Use std::counting_semaphore

src/base/semaphore.h

@@ -1,41 +0,0 @@
-#ifndef BASE_SEMAPHORE_H
-#define BASE_SEMAPHORE_H
-
-#include <condition_variable>
-#include <mutex>
-
-#include "base/log.h"
-
-namespace base {
-
-class Semaphore {
- public:
-  Semaphore(int count = 0) : count_(count) {}
-
-  void Acquire() {
-    std::unique_lock<std::mutex> scoped_lock(mutex_);
-    cv_.wait(scoped_lock, [&]() { return count_ > 0; });
-    --count_;
-    DCHECK(count_ >= 0);
-  }
-
-  void Release() {
-    {
-      std::lock_guard<std::mutex> scoped_lock(mutex_);
-      ++count_;
-    }
-    cv_.notify_one();
-  }
-
- private:
-  std::condition_variable cv_;
-  std::mutex mutex_;
-  int count_ = 0;
-
-  Semaphore(Semaphore const&) = delete;
-  Semaphore& operator=(Semaphore const&) = delete;
-};
-
-}  // namespace base
-
-#endif  // BASE_SEMAPHORE_H

src/base/task_runner.cc

@@ -1,5 +1,7 @@
 #include "base/task_runner.h"
 
+#include <thread>
+
 #include "base/log.h"
 
 namespace {
@@ -33,7 +35,7 @@ TaskRunner* TaskRunner::GetThreadLocalTaskRunner() {
 void TaskRunner::PostTask(const Location& from, Closure task) {
   DCHECK(task) << LOCATION(from);
 
-  task_count_.fetch_add(1, std::memory_order_relaxed);
+  task_count_.fetch_add(1, std::memory_order_release);
   std::lock_guard<std::mutex> scoped_lock(lock_);
   queue_.emplace_back(from, std::move(task));
 }
@@ -68,7 +70,7 @@ void TaskRunner::MultiConsumerRun() {
 #endif
 
     task_cb();
-    task_count_.fetch_sub(1, std::memory_order_relaxed);
+    task_count_.fetch_sub(1, std::memory_order_release);
   }
 }
 
@@ -90,16 +92,13 @@ void TaskRunner::SingleConsumerRun() {
 #endif
 
     task_cb();
-    task_count_.fetch_sub(1, std::memory_order_relaxed);
+    task_count_.fetch_sub(1, std::memory_order_release);
   }
-  cv_.notify_one();
 }
 
 void TaskRunner::WaitForCompletion() {
-  std::unique_lock<std::mutex> scoped_lock(lock_);
-  cv_.wait(scoped_lock, [&]() -> bool {
-    return task_count_.load(std::memory_order_relaxed) == 0;
-  });
+  while (task_count_.load(std::memory_order_acquire) > 0)
+    std::this_thread::yield();
 }
 
 }  // namespace base

src/base/task_runner.h

@@ -2,7 +2,6 @@
 #define BASE_TASK_RUNNER_H
 
 #include <atomic>
-#include <condition_variable>
 #include <deque>
 #include <memory>
 #include <mutex>
@@ -74,7 +73,6 @@ class TaskRunner {
 
   std::deque<Task> queue_;
   mutable std::mutex lock_;
-  std::condition_variable cv_;
   std::atomic<size_t> task_count_{0};
 
   static thread_local std::unique_ptr<TaskRunner> thread_local_task_runner;

src/base/thread_pool.cc

@@ -33,7 +33,7 @@ void ThreadPool::Shutdown() {
     return;
 
   quit_.store(true, std::memory_order_relaxed);
-  semaphore_.Release();
+  semaphore_.release(threads_.size());
 
   for (auto& thread : threads_)
     thread.join();
@@ -44,7 +44,7 @@ void ThreadPool::PostTask(const Location& from, Closure task) {
   DCHECK((!threads_.empty()));
 
   task_runner_.PostTask(from, std::move(task));
-  semaphore_.Release();
+  semaphore_.release();
 }
 
 void ThreadPool::PostTaskAndReply(const Location& from,
@@ -53,17 +53,15 @@ void ThreadPool::PostTaskAndReply(const Location& from,
   DCHECK((!threads_.empty()));
 
   task_runner_.PostTaskAndReply(from, std::move(task), std::move(reply));
-  semaphore_.Release();
+  semaphore_.release();
 }
 
 void ThreadPool::WorkerMain() {
   for (;;) {
-    semaphore_.Acquire();
+    semaphore_.acquire();
 
-    if (quit_.load(std::memory_order_relaxed)) {
-      semaphore_.Release();
+    if (quit_.load(std::memory_order_relaxed))
       return;
-    }
 
     task_runner_.MultiConsumerRun();
   }

src/base/thread_pool.h

@@ -2,11 +2,11 @@
 #define BASE_THREAD_POOL_H
 
 #include <atomic>
+#include <semaphore>
 #include <thread>
 #include <vector>
 
 #include "base/closure.h"
-#include "base/semaphore.h"
 #include "base/task_runner.h"
 
 namespace base {
@@ -36,13 +36,13 @@ class ThreadPool {
                                   std::function<void(ReturnType)> reply) {
     task_runner_.PostTaskAndReplyWithResult(from, std::move(task),
                                             std::move(reply));
-    semaphore_.Release();
+    semaphore_.release();
   }
 
  private:
   std::vector<std::thread> threads_;
 
-  Semaphore semaphore_;
+  std::counting_semaphore<> semaphore_{0};
   std::atomic<bool> quit_{false};
 
   base::TaskRunner task_runner_;

src/engine/renderer/opengl/renderer_opengl.cc

@@ -184,7 +184,7 @@ void RendererOpenGL::SetUniform(uint64_t resource_id,
 void RendererOpenGL::Present() {
   EnqueueCommand(std::make_unique<CmdPresent>());
 #ifdef THREADED_RENDERING
-  draw_complete_semaphore_.Acquire();
+  draw_complete_semaphore_.acquire();
 #endif  // THREADED_RENDERING
   fps_++;
 }

src/engine/renderer/opengl/renderer_opengl.h

@@ -13,9 +13,8 @@
 #include <deque>
 #include <future>
 #include <mutex>
+#include <semaphore>
 #include <thread>
-
-#include "base/semaphore.h"
 #endif  // THREADED_RENDERING
 
 #include "engine/renderer/opengl/opengl.h"
@@ -147,7 +146,7 @@ class RendererOpenGL : public Renderer {
   std::thread render_thread_;
   bool terminate_render_thread_ = false;
 
-  base::Semaphore draw_complete_semaphore_;
+  std::counting_semaphore<> draw_complete_semaphore_{0};
 
   base::TaskRunner* main_thread_task_runner_;
 #endif  // THREADED_RENDERING

src/engine/renderer/opengl/renderer_opengl_android.cc

@@ -58,7 +58,7 @@ void RendererOpenGL::HandleCmdPresent(RenderCommand* cmd) {
     return;
   }
 #ifdef THREADED_RENDERING
-  draw_complete_semaphore_.Release();
+  draw_complete_semaphore_.release();
 #endif  // THREADED_RENDERING
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   active_shader_id_ = 0;

src/engine/renderer/opengl/renderer_opengl_linux.cc

@@ -55,7 +55,7 @@ void RendererOpenGL::HandleCmdPresent(RenderCommand* cmd) {
   if (display_) {
     glXSwapBuffers(display_, window_);
 #ifdef THREADED_RENDERING
-    draw_complete_semaphore_.Release();
+    draw_complete_semaphore_.release();
 #endif  // THREADED_RENDERING
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
     active_shader_id_ = 0;

src/engine/renderer/vulkan/renderer_vulkan.cc

@@ -295,7 +295,7 @@ uint64_t RendererVulkan::CreateGeometry(std::unique_ptr<Mesh> mesh) {
     // Transfer mesh ownership to the background thread.
     std::unique_ptr<Mesh> own(mesh);
   });
-  semaphore_.Release();
+  semaphore_.release();
 
   return last_resource_id_;
 }
@@ -387,7 +387,7 @@ void RendererVulkan::UpdateTexture(uint64_t resource_id,
     // Transfer image ownership to the background thread.
     std::unique_ptr<Image> own(image);
   });
-  semaphore_.Release();
+  semaphore_.release();
 }
 
 void RendererVulkan::DestroyTexture(uint64_t resource_id) {
@@ -867,7 +867,7 @@ void RendererVulkan::Shutdown() {
   DestroyAllResources();
 
   quit_.store(true, std::memory_order_relaxed);
-  semaphore_.Release();
+  semaphore_.release();
   setup_thread_.join();
 
   vkDeviceWaitIdle(device_);
@@ -1877,7 +1877,7 @@ void RendererVulkan::SetupThreadMain(int preallocate) {
   }
 
   for (;;) {
-    semaphore_.Acquire();
+    semaphore_.acquire();
     if (quit_.load(std::memory_order_relaxed))
       break;
 

src/engine/renderer/vulkan/renderer_vulkan.h

@@ -3,6 +3,7 @@
 
 #include <atomic>
 #include <memory>
+#include <semaphore>
 #include <string>
 #include <thread>
 #include <tuple>
@@ -11,7 +12,6 @@
 
 #include "engine/renderer/vulkan/vulkan_context.h"
 
-#include "base/semaphore.h"
 #include "base/task_runner.h"
 #include "engine/renderer/renderer.h"
 #include "third_party/vma/vk_mem_alloc.h"
@@ -181,7 +181,7 @@ class RendererVulkan : public Renderer {
 
   std::thread setup_thread_;
   base::TaskRunner task_runner_;
-  base::Semaphore semaphore_;
+  std::counting_semaphore<> semaphore_{0};
   std::atomic<bool> quit_{false};
 
   bool InitializeInternal();