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 }