jdk-24/hotspot/src/share/vm/runtime/synchronizer.hpp

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#ifndef SHARE_VM_RUNTIME_SYNCHRONIZER_HPP
#define SHARE_VM_RUNTIME_SYNCHRONIZER_HPP

#include "oops/markOop.hpp"
#include "runtime/basicLock.hpp"
#include "runtime/handles.hpp"
#include "runtime/perfData.hpp"
#include "utilities/top.hpp"


class ObjectMonitor;

class ObjectSynchronizer : AllStatic {
  friend class VMStructs;
 public:
  typedef enum {
    owner_self,
    owner_none,
    owner_other
  } LockOwnership;
  // exit must be implemented non-blocking, since the compiler cannot easily handle
  // deoptimization at monitor exit. Hence, it does not take a Handle argument.

  // This is full version of monitor enter and exit. I choose not
  // to use enter() and exit() in order to make sure user be ware
  // of the performance and semantics difference. They are normally
  // used by ObjectLocker etc. The interpreter and compiler use
  // assembly copies of these routines. Please keep them synchronized.
  //
  // attempt_rebias flag is used by UseBiasedLocking implementation
  static void fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias,
                         TRAPS);
  static void fast_exit(oop obj, BasicLock* lock, Thread* THREAD);

  // WARNING: They are ONLY used to handle the slow cases. They should
  // only be used when the fast cases failed. Use of these functions
  // without previous fast case check may cause fatal error.
  static void slow_enter(Handle obj, BasicLock* lock, TRAPS);
  static void slow_exit(oop obj, BasicLock* lock, Thread* THREAD);

  // Used only to handle jni locks or other unmatched monitor enter/exit
  // Internally they will use heavy weight monitor.
  static void jni_enter(Handle obj, TRAPS);
  static void jni_exit(oop obj, Thread* THREAD);

  // Handle all interpreter, compiler and jni cases
  static int  wait(Handle obj, jlong millis, TRAPS);
  static void notify(Handle obj, TRAPS);
  static void notifyall(Handle obj, TRAPS);

  static bool quick_enter(oop obj, Thread* Self, BasicLock* Lock);

  // Special internal-use-only method for use by JVM infrastructure
  // that needs to wait() on a java-level object but that can't risk
  // throwing unexpected InterruptedExecutionExceptions.
  static void waitUninterruptibly(Handle obj, jlong Millis, Thread * THREAD);

  // used by classloading to free classloader object lock,
  // wait on an internal lock, and reclaim original lock
  // with original recursion count
  static intptr_t complete_exit(Handle obj, TRAPS);
  static void reenter (Handle obj, intptr_t recursion, TRAPS);

  // thread-specific and global objectMonitor free list accessors
  static void verifyInUse(Thread * Self);
  static ObjectMonitor * omAlloc(Thread * Self);
  static void omRelease(Thread * Self, ObjectMonitor * m,
                        bool FromPerThreadAlloc);
  static void omFlush(Thread * Self);

  // Inflate light weight monitor to heavy weight monitor
  static ObjectMonitor* inflate(Thread * Self, oop obj);
  // This version is only for internal use
  static ObjectMonitor* inflate_helper(oop obj);

  // Returns the identity hash value for an oop
  // NOTE: It may cause monitor inflation
  static intptr_t identity_hash_value_for(Handle obj);
  static intptr_t FastHashCode(Thread * Self, oop obj);

  // java.lang.Thread support
  static bool current_thread_holds_lock(JavaThread* thread, Handle h_obj);
  static LockOwnership query_lock_ownership(JavaThread * self, Handle h_obj);

  static JavaThread* get_lock_owner(Handle h_obj, bool doLock);

  // JNI detach support
  static void release_monitors_owned_by_thread(TRAPS);
  static void monitors_iterate(MonitorClosure* m);

  // GC: we current use aggressive monitor deflation policy
  // Basically we deflate all monitors that are not busy.
  // An adaptive profile-based deflation policy could be used if needed
  static void deflate_idle_monitors();
  // For a given monitor list: global or per-thread, deflate idle monitors
  static int deflate_monitor_list(ObjectMonitor** listheadp,
                                  ObjectMonitor** freeHeadp,
                                  ObjectMonitor** freeTailp);
  static bool deflate_monitor(ObjectMonitor* mid, oop obj,
                              ObjectMonitor** freeHeadp,
                              ObjectMonitor** freeTailp);
  static void oops_do(OopClosure* f);

  // debugging
  static void sanity_checks(const bool verbose,
                            const unsigned int cache_line_size,
                            int *error_cnt_ptr, int *warning_cnt_ptr);
  static void verify() PRODUCT_RETURN;
  static int  verify_objmon_isinpool(ObjectMonitor *addr) PRODUCT_RETURN0;

  static void RegisterSpinCallback(int(*)(intptr_t, int), intptr_t);

 private:
  enum { _BLOCKSIZE = 128 };
  // global list of blocks of monitors
  // gBlockList is really PaddedEnd<ObjectMonitor> *, but we don't
  // want to expose the PaddedEnd template more than necessary.
  static ObjectMonitor * gBlockList;
  // global monitor free list
  static ObjectMonitor * volatile gFreeList;
  // global monitor in-use list, for moribund threads,
  // monitors they inflated need to be scanned for deflation
  static ObjectMonitor * volatile gOmInUseList;
  // count of entries in gOmInUseList
  static int gOmInUseCount;
};

// ObjectLocker enforced balanced locking and can never thrown an
// IllegalMonitorStateException. However, a pending exception may
// have to pass through, and we must also be able to deal with
// asynchronous exceptions. The caller is responsible for checking
// the threads pending exception if needed.
// doLock was added to support classloading with UnsyncloadClass which
// requires flag based choice of locking the classloader lock.
class ObjectLocker : public StackObj {
 private:
  Thread*   _thread;
  Handle    _obj;
  BasicLock _lock;
  bool      _dolock;   // default true
 public:
  ObjectLocker(Handle obj, Thread* thread, bool doLock = true);
  ~ObjectLocker();

  // Monitor behavior
  void wait(TRAPS)  { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
  void notify_all(TRAPS)  { ObjectSynchronizer::notifyall(_obj, CHECK); }
  void waitUninterruptibly(TRAPS) { ObjectSynchronizer::waitUninterruptibly(_obj, 0, CHECK); }
  // complete_exit gives up lock completely, returning recursion count
  // reenter reclaims lock with original recursion count
  intptr_t complete_exit(TRAPS)  { return ObjectSynchronizer::complete_exit(_obj, THREAD); }
  void reenter(intptr_t recursion, TRAPS)  { ObjectSynchronizer::reenter(_obj, recursion, CHECK); }
};

#endif // SHARE_VM_RUNTIME_SYNCHRONIZER_HPP