rev 57079 : imported patch 8234796

   1 /*
   2  * Copyright (c) 2017, 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
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_RUNTIME_HANDSHAKE_HPP
  26 #define SHARE_RUNTIME_HANDSHAKE_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "runtime/flags/flagSetting.hpp"
  30 #include "runtime/semaphore.hpp"
  31 
  32 class ThreadClosure;
  33 class JavaThread;
  34 
  35 // A handshake operation is a callback that is executed for each JavaThread
  36 // while that thread is in a safepoint safe state. The callback is executed
  37 // either by the thread itself or by the VM thread while keeping the thread
  38 // in a blocked state. A handshake can be performed with a single
  39 // JavaThread as well.






















  40 class Handshake : public AllStatic {
  41  public:
  42   // Execution of handshake operation
  43   static void execute(ThreadClosure* thread_cl);
  44   static bool execute(ThreadClosure* thread_cl, JavaThread* target);
  45 };
  46 
  47 class HandshakeOperation;
  48 
  49 // The HandshakeState keep tracks of an ongoing handshake for one JavaThread.
  50 // VM thread and JavaThread are serialized with the semaphore making sure
  51 // the operation is only done by either VM thread on behalf of the JavaThread
  52 // or the JavaThread itself.
  53 class HandshakeState {
  54   HandshakeOperation* volatile _operation;
  55 
  56   Semaphore _semaphore;
  57   bool _thread_in_process_handshake;
  58 
  59   bool claim_handshake_for_vmthread();
  60   bool vmthread_can_process_handshake(JavaThread* target);
  61 
  62   void clear_handshake(JavaThread* thread);
  63 
  64   void process_self_inner(JavaThread* thread);
  65 public:
  66   HandshakeState();
  67 
  68   void set_operation(JavaThread* thread, HandshakeOperation* op);
  69 
  70   bool has_operation() const {
  71     return _operation != NULL;
  72   }
  73 
  74   void process_by_self(JavaThread* thread) {
  75     if (!_thread_in_process_handshake) {
  76       FlagSetting fs(_thread_in_process_handshake, true);
  77       process_self_inner(thread);
  78     }
  79   }
  80 
  81   void process_by_vmthread(JavaThread* target);
  82 };
  83 
  84 #endif // SHARE_RUNTIME_HANDSHAKE_HPP
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