  } else {
-    descriptor_pool = current_pool->second;
+  {
+    Lock lock(desc_pool_mutex_);
+    DescriptorPoolMap::iterator current_pool =
+        cached_descriptor_pool_.find(std::this_thread::get_id());
+    if (current_pool == cached_descriptor_pool_.end()) {
+      descriptor_pool =
+          (cached_descriptor_pool_[std::this_thread::get_id()] =
+               std::make_shared<DescriptorPoolVK>(weak_from_this()));
+    } else {
+      descriptor_pool = current_pool->second;
+    }
   }
 
   auto tracked_objects = std::make_shared<TrackedObjectsVK>(
@@ -668,7 +671,10 @@ void ContextVK::InitializeCommonlyUsedShadersIfNeeded() const {
 }
 
 void ContextVK::DisposeThreadLocalCachedResources() {
-  cached_descriptor_pool_.erase(std::this_thread::get_id());
+  {
+    Lock lock(desc_pool_mutex_);
+    cached_descriptor_pool_.erase(std::this_thread::get_id());
+  }
   command_pool_recycler_->Dispose();
 }
 
diff --git a/engine/src/flutter/impeller/renderer/backend/vulkan/context_vk.h b/engine/src/flutter/impeller/renderer/backend/vulkan/context_vk.h
index 91d4506312d..013e627dad1 100644
--- a/engine/src/flutter/impeller/renderer/backend/vulkan/context_vk.h
+++ b/engine/src/flutter/impeller/renderer/backend/vulkan/context_vk.h
@@ -234,7 +234,9 @@ class ContextVK final : public Context,
   using DescriptorPoolMap =
       std::unordered_map<std::thread::id, std::shared_ptr<DescriptorPoolVK>>;
 
-  mutable DescriptorPoolMap cached_descriptor_pool_;
+  mutable Mutex desc_pool_mutex_;
+  mutable DescriptorPoolMap IPLR_GUARDED_BY(desc_pool_mutex_)
+      cached_descriptor_pool_;
   bool should_disable_surface_control_ = false;
   bool should_batch_cmd_buffers_ = false;
   std::vector<std::shared_ptr<CommandBuffer>> pending_command_buffers_;