301 };
 302 
 303 // A closure that is applied without any arguments.
 304 class VoidClosure : public StackObj {
 305  public:
 306   // I would have liked to declare this a pure virtual, but that breaks
 307   // in mysterious ways, for unknown reasons.
 308   virtual void do_void();
 309 };
 310 
 311 
 312 // YieldClosure is intended for use by iteration loops
 313 // to incrementalize their work, allowing interleaving
 314 // of an interruptable task so as to allow other
 315 // threads to run (which may not otherwise be able to access
 316 // exclusive resources, for instance). Additionally, the
 317 // closure also allows for aborting an ongoing iteration
 318 // by means of checking the return value from the polling
 319 // call.
 320 class YieldClosure : public StackObj {
 321   public:
 322    virtual bool should_return() = 0;


 323 };
 324 
 325 // Abstract closure for serializing data (read or write).
 326 
 327 class SerializeClosure : public Closure {
 328 public:
 329   // Return bool indicating whether closure implements read or write.
 330   virtual bool reading() const = 0;
 331 
 332   // Read/write the void pointer pointed to by p.
 333   virtual void do_ptr(void** p) = 0;
 334 
 335   // Read/write the 32-bit unsigned integer pointed to by p.
 336   virtual void do_u4(u4* p) = 0;
 337 
 338   // Read/write the region specified.
 339   virtual void do_region(u_char* start, size_t size) = 0;
 340 
 341   // Check/write the tag.  If reading, then compare the tag against
 342   // the passed in value and fail is they don't match.  This allows

 301 };
 302 
 303 // A closure that is applied without any arguments.
 304 class VoidClosure : public StackObj {
 305  public:
 306   // I would have liked to declare this a pure virtual, but that breaks
 307   // in mysterious ways, for unknown reasons.
 308   virtual void do_void();
 309 };
 310 
 311 
 312 // YieldClosure is intended for use by iteration loops
 313 // to incrementalize their work, allowing interleaving
 314 // of an interruptable task so as to allow other
 315 // threads to run (which may not otherwise be able to access
 316 // exclusive resources, for instance). Additionally, the
 317 // closure also allows for aborting an ongoing iteration
 318 // by means of checking the return value from the polling
 319 // call.
 320 class YieldClosure : public StackObj {
 321 public:
 322  virtual bool should_return() = 0;
 323  // Yield on a fine-grain level. The check in case of not yielding should be very fast.
 324  virtual bool should_return_fine_grain() { return false; }
 325 };
 326 
 327 // Abstract closure for serializing data (read or write).
 328 
 329 class SerializeClosure : public Closure {
 330 public:
 331   // Return bool indicating whether closure implements read or write.
 332   virtual bool reading() const = 0;
 333 
 334   // Read/write the void pointer pointed to by p.
 335   virtual void do_ptr(void** p) = 0;
 336 
 337   // Read/write the 32-bit unsigned integer pointed to by p.
 338   virtual void do_u4(u4* p) = 0;
 339 
 340   // Read/write the region specified.
 341   virtual void do_region(u_char* start, size_t size) = 0;
 342 
 343   // Check/write the tag.  If reading, then compare the tag against
 344   // the passed in value and fail is they don't match.  This allows