view src/share/vm/runtime/jniPeriodicChecker.cpp @ 1716:be3f9c242c9d

6948538: CMS: BOT walkers can fall into object allocation and initialization cracks Summary: GC workers now recognize an intermediate transient state of blocks which are allocated but have not yet completed initialization. blk_start() calls do not attempt to determine the size of a block in the transient state, rather waiting for the block to become initialized so that it is safe to query its size. Audited and ensured the order of initialization of object fields (klass, free bit and size) to respect block state transition protocol. Also included some new assertion checking code enabled in debug mode. Reviewed-by: chrisphi, johnc, poonam
author ysr
date Mon, 16 Aug 2010 15:58:42 -0700
parents c18cbe5936b8
children f95d63e2154a
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/*
 * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

# include "incls/_precompiled.incl"
# include "incls/_jniPeriodicChecker.cpp.incl"


// --------------------------------------------------------
// Class to aid in periodic checking under CheckJNICalls
class JniPeriodicCheckerTask : public PeriodicTask {
  public:
     JniPeriodicCheckerTask(int interval_time) : PeriodicTask(interval_time) {}
     void task() { os::run_periodic_checks(); }
     static void engage();
     static void disengage();
};


//----------------------------------------------------------
// Implementation of JniPeriodicChecker

JniPeriodicCheckerTask*              JniPeriodicChecker::_task   = NULL;

/*
 * The engage() method is called at initialization time via
 * Thread::create_vm() to initialize the JniPeriodicChecker and
 * register it with the WatcherThread as a periodic task.
 */
void JniPeriodicChecker::engage() {
  if (CheckJNICalls && !is_active()) {
    // start up the periodic task
    _task = new JniPeriodicCheckerTask(10);
    _task->enroll();
  }
}


/*
 * the disengage() method is responsible for deactivating the periodic
 * task. This  method is called from before_exit() in java.cpp and is only called
 * after the WatcherThread has been stopped.
 */
void JniPeriodicChecker::disengage() {
  if (CheckJNICalls && is_active()) {
    // remove JniPeriodicChecker
    _task->disenroll();
    delete _task;
    _task = NULL;
  }
}

void jniPeriodicChecker_exit() {
  if (!CheckJNICalls) return;
}