--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/os/windows/vm/threadCritical_windows.cpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,106 @@
+/*
+ * Copyright 2001-2003 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/_threadCritical_windows.cpp.incl"
+
+// 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--;
+  }
+}