[platform] Implement a worker pool

src/libplatform/default-platform.h

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-#ifndef V8_DEFAULT_PLATFORM_H_
-#define V8_DEFAULT_PLATFORM_H_
+#ifndef V8_LIBPLATFORM_DEFAULT_PLATFORM_H_
+#define V8_LIBPLATFORM_DEFAULT_PLATFORM_H_
 
-#include "v8.h"
+#include "../../include/v8-platform.h"
+// TODO(jochen): We should have our own version of globals.h.
+#include "../globals.h"
 
 namespace v8 {
 namespace internal {
 
+class TaskQueue;
+class Thread;
+class WorkerThread;
+
 class DefaultPlatform : public Platform {
  public:
   DefaultPlatform();
   virtual ~DefaultPlatform();
 
+  // TODO(jochen): This shouldn't be static.
+  static void SetThreadPoolSize(int thread_pool_size);
+
   // v8::Platform implementation.
   virtual void CallOnBackgroundThread(
       Task *task, ExpectedRuntime expected_runtime) V8_OVERRIDE;
   virtual void CallOnForegroundThread(v8::Isolate *isolate,
                                       Task *task) V8_OVERRIDE;
 
  private:
+  void EnsureThreadPoolStarted();
+
+  static const int kMaxThreadPoolSize = 4;
+
+  WorkerThread** thread_pool_;
+  // TODO(jochen): This shouldn't be a static.
+  static int thread_pool_size_;

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

I don't think we can have static members here. This may be a problem when we
have multiple isolates per process?

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

there's only one default platform per process.

[Hannes Payer (out of office), 2013/12/11 12:07:27]

As discussed offline, TSAN will not like that in a build with two isolates per
process.

+  TaskQueue* queue_;
+
   DISALLOW_COPY_AND_ASSIGN(DefaultPlatform);
 };
 
 
 } }  // namespace v8::internal
 
 
-#endif  // V8_DEFAULT_PLATFORM_H_
+#endif  // V8_LIBPLATFORM_DEFAULT_PLATFORM_H_