src/hotspot/share/runtime/lockStack.hpp

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#ifndef SHARE_RUNTIME_LOCKSTACK_HPP
#define SHARE_RUNTIME_LOCKSTACK_HPP

#include "oops/oopsHierarchy.hpp"
#include "utilities/globalDefinitions.hpp"
#include "utilities/sizes.hpp"

class JavaThread;
class OopClosure;
class outputStream;

class LockStack {
  friend class VMStructs;
private:
  static const int CAPACITY = 8;

  // TODO: It would be very useful if JavaThread::lock_stack_offset() and friends were constexpr,
  // but this is currently not the case because we're using offset_of() which is non-constexpr,
  // GCC would warn about non-standard-layout types if we were using offsetof() (which *is* constexpr).
  static const int lock_stack_offset;
  static const int lock_stack_top_offset;
  static const int lock_stack_base_offset;

  // The offset of the next element, in bytes, relative to the JavaThread structure.
  // We do this instead of a simple index into the array because this allows for
  // efficient addressing in generated code.
  uint32_t _top;
  oop _base[CAPACITY];

  // Get the owning thread of this lock-stack.
  inline JavaThread* get_thread() const;

  // Tests if the calling thread is the thread that owns this lock-stack.
  bool is_owning_thread() const;

  // Verifies consistency of the lock-stack.
  void verify(const char* msg) const PRODUCT_RETURN;

  // Given an offset (in bytes) calculate the index into the lock-stack.
  static inline int to_index(uint32_t offset);

public:
  static ByteSize top_offset()  { return byte_offset_of(LockStack, _top); }
  static ByteSize base_offset() { return byte_offset_of(LockStack, _base); }

  LockStack(JavaThread* jt);

  // The boundary indicies of the lock-stack.
  static uint32_t start_offset();
  static uint32_t end_offset();

  // Return true if we have room to push onto this lock-stack, false otherwise.
  inline bool can_push() const;

  // Pushes an oop on this lock-stack.
  inline void push(oop o);

  // Pops an oop from this lock-stack.
  inline oop pop();

  // Removes an oop from an arbitrary location of this lock-stack.
  inline void remove(oop o);

  // Tests whether the oop is on this lock-stack.
  inline bool contains(oop o) const;

  // GC support
  inline void oops_do(OopClosure* cl);

  // Printing
  void print_on(outputStream* st);
};

#endif // SHARE_RUNTIME_LOCKSTACK_HPP