Implement WaitableEvent and WorkerTaskPool for multi-threaded tasks

This patch adds the basic implementation of WaitableEvent and
WorkerTaskPool for multi-threaded tasks in Dawn (for example, the
multi-threaded implementation of CreateReady*Pipeline()).

BUG=dawn:529
TEST=dawn_unittests

Change-Id: Ibf84348f4c0f0d26badc19ae94cd536cef89d084
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/36360
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>

src/dawn_platform/BUILD.gn

@@ -25,6 +25,8 @@ dawn_component("dawn_platform") {
     "${dawn_root}/src/include/dawn_platform/DawnPlatform.h",
     "${dawn_root}/src/include/dawn_platform/dawn_platform_export.h",
     "DawnPlatform.cpp",
+    "WorkerThread.cpp",
+    "WorkerThread.h",
     "tracing/EventTracer.cpp",
     "tracing/EventTracer.h",
     "tracing/TraceEvent.h",

src/dawn_platform/CMakeLists.txt

@@ -23,6 +23,8 @@ target_sources(dawn_platform PRIVATE
     "${DAWN_INCLUDE_DIR}/dawn_platform/DawnPlatform.h"
     "${DAWN_INCLUDE_DIR}/dawn_platform/dawn_platform_export.h"
     "DawnPlatform.cpp"
+    "WorkerThread.cpp"
+    "WorkerThread.h"
     "tracing/EventTracer.cpp"
     "tracing/EventTracer.h"
     "tracing/TraceEvent.h"

src/dawn_platform/DawnPlatform.cpp

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include "dawn_platform/DawnPlatform.h"
+#include "dawn_platform/WorkerThread.h"
 
 #include "common/Assert.h"
 
@@ -55,4 +56,8 @@ namespace dawn_platform {
         return nullptr;
     }
 
+    std::unique_ptr<dawn_platform::WorkerTaskPool> Platform::CreateWorkerTaskPool() {
+        return std::make_unique<AsyncWorkerThreadPool>();
+    }
+
 }  // namespace dawn_platform

src/dawn_platform/WorkerThread.cpp

@@ -0,0 +1,51 @@
+// Copyright 2021 The Dawn Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "dawn_platform/WorkerThread.h"
+
+#include <future>
+
+#include "common/Assert.h"
+
+namespace {
+
+    class AsyncWaitableEvent final : public dawn_platform::WaitableEvent {
+      public:
+        explicit AsyncWaitableEvent(std::function<void()> func) {
+            mFuture = std::async(std::launch::async, func);
+        }
+        virtual ~AsyncWaitableEvent() override {
+            ASSERT(IsComplete());
+        }
+        void Wait() override {
+            ASSERT(mFuture.valid());
+            mFuture.wait();
+        }
+        bool IsComplete() override {
+            ASSERT(mFuture.valid());
+            return mFuture.wait_for(std::chrono::seconds(0)) == std::future_status::ready;
+        }
+
+      private:
+        std::future<void> mFuture;
+    };
+
+}  // anonymous namespace
+
+std::unique_ptr<dawn_platform::WaitableEvent> AsyncWorkerThreadPool::PostWorkerTask(
+    dawn_platform::PostWorkerTaskCallback callback,
+    void* userdata) {
+    std::function<void()> doTask = [callback, userdata]() { callback(userdata); };
+    return std::make_unique<AsyncWaitableEvent>(doTask);
+}

src/dawn_platform/WorkerThread.h

@@ -0,0 +1,28 @@
+// Copyright 2021 The Dawn Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef COMMON_WORKERTHREAD_H_
+#define COMMON_WORKERTHREAD_H_
+
+#include "common/NonCopyable.h"
+#include "dawn_platform/DawnPlatform.h"
+
+class AsyncWorkerThreadPool : public dawn_platform::WorkerTaskPool, public NonCopyable {
+  public:
+    std::unique_ptr<dawn_platform::WaitableEvent> PostWorkerTask(
+        dawn_platform::PostWorkerTaskCallback callback,
+        void* userdata) override;
+};
+
+#endif