1 /*

     2  * Copyright (c) 2014, 2015, 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/g1/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   assert(!Thread::current()->is_suspendible_thread(), "Thread already joined");

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

    38   while (_suspend_all) {

    39     ml.wait(Mutex::_no_safepoint_check_flag);

    40   }

    41   _nthreads++;

    42   DEBUG_ONLY(Thread::current()->set_suspendible_thread();)

    43 }

    44 

    45 void SuspendibleThreadSet::leave() {

    46   assert(Thread::current()->is_suspendible_thread(), "Thread not joined");

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

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

    49   DEBUG_ONLY(Thread::current()->clear_suspendible_thread();)

    50   _nthreads--;

    51   if (_suspend_all) {

    52     ml.notify_all();

    53   }

    54 }

    55 

    56 void SuspendibleThreadSet::yield() {

    57   assert(Thread::current()->is_suspendible_thread(), "Must have joined");

    58   if (_suspend_all) {

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

    60     if (_suspend_all) {

    61       _nthreads_stopped++;

    62       if (_nthreads_stopped == _nthreads) {

    63         if (ConcGCYieldTimeout > 0) {

    64           double now = os::elapsedTime();

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

    66         }

    67       }

    68       ml.notify_all();

    69       while (_suspend_all) {

    70         ml.wait(Mutex::_no_safepoint_check_flag);

    71       }

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

    73       _nthreads_stopped--;

    74       ml.notify_all();

    75     }

    76   }

    77 }

    78 

    79 void SuspendibleThreadSet::synchronize() {

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

    81   if (ConcGCYieldTimeout > 0) {

    82     _suspend_all_start = os::elapsedTime();

    83   }

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

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

    86   _suspend_all = true;

    87   while (_nthreads_stopped < _nthreads) {

    88     ml.wait(Mutex::_no_safepoint_check_flag);

    89   }

    90 }

    91 

    92 void SuspendibleThreadSet::desynchronize() {

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

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

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

    96   _suspend_all = false;

    97   ml.notify_all();

    98 }