[platform] Implement a worker pool

src/libplatform/task-queue.cc

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-#include "v8.h"
+#include "task-queue.h"
 
-#include "default-platform.h"
+// TODO(jochen): We should have our own version of checks.h.
+#include "../checks.h"
 
 namespace v8 {
 namespace internal {
 
-
-DefaultPlatform::DefaultPlatform() {}
+TaskQueue::TaskQueue() : process_queue_semaphore_(0), terminated_(false) {}
 
 
-DefaultPlatform::~DefaultPlatform() {}
-
-void DefaultPlatform::CallOnBackgroundThread(Task *task,
-                                             ExpectedRuntime expected_runtime) {
-  // TODO(jochen): implement.
-  task->Run();
-  delete task;
+TaskQueue::~TaskQueue() {
+  LockGuard<Mutex> guard(&lock_);
+  ASSERT(terminated_);
+  ASSERT(task_queue_.empty());
 }
 
 
-void DefaultPlatform::CallOnForegroundThread(v8::Isolate* isolate, Task* task) {
-  // TODO(jochen): implement.
-  task->Run();
-  delete task;
+void TaskQueue::Append(Task* task) {
+  LockGuard<Mutex> guard(&lock_);
+  ASSERT(!terminated_);
+  task_queue_.push(task);
+  process_queue_semaphore_.Signal();
 }
 
 
+Task* TaskQueue::GetNext() {
+  for (;;) {
+    {
+      LockGuard<Mutex> guard(&lock_);
+      if (!task_queue_.empty()) {
+        Task* result = task_queue_.front();
+        task_queue_.pop();
+        return result;
+      }
+      if (terminated_) {
+        process_queue_semaphore_.Signal();

[Hannes Payer (out of office), 2013/12/09 18:50:51]

Why do you need that signal? The thread that terminates the task queue is not
going to wait.

[jochen (gone - plz use gerrit), 2013/12/09 19:04:31]

There can be multiple threads waiting on the semaphore and all need to be woken
up.

+        return NULL;
+      }
+    }
+    process_queue_semaphore_.Wait();
+  }
+}
+
+
+void TaskQueue::Terminate() {
+  LockGuard<Mutex> guard(&lock_);
+  ASSERT(!terminated_);
+  terminated_ = true;
+  process_queue_semaphore_.Signal();
+}
+
 } }  // namespace v8::internal