/*

 * Copyright 1997-2007 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 *

 */

# include "incls/_precompiled.incl"

# include "incls/_gcLocker.cpp.incl"

volatile jint GC_locker::_jni_lock_count = 0;

volatile jint GC_locker::_lock_count     = 0;

volatile bool GC_locker::_needs_gc       = false;

volatile bool GC_locker::_doing_gc       = false;

void GC_locker::stall_until_clear() {

  assert(!JavaThread::current()->in_critical(), "Would deadlock");

  MutexLocker   ml(JNICritical_lock);

  // Wait for _needs_gc  to be cleared

  while (GC_locker::needs_gc()) {

    JNICritical_lock->wait();

  }

}

void GC_locker::jni_lock_slow() {

  MutexLocker mu(JNICritical_lock);

  // Block entering threads if we know at least one thread is in a

  // JNI critical region and we need a GC.

  // We check that at least one thread is in a critical region before

  // blocking because blocked threads are woken up by a thread exiting

  // a JNI critical region.

  while ((is_jni_active() && needs_gc()) || _doing_gc) {

    JNICritical_lock->wait();

  }

  jni_lock();

}

void GC_locker::jni_unlock_slow() {

  MutexLocker mu(JNICritical_lock);

  jni_unlock();

  if (needs_gc() && !is_jni_active()) {

    // We're the last thread out. Cause a GC to occur.

    // GC will also check is_active, so this check is not

    // strictly needed. It's added here to make it clear that

    // the GC will NOT be performed if any other caller

    // of GC_locker::lock() still needs GC locked.

    if (!is_active()) {

      _doing_gc = true;

      {

        // Must give up the lock while at a safepoint

        MutexUnlocker munlock(JNICritical_lock);

        Universe::heap()->collect(GCCause::_gc_locker);

      }

      _doing_gc = false;

    }

    clear_needs_gc();

    JNICritical_lock->notify_all();

  }

}

// Implementation of No_GC_Verifier

#ifdef ASSERT

No_GC_Verifier::No_GC_Verifier(bool verifygc) {

  _verifygc = verifygc;

  if (_verifygc) {

    CollectedHeap* h = Universe::heap();

    assert(!h->is_gc_active(), "GC active during No_GC_Verifier");

    _old_invocations = h->total_collections();

  }

}

No_GC_Verifier::~No_GC_Verifier() {

  if (_verifygc) {

    CollectedHeap* h = Universe::heap();

    assert(!h->is_gc_active(), "GC active during No_GC_Verifier");

    if (_old_invocations != h->total_collections()) {

      fatal("collection in a No_GC_Verifier secured function");

    }

  }

}

Pause_No_GC_Verifier::Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {

  _ngcv = ngcv;

  if (_ngcv->_verifygc) {

    // if we were verifying, then make sure that nothing is

    // wrong before we "pause" verification

    CollectedHeap* h = Universe::heap();

    assert(!h->is_gc_active(), "GC active during No_GC_Verifier");

    if (_ngcv->_old_invocations != h->total_collections()) {

      fatal("collection in a No_GC_Verifier secured function");

    }

  }

}

Pause_No_GC_Verifier::~Pause_No_GC_Verifier() {

  if (_ngcv->_verifygc) {

    // if we were verifying before, then reenable verification

    CollectedHeap* h = Universe::heap();

    assert(!h->is_gc_active(), "GC active during No_GC_Verifier");

    _ngcv->_old_invocations = h->total_collections();

  }

}

// JRT_LEAF rules:

// A JRT_LEAF method may not interfere with safepointing by

//   1) acquiring or blocking on a Mutex or JavaLock - checked

//   2) allocating heap memory - checked

//   3) executing a VM operation - checked

//   4) executing a system call (including malloc) that could block or grab a lock

//   5) invoking GC

//   6) reaching a safepoint

//   7) running too long

// Nor may any method it calls.

JRT_Leaf_Verifier::JRT_Leaf_Verifier()

  : No_Safepoint_Verifier(true, JRT_Leaf_Verifier::should_verify_GC())

{

}

JRT_Leaf_Verifier::~JRT_Leaf_Verifier()

{

}

bool JRT_Leaf_Verifier::should_verify_GC() {

  switch (JavaThread::current()->thread_state()) {

  case _thread_in_Java:

    // is in a leaf routine, there must be no safepoint.

    return true;

  case _thread_in_native:

    // A native thread is not subject to safepoints.

    // Even while it is in a leaf routine, GC is ok

    return false;

  default:

    // Leaf routines cannot be called from other contexts.

    ShouldNotReachHere();

    return false;

  }

}

#endif