/*

 * 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.

 *

 */

// OS-includes here

# include <windows.h>

# include <winbase.h>

//

// See threadCritical.hpp for details of this class.

//

static bool initialized = false;

static volatile jint lock_count = -1;

static HANDLE lock_event;

static DWORD lock_owner = -1;

//

// Note that Microsoft's critical region code contains a race

// condition, and is not suitable for use. A thread holding the

// critical section cannot safely suspend a thread attempting

// to enter the critical region. The failure mode is that both

// threads are permanently suspended.

//

// I experiemented with the use of ordinary windows mutex objects

// and found them ~30 times slower than the critical region code.

//

void ThreadCritical::initialize() {

}

void ThreadCritical::release() {

  assert(lock_owner == -1, "Mutex being deleted while owned.");

  assert(lock_count == -1, "Mutex being deleted while recursively locked");

  assert(lock_event != NULL, "Sanity check");

  CloseHandle(lock_event);

}

ThreadCritical::ThreadCritical() {

  DWORD current_thread = GetCurrentThreadId();

  if (lock_owner != current_thread) {

    // Grab the lock before doing anything.

    while (Atomic::cmpxchg(0, &lock_count, -1) != -1) {

      if (initialized) {

        DWORD ret = WaitForSingleObject(lock_event,  INFINITE);

        assert(ret == WAIT_OBJECT_0, "unexpected return value from WaitForSingleObject");

      }

    }

    // Make sure the event object is allocated.

    if (!initialized) {

      // Locking will not work correctly unless this is autoreset.

      lock_event = CreateEvent(NULL, false, false, NULL);

      initialized = true;

    }

    assert(lock_owner == -1, "Lock acquired illegally.");

    lock_owner = current_thread;

  } else {

    // Atomicity isn't required. Bump the recursion count.

    lock_count++;

  }

  assert(lock_owner == GetCurrentThreadId(), "Lock acquired illegally.");

}

ThreadCritical::~ThreadCritical() {

  assert(lock_owner == GetCurrentThreadId(), "unlock attempt by wrong thread");

  assert(lock_count >= 0, "Attempt to unlock when already unlocked");

  if (lock_count == 0) {

    // We're going to unlock

    lock_owner = -1;

    lock_count = -1;

    // No lost wakeups, lock_event stays signaled until reset.

    DWORD ret = SetEvent(lock_event);

    assert(ret != 0, "unexpected return value from SetEvent");

  } else {

    // Just unwinding a recursive lock;

    lock_count--;

  }

}