1 /*
   2  * Copyright (c) 1998, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
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  23  */
  24 
  25 #ifndef SHARE_RUNTIME_BASICLOCK_HPP
  26 #define SHARE_RUNTIME_BASICLOCK_HPP
  27 
  28 #include "oops/markWord.hpp"
  29 #include "runtime/atomic.hpp"
  30 #include "runtime/handles.hpp"
  31 
  32 class BasicLock {
  33   friend class VMStructs;
  34   friend class JVMCIVMStructs;
  35  private:
  36   volatile markWord _displaced_header;
  37  public:
  38   markWord displaced_header() const {
  39     return Atomic::load(&_displaced_header);
  40   }
  41 
  42   void set_displaced_header(markWord header) {
  43     Atomic::store(header, &_displaced_header);
  44   }
  45 
  46   void print_on(outputStream* st) const;
  47 
  48   // move a basic lock (used during deoptimization
  49   void move_to(oop obj, BasicLock* dest);
  50 
  51   static int displaced_header_offset_in_bytes()       { return offset_of(BasicLock, _displaced_header); }
  52 };
  53 
  54 // A BasicObjectLock associates a specific Java object with a BasicLock.
  55 // It is currently embedded in an interpreter frame.
  56 
  57 // Because some machines have alignment restrictions on the control stack,
  58 // the actual space allocated by the interpreter may include padding words
  59 // after the end of the BasicObjectLock.  Also, in order to guarantee
  60 // alignment of the embedded BasicLock objects on such machines, we
  61 // put the embedded BasicLock at the beginning of the struct.
  62 
  63 class BasicObjectLock {
  64   friend class VMStructs;
  65  private:
  66   BasicLock _lock;                                    // the lock, must be double word aligned
  67   oop       _obj;                                     // object holds the lock;
  68 
  69  public:
  70   // Manipulation
  71   oop      obj() const                                { return _obj;  }
  72   void set_obj(oop obj)                               { _obj = obj; }
  73   BasicLock* lock()                                   { return &_lock; }
  74 
  75   // Note: Use frame::interpreter_frame_monitor_size() for the size of BasicObjectLocks
  76   //       in interpreter activation frames since it includes machine-specific padding.
  77   static int size()                                   { return sizeof(BasicObjectLock)/wordSize; }
  78 
  79   // GC support
  80   void oops_do(OopClosure* f) { f->do_oop(&_obj); }
  81 
  82   static int obj_offset_in_bytes()                    { return offset_of(BasicObjectLock, _obj);  }
  83   static int lock_offset_in_bytes()                   { return offset_of(BasicObjectLock, _lock); }
  84 };
  85 
  86 
  87 #endif // SHARE_RUNTIME_BASICLOCK_HPP