1 /*

     2  * Copyright (c) 2014, 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 #include "precompiled.hpp"

    26 #include "gc_implementation/shared/suspendibleThreadSet.hpp"

    27 #include "runtime/mutexLocker.hpp"

    28 #include "runtime/thread.inline.hpp"

    29 

    30 uint   SuspendibleThreadSet::_nthreads          = 0;

    31 uint   SuspendibleThreadSet::_nthreads_stopped  = 0;

    32 bool   SuspendibleThreadSet::_suspend_all       = false;

    33 double SuspendibleThreadSet::_suspend_all_start = 0.0;

    34 

    35 void SuspendibleThreadSet::join() {

    36   MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);

    37   while (_suspend_all) {

    38     ml.wait(Mutex::_no_safepoint_check_flag);

    39   }

    40   _nthreads++;

    41 }

    42 

    43 void SuspendibleThreadSet::leave() {

    44   MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);

    45   assert(_nthreads > 0, "Invalid");

    46   _nthreads--;

    47   if (_suspend_all) {

    48     ml.notify_all();

    49   }

    50 }

    51 

    52 void SuspendibleThreadSet::yield() {

    53   if (_suspend_all) {

    54     MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);

    55     if (_suspend_all) {

    56       _nthreads_stopped++;

    57       if (_nthreads_stopped == _nthreads) {

    58         if (ConcGCYieldTimeout > 0) {

    59           double now = os::elapsedTime();

    60           guarantee((now - _suspend_all_start) * 1000.0 < (double)ConcGCYieldTimeout, "Long delay");

    61         }

    62       }

    63       ml.notify_all();

    64       while (_suspend_all) {

    65         ml.wait(Mutex::_no_safepoint_check_flag);

    66       }

    67       assert(_nthreads_stopped > 0, "Invalid");

    68       _nthreads_stopped--;

    69       ml.notify_all();

    70     }

    71   }

    72 }

    73 

    74 void SuspendibleThreadSet::synchronize() {

    75   assert(Thread::current()->is_VM_thread(), "Must be the VM thread");

    76   if (ConcGCYieldTimeout > 0) {

    77     _suspend_all_start = os::elapsedTime();

    78   }

    79   MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);

    80   assert(!_suspend_all, "Only one at a time");

    81   _suspend_all = true;

    82   while (_nthreads_stopped < _nthreads) {

    83     ml.wait(Mutex::_no_safepoint_check_flag);

    84   }

    85 }

    86 

    87 void SuspendibleThreadSet::desynchronize() {

    88   assert(Thread::current()->is_VM_thread(), "Must be the VM thread");

    89   MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);

    90   assert(_nthreads_stopped == _nthreads, "Invalid");

    91   _suspend_all = false;

    92   ml.notify_all();

    93 }