src/dawn/tests/end2end/DeviceLostTests.cpp - dawn - Git at Google

 // Copyright 2019 The Dawn & Tint Authors
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are met:
 //
 // 1. Redistributions of source code must retain the above copyright notice, this
 //    list of conditions and the following disclaimer.
 //
 // 2. Redistributions in binary form must reproduce the above copyright notice,
 //    this list of conditions and the following disclaimer in the documentation
 //    and/or other materials provided with the distribution.
 //
 // 3. Neither the name of the copyright holder nor the names of its
 //    contributors may be used to endorse or promote products derived from
 //    this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 #include <cstring>
 #include <memory>
 #include <string>

 #include "dawn/tests/DawnTest.h"
 #include "dawn/tests/MockCallback.h"
 #include "dawn/utils/ComboRenderPipelineDescriptor.h"
 #include "dawn/utils/WGPUHelpers.h"
 #include "gmock/gmock.h"

 namespace dawn {
 namespace {

 using testing::_;
 using testing::Exactly;
 using testing::MockCallback;

 class MockQueueWorkDoneCallback {
   public:
     MOCK_METHOD(void, Call, (WGPUQueueWorkDoneStatus status, void* userdata));
 };

 static std::unique_ptr<MockQueueWorkDoneCallback> mockQueueWorkDoneCallback;
 static void ToMockQueueWorkDone(WGPUQueueWorkDoneStatus status, void* userdata) {
     mockQueueWorkDoneCallback->Call(status, userdata);
 }

 static const int fakeUserData = 0;

 class DeviceLostTest : public DawnTest {
   protected:
     void SetUp() override {
         DawnTest::SetUp();
         DAWN_TEST_UNSUPPORTED_IF(UsesWire());
         mockQueueWorkDoneCallback = std::make_unique<MockQueueWorkDoneCallback>();
     }

     void TearDown() override {
         instance.ProcessEvents();  // Flush all callbacks.
         mockQueueWorkDoneCallback = nullptr;
         DawnTest::TearDown();
     }

     static void MapFailCallback(WGPUBufferMapAsyncStatus status, void* userdata) {
         EXPECT_EQ(WGPUBufferMapAsyncStatus_DeviceLost, status);
         EXPECT_EQ(&fakeUserData, userdata);
     }

     void MapAsyncAndWait(const wgpu::Buffer& buffer,
                          wgpu::MapMode mode,
                          size_t offset,
                          size_t size) {
         bool done = false;
         buffer.MapAsync(
             mode, offset, size,
             [](WGPUBufferMapAsyncStatus status, void* userdata) {
                 ASSERT_EQ(WGPUBufferMapAsyncStatus_Success, status);
                 *static_cast<bool*>(userdata) = true;
             },
             &done);

         while (!done) {
             WaitABit();
         }
     }

     template <typename T>
     void ExpectObjectIsError(const T& object) {
         EXPECT_TRUE(dawn::native::CheckIsErrorForTesting(object.Get()));
     }
 };

 // Test that DeviceLostCallback is invoked when LostForTestimg is called
 TEST_P(DeviceLostTest, DeviceLostCallbackIsCalled) {
     LoseDeviceForTesting();
 }

 // Test that submit fails after the device is lost
 TEST_P(DeviceLostTest, SubmitAfterDeviceLost) {
     wgpu::CommandBuffer commands;
     wgpu::CommandEncoder encoder = device.CreateCommandEncoder();
     commands = encoder.Finish();

     LoseDeviceForTesting();
     queue.Submit(0, &commands);
 }

 // Test that CreateBindGroupLayout fails when device is lost
 TEST_P(DeviceLostTest, CreateBindGroupLayoutFails) {
     LoseDeviceForTesting();

     wgpu::BindGroupLayoutEntry entry;
     entry.binding = 0;
     entry.visibility = wgpu::ShaderStage::None;
     entry.buffer.type = wgpu::BufferBindingType::Uniform;
     wgpu::BindGroupLayoutDescriptor descriptor;
     descriptor.entryCount = 1;
     descriptor.entries = &entry;
     ExpectObjectIsError(device.CreateBindGroupLayout(&descriptor));
 }

 // Test that GetBindGroupLayout fails when device is lost
 TEST_P(DeviceLostTest, GetBindGroupLayoutFails) {
     wgpu::ShaderModule csModule = utils::CreateShaderModule(device, R"(
         struct UniformBuffer {
             pos : vec4f
         }
         @group(0) @binding(0) var<uniform> ubo : UniformBuffer;
         @compute @workgroup_size(1) fn main() {
         })");

     wgpu::ComputePipelineDescriptor descriptor;
     descriptor.layout = nullptr;
     descriptor.compute.module = csModule;

     wgpu::ComputePipeline pipeline = device.CreateComputePipeline(&descriptor);

     LoseDeviceForTesting();
     ExpectObjectIsError(pipeline.GetBindGroupLayout(0));
 }

 // Test that CreateBindGroup fails when device is lost
 TEST_P(DeviceLostTest, CreateBindGroupFails) {
     LoseDeviceForTesting();

     wgpu::BindGroupEntry entry;
     entry.binding = 0;
     entry.sampler = nullptr;
     entry.textureView = nullptr;
     entry.buffer = nullptr;
     entry.offset = 0;
     entry.size = 0;

     wgpu::BindGroupDescriptor descriptor;
     descriptor.layout = nullptr;
     descriptor.entryCount = 1;
     descriptor.entries = &entry;
     ExpectObjectIsError(device.CreateBindGroup(&descriptor));
 }

 // Test that CreatePipelineLayout fails when device is lost
 TEST_P(DeviceLostTest, CreatePipelineLayoutFails) {
     LoseDeviceForTesting();

     wgpu::PipelineLayoutDescriptor descriptor;
     descriptor.bindGroupLayoutCount = 0;
     descriptor.bindGroupLayouts = nullptr;
     ExpectObjectIsError(device.CreatePipelineLayout(&descriptor));
 }

 // Tests that CreateRenderBundleEncoder fails when device is lost
 TEST_P(DeviceLostTest, CreateRenderBundleEncoderFails) {
     LoseDeviceForTesting();

     wgpu::RenderBundleEncoderDescriptor descriptor;
     descriptor.colorFormatCount = 0;
     descriptor.colorFormats = nullptr;
     ExpectObjectIsError(device.CreateRenderBundleEncoder(&descriptor));
 }

 // Tests that CreateComputePipeline fails when device is lost
 TEST_P(DeviceLostTest, CreateComputePipelineFails) {
     LoseDeviceForTesting();

     wgpu::ComputePipelineDescriptor descriptor = {};
     descriptor.layout = nullptr;
     descriptor.compute.module = nullptr;
     ExpectObjectIsError(device.CreateComputePipeline(&descriptor));
 }

 // Tests that CreateRenderPipeline fails when device is lost
 TEST_P(DeviceLostTest, CreateRenderPipelineFails) {
     LoseDeviceForTesting();

     utils::ComboRenderPipelineDescriptor descriptor;
     ExpectObjectIsError(device.CreateRenderPipeline(&descriptor));
 }

 // Tests that CreateSampler fails when device is lost
 TEST_P(DeviceLostTest, CreateSamplerFails) {
     LoseDeviceForTesting();

     ExpectObjectIsError(device.CreateSampler());
 }

 // Tests that CreateShaderModule fails when device is lost
 TEST_P(DeviceLostTest, CreateShaderModuleFails) {
     LoseDeviceForTesting();

     ExpectObjectIsError(utils::CreateShaderModule(device, R"(
         @fragment
         fn main(@location(0) color : vec4f) -> @location(0) vec4f {
             return color;
         })"));
 }

 // Note that no device lost tests are done for swapchain because it is awkward to create a
 // wgpu::Surface in this file. SwapChainValidationTests.CreateSwapChainFailsAfterDevLost covers
 // this validation.

 // Tests that CreateTexture fails when device is lost
 TEST_P(DeviceLostTest, CreateTextureFails) {
     LoseDeviceForTesting();

     wgpu::TextureDescriptor descriptor;
     descriptor.size.width = 4;
     descriptor.size.height = 4;
     descriptor.size.depthOrArrayLayers = 1;
     descriptor.mipLevelCount = 1;
     descriptor.dimension = wgpu::TextureDimension::e2D;
     descriptor.usage = wgpu::TextureUsage::RenderAttachment;

     ExpectObjectIsError(device.CreateTexture(&descriptor));
 }

 // Test that CreateBuffer fails when device is lost
 TEST_P(DeviceLostTest, CreateBufferFails) {
     LoseDeviceForTesting();

     wgpu::BufferDescriptor bufferDescriptor;
     bufferDescriptor.size = sizeof(float);
     bufferDescriptor.usage = wgpu::BufferUsage::CopySrc;
     ExpectObjectIsError(device.CreateBuffer(&bufferDescriptor));
 }

 // Test that buffer.MapAsync for writing fails after device is lost
 TEST_P(DeviceLostTest, BufferMapAsyncFailsForWriting) {
     wgpu::BufferDescriptor bufferDescriptor;
     bufferDescriptor.size = 4;
     bufferDescriptor.usage = wgpu::BufferUsage::MapWrite;
     wgpu::Buffer buffer = device.CreateBuffer(&bufferDescriptor);

     LoseDeviceForTesting();
     buffer.MapAsync(wgpu::MapMode::Write, 0, 4, MapFailCallback, const_cast<int*>(&fakeUserData));
 }

 // Test that BufferMapAsync for writing calls back with device lost status when device lost after
 // mapping
 TEST_P(DeviceLostTest, BufferMapAsyncBeforeLossFailsForWriting) {
     wgpu::BufferDescriptor bufferDescriptor;
     bufferDescriptor.size = 4;
     bufferDescriptor.usage = wgpu::BufferUsage::MapWrite;
     wgpu::Buffer buffer = device.CreateBuffer(&bufferDescriptor);

     buffer.MapAsync(wgpu::MapMode::Write, 0, 4, MapFailCallback, const_cast<int*>(&fakeUserData));

     LoseDeviceForTesting();
 }

 // Test that buffer.Unmap after device is lost
 TEST_P(DeviceLostTest, BufferUnmapAfterDeviceLost) {
     wgpu::BufferDescriptor bufferDescriptor;
     bufferDescriptor.size = sizeof(float);
     bufferDescriptor.usage = wgpu::BufferUsage::MapWrite;
     bufferDescriptor.mappedAtCreation = true;
     wgpu::Buffer buffer = device.CreateBuffer(&bufferDescriptor);

     LoseDeviceForTesting();
     buffer.Unmap();
 }

 // Test that mappedAtCreation fails after device is lost
 TEST_P(DeviceLostTest, CreateBufferMappedAtCreationFails) {
     wgpu::BufferDescriptor bufferDescriptor;
     bufferDescriptor.size = sizeof(float);
     bufferDescriptor.usage = wgpu::BufferUsage::MapWrite;
     bufferDescriptor.mappedAtCreation = true;

     LoseDeviceForTesting();
     ExpectObjectIsError(device.CreateBuffer(&bufferDescriptor));
 }

 // Test that BufferMapAsync for reading fails after device is lost
 TEST_P(DeviceLostTest, BufferMapAsyncFailsForReading) {
     wgpu::BufferDescriptor bufferDescriptor;
     bufferDescriptor.size = 4;
     bufferDescriptor.usage = wgpu::BufferUsage::MapRead | wgpu::BufferUsage::CopyDst;

     wgpu::Buffer buffer = device.CreateBuffer(&bufferDescriptor);

     LoseDeviceForTesting();
     buffer.MapAsync(wgpu::MapMode::Read, 0, 4, MapFailCallback, const_cast<int*>(&fakeUserData));
 }

 // Test that BufferMapAsync for reading calls back with device lost status when device lost after
 // mapping
 TEST_P(DeviceLostTest, BufferMapAsyncBeforeLossFailsForReading) {
     wgpu::BufferDescriptor bufferDescriptor;
     bufferDescriptor.size = sizeof(float);
     bufferDescriptor.usage = wgpu::BufferUsage::MapRead | wgpu::BufferUsage::CopyDst;

     wgpu::Buffer buffer = device.CreateBuffer(&bufferDescriptor);

     buffer.MapAsync(wgpu::MapMode::Read, 0, 4, MapFailCallback, const_cast<int*>(&fakeUserData));

     LoseDeviceForTesting();
 }

 // Test that WriteBuffer after device is lost
 TEST_P(DeviceLostTest, WriteBufferAfterDeviceLost) {
     wgpu::BufferDescriptor bufferDescriptor;
     bufferDescriptor.size = sizeof(float);
     bufferDescriptor.usage = wgpu::BufferUsage::MapRead | wgpu::BufferUsage::CopyDst;

     wgpu::Buffer buffer = device.CreateBuffer(&bufferDescriptor);

     LoseDeviceForTesting();
     float data = 12.0f;
     queue.WriteBuffer(buffer, 0, &data, sizeof(data));
 }

 // Test it's possible to GetMappedRange on a buffer created mapped after device loss
 TEST_P(DeviceLostTest, GetMappedRange_CreateBufferMappedAtCreationAfterLoss) {
     LoseDeviceForTesting();

     wgpu::BufferDescriptor desc;
     desc.size = 4;
     desc.usage = wgpu::BufferUsage::CopySrc;
     desc.mappedAtCreation = true;
     wgpu::Buffer buffer = device.CreateBuffer(&desc);
     ExpectObjectIsError(buffer);

     ASSERT_NE(buffer.GetMappedRange(), nullptr);
 }

 // Test that device loss doesn't change the result of GetMappedRange, mappedAtCreation version.
 TEST_P(DeviceLostTest, GetMappedRange_CreateBufferMappedAtCreationBeforeLoss) {
     wgpu::BufferDescriptor desc;
     desc.size = 4;
     desc.usage = wgpu::BufferUsage::CopySrc;
     desc.mappedAtCreation = true;
     wgpu::Buffer buffer = device.CreateBuffer(&desc);

     void* rangeBeforeLoss = buffer.GetMappedRange();
     LoseDeviceForTesting();

     ASSERT_NE(buffer.GetMappedRange(), nullptr);
     ASSERT_EQ(buffer.GetMappedRange(), rangeBeforeLoss);
 }

 // Test that device loss doesn't change the result of GetMappedRange, mapping for reading version.
 TEST_P(DeviceLostTest, GetMappedRange_MapAsyncReading) {
     wgpu::BufferDescriptor desc;
     desc.size = 4;
     desc.usage = wgpu::BufferUsage::MapRead | wgpu::BufferUsage::CopyDst;
     wgpu::Buffer buffer = device.CreateBuffer(&desc);

     MapAsyncAndWait(buffer, wgpu::MapMode::Read, 0, 4);
     queue.Submit(0, nullptr);

     const void* rangeBeforeLoss = buffer.GetConstMappedRange();
     LoseDeviceForTesting();

     ASSERT_NE(buffer.GetConstMappedRange(), nullptr);
     ASSERT_EQ(buffer.GetConstMappedRange(), rangeBeforeLoss);
 }

 // Test that device loss doesn't change the result of GetMappedRange, mapping for writing version.
 TEST_P(DeviceLostTest, GetMappedRange_MapAsyncWriting) {
     wgpu::BufferDescriptor desc;
     desc.size = 4;
     desc.usage = wgpu::BufferUsage::MapWrite | wgpu::BufferUsage::CopySrc;
     wgpu::Buffer buffer = device.CreateBuffer(&desc);

     MapAsyncAndWait(buffer, wgpu::MapMode::Write, 0, 4);
     queue.Submit(0, nullptr);

     const void* rangeBeforeLoss = buffer.GetConstMappedRange();
     LoseDeviceForTesting();

     ASSERT_NE(buffer.GetConstMappedRange(), nullptr);
     ASSERT_EQ(buffer.GetConstMappedRange(), rangeBeforeLoss);
 }

 // TODO(dawn:929): mapasync read + resolve + loss getmappedrange != nullptr.
 // TODO(dawn:929): mapasync write + resolve + loss getmappedrange != nullptr.

 // Test that Command Encoder Finish fails when device lost
 TEST_P(DeviceLostTest, CommandEncoderFinishFails) {
     wgpu::CommandBuffer commands;
     wgpu::CommandEncoder encoder = device.CreateCommandEncoder();

     LoseDeviceForTesting();
     ExpectObjectIsError(encoder.Finish());
 }

 // Test that QueueOnSubmittedWorkDone after device is lost.
 TEST_P(DeviceLostTest, QueueOnSubmittedWorkDoneAfterDeviceLost) {
     LoseDeviceForTesting();

     // callback should have device lost status
     EXPECT_CALL(*mockQueueWorkDoneCallback, Call(WGPUQueueWorkDoneStatus_DeviceLost, nullptr))
         .Times(1);
     queue.OnSubmittedWorkDone(ToMockQueueWorkDone, nullptr);
 }

 // Test that QueueOnSubmittedWorkDone when the device is lost after calling OnSubmittedWorkDone
 TEST_P(DeviceLostTest, QueueOnSubmittedWorkDoneBeforeLossFails) {
     // callback should have device lost status
     EXPECT_CALL(*mockQueueWorkDoneCallback, Call(WGPUQueueWorkDoneStatus_DeviceLost, nullptr))
         .Times(1);
     queue.OnSubmittedWorkDone(ToMockQueueWorkDone, nullptr);

     LoseDeviceForTesting();
 }

 // Test that LostForTesting can only be called on one time
 TEST_P(DeviceLostTest, LoseDeviceForTestingOnce) {
     // First LoseDeviceForTesting call should occur normally. The callback is already set in SetUp.
     LoseDeviceForTesting();

     device.ForceLoss(wgpu::DeviceLostReason::Undefined, "Device lost for testing");
     FlushWire();
     testing::Mock::VerifyAndClearExpectations(&mDeviceLostCallback);
 }

 TEST_P(DeviceLostTest, DeviceLostDoesntCallUncapturedError) {
     // Since the device has a default error callback set that fails if it is called, we just need
     // to lose the device and verify no failures.
     LoseDeviceForTesting();
 }

 // Test that WGPUCreatePipelineAsyncStatus_Success is returned when device is lost
 // before the callback of Create*PipelineAsync() is called.
 TEST_P(DeviceLostTest, DeviceLostBeforeCreatePipelineAsyncCallback) {
     wgpu::ShaderModule csModule = utils::CreateShaderModule(device, R"(
         @compute @workgroup_size(1) fn main() {
         })");

     wgpu::ComputePipelineDescriptor descriptor;
     descriptor.compute.module = csModule;

     auto callback = [](WGPUCreatePipelineAsyncStatus status, WGPUComputePipeline returnPipeline,
                        const char* message, void* userdata) {
         EXPECT_EQ(WGPUCreatePipelineAsyncStatus_Success, status);
         EXPECT_NE(returnPipeline, nullptr);
         wgpu::ComputePipeline::Acquire(returnPipeline);
     };

     device.CreateComputePipelineAsync(&descriptor, callback, nullptr);
     LoseDeviceForTesting();
     // Need to call ProcessEvents, otherwise it will be an instance drop as LoseDeviceForTesting
     // is the last statement of the test body.
     // TODO(dawn:2353): Update to use WGPUCreateComputePipelineAsyncCallbackInfo version of
     // CreateComputePipelineAsync and then we don't need to call ProcessEvents explicitly
     GetInstance().ProcessEvents();
 }

 // This is a regression test for crbug.com/1212385 where Dawn didn't clean up all
 // references to bind group layouts such that the cache was non-empty at the end
 // of shut down.
 TEST_P(DeviceLostTest, FreeBindGroupAfterDeviceLossWithPendingCommands) {
     wgpu::BindGroupLayout bgl = utils::MakeBindGroupLayout(
         device, {{0, wgpu::ShaderStage::Fragment, wgpu::BufferBindingType::Storage}});

     wgpu::BufferDescriptor bufferDesc;
     bufferDesc.size = sizeof(float);
     bufferDesc.usage = wgpu::BufferUsage::Storage;
     wgpu::Buffer buffer = device.CreateBuffer(&bufferDesc);

     wgpu::BindGroup bg = utils::MakeBindGroup(device, bgl, {{0, buffer, 0, sizeof(float)}});

     // Advance the pending command serial. We only a need a couple of these to repro the bug,
     // but include extra so this does not become a change-detecting test if the specific serial
     // value is sensitive.
     queue.Submit(0, nullptr);
     queue.Submit(0, nullptr);
     queue.Submit(0, nullptr);
     queue.Submit(0, nullptr);
     queue.Submit(0, nullptr);
     queue.Submit(0, nullptr);

     LoseDeviceForTesting();

     // Releasing the bing group places the bind group layout into a queue in the Vulkan backend
     // for recycling of descriptor sets. So, after these release calls there is still one last
     // reference to the BGL which wouldn't be freed until the pending serial passes.
     // Since the device is lost, destruction will clean up immediately without waiting for the
     // serial. The implementation needs to be sure to clear these BGL references. At the end of
     // Device shut down, we DAWN_ASSERT that the BGL cache is empty.
     bgl = nullptr;
     bg = nullptr;
 }

 // This is a regression test for crbug.com/1365011 where ending a render pass with an indirect draw
 // in it after the device is lost would cause render commands to be leaked.
 TEST_P(DeviceLostTest, DeviceLostInRenderPassWithDrawIndirect) {
     utils::BasicRenderPass renderPass = utils::CreateBasicRenderPass(device, 4u, 4u);
     utils::ComboRenderPipelineDescriptor desc;
     desc.vertex.module = utils::CreateShaderModule(device, R"(
         @vertex fn main(@builtin(vertex_index) i : u32) -> @builtin(position) vec4f {
             var pos = array(
                 vec2f(-1.0, -1.0),
                 vec2f(3.0, -1.0),
                 vec2f(-1.0, 3.0));
             return vec4f(pos[i], 0.0, 1.0);
         }
     )");
     desc.cFragment.module = utils::CreateShaderModule(device, R"(
         @fragment fn main() -> @location(0) vec4f {
             return vec4f(0.0, 1.0, 0.0, 1.0);
         }
     )");
     desc.cTargets[0].format = renderPass.colorFormat;
     wgpu::Buffer indirectBuffer =
         utils::CreateBufferFromData<uint32_t>(device, wgpu::BufferUsage::Indirect, {3, 1, 0, 0});
     wgpu::RenderPipeline pipeline = device.CreateRenderPipeline(&desc);
     wgpu::CommandEncoder encoder = device.CreateCommandEncoder();
     wgpu::RenderPassEncoder pass = encoder.BeginRenderPass(&renderPass.renderPassInfo);
     pass.SetPipeline(pipeline);
     pass.DrawIndirect(indirectBuffer, 0);
     LoseDeviceForTesting();
     pass.End();
 }

 // Attempting to set an object label after device loss should not cause an error.
 TEST_P(DeviceLostTest, SetLabelAfterDeviceLoss) {
     DAWN_TEST_UNSUPPORTED_IF(UsesWire());
     std::string label = "test";
     wgpu::BufferDescriptor descriptor;
     descriptor.size = 4;
     descriptor.usage = wgpu::BufferUsage::Uniform;
     wgpu::Buffer buffer = device.CreateBuffer(&descriptor);
     LoseDeviceForTesting();
     buffer.SetLabel(label.c_str());
 }

 DAWN_INSTANTIATE_TEST(DeviceLostTest,
                       D3D11Backend(),
                       D3D12Backend(),
                       MetalBackend(),
                       NullBackend(),
                       OpenGLBackend(),
                       OpenGLESBackend(),
                       VulkanBackend());

 }  // anonymous namespace
 }  // namespace dawn
	// Copyright 2019 The Dawn & Tint Authors
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are met:
	//
	// 1. Redistributions of source code must retain the above copyright notice, this
	// list of conditions and the following disclaimer.
	//
	// 2. Redistributions in binary form must reproduce the above copyright notice,
	// this list of conditions and the following disclaimer in the documentation
	// and/or other materials provided with the distribution.
	//
	// 3. Neither the name of the copyright holder nor the names of its
	// contributors may be used to endorse or promote products derived from
	// this software without specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
	// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
	// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
	// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
	// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	#include <cstring>
	#include <memory>
	#include <string>

	#include "dawn/tests/DawnTest.h"
	#include "dawn/tests/MockCallback.h"
	#include "dawn/utils/ComboRenderPipelineDescriptor.h"
	#include "dawn/utils/WGPUHelpers.h"
	#include "gmock/gmock.h"

	namespace dawn {
	namespace {

	using testing::_;
	using testing::Exactly;
	using testing::MockCallback;

	class MockQueueWorkDoneCallback {
	public:
	MOCK_METHOD(void, Call, (WGPUQueueWorkDoneStatus status, void* userdata));
	};

	static std::unique_ptr<MockQueueWorkDoneCallback> mockQueueWorkDoneCallback;
	static void ToMockQueueWorkDone(WGPUQueueWorkDoneStatus status, void* userdata) {
	mockQueueWorkDoneCallback->Call(status, userdata);
	}

	static const int fakeUserData = 0;

	class DeviceLostTest : public DawnTest {
	protected:
	void SetUp() override {
	DawnTest::SetUp();
	DAWN_TEST_UNSUPPORTED_IF(UsesWire());
	mockQueueWorkDoneCallback = std::make_unique<MockQueueWorkDoneCallback>();
	}

	void TearDown() override {
	instance.ProcessEvents(); // Flush all callbacks.
	mockQueueWorkDoneCallback = nullptr;
	DawnTest::TearDown();
	}

	static void MapFailCallback(WGPUBufferMapAsyncStatus status, void* userdata) {
	EXPECT_EQ(WGPUBufferMapAsyncStatus_DeviceLost, status);
	EXPECT_EQ(&fakeUserData, userdata);
	}

	void MapAsyncAndWait(const wgpu::Buffer& buffer,
	wgpu::MapMode mode,
	size_t offset,
	size_t size) {
	bool done = false;
	buffer.MapAsync(
	mode, offset, size,
	[](WGPUBufferMapAsyncStatus status, void* userdata) {
	ASSERT_EQ(WGPUBufferMapAsyncStatus_Success, status);
	static_cast<bool>(userdata) = true;
	},
	&done);

	while (!done) {
	WaitABit();
	}
	}

	template <typename T>
	void ExpectObjectIsError(const T& object) {
	EXPECT_TRUE(dawn::native::CheckIsErrorForTesting(object.Get()));
	}
	};

	// Test that DeviceLostCallback is invoked when LostForTestimg is called
	TEST_P(DeviceLostTest, DeviceLostCallbackIsCalled) {
	LoseDeviceForTesting();
	}

	// Test that submit fails after the device is lost
	TEST_P(DeviceLostTest, SubmitAfterDeviceLost) {
	wgpu::CommandBuffer commands;
	wgpu::CommandEncoder encoder = device.CreateCommandEncoder();
	commands = encoder.Finish();

	LoseDeviceForTesting();
	queue.Submit(0, &commands);
	}

	// Test that CreateBindGroupLayout fails when device is lost
	TEST_P(DeviceLostTest, CreateBindGroupLayoutFails) {
	LoseDeviceForTesting();

	wgpu::BindGroupLayoutEntry entry;
	entry.binding = 0;
	entry.visibility = wgpu::ShaderStage::None;
	entry.buffer.type = wgpu::BufferBindingType::Uniform;
	wgpu::BindGroupLayoutDescriptor descriptor;
	descriptor.entryCount = 1;
	descriptor.entries = &entry;
	ExpectObjectIsError(device.CreateBindGroupLayout(&descriptor));
	}

	// Test that GetBindGroupLayout fails when device is lost
	TEST_P(DeviceLostTest, GetBindGroupLayoutFails) {
	wgpu::ShaderModule csModule = utils::CreateShaderModule(device, R"(
	struct UniformBuffer {
	pos : vec4f
	}
	@group(0) @binding(0) var<uniform> ubo : UniformBuffer;
	@compute @workgroup_size(1) fn main() {
	})");

	wgpu::ComputePipelineDescriptor descriptor;
	descriptor.layout = nullptr;
	descriptor.compute.module = csModule;

	wgpu::ComputePipeline pipeline = device.CreateComputePipeline(&descriptor);

	LoseDeviceForTesting();
	ExpectObjectIsError(pipeline.GetBindGroupLayout(0));
	}

	// Test that CreateBindGroup fails when device is lost
	TEST_P(DeviceLostTest, CreateBindGroupFails) {
	LoseDeviceForTesting();

	wgpu::BindGroupEntry entry;
	entry.binding = 0;
	entry.sampler = nullptr;
	entry.textureView = nullptr;
	entry.buffer = nullptr;
	entry.offset = 0;
	entry.size = 0;

	wgpu::BindGroupDescriptor descriptor;
	descriptor.layout = nullptr;
	descriptor.entryCount = 1;
	descriptor.entries = &entry;
	ExpectObjectIsError(device.CreateBindGroup(&descriptor));
	}

	// Test that CreatePipelineLayout fails when device is lost
	TEST_P(DeviceLostTest, CreatePipelineLayoutFails) {
	LoseDeviceForTesting();

	wgpu::PipelineLayoutDescriptor descriptor;
	descriptor.bindGroupLayoutCount = 0;
	descriptor.bindGroupLayouts = nullptr;
	ExpectObjectIsError(device.CreatePipelineLayout(&descriptor));
	}

	// Tests that CreateRenderBundleEncoder fails when device is lost
	TEST_P(DeviceLostTest, CreateRenderBundleEncoderFails) {
	LoseDeviceForTesting();

	wgpu::RenderBundleEncoderDescriptor descriptor;
	descriptor.colorFormatCount = 0;
	descriptor.colorFormats = nullptr;
	ExpectObjectIsError(device.CreateRenderBundleEncoder(&descriptor));
	}

	// Tests that CreateComputePipeline fails when device is lost
	TEST_P(DeviceLostTest, CreateComputePipelineFails) {
	LoseDeviceForTesting();

	wgpu::ComputePipelineDescriptor descriptor = {};
	descriptor.layout = nullptr;
	descriptor.compute.module = nullptr;
	ExpectObjectIsError(device.CreateComputePipeline(&descriptor));
	}

	// Tests that CreateRenderPipeline fails when device is lost
	TEST_P(DeviceLostTest, CreateRenderPipelineFails) {
	LoseDeviceForTesting();

	utils::ComboRenderPipelineDescriptor descriptor;
	ExpectObjectIsError(device.CreateRenderPipeline(&descriptor));
	}

	// Tests that CreateSampler fails when device is lost
	TEST_P(DeviceLostTest, CreateSamplerFails) {
	LoseDeviceForTesting();

	ExpectObjectIsError(device.CreateSampler());
	}

	// Tests that CreateShaderModule fails when device is lost
	TEST_P(DeviceLostTest, CreateShaderModuleFails) {
	LoseDeviceForTesting();

	ExpectObjectIsError(utils::CreateShaderModule(device, R"(
	@fragment
	fn main(@location(0) color : vec4f) -> @location(0) vec4f {
	return color;
	})"));
	}

	// Note that no device lost tests are done for swapchain because it is awkward to create a
	// wgpu::Surface in this file. SwapChainValidationTests.CreateSwapChainFailsAfterDevLost covers
	// this validation.

	// Tests that CreateTexture fails when device is lost
	TEST_P(DeviceLostTest, CreateTextureFails) {
	LoseDeviceForTesting();

	wgpu::TextureDescriptor descriptor;
	descriptor.size.width = 4;
	descriptor.size.height = 4;
	descriptor.size.depthOrArrayLayers = 1;
	descriptor.mipLevelCount = 1;
	descriptor.dimension = wgpu::TextureDimension::e2D;
	descriptor.usage = wgpu::TextureUsage::RenderAttachment;

	ExpectObjectIsError(device.CreateTexture(&descriptor));
	}

	// Test that CreateBuffer fails when device is lost
	TEST_P(DeviceLostTest, CreateBufferFails) {
	LoseDeviceForTesting();

	wgpu::BufferDescriptor bufferDescriptor;
	bufferDescriptor.size = sizeof(float);
	bufferDescriptor.usage = wgpu::BufferUsage::CopySrc;
	ExpectObjectIsError(device.CreateBuffer(&bufferDescriptor));
	}

	// Test that buffer.MapAsync for writing fails after device is lost
	TEST_P(DeviceLostTest, BufferMapAsyncFailsForWriting) {
	wgpu::BufferDescriptor bufferDescriptor;
	bufferDescriptor.size = 4;
	bufferDescriptor.usage = wgpu::BufferUsage::MapWrite;
	wgpu::Buffer buffer = device.CreateBuffer(&bufferDescriptor);

	LoseDeviceForTesting();
	buffer.MapAsync(wgpu::MapMode::Write, 0, 4, MapFailCallback, const_cast<int*>(&fakeUserData));
	}

	// Test that BufferMapAsync for writing calls back with device lost status when device lost after
	// mapping
	TEST_P(DeviceLostTest, BufferMapAsyncBeforeLossFailsForWriting) {
	wgpu::BufferDescriptor bufferDescriptor;
	bufferDescriptor.size = 4;
	bufferDescriptor.usage = wgpu::BufferUsage::MapWrite;
	wgpu::Buffer buffer = device.CreateBuffer(&bufferDescriptor);

	buffer.MapAsync(wgpu::MapMode::Write, 0, 4, MapFailCallback, const_cast<int*>(&fakeUserData));

	LoseDeviceForTesting();
	}

	// Test that buffer.Unmap after device is lost
	TEST_P(DeviceLostTest, BufferUnmapAfterDeviceLost) {
	wgpu::BufferDescriptor bufferDescriptor;
	bufferDescriptor.size = sizeof(float);
	bufferDescriptor.usage = wgpu::BufferUsage::MapWrite;
	bufferDescriptor.mappedAtCreation = true;
	wgpu::Buffer buffer = device.CreateBuffer(&bufferDescriptor);

	LoseDeviceForTesting();
	buffer.Unmap();
	}

	// Test that mappedAtCreation fails after device is lost
	TEST_P(DeviceLostTest, CreateBufferMappedAtCreationFails) {
	wgpu::BufferDescriptor bufferDescriptor;
	bufferDescriptor.size = sizeof(float);
	bufferDescriptor.usage = wgpu::BufferUsage::MapWrite;
	bufferDescriptor.mappedAtCreation = true;

	LoseDeviceForTesting();
	ExpectObjectIsError(device.CreateBuffer(&bufferDescriptor));
	}

	// Test that BufferMapAsync for reading fails after device is lost
	TEST_P(DeviceLostTest, BufferMapAsyncFailsForReading) {
	wgpu::BufferDescriptor bufferDescriptor;
	bufferDescriptor.size = 4;
	bufferDescriptor.usage = wgpu::BufferUsage::MapRead \| wgpu::BufferUsage::CopyDst;

	wgpu::Buffer buffer = device.CreateBuffer(&bufferDescriptor);

	LoseDeviceForTesting();
	buffer.MapAsync(wgpu::MapMode::Read, 0, 4, MapFailCallback, const_cast<int*>(&fakeUserData));
	}

	// Test that BufferMapAsync for reading calls back with device lost status when device lost after
	// mapping
	TEST_P(DeviceLostTest, BufferMapAsyncBeforeLossFailsForReading) {
	wgpu::BufferDescriptor bufferDescriptor;
	bufferDescriptor.size = sizeof(float);
	bufferDescriptor.usage = wgpu::BufferUsage::MapRead \| wgpu::BufferUsage::CopyDst;

	wgpu::Buffer buffer = device.CreateBuffer(&bufferDescriptor);

	buffer.MapAsync(wgpu::MapMode::Read, 0, 4, MapFailCallback, const_cast<int*>(&fakeUserData));

	LoseDeviceForTesting();
	}

	// Test that WriteBuffer after device is lost
	TEST_P(DeviceLostTest, WriteBufferAfterDeviceLost) {
	wgpu::BufferDescriptor bufferDescriptor;
	bufferDescriptor.size = sizeof(float);
	bufferDescriptor.usage = wgpu::BufferUsage::MapRead \| wgpu::BufferUsage::CopyDst;

	wgpu::Buffer buffer = device.CreateBuffer(&bufferDescriptor);

	LoseDeviceForTesting();
	float data = 12.0f;
	queue.WriteBuffer(buffer, 0, &data, sizeof(data));
	}

	// Test it's possible to GetMappedRange on a buffer created mapped after device loss
	TEST_P(DeviceLostTest, GetMappedRange_CreateBufferMappedAtCreationAfterLoss) {
	LoseDeviceForTesting();

	wgpu::BufferDescriptor desc;
	desc.size = 4;
	desc.usage = wgpu::BufferUsage::CopySrc;
	desc.mappedAtCreation = true;
	wgpu::Buffer buffer = device.CreateBuffer(&desc);
	ExpectObjectIsError(buffer);

	ASSERT_NE(buffer.GetMappedRange(), nullptr);
	}

	// Test that device loss doesn't change the result of GetMappedRange, mappedAtCreation version.
	TEST_P(DeviceLostTest, GetMappedRange_CreateBufferMappedAtCreationBeforeLoss) {
	wgpu::BufferDescriptor desc;
	desc.size = 4;
	desc.usage = wgpu::BufferUsage::CopySrc;
	desc.mappedAtCreation = true;
	wgpu::Buffer buffer = device.CreateBuffer(&desc);

	void* rangeBeforeLoss = buffer.GetMappedRange();
	LoseDeviceForTesting();

	ASSERT_NE(buffer.GetMappedRange(), nullptr);
	ASSERT_EQ(buffer.GetMappedRange(), rangeBeforeLoss);
	}

	// Test that device loss doesn't change the result of GetMappedRange, mapping for reading version.
	TEST_P(DeviceLostTest, GetMappedRange_MapAsyncReading) {
	wgpu::BufferDescriptor desc;
	desc.size = 4;
	desc.usage = wgpu::BufferUsage::MapRead \| wgpu::BufferUsage::CopyDst;
	wgpu::Buffer buffer = device.CreateBuffer(&desc);

	MapAsyncAndWait(buffer, wgpu::MapMode::Read, 0, 4);
	queue.Submit(0, nullptr);

	const void* rangeBeforeLoss = buffer.GetConstMappedRange();
	LoseDeviceForTesting();

	ASSERT_NE(buffer.GetConstMappedRange(), nullptr);
	ASSERT_EQ(buffer.GetConstMappedRange(), rangeBeforeLoss);
	}

	// Test that device loss doesn't change the result of GetMappedRange, mapping for writing version.
	TEST_P(DeviceLostTest, GetMappedRange_MapAsyncWriting) {
	wgpu::BufferDescriptor desc;
	desc.size = 4;
	desc.usage = wgpu::BufferUsage::MapWrite \| wgpu::BufferUsage::CopySrc;
	wgpu::Buffer buffer = device.CreateBuffer(&desc);

	MapAsyncAndWait(buffer, wgpu::MapMode::Write, 0, 4);
	queue.Submit(0, nullptr);

	const void* rangeBeforeLoss = buffer.GetConstMappedRange();
	LoseDeviceForTesting();

	ASSERT_NE(buffer.GetConstMappedRange(), nullptr);
	ASSERT_EQ(buffer.GetConstMappedRange(), rangeBeforeLoss);
	}

	// TODO(dawn:929): mapasync read + resolve + loss getmappedrange != nullptr.
	// TODO(dawn:929): mapasync write + resolve + loss getmappedrange != nullptr.

	// Test that Command Encoder Finish fails when device lost
	TEST_P(DeviceLostTest, CommandEncoderFinishFails) {
	wgpu::CommandBuffer commands;
	wgpu::CommandEncoder encoder = device.CreateCommandEncoder();

	LoseDeviceForTesting();
	ExpectObjectIsError(encoder.Finish());
	}

	// Test that QueueOnSubmittedWorkDone after device is lost.
	TEST_P(DeviceLostTest, QueueOnSubmittedWorkDoneAfterDeviceLost) {
	LoseDeviceForTesting();

	// callback should have device lost status
	EXPECT_CALL(*mockQueueWorkDoneCallback, Call(WGPUQueueWorkDoneStatus_DeviceLost, nullptr))
	.Times(1);
	queue.OnSubmittedWorkDone(ToMockQueueWorkDone, nullptr);
	}

	// Test that QueueOnSubmittedWorkDone when the device is lost after calling OnSubmittedWorkDone
	TEST_P(DeviceLostTest, QueueOnSubmittedWorkDoneBeforeLossFails) {
	// callback should have device lost status
	EXPECT_CALL(*mockQueueWorkDoneCallback, Call(WGPUQueueWorkDoneStatus_DeviceLost, nullptr))
	.Times(1);
	queue.OnSubmittedWorkDone(ToMockQueueWorkDone, nullptr);

	LoseDeviceForTesting();
	}

	// Test that LostForTesting can only be called on one time
	TEST_P(DeviceLostTest, LoseDeviceForTestingOnce) {
	// First LoseDeviceForTesting call should occur normally. The callback is already set in SetUp.
	LoseDeviceForTesting();

	device.ForceLoss(wgpu::DeviceLostReason::Undefined, "Device lost for testing");
	FlushWire();
	testing::Mock::VerifyAndClearExpectations(&mDeviceLostCallback);
	}

	TEST_P(DeviceLostTest, DeviceLostDoesntCallUncapturedError) {
	// Since the device has a default error callback set that fails if it is called, we just need
	// to lose the device and verify no failures.
	LoseDeviceForTesting();
	}

	// Test that WGPUCreatePipelineAsyncStatus_Success is returned when device is lost
	// before the callback of Create*PipelineAsync() is called.
	TEST_P(DeviceLostTest, DeviceLostBeforeCreatePipelineAsyncCallback) {
	wgpu::ShaderModule csModule = utils::CreateShaderModule(device, R"(
	@compute @workgroup_size(1) fn main() {
	})");

	wgpu::ComputePipelineDescriptor descriptor;
	descriptor.compute.module = csModule;

	auto callback = [](WGPUCreatePipelineAsyncStatus status, WGPUComputePipeline returnPipeline,
	const char* message, void* userdata) {
	EXPECT_EQ(WGPUCreatePipelineAsyncStatus_Success, status);
	EXPECT_NE(returnPipeline, nullptr);
	wgpu::ComputePipeline::Acquire(returnPipeline);
	};

	device.CreateComputePipelineAsync(&descriptor, callback, nullptr);
	LoseDeviceForTesting();
	// Need to call ProcessEvents, otherwise it will be an instance drop as LoseDeviceForTesting
	// is the last statement of the test body.
	// TODO(dawn:2353): Update to use WGPUCreateComputePipelineAsyncCallbackInfo version of
	// CreateComputePipelineAsync and then we don't need to call ProcessEvents explicitly
	GetInstance().ProcessEvents();
	}

	// This is a regression test for crbug.com/1212385 where Dawn didn't clean up all
	// references to bind group layouts such that the cache was non-empty at the end
	// of shut down.
	TEST_P(DeviceLostTest, FreeBindGroupAfterDeviceLossWithPendingCommands) {
	wgpu::BindGroupLayout bgl = utils::MakeBindGroupLayout(
	device, {{0, wgpu::ShaderStage::Fragment, wgpu::BufferBindingType::Storage}});

	wgpu::BufferDescriptor bufferDesc;
	bufferDesc.size = sizeof(float);
	bufferDesc.usage = wgpu::BufferUsage::Storage;
	wgpu::Buffer buffer = device.CreateBuffer(&bufferDesc);

	wgpu::BindGroup bg = utils::MakeBindGroup(device, bgl, {{0, buffer, 0, sizeof(float)}});

	// Advance the pending command serial. We only a need a couple of these to repro the bug,
	// but include extra so this does not become a change-detecting test if the specific serial
	// value is sensitive.
	queue.Submit(0, nullptr);
	queue.Submit(0, nullptr);
	queue.Submit(0, nullptr);
	queue.Submit(0, nullptr);
	queue.Submit(0, nullptr);
	queue.Submit(0, nullptr);

	LoseDeviceForTesting();

	// Releasing the bing group places the bind group layout into a queue in the Vulkan backend
	// for recycling of descriptor sets. So, after these release calls there is still one last
	// reference to the BGL which wouldn't be freed until the pending serial passes.
	// Since the device is lost, destruction will clean up immediately without waiting for the
	// serial. The implementation needs to be sure to clear these BGL references. At the end of
	// Device shut down, we DAWN_ASSERT that the BGL cache is empty.
	bgl = nullptr;
	bg = nullptr;
	}

	// This is a regression test for crbug.com/1365011 where ending a render pass with an indirect draw
	// in it after the device is lost would cause render commands to be leaked.
	TEST_P(DeviceLostTest, DeviceLostInRenderPassWithDrawIndirect) {
	utils::BasicRenderPass renderPass = utils::CreateBasicRenderPass(device, 4u, 4u);
	utils::ComboRenderPipelineDescriptor desc;
	desc.vertex.module = utils::CreateShaderModule(device, R"(
	@vertex fn main(@builtin(vertex_index) i : u32) -> @builtin(position) vec4f {
	var pos = array(
	vec2f(-1.0, -1.0),
	vec2f(3.0, -1.0),
	vec2f(-1.0, 3.0));
	return vec4f(pos[i], 0.0, 1.0);
	}
	)");
	desc.cFragment.module = utils::CreateShaderModule(device, R"(
	@fragment fn main() -> @location(0) vec4f {
	return vec4f(0.0, 1.0, 0.0, 1.0);
	}
	)");
	desc.cTargets[0].format = renderPass.colorFormat;
	wgpu::Buffer indirectBuffer =
	utils::CreateBufferFromData<uint32_t>(device, wgpu::BufferUsage::Indirect, {3, 1, 0, 0});
	wgpu::RenderPipeline pipeline = device.CreateRenderPipeline(&desc);
	wgpu::CommandEncoder encoder = device.CreateCommandEncoder();
	wgpu::RenderPassEncoder pass = encoder.BeginRenderPass(&renderPass.renderPassInfo);
	pass.SetPipeline(pipeline);
	pass.DrawIndirect(indirectBuffer, 0);
	LoseDeviceForTesting();
	pass.End();
	}

	// Attempting to set an object label after device loss should not cause an error.
	TEST_P(DeviceLostTest, SetLabelAfterDeviceLoss) {
	DAWN_TEST_UNSUPPORTED_IF(UsesWire());
	std::string label = "test";
	wgpu::BufferDescriptor descriptor;
	descriptor.size = 4;
	descriptor.usage = wgpu::BufferUsage::Uniform;
	wgpu::Buffer buffer = device.CreateBuffer(&descriptor);
	LoseDeviceForTesting();
	buffer.SetLabel(label.c_str());
	}

	DAWN_INSTANTIATE_TEST(DeviceLostTest,
	D3D11Backend(),
	D3D12Backend(),
	MetalBackend(),
	NullBackend(),
	OpenGLBackend(),
	OpenGLESBackend(),
	VulkanBackend());

	} // anonymous namespace
	} // namespace dawn