Track TextureViews in Textures so that they can be chain-destroyed.

- Adds Prepend function to LinkedList to avoid directly using the
  insert functions on the LinkNodes. (And tests for this as well.)
- Adds ApiObjectList class for tracking lists of objects for
  destruction.
- Renames and virtualizes some tracking interfaces so that they can be
  overriden for the TextureView/Texture cases.
- Removes explicit destroying of TextureViews from Device since
  destroying Textures will destroy TextureViews now.

Fixed: dawn:1355
Change-Id: I3522383ea7724d6e41ac0c805793a6c34d9bec27
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/101762
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Loko Kung <lokokung@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>

src/dawn/common/LinkedList.h

@@ -185,6 +185,9 @@ class LinkedList {
     // Appends |e| to the end of the linked list.
     void Append(LinkNode<T>* e) { e->InsertBefore(&root_); }
 
+    // Prepends |e| to the front og the linked list.
+    void Prepend(LinkNode<T>* e) { e->InsertAfter(&root_); }
+
     // Moves all elements (in order) of the list and appends them into |l| leaving the list empty.
     void MoveInto(LinkedList<T>* l) {
         if (empty()) {

src/dawn/native/BindGroup.cpp

@@ -450,11 +450,11 @@ BindGroupBase::BindGroupBase(DeviceBase* device,
         }
     }
 
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 BindGroupBase::BindGroupBase(DeviceBase* device) : ApiObjectBase(device, kLabelNotImplemented) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 BindGroupBase::~BindGroupBase() = default;

src/dawn/native/BindGroupLayout.cpp

@@ -481,7 +481,7 @@ BindGroupLayoutBase::BindGroupLayoutBase(DeviceBase* device,
                                          const BindGroupLayoutDescriptor* descriptor,
                                          PipelineCompatibilityToken pipelineCompatibilityToken)
     : BindGroupLayoutBase(device, descriptor, pipelineCompatibilityToken, kUntrackedByDevice) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 BindGroupLayoutBase::BindGroupLayoutBase(DeviceBase* device, ObjectBase::ErrorTag tag)
@@ -489,7 +489,7 @@ BindGroupLayoutBase::BindGroupLayoutBase(DeviceBase* device, ObjectBase::ErrorTa
 
 BindGroupLayoutBase::BindGroupLayoutBase(DeviceBase* device)
     : ApiObjectBase(device, kLabelNotImplemented) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 BindGroupLayoutBase::~BindGroupLayoutBase() = default;

src/dawn/native/Buffer.cpp

@@ -68,7 +68,7 @@ class ErrorBuffer final : public BufferBase {
             }
             // Since error buffers in this case may allocate memory, we need to track them
             // for destruction on the device.
-            TrackInDevice();
+            GetObjectTrackingList()->Track(this);
         }
     }
 
@@ -152,7 +152,7 @@ BufferBase::BufferBase(DeviceBase* device, const BufferDescriptor* descriptor)
         mUsage |= kInternalStorageBuffer;
     }
 
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 BufferBase::BufferBase(DeviceBase* device,
@@ -171,7 +171,7 @@ BufferBase::BufferBase(DeviceBase* device,
 
 BufferBase::BufferBase(DeviceBase* device, BufferState state)
     : ApiObjectBase(device, kLabelNotImplemented), mState(state) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 BufferBase::~BufferBase() {

src/dawn/native/CommandBuffer.cpp

@@ -30,12 +30,12 @@ CommandBufferBase::CommandBufferBase(CommandEncoder* encoder,
     : ApiObjectBase(encoder->GetDevice(), descriptor->label),
       mCommands(encoder->AcquireCommands()),
       mResourceUsages(encoder->AcquireResourceUsages()) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 CommandBufferBase::CommandBufferBase(DeviceBase* device)
     : ApiObjectBase(device, kLabelNotImplemented) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 CommandBufferBase::CommandBufferBase(DeviceBase* device, ObjectBase::ErrorTag tag)

src/dawn/native/CommandEncoder.cpp

@@ -718,7 +718,7 @@ CommandEncoder* CommandEncoder::MakeError(DeviceBase* device) {
 
 CommandEncoder::CommandEncoder(DeviceBase* device, const CommandEncoderDescriptor* descriptor)
     : ApiObjectBase(device, descriptor->label), mEncodingContext(device, this) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 
     const DawnEncoderInternalUsageDescriptor* internalUsageDesc = nullptr;
     FindInChain(descriptor->nextInChain, &internalUsageDesc);

src/dawn/native/ComputePassEncoder.cpp

@@ -114,7 +114,7 @@ ComputePassEncoder::ComputePassEncoder(DeviceBase* device,
                                        EncodingContext* encodingContext)
     : ProgrammableEncoder(device, descriptor->label, encodingContext),
       mCommandEncoder(commandEncoder) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 // static

src/dawn/native/ComputePipeline.cpp

@@ -47,14 +47,14 @@ ComputePipelineBase::ComputePipelineBase(DeviceBase* device,
           {{SingleShaderStage::Compute, descriptor->compute.module, descriptor->compute.entryPoint,
             descriptor->compute.constantCount, descriptor->compute.constants}}) {
     SetContentHash(ComputeContentHash());
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 
     // Initialize the cache key to include the cache type and device information.
     StreamIn(&mCacheKey, CacheKey::Type::ComputePipeline, device->GetCacheKey());
 }
 
 ComputePipelineBase::ComputePipelineBase(DeviceBase* device) : PipelineBase(device) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 ComputePipelineBase::ComputePipelineBase(DeviceBase* device, ObjectBase::ErrorTag tag)

src/dawn/native/Device.cpp

@@ -338,7 +338,7 @@ void DeviceBase::DestroyObjects() {
     // can destroy the frontend cache.
 
     // clang-format off
-        static constexpr std::array<ObjectType, 19> kObjectTypeDependencyOrder = {
+        static constexpr std::array<ObjectType, 18> kObjectTypeDependencyOrder = {
             ObjectType::ComputePassEncoder,
             ObjectType::RenderPassEncoder,
             ObjectType::RenderBundleEncoder,
@@ -353,26 +353,15 @@ void DeviceBase::DestroyObjects() {
             ObjectType::BindGroupLayout,
             ObjectType::ShaderModule,
             ObjectType::ExternalTexture,
-            ObjectType::TextureView,
-            ObjectType::Texture,
+            ObjectType::Texture,  // Note that Textures own the TextureViews.
             ObjectType::QuerySet,
             ObjectType::Sampler,
             ObjectType::Buffer,
         };
     // clang-format on
 
-    // We first move all objects out from the tracking list into a separate list so that we can
-    // avoid locking the same mutex twice. We can then iterate across the separate list to call
-    // the actual destroy function.
-    LinkedList<ApiObjectBase> objects;
     for (ObjectType type : kObjectTypeDependencyOrder) {
-        ApiObjectList& objList = mObjectLists[type];
-        const std::lock_guard<std::mutex> lock(objList.mutex);
-        objList.objects.MoveInto(&objects);
-    }
-    while (!objects.empty()) {
-        // The destroy call should also remove the object from the list.
-        objects.head()->value()->Destroy();
+        mObjectLists[type].Destroy();
     }
 }
 
@@ -685,14 +674,8 @@ bool DeviceBase::IsLost() const {
     return mState != State::Alive;
 }
 
-void DeviceBase::TrackObject(ApiObjectBase* object) {
-    ApiObjectList& objectList = mObjectLists[object->GetType()];
-    std::lock_guard<std::mutex> lock(objectList.mutex);
-    object->InsertBefore(objectList.objects.head());
-}
-
-std::mutex* DeviceBase::GetObjectListMutex(ObjectType type) {
-    return &mObjectLists[type].mutex;
+ApiObjectList* DeviceBase::GetObjectTrackingList(ObjectType type) {
+    return &mObjectLists[type];
 }
 
 AdapterBase* DeviceBase::GetAdapter() const {

src/dawn/native/Device.h

@@ -333,8 +333,7 @@ class DeviceBase : public RefCountedWithExternalCount {
     };
     State GetState() const;
     bool IsLost() const;
-    void TrackObject(ApiObjectBase* object);
-    std::mutex* GetObjectListMutex(ObjectType type);
+    ApiObjectList* GetObjectTrackingList(ObjectType type);
 
     std::vector<const char*> GetTogglesUsed() const;
     WGSLExtensionSet GetWGSLExtensionAllowList() const;
@@ -548,12 +547,6 @@ class DeviceBase : public RefCountedWithExternalCount {
 
     State mState = State::BeingCreated;
 
-    // Encompasses the mutex and the actual list that contains all live objects "owned" by the
-    // device.
-    struct ApiObjectList {
-        std::mutex mutex;
-        LinkedList<ApiObjectBase> objects;
-    };
     PerObjectType<ApiObjectList> mObjectLists;
 
     FormatTable mFormatTable;

src/dawn/native/ExternalTexture.cpp

@@ -115,12 +115,12 @@ ResultOrError<Ref<ExternalTextureBase>> ExternalTextureBase::Create(
 ExternalTextureBase::ExternalTextureBase(DeviceBase* device,
                                          const ExternalTextureDescriptor* descriptor)
     : ApiObjectBase(device, descriptor->label), mState(ExternalTextureState::Alive) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 ExternalTextureBase::ExternalTextureBase(DeviceBase* device)
     : ApiObjectBase(device, kLabelNotImplemented), mState(ExternalTextureState::Alive) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 // Error external texture cannot be used in bind group.

src/dawn/native/ObjectBase.cpp

@@ -37,6 +37,31 @@ DeviceBase* ObjectBase::GetDevice() const {
     return mDevice.Get();
 }
 
+void ApiObjectList::Track(ApiObjectBase* object) {
+    if (mMarkedDestroyed) {
+        object->DestroyImpl();
+        return;
+    }
+    std::lock_guard<std::mutex> lock(mMutex);
+    mObjects.Prepend(object);
+}
+
+bool ApiObjectList::Untrack(ApiObjectBase* object) {
+    std::lock_guard<std::mutex> lock(mMutex);
+    return object->RemoveFromList();
+}
+
+void ApiObjectList::Destroy() {
+    std::lock_guard<std::mutex> lock(mMutex);
+    mMarkedDestroyed = true;
+    while (!mObjects.empty()) {
+        auto* head = mObjects.head();
+        bool removed = head->RemoveFromList();
+        ASSERT(removed);
+        head->value()->DestroyImpl();
+    }
+}
+
 ApiObjectBase::ApiObjectBase(DeviceBase* device, const char* label) : ObjectBase(device) {
     if (label) {
         mLabel = label;
@@ -71,14 +96,18 @@ void ApiObjectBase::DeleteThis() {
     RefCounted::DeleteThis();
 }
 
-void ApiObjectBase::TrackInDevice() {
+ApiObjectList* ApiObjectBase::GetObjectTrackingList() {
     ASSERT(GetDevice() != nullptr);
-    GetDevice()->TrackObject(this);
+    return GetDevice()->GetObjectTrackingList(GetType());
 }
 
 void ApiObjectBase::Destroy() {
-    const std::lock_guard<std::mutex> lock(*GetDevice()->GetObjectListMutex(GetType()));
-    if (RemoveFromList()) {
+    if (!IsAlive()) {
+        return;
+    }
+    ApiObjectList* list = GetObjectTrackingList();
+    ASSERT(list != nullptr);
+    if (list->Untrack(this)) {
         DestroyImpl();
     }
 }

src/dawn/native/ObjectBase.h

@@ -15,6 +15,7 @@
 #ifndef SRC_DAWN_NATIVE_OBJECTBASE_H_
 #define SRC_DAWN_NATIVE_OBJECTBASE_H_
 
+#include <mutex>
 #include <string>
 
 #include "dawn/common/LinkedList.h"
@@ -23,6 +24,7 @@
 
 namespace dawn::native {
 
+class ApiObjectBase;
 class DeviceBase;
 
 class ErrorMonad : public RefCounted {
@@ -48,6 +50,26 @@ class ObjectBase : public ErrorMonad {
     Ref<DeviceBase> mDevice;
 };
 
+// Generic object list with a mutex for tracking for destruction.
+class ApiObjectList {
+  public:
+    // Tracks an object if the list is not destroyed. If the list is destroyed, destroys the object.
+    void Track(ApiObjectBase* object);
+
+    // Returns true iff the object was removed from the list.
+    bool Untrack(ApiObjectBase* object);
+
+    // Destroys and removes all the objects tracked in the list.
+    void Destroy();
+
+  private:
+    // Boolean used to mark the list so that on subsequent calls to Untrack, we don't need to
+    // reaquire the lock, and Track on new objects immediately destroys them.
+    bool mMarkedDestroyed = false;
+    std::mutex mMutex;
+    LinkedList<ApiObjectBase> mObjects;
+};
+
 class ApiObjectBase : public ObjectBase, public LinkNode<ApiObjectBase> {
   public:
     struct LabelNotImplementedTag {};
@@ -85,7 +107,11 @@ class ApiObjectBase : public ObjectBase, public LinkNode<ApiObjectBase> {
     // and they should ensure that their overriding versions call this underlying version
     // somewhere.
     void DeleteThis() override;
-    void TrackInDevice();
+
+    // Returns the list where this object may be tracked for future destruction. This can be
+    // overrided to create hierarchical object tracking ownership:
+    //   i.e. Device -[tracks]-> Texture -[tracks]-> TextureView.
+    virtual ApiObjectList* GetObjectTrackingList();
 
     // Sub-classes may override this function multiple times. Whenever overriding this function,
     // however, users should be sure to call their parent's version in the new override to make
@@ -94,6 +120,8 @@ class ApiObjectBase : public ObjectBase, public LinkNode<ApiObjectBase> {
     virtual void DestroyImpl() = 0;
 
   private:
+    friend class ApiObjectList;
+
     virtual void SetLabelImpl();
 
     std::string mLabel;

src/dawn/native/PipelineLayout.cpp

@@ -71,12 +71,12 @@ PipelineLayoutBase::PipelineLayoutBase(DeviceBase* device,
 PipelineLayoutBase::PipelineLayoutBase(DeviceBase* device,
                                        const PipelineLayoutDescriptor* descriptor)
     : PipelineLayoutBase(device, descriptor, kUntrackedByDevice) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 PipelineLayoutBase::PipelineLayoutBase(DeviceBase* device)
     : ApiObjectBase(device, kLabelNotImplemented) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 PipelineLayoutBase::PipelineLayoutBase(DeviceBase* device, ObjectBase::ErrorTag tag)

src/dawn/native/QuerySet.cpp

@@ -107,11 +107,11 @@ QuerySetBase::QuerySetBase(DeviceBase* device, const QuerySetDescriptor* descrip
     }
 
     mQueryAvailability.resize(descriptor->count);
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 QuerySetBase::QuerySetBase(DeviceBase* device) : ApiObjectBase(device, kLabelNotImplemented) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 QuerySetBase::QuerySetBase(DeviceBase* device,

src/dawn/native/RenderBundle.cpp

@@ -39,7 +39,7 @@ RenderBundleBase::RenderBundleBase(RenderBundleEncoder* encoder,
       mStencilReadOnly(stencilReadOnly),
       mDrawCount(encoder->GetDrawCount()),
       mResourceUsage(std::move(resourceUsage)) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 void RenderBundleBase::DestroyImpl() {

src/dawn/native/RenderBundleEncoder.cpp

@@ -100,7 +100,7 @@ RenderBundleEncoder::RenderBundleEncoder(DeviceBase* device,
                         descriptor->depthReadOnly,
                         descriptor->stencilReadOnly),
       mBundleEncodingContext(device, this) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 RenderBundleEncoder::RenderBundleEncoder(DeviceBase* device, ErrorTag errorTag)

src/dawn/native/RenderPassEncoder.cpp

@@ -76,7 +76,7 @@ RenderPassEncoder::RenderPassEncoder(DeviceBase* device,
     if (maxDrawCountInfo) {
         mMaxDrawCount = maxDrawCountInfo->maxDrawCount;
     }
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 // static

src/dawn/native/RenderPipeline.cpp

@@ -616,14 +616,14 @@ RenderPipelineBase::RenderPipelineBase(DeviceBase* device,
     }
 
     SetContentHash(ComputeContentHash());
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 
     // Initialize the cache key to include the cache type and device information.
     StreamIn(&mCacheKey, CacheKey::Type::RenderPipeline, device->GetCacheKey());
 }
 
 RenderPipelineBase::RenderPipelineBase(DeviceBase* device) : PipelineBase(device) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 RenderPipelineBase::RenderPipelineBase(DeviceBase* device, ObjectBase::ErrorTag tag)

src/dawn/native/Sampler.cpp

@@ -86,11 +86,11 @@ SamplerBase::SamplerBase(DeviceBase* device,
 
 SamplerBase::SamplerBase(DeviceBase* device, const SamplerDescriptor* descriptor)
     : SamplerBase(device, descriptor, kUntrackedByDevice) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 SamplerBase::SamplerBase(DeviceBase* device) : ApiObjectBase(device, kLabelNotImplemented) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 SamplerBase::SamplerBase(DeviceBase* device, ObjectBase::ErrorTag tag)

src/dawn/native/ShaderModule.cpp

@@ -1089,12 +1089,12 @@ ShaderModuleBase::ShaderModuleBase(DeviceBase* device,
 
 ShaderModuleBase::ShaderModuleBase(DeviceBase* device, const ShaderModuleDescriptor* descriptor)
     : ShaderModuleBase(device, descriptor, kUntrackedByDevice) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 ShaderModuleBase::ShaderModuleBase(DeviceBase* device)
     : ApiObjectBase(device, kLabelNotImplemented) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 ShaderModuleBase::ShaderModuleBase(DeviceBase* device, ObjectBase::ErrorTag tag)

src/dawn/native/SwapChain.cpp

@@ -117,7 +117,7 @@ TextureDescriptor GetSwapChainBaseTextureDescriptor(NewSwapChainBase* swapChain)
 // SwapChainBase
 
 SwapChainBase::SwapChainBase(DeviceBase* device) : ApiObjectBase(device, kLabelNotImplemented) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 SwapChainBase::SwapChainBase(DeviceBase* device, ObjectBase::ErrorTag tag)

src/dawn/native/Texture.cpp

@@ -552,7 +552,7 @@ TextureBase::TextureBase(DeviceBase* device,
     if (internalUsageDesc != nullptr) {
         mInternalUsage |= internalUsageDesc->internalUsage;
     }
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 TextureBase::~TextureBase() = default;
@@ -561,7 +561,7 @@ static constexpr Format kUnusedFormat;
 
 TextureBase::TextureBase(DeviceBase* device, TextureState state)
     : ApiObjectBase(device, kLabelNotImplemented), mFormat(kUnusedFormat), mState(state) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 TextureBase::TextureBase(DeviceBase* device,
@@ -578,6 +578,9 @@ TextureBase::TextureBase(DeviceBase* device,
 
 void TextureBase::DestroyImpl() {
     mState = TextureState::Destroyed;
+
+    // Destroy all of the views associated with the texture as well.
+    mTextureViews.Destroy();
 }
 
 // static
@@ -766,6 +769,10 @@ ResultOrError<Ref<TextureViewBase>> TextureBase::CreateView(
     return GetDevice()->CreateTextureView(this, descriptor);
 }
 
+ApiObjectList* TextureBase::GetViewTrackingList() {
+    return &mTextureViews;
+}
+
 TextureViewBase* TextureBase::APICreateView(const TextureViewDescriptor* descriptor) {
     DeviceBase* device = GetDevice();
 
@@ -831,14 +838,14 @@ TextureViewBase::TextureViewBase(TextureBase* texture, const TextureViewDescript
       mRange({ConvertViewAspect(mFormat, descriptor->aspect),
               {descriptor->baseArrayLayer, descriptor->arrayLayerCount},
               {descriptor->baseMipLevel, descriptor->mipLevelCount}}) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 TextureViewBase::TextureViewBase(TextureBase* texture)
     : ApiObjectBase(texture->GetDevice(), kLabelNotImplemented),
       mTexture(texture),
       mFormat(kUnusedFormat) {
-    TrackInDevice();
+    GetObjectTrackingList()->Track(this);
 }
 
 TextureViewBase::TextureViewBase(DeviceBase* device, ObjectBase::ErrorTag tag)
@@ -907,4 +914,9 @@ const SubresourceRange& TextureViewBase::GetSubresourceRange() const {
     return mRange;
 }
 
+ApiObjectList* TextureViewBase::GetObjectTrackingList() {
+    ASSERT(!IsError());
+    return mTexture->GetViewTrackingList();
+}
+
 }  // namespace dawn::native

src/dawn/native/Texture.h

@@ -92,6 +92,7 @@ class TextureBase : public ApiObjectBase {
 
     ResultOrError<Ref<TextureViewBase>> CreateView(
         const TextureViewDescriptor* descriptor = nullptr);
+    ApiObjectList* GetViewTrackingList();
 
     // Dawn API
     TextureViewBase* APICreateView(const TextureViewDescriptor* descriptor = nullptr);
@@ -129,6 +130,10 @@ class TextureBase : public ApiObjectBase {
     TextureState mState;
     wgpu::TextureFormat mFormatEnumForReflection;
 
+    // Textures track texture views created from them so that they can be destroyed when the texture
+    // is destroyed.
+    ApiObjectList mTextureViews;
+
     // TODO(crbug.com/dawn/845): Use a more optimized data structure to save space
     std::vector<bool> mIsSubresourceContentInitializedAtIndex;
 };
@@ -162,6 +167,8 @@ class TextureViewBase : public ApiObjectBase {
   private:
     TextureViewBase(DeviceBase* device, ObjectBase::ErrorTag tag);
 
+    ApiObjectList* GetObjectTrackingList() override;
+
     Ref<TextureBase> mTexture;
 
     const Format& mFormat;

src/dawn/tests/unittests/LinkedListTests.cpp

@@ -117,6 +117,41 @@ TEST(LinkedList, Append) {
     }
 }
 
+TEST(LinkedList, Prepend) {
+    LinkedList<Node> list;
+    ExpectListContents(list, 0, nullptr);
+
+    Node n1(1);
+    list.Prepend(&n1);
+
+    EXPECT_EQ(&n1, list.head());
+    EXPECT_EQ(&n1, list.tail());
+    {
+        const int expected[] = {1};
+        ExpectListContents(list, 1, expected);
+    }
+
+    Node n2(2);
+    list.Prepend(&n2);
+
+    EXPECT_EQ(&n2, list.head());
+    EXPECT_EQ(&n1, list.tail());
+    {
+        const int expected[] = {2, 1};
+        ExpectListContents(list, 2, expected);
+    }
+
+    Node n3(3);
+    list.Prepend(&n3);
+
+    EXPECT_EQ(&n3, list.head());
+    EXPECT_EQ(&n1, list.tail());
+    {
+        const int expected[] = {3, 2, 1};
+        ExpectListContents(list, 3, expected);
+    }
+}
+
 TEST(LinkedList, RemoveFromList) {
     LinkedList<Node> list;