1 /*

     2  * Copyright (c) 2017, 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_VM_RUNTIME_HANDSHAKE_HPP

    26 #define SHARE_VM_RUNTIME_HANDSHAKE_HPP

    27 

    28 #include "memory/allocation.hpp"

    29 #include "runtime/semaphore.hpp"

    30 

    31 class ThreadClosure;

    32 class JavaThread;

    33 

    34 // A handshake operation is a callback that is executed for each JavaThread

    35 // while that thread is in a safepoint safe state. The callback is executed

    36 // either by the thread itself or by the VM thread while keeping the thread

    37 // in a blocked state. A handshake can be performed with a single

    38 // JavaThread as well.

    39 class Handshake : public AllStatic {

    40  public:

    41   // Execution of handshake operation

    42   static void execute(ThreadClosure* thread_cl);

    43   static bool execute(ThreadClosure* thread_cl, JavaThread* target);

    44 };

    45 

    46 class HandshakeOperation;

    47 

    48 // The HandshakeState keep tracks of an ongoing handshake for one JavaThread.

    49 // VM thread and JavaThread are serialized with the semaphore making sure

    50 // the operation is only done by either VM thread on behalf of the JavaThread

    51 // or the JavaThread itself.

    52 class HandshakeState VALUE_OBJ_CLASS_SPEC {

    53   HandshakeOperation* volatile _operation;

    54 

    55   Semaphore _semaphore;

    56   bool _vmthread_holds_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   void cancel_inner(JavaThread* thread);

    64 

    65   void process_self_inner(JavaThread* thread);

    66 public:

    67   HandshakeState();

    68 

    69   void set_operation(JavaThread* thread, HandshakeOperation* op);

    70 

    71   bool has_operation() const {

    72     return _operation != NULL;

    73   }

    74 

    75   void cancel(JavaThread* thread) {

    76     if (!_thread_in_process_handshake) {

    77       FlagSetting fs(_thread_in_process_handshake, true);

    78       cancel_inner(thread);

    79     }

    80   }

    81 

    82   void process_by_self(JavaThread* thread) {

    83     if (!_thread_in_process_handshake) {

    84       FlagSetting fs(_thread_in_process_handshake, true);

    85       process_self_inner(thread);

    86     }

    87   }

    88   void process_by_vmthread(JavaThread* target);

    89 };

    90 

    91 #endif // SHARE_VM_RUNTIME_HANDSHAKE_HPP