src/os/windows/vm/attachListener_windows.cpp - platform/external/jetbrains/jdk8u_hotspot - Git at Google

 /*
  * Copyright (c) 2005, 2013, 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 "precompiled.hpp"
 #include "runtime/interfaceSupport.hpp"
 #include "runtime/os.hpp"
 #include "services/attachListener.hpp"
 #include "services/dtraceAttacher.hpp"

 #include <windows.h>
 #include <signal.h>             // SIGBREAK

 // The AttachListener thread services a queue of operations. It blocks in the dequeue
 // function until an operation is enqueued. A client enqueues an operation by creating
 // a thread in this process using the Win32 CreateRemoteThread function. That thread
 // executes a small stub generated by the client. The stub invokes the
 // JVM_EnqueueOperation function which checks the operation parameters and enqueues
 // the operation to the queue serviced by the attach listener. The thread created by
 // the client is a native thread and is restricted to a single page of stack. To keep
 // it simple operations are pre-allocated at initialization time. An enqueue thus
 // takes a preallocated operation, populates the operation parameters, adds it to
 // queue and wakes up the attach listener.
 //
 // When an operation has completed the attach listener is required to send the
 // operation result and any result data to the client. In this implementation the
 // client is a pipe server. In the enqueue operation it provides the name of pipe
 // to this process. When the operation is completed this process opens the pipe and
 // sends the result and output back to the client. Note that writing to the pipe
 // (and flushing the output) is a blocking operation. This means that a non-responsive
 // client could potentially hang the attach listener thread indefinitely. In that
 // case no new operations would be executed but the VM would continue as normal.
 // As only suitably privileged processes can open this process we concluded that
 // this wasn't worth worrying about.


 // forward reference
 class Win32AttachOperation;


 class Win32AttachListener: AllStatic {
  private:
   enum {
     preallocate_count = 4                   // number of preallocated operations
   };

   // protects the preallocated list and the operation list
   static HANDLE _mutex;

   // head of preallocated operations list
   static Win32AttachOperation* _avail;

   // head and tail of enqueue operations list
   static Win32AttachOperation* _head;
   static Win32AttachOperation* _tail;


   static Win32AttachOperation* head()                       { return _head; }
   static void set_head(Win32AttachOperation* head)          { _head = head; }

   static Win32AttachOperation* tail()                       { return _tail; }
   static void set_tail(Win32AttachOperation* tail)          { _tail = tail; }


   // used to wakeup the listener
   static HANDLE _wakeup;
   static HANDLE wakeup()                                    { return _wakeup; }

  public:
   enum {
     ATTACH_ERROR_DISABLED               = 100,              // error codes
     ATTACH_ERROR_RESOURCE               = 101,
     ATTACH_ERROR_ILLEGALARG             = 102,
     ATTACH_ERROR_INTERNAL               = 103
   };

   static int init();
   static HANDLE mutex()                                     { return _mutex; }

   static Win32AttachOperation* available()                  { return _avail; }
   static void set_available(Win32AttachOperation* avail)    { _avail = avail; }

   // enqueue an operation to the end of the list
   static int enqueue(char* cmd, char* arg1, char* arg2, char* arg3, char* pipename);

   // dequeue an operation from from head of the list
   static Win32AttachOperation* dequeue();
 };

 // statics
 HANDLE Win32AttachListener::_mutex;
 HANDLE Win32AttachListener::_wakeup;
 Win32AttachOperation* Win32AttachListener::_avail;
 Win32AttachOperation* Win32AttachListener::_head;
 Win32AttachOperation* Win32AttachListener::_tail;


 // Win32AttachOperation is an AttachOperation that additionally encapsulates the name
 // of a pipe which is used to send the operation reply/output to the client.
 // Win32AttachOperation can also be linked in a list.

 class Win32AttachOperation: public AttachOperation {
  private:
   friend class Win32AttachListener;

   enum {
     pipe_name_max = 256             // maximum pipe name
   };

   char _pipe[pipe_name_max+1];

   const char* pipe() const                              { return _pipe; }
   void set_pipe(const char* pipe) {
     assert(strlen(pipe) <= pipe_name_max, "execeds maximum length of pipe name");
     strcpy(_pipe, pipe);
   }

   HANDLE open_pipe();
   static BOOL write_pipe(HANDLE hPipe, char* buf, int len);

   Win32AttachOperation* _next;

   Win32AttachOperation* next() const                    { return _next; }
   void set_next(Win32AttachOperation* next)             { _next = next; }

   // noarg constructor as operation is preallocated
   Win32AttachOperation() : AttachOperation("<noname>") {
     set_pipe("<nopipe>");
     set_next(NULL);
   }

  public:
   void Win32AttachOperation::complete(jint result, bufferedStream* result_stream);
 };


 // preallocate the required number of operations
 int Win32AttachListener::init() {
   _mutex = (void*)::CreateMutex(NULL, FALSE, NULL);
   guarantee(_mutex != (HANDLE)NULL, "mutex creation failed");

   _wakeup = ::CreateSemaphore(NULL, 0, 1, NULL);
   guarantee(_wakeup != (HANDLE)NULL, "semaphore creation failed");

   set_head(NULL);
   set_tail(NULL);

   // preallocate a few operations
   set_available(NULL);
   for (int i=0; i<preallocate_count; i++) {
     Win32AttachOperation* op = new Win32AttachOperation();
     op->set_next(available());
     set_available(op);
   }

   return 0;
 }

 // Enqueue an operation. This is called from a native thread that is not attached to VM.
 // Also we need to be careful not to execute anything that results in more than a 4k stack.
 //
 int Win32AttachListener::enqueue(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) {
   // listener not running
   if (!AttachListener::is_initialized()) {
     return ATTACH_ERROR_DISABLED;
   }

   // check that all paramteres to the operation
   if (strlen(cmd) > AttachOperation::name_length_max) return ATTACH_ERROR_ILLEGALARG;
   if (strlen(arg0) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG;
   if (strlen(arg0) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG;
   if (strlen(pipename) > Win32AttachOperation::pipe_name_max) return ATTACH_ERROR_ILLEGALARG;

   // check for a well-formed pipename
   if (strstr(pipename, "\\\\.\\pipe\\") != pipename) return ATTACH_ERROR_ILLEGALARG;

   // grab the lock for the list
   DWORD res = ::WaitForSingleObject(mutex(), INFINITE);
   if (res != WAIT_OBJECT_0) {
     return ATTACH_ERROR_INTERNAL;
   }

   // try to get an operation from the available list
   Win32AttachOperation* op = available();
   if (op != NULL) {
     set_available(op->next());

     // add to end (tail) of list
     op->set_next(NULL);
     if (tail() == NULL) {
       set_head(op);
     } else {
       tail()->set_next(op);
     }
     set_tail(op);

     op->set_name(cmd);
     op->set_arg(0, arg0);
     op->set_arg(1, arg1);
     op->set_arg(2, arg2);
     op->set_pipe(pipename);

     // wakeup the thread waiting for operations
     ::ReleaseSemaphore(wakeup(), 1, NULL);
   }
   ::ReleaseMutex(mutex());

   return (op != NULL) ? 0 : ATTACH_ERROR_RESOURCE;
 }


 // dequeue the operation from the head of the operation list. If
 Win32AttachOperation* Win32AttachListener::dequeue() {
   for (;;) {
     DWORD res = ::WaitForSingleObject(wakeup(), INFINITE);
     guarantee(res == WAIT_OBJECT_0, "wait failed");

     res = ::WaitForSingleObject(mutex(), INFINITE);
     guarantee(res == WAIT_OBJECT_0, "wait failed");

     Win32AttachOperation* op = head();
     if (op != NULL) {
       set_head(op->next());
       if (head() == NULL) {     // list is empty
         set_tail(NULL);
       }
     }
     ::ReleaseMutex(mutex());

     if (op != NULL) {
       return op;
     }
   }
 }


 // open the pipe to the client
 HANDLE Win32AttachOperation::open_pipe() {
   HANDLE hPipe;

   hPipe = ::CreateFile( pipe(),  // pipe name
                         GENERIC_WRITE,   // write only
                         0,              // no sharing
                         NULL,           // default security attributes
                         OPEN_EXISTING,  // opens existing pipe
                         0,              // default attributes
                         NULL);          // no template file

   if (hPipe != INVALID_HANDLE_VALUE) {
     // shouldn't happen as there is a pipe created per operation
     if (::GetLastError() == ERROR_PIPE_BUSY) {
       return INVALID_HANDLE_VALUE;
     }
   }
   return hPipe;
 }

 // write to the pipe
 BOOL Win32AttachOperation::write_pipe(HANDLE hPipe, char* buf, int len) {
   do {
     DWORD nwrote;

     BOOL fSuccess = WriteFile(  hPipe,                  // pipe handle
                                 (LPCVOID)buf,           // message
                                 (DWORD)len,             // message length
                                 &nwrote,                // bytes written
                                 NULL);                  // not overlapped
     if (!fSuccess) {
       return fSuccess;
     }
     buf += nwrote;
     len -= nwrote;
   }
   while (len > 0);
   return TRUE;
 }

 // Complete the operation:
 //   - open the pipe to the client
 //   - write the operation result (a jint)
 //   - write the operation output (the result stream)
 //
 void Win32AttachOperation::complete(jint result, bufferedStream* result_stream) {
   JavaThread* thread = JavaThread::current();
   ThreadBlockInVM tbivm(thread);

   thread->set_suspend_equivalent();
   // cleared by handle_special_suspend_equivalent_condition() or
   // java_suspend_self() via check_and_wait_while_suspended()

   HANDLE hPipe = open_pipe();
   if (hPipe != INVALID_HANDLE_VALUE) {
     BOOL fSuccess;

     char msg[32];
     sprintf(msg, "%d\n", result);

     fSuccess = write_pipe(hPipe, msg, (int)strlen(msg));
     if (fSuccess) {
       write_pipe(hPipe, (char*) result_stream->base(), (int)(result_stream->size()));
     }

     // Need to flush buffers
     FlushFileBuffers(hPipe);
     CloseHandle(hPipe);
   }

   DWORD res = ::WaitForSingleObject(Win32AttachListener::mutex(), INFINITE);
   if (res == WAIT_OBJECT_0) {

     // put the operation back on the available list
     set_next(Win32AttachListener::available());
     Win32AttachListener::set_available(this);

     ::ReleaseMutex(Win32AttachListener::mutex());
   }

   // were we externally suspended while we were waiting?
   thread->check_and_wait_while_suspended();
 }


 // AttachOperation functions

 AttachOperation* AttachListener::dequeue() {
   JavaThread* thread = JavaThread::current();
   ThreadBlockInVM tbivm(thread);

   thread->set_suspend_equivalent();
   // cleared by handle_special_suspend_equivalent_condition() or
   // java_suspend_self() via check_and_wait_while_suspended()

   AttachOperation* op = Win32AttachListener::dequeue();

   // were we externally suspended while we were waiting?
   thread->check_and_wait_while_suspended();

   return op;
 }

 void AttachListener::vm_start() {
   // nothing to do
 }

 int AttachListener::pd_init() {
   return Win32AttachListener::init();
 }

 // always startup on Windows NT/2000/XP
 bool AttachListener::init_at_startup() {
   return os::win32::is_nt();
 }

 // no trigger mechanism on Windows to start Attach Listener lazily
 bool AttachListener::is_init_trigger() {
   return false;
 }

 void AttachListener::abort() {
   // nothing to do
 }

 void AttachListener::pd_data_dump() {
   os::signal_notify(SIGBREAK);
 }

 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
   return NULL;
 }

 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
   out->print_cr("flag '%s' cannot be changed", op->arg(0));
   return JNI_ERR;
 }

 void AttachListener::pd_detachall() {
   // do nothing for now
 }

 // Native thread started by remote client executes this.
 extern "C" {
   JNIEXPORT jint JNICALL
     JVM_EnqueueOperation(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) {
       return (jint)Win32AttachListener::enqueue(cmd, arg0, arg1, arg2, pipename);
     }

 } // extern
	/*
	* Copyright (c) 2005, 2013, 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 "precompiled.hpp"
	#include "runtime/interfaceSupport.hpp"
	#include "runtime/os.hpp"
	#include "services/attachListener.hpp"
	#include "services/dtraceAttacher.hpp"

	#include <windows.h>
	#include <signal.h> // SIGBREAK

	// The AttachListener thread services a queue of operations. It blocks in the dequeue
	// function until an operation is enqueued. A client enqueues an operation by creating
	// a thread in this process using the Win32 CreateRemoteThread function. That thread
	// executes a small stub generated by the client. The stub invokes the
	// JVM_EnqueueOperation function which checks the operation parameters and enqueues
	// the operation to the queue serviced by the attach listener. The thread created by
	// the client is a native thread and is restricted to a single page of stack. To keep
	// it simple operations are pre-allocated at initialization time. An enqueue thus
	// takes a preallocated operation, populates the operation parameters, adds it to
	// queue and wakes up the attach listener.
	//
	// When an operation has completed the attach listener is required to send the
	// operation result and any result data to the client. In this implementation the
	// client is a pipe server. In the enqueue operation it provides the name of pipe
	// to this process. When the operation is completed this process opens the pipe and
	// sends the result and output back to the client. Note that writing to the pipe
	// (and flushing the output) is a blocking operation. This means that a non-responsive
	// client could potentially hang the attach listener thread indefinitely. In that
	// case no new operations would be executed but the VM would continue as normal.
	// As only suitably privileged processes can open this process we concluded that
	// this wasn't worth worrying about.


	// forward reference
	class Win32AttachOperation;


	class Win32AttachListener: AllStatic {
	private:
	enum {
	preallocate_count = 4 // number of preallocated operations
	};

	// protects the preallocated list and the operation list
	static HANDLE _mutex;

	// head of preallocated operations list
	static Win32AttachOperation* _avail;

	// head and tail of enqueue operations list
	static Win32AttachOperation* _head;
	static Win32AttachOperation* _tail;


	static Win32AttachOperation* head() { return _head; }
	static void set_head(Win32AttachOperation* head) { _head = head; }

	static Win32AttachOperation* tail() { return _tail; }
	static void set_tail(Win32AttachOperation* tail) { _tail = tail; }


	// used to wakeup the listener
	static HANDLE _wakeup;
	static HANDLE wakeup() { return _wakeup; }

	public:
	enum {
	ATTACH_ERROR_DISABLED = 100, // error codes
	ATTACH_ERROR_RESOURCE = 101,
	ATTACH_ERROR_ILLEGALARG = 102,
	ATTACH_ERROR_INTERNAL = 103
	};

	static int init();
	static HANDLE mutex() { return _mutex; }

	static Win32AttachOperation* available() { return _avail; }
	static void set_available(Win32AttachOperation* avail) { _avail = avail; }

	// enqueue an operation to the end of the list
	static int enqueue(char* cmd, char* arg1, char* arg2, char* arg3, char* pipename);

	// dequeue an operation from from head of the list
	static Win32AttachOperation* dequeue();
	};

	// statics
	HANDLE Win32AttachListener::_mutex;
	HANDLE Win32AttachListener::_wakeup;
	Win32AttachOperation* Win32AttachListener::_avail;
	Win32AttachOperation* Win32AttachListener::_head;
	Win32AttachOperation* Win32AttachListener::_tail;


	// Win32AttachOperation is an AttachOperation that additionally encapsulates the name
	// of a pipe which is used to send the operation reply/output to the client.
	// Win32AttachOperation can also be linked in a list.

	class Win32AttachOperation: public AttachOperation {
	private:
	friend class Win32AttachListener;

	enum {
	pipe_name_max = 256 // maximum pipe name
	};

	char _pipe[pipe_name_max+1];

	const char* pipe() const { return _pipe; }
	void set_pipe(const char* pipe) {
	assert(strlen(pipe) <= pipe_name_max, "execeds maximum length of pipe name");
	strcpy(_pipe, pipe);
	}

	HANDLE open_pipe();
	static BOOL write_pipe(HANDLE hPipe, char* buf, int len);

	Win32AttachOperation* _next;

	Win32AttachOperation* next() const { return _next; }
	void set_next(Win32AttachOperation* next) { _next = next; }

	// noarg constructor as operation is preallocated
	Win32AttachOperation() : AttachOperation("<noname>") {
	set_pipe("<nopipe>");
	set_next(NULL);
	}

	public:
	void Win32AttachOperation::complete(jint result, bufferedStream* result_stream);
	};


	// preallocate the required number of operations
	int Win32AttachListener::init() {
	_mutex = (void*)::CreateMutex(NULL, FALSE, NULL);
	guarantee(_mutex != (HANDLE)NULL, "mutex creation failed");

	_wakeup = ::CreateSemaphore(NULL, 0, 1, NULL);
	guarantee(_wakeup != (HANDLE)NULL, "semaphore creation failed");

	set_head(NULL);
	set_tail(NULL);

	// preallocate a few operations
	set_available(NULL);
	for (int i=0; i<preallocate_count; i++) {
	Win32AttachOperation* op = new Win32AttachOperation();
	op->set_next(available());
	set_available(op);
	}

	return 0;
	}

	// Enqueue an operation. This is called from a native thread that is not attached to VM.
	// Also we need to be careful not to execute anything that results in more than a 4k stack.
	//
	int Win32AttachListener::enqueue(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) {
	// listener not running
	if (!AttachListener::is_initialized()) {
	return ATTACH_ERROR_DISABLED;
	}

	// check that all paramteres to the operation
	if (strlen(cmd) > AttachOperation::name_length_max) return ATTACH_ERROR_ILLEGALARG;
	if (strlen(arg0) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG;
	if (strlen(arg0) > AttachOperation::arg_length_max) return ATTACH_ERROR_ILLEGALARG;
	if (strlen(pipename) > Win32AttachOperation::pipe_name_max) return ATTACH_ERROR_ILLEGALARG;

	// check for a well-formed pipename
	if (strstr(pipename, "\\\\.\\pipe\\") != pipename) return ATTACH_ERROR_ILLEGALARG;

	// grab the lock for the list
	DWORD res = ::WaitForSingleObject(mutex(), INFINITE);
	if (res != WAIT_OBJECT_0) {
	return ATTACH_ERROR_INTERNAL;
	}

	// try to get an operation from the available list
	Win32AttachOperation* op = available();
	if (op != NULL) {
	set_available(op->next());

	// add to end (tail) of list
	op->set_next(NULL);
	if (tail() == NULL) {
	set_head(op);
	} else {
	tail()->set_next(op);
	}
	set_tail(op);

	op->set_name(cmd);
	op->set_arg(0, arg0);
	op->set_arg(1, arg1);
	op->set_arg(2, arg2);
	op->set_pipe(pipename);

	// wakeup the thread waiting for operations
	::ReleaseSemaphore(wakeup(), 1, NULL);
	}
	::ReleaseMutex(mutex());

	return (op != NULL) ? 0 : ATTACH_ERROR_RESOURCE;
	}


	// dequeue the operation from the head of the operation list. If
	Win32AttachOperation* Win32AttachListener::dequeue() {
	for (;;) {
	DWORD res = ::WaitForSingleObject(wakeup(), INFINITE);
	guarantee(res == WAIT_OBJECT_0, "wait failed");

	res = ::WaitForSingleObject(mutex(), INFINITE);
	guarantee(res == WAIT_OBJECT_0, "wait failed");

	Win32AttachOperation* op = head();
	if (op != NULL) {
	set_head(op->next());
	if (head() == NULL) { // list is empty
	set_tail(NULL);
	}
	}
	::ReleaseMutex(mutex());

	if (op != NULL) {
	return op;
	}
	}
	}


	// open the pipe to the client
	HANDLE Win32AttachOperation::open_pipe() {
	HANDLE hPipe;

	hPipe = ::CreateFile( pipe(), // pipe name
	GENERIC_WRITE, // write only
	0, // no sharing
	NULL, // default security attributes
	OPEN_EXISTING, // opens existing pipe
	0, // default attributes
	NULL); // no template file

	if (hPipe != INVALID_HANDLE_VALUE) {
	// shouldn't happen as there is a pipe created per operation
	if (::GetLastError() == ERROR_PIPE_BUSY) {
	return INVALID_HANDLE_VALUE;
	}
	}
	return hPipe;
	}

	// write to the pipe
	BOOL Win32AttachOperation::write_pipe(HANDLE hPipe, char* buf, int len) {
	do {
	DWORD nwrote;

	BOOL fSuccess = WriteFile( hPipe, // pipe handle
	(LPCVOID)buf, // message
	(DWORD)len, // message length
	&nwrote, // bytes written
	NULL); // not overlapped
	if (!fSuccess) {
	return fSuccess;
	}
	buf += nwrote;
	len -= nwrote;
	}
	while (len > 0);
	return TRUE;
	}

	// Complete the operation:
	// - open the pipe to the client
	// - write the operation result (a jint)
	// - write the operation output (the result stream)
	//
	void Win32AttachOperation::complete(jint result, bufferedStream* result_stream) {
	JavaThread* thread = JavaThread::current();
	ThreadBlockInVM tbivm(thread);

	thread->set_suspend_equivalent();
	// cleared by handle_special_suspend_equivalent_condition() or
	// java_suspend_self() via check_and_wait_while_suspended()

	HANDLE hPipe = open_pipe();
	if (hPipe != INVALID_HANDLE_VALUE) {
	BOOL fSuccess;

	char msg[32];
	sprintf(msg, "%d\n", result);

	fSuccess = write_pipe(hPipe, msg, (int)strlen(msg));
	if (fSuccess) {
	write_pipe(hPipe, (char*) result_stream->base(), (int)(result_stream->size()));
	}

	// Need to flush buffers
	FlushFileBuffers(hPipe);
	CloseHandle(hPipe);
	}

	DWORD res = ::WaitForSingleObject(Win32AttachListener::mutex(), INFINITE);
	if (res == WAIT_OBJECT_0) {

	// put the operation back on the available list
	set_next(Win32AttachListener::available());
	Win32AttachListener::set_available(this);

	::ReleaseMutex(Win32AttachListener::mutex());
	}

	// were we externally suspended while we were waiting?
	thread->check_and_wait_while_suspended();
	}


	// AttachOperation functions

	AttachOperation* AttachListener::dequeue() {
	JavaThread* thread = JavaThread::current();
	ThreadBlockInVM tbivm(thread);

	thread->set_suspend_equivalent();
	// cleared by handle_special_suspend_equivalent_condition() or
	// java_suspend_self() via check_and_wait_while_suspended()

	AttachOperation* op = Win32AttachListener::dequeue();

	// were we externally suspended while we were waiting?
	thread->check_and_wait_while_suspended();

	return op;
	}

	void AttachListener::vm_start() {
	// nothing to do
	}

	int AttachListener::pd_init() {
	return Win32AttachListener::init();
	}

	// always startup on Windows NT/2000/XP
	bool AttachListener::init_at_startup() {
	return os::win32::is_nt();
	}

	// no trigger mechanism on Windows to start Attach Listener lazily
	bool AttachListener::is_init_trigger() {
	return false;
	}

	void AttachListener::abort() {
	// nothing to do
	}

	void AttachListener::pd_data_dump() {
	os::signal_notify(SIGBREAK);
	}

	AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
	return NULL;
	}

	jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
	out->print_cr("flag '%s' cannot be changed", op->arg(0));
	return JNI_ERR;
	}

	void AttachListener::pd_detachall() {
	// do nothing for now
	}

	// Native thread started by remote client executes this.
	extern "C" {
	JNIEXPORT jint JNICALL
	JVM_EnqueueOperation(char* cmd, char* arg0, char* arg1, char* arg2, char* pipename) {
	return (jint)Win32AttachListener::enqueue(cmd, arg0, arg1, arg2, pipename);
	}

	} // extern