win32-threads.cc

// win32-threads.cc - interface between libjava and Win32 threads.

/* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2006 Free Software
   Foundation, Inc.

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

#include <config.h>

// If we're using the Boehm GC, then we need to override some of the
// thread primitives.  This is fairly gross.
#ifdef HAVE_BOEHM_GC
extern "C"
{
#include <gc.h>
// <windows.h> #define's STRICT, which conflicts with Modifier.h
#undef STRICT
};
#endif /* HAVE_BOEHM_GC */

#include <gcj/cni.h>
#include <jvm.h>
#include <java/lang/Thread.h>
#include <java/lang/System.h>

#include <errno.h>

#ifndef ETIMEDOUT
#define ETIMEDOUT 116
#endif

// This is used to implement thread startup.
struct starter
{
  _Jv_ThreadStartFunc *method;
  _Jv_Thread_t *data;
};

// Controls access to the variable below
static HANDLE daemon_mutex;
static HANDLE daemon_cond;
// Number of non-daemon threads - _Jv_ThreadWait returns when this is 0
static int non_daemon_count;

// TLS key get Java object representing the thread
DWORD _Jv_ThreadKey;
// TLS key to get _Jv_Thread_t* representing the thread
DWORD _Jv_ThreadDataKey;

//
// These are the flags that can appear in _Jv_Thread_t.
//

// Thread started.
#define FLAG_START   0x01
// Thread is daemon.
#define FLAG_DAEMON  0x02

//
// Helper
//
inline bool
compare_and_exchange(LONG volatile* dest, LONG cmp, LONG xchg)
{
  return InterlockedCompareExchange((LONG*) dest, xchg, cmp) == cmp;
    // Seems like a bug in the MinGW headers that we have to do this cast.
}

//
// Condition variables.
//

// we do lazy creation of Events since CreateEvent() is insanely
// expensive, and because the rest of libgcj will call _Jv_CondInit
// when only a mutex is needed.

inline void
ensure_condvar_initialized(_Jv_ConditionVariable_t *cv)
{
  if (cv->ev[0] == 0)
    {
      cv->ev[0] = CreateEvent (NULL, 0, 0, NULL);
      if (cv->ev[0] == 0) JvFail("CreateEvent() failed");

      cv->ev[1] = CreateEvent (NULL, 1, 0, NULL);
      if (cv->ev[1] == 0) JvFail("CreateEvent() failed");
    }
}

inline void
ensure_interrupt_event_initialized(HANDLE& rhEvent)
{
  if (!rhEvent)
    {
      rhEvent = CreateEvent (NULL, 0, 0, NULL);
      if (!rhEvent) JvFail("CreateEvent() failed");
    }
}

// Reimplementation of the general algorithm described at
// http://www.cs.wustl.edu/~schmidt/win32-cv-1.html (isomorphic to
// 3.2, not a cut-and-paste).

int
_Jv_CondWait(_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu, jlong millis, jint nanos)
{
  if (mu->owner != GetCurrentThreadId ( ))
    return _JV_NOT_OWNER;

  _Jv_Thread_t *current = _Jv_ThreadCurrentData ();
  java::lang::Thread *current_obj = _Jv_ThreadCurrent ();

  // Now that we hold the interrupt mutex, check if this thread has been 
  // interrupted already.
  EnterCriticalSection (&current->interrupt_mutex);
  ensure_interrupt_event_initialized (current->interrupt_event);
  jboolean interrupted = current_obj->interrupt_flag;
  LeaveCriticalSection (&current->interrupt_mutex);

  if (interrupted)
    {
      return _JV_INTERRUPTED;
    }

  EnterCriticalSection (&cv->count_mutex);
  ensure_condvar_initialized (cv);
  cv->blocked_count++;
  LeaveCriticalSection (&cv->count_mutex);

  DWORD time;
  if ((millis == 0) && (nanos > 0)) time = 1;
  else if (millis == 0) time = INFINITE;
  else time = millis;

  // Record the current lock depth, so it can be restored
  // when we reacquire it.
  int count = mu->refcount;
  int curcount = count;

  // Call _Jv_MutexUnlock repeatedly until this thread
  // has completely released the monitor.
  while (curcount > 0)
    {  
      _Jv_MutexUnlock (mu);
      --curcount;
    }

  // Set up our array of three events:
  // - the auto-reset event (for notify())
  // - the manual-reset event (for notifyAll())
  // - the interrupt event (for interrupt())
  // We wait for any one of these to be signaled.
  HANDLE arh[3];
  arh[0] = cv->ev[0];
  arh[1] = cv->ev[1];
  arh[2] = current->interrupt_event;
  DWORD rval = WaitForMultipleObjects (3, arh, 0, time);

  EnterCriticalSection (&current->interrupt_mutex);

  // If we were unblocked by the third event (our thread's interrupt
  // event), set the thread's interrupt flag. I think this sanity
  // check guards against someone resetting our interrupt flag
  // in the time between when interrupt_mutex is released in
  // _Jv_ThreadInterrupt and the interval of time between the
  // WaitForMultipleObjects call we just made and our acquisition
  // of interrupt_mutex.
  if (rval == (WAIT_OBJECT_0 + 2))
    current_obj->interrupt_flag = true;
    
  interrupted = current_obj->interrupt_flag;
  LeaveCriticalSection (&current->interrupt_mutex);

  EnterCriticalSection(&cv->count_mutex);
  cv->blocked_count--;
  // If we were unblocked by the second event (the broadcast one)
  // and nobody is left, then reset the event.
  int last_waiter = (rval == (WAIT_OBJECT_0 + 1)) && (cv->blocked_count == 0);
  LeaveCriticalSection(&cv->count_mutex);

  if (last_waiter)
    ResetEvent (cv->ev[1]);

  // Call _Jv_MutexLock repeatedly until the mutex's refcount is the
  // same as before we originally released it.
  while (curcount < count)
    {  
      _Jv_MutexLock (mu);
      ++curcount;
    }
  
  return interrupted ? _JV_INTERRUPTED : 0;
}

void
_Jv_CondInit (_Jv_ConditionVariable_t *cv)
{
  // we do lazy creation of Events since CreateEvent() is insanely expensive
  cv->ev[0] = 0;
  InitializeCriticalSection (&cv->count_mutex);
  cv->blocked_count = 0;
}

void
_Jv_CondDestroy (_Jv_ConditionVariable_t *cv)
{
  if (cv->ev[0] != 0)
    {
      CloseHandle (cv->ev[0]);
      CloseHandle (cv->ev[1]);

      cv->ev[0] = 0;
    }

  DeleteCriticalSection (&cv->count_mutex);
}

int
_Jv_CondNotify (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu)
{
  if (mu->owner != GetCurrentThreadId ( ))
    return _JV_NOT_OWNER;

  EnterCriticalSection (&cv->count_mutex);
  ensure_condvar_initialized (cv);
  int somebody_is_blocked = cv->blocked_count > 0;
  LeaveCriticalSection (&cv->count_mutex);

  if (somebody_is_blocked)
    SetEvent (cv->ev[0]);

  return 0;
}

int
_Jv_CondNotifyAll (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu)
{
  if (mu->owner != GetCurrentThreadId ( ))
    return _JV_NOT_OWNER;

  EnterCriticalSection (&cv->count_mutex);
  ensure_condvar_initialized (cv);
  int somebody_is_blocked = cv->blocked_count > 0;
  LeaveCriticalSection (&cv->count_mutex);

  if (somebody_is_blocked)
    SetEvent (cv->ev[1]);

  return 0;
}

//
// Threads.
//

void
_Jv_InitThreads (void)
{
  _Jv_ThreadKey = TlsAlloc();
  _Jv_ThreadDataKey = TlsAlloc();
  daemon_mutex = CreateMutex (NULL, 0, NULL);
  daemon_cond = CreateEvent (NULL, 1, 0, NULL);
  non_daemon_count = 0;
}

_Jv_Thread_t *
_Jv_ThreadInitData (java::lang::Thread* obj)
{
  _Jv_Thread_t *data = (_Jv_Thread_t*)_Jv_Malloc(sizeof(_Jv_Thread_t));
  data->flags = 0;
  data->handle = 0;
  data->thread_obj = obj;
  data->interrupt_event = 0;
  InitializeCriticalSection (&data->interrupt_mutex);

  return data;
}

void
_Jv_ThreadDestroyData (_Jv_Thread_t *data)
{
  DeleteCriticalSection (&data->interrupt_mutex);
  if (data->interrupt_event)
    CloseHandle(data->interrupt_event);
  CloseHandle(data->handle);
  _Jv_Free(data);
}

void
_Jv_ThreadSetPriority (_Jv_Thread_t *data, jint prio)
{
  int actual = THREAD_PRIORITY_NORMAL;

  if (data->flags & FLAG_START)
    {
      switch (prio)
        {
          case 10:
            actual = THREAD_PRIORITY_TIME_CRITICAL;
            break;
          case 9:
            actual = THREAD_PRIORITY_HIGHEST;
            break;
          case 8:
          case 7:
            actual = THREAD_PRIORITY_ABOVE_NORMAL;
            break;
          case 6:
          case 5:
            actual = THREAD_PRIORITY_NORMAL;
            break;
          case 4:
          case 3:
            actual = THREAD_PRIORITY_BELOW_NORMAL;
            break;
          case 2:
            actual = THREAD_PRIORITY_LOWEST;
            break;
          case 1:
            actual = THREAD_PRIORITY_IDLE;
            break;
        }
      SetThreadPriority(data->handle, actual);
    }
}

void
_Jv_ThreadRegister (_Jv_Thread_t *data)
{
  TlsSetValue (_Jv_ThreadKey, data->thread_obj);
  TlsSetValue (_Jv_ThreadDataKey, data);
}

void
_Jv_ThreadUnRegister ()
{
  TlsSetValue (_Jv_ThreadKey, NULL);
  TlsSetValue (_Jv_ThreadDataKey, NULL);
}

// This function is called when a thread is started.  We don't arrange
// to call the `run' method directly, because this function must
// return a value.
static DWORD WINAPI
really_start (void* x)
{
  struct starter *info = (struct starter *) x;

  _Jv_ThreadRegister (info->data);

  info->method (info->data->thread_obj);

  if (! (info->data->flags & FLAG_DAEMON))
    {
      WaitForSingleObject (daemon_mutex, INFINITE);
      non_daemon_count--;
      if (! non_daemon_count)
        SetEvent (daemon_cond);
      ReleaseMutex (daemon_mutex);
    }

  return 0;
}

void
_Jv_ThreadStart (java::lang::Thread *thread, _Jv_Thread_t *data, _Jv_ThreadStartFunc *meth)
{
  DWORD id;
  struct starter *info;

  // Do nothing if thread has already started
  if (data->flags & FLAG_START)
    return;
  data->flags |= FLAG_START;

  info = (struct starter *) _Jv_AllocBytes (sizeof (struct starter));
  info->method = meth;
  info->data = data;

  if (! thread->isDaemon ())
    {
      WaitForSingleObject (daemon_mutex, INFINITE);
      non_daemon_count++;
      ReleaseMutex (daemon_mutex);
    }
  else
    data->flags |= FLAG_DAEMON;

  data->handle = GC_CreateThread(NULL, 0, really_start, info, 0, &id);
  _Jv_ThreadSetPriority(data, thread->getPriority());
}

void
_Jv_ThreadWait (void)
{
  WaitForSingleObject (daemon_mutex, INFINITE);
  if (non_daemon_count)
    {
      ReleaseMutex (daemon_mutex);
      WaitForSingleObject (daemon_cond, INFINITE);
    }
}

//
// Interrupt support
//

HANDLE
_Jv_Win32GetInterruptEvent (void)
{
  _Jv_Thread_t *current = _Jv_ThreadCurrentData ();
  EnterCriticalSection (&current->interrupt_mutex);
  ensure_interrupt_event_initialized (current->interrupt_event);
  HANDLE hEvent = current->interrupt_event;
  LeaveCriticalSection (&current->interrupt_mutex);
  return hEvent;
}

void
_Jv_ThreadInterrupt (_Jv_Thread_t *data)
{
  EnterCriticalSection (&data->interrupt_mutex);
  ensure_interrupt_event_initialized (data->interrupt_event);
  data->thread_obj->interrupt_flag = true;
  SetEvent (data->interrupt_event);
  LeaveCriticalSection (&data->interrupt_mutex);
}

// park() / unpark() support

void
ParkHelper::init ()
{
  // We initialize our critical section, but not our event.
  InitializeCriticalSection (&cs);
  event = NULL;
}

void
ParkHelper::init_event()
{
  EnterCriticalSection (&cs);
  if (!event)
    {
      // Create an auto-reset event.
      event = CreateEvent(NULL, 0, 0, NULL);
      if (!event) JvFail("CreateEvent() failed");
    }
  LeaveCriticalSection (&cs);
}

void
ParkHelper::deactivate ()
{
  permit = ::java::lang::Thread::THREAD_PARK_DEAD;
}

void
ParkHelper::destroy()
{
  if (event) CloseHandle (event);
  DeleteCriticalSection (&cs);
}

/**
 * Releases the block on a thread created by _Jv_ThreadPark().  This
 * method can also be used to terminate a blockage caused by a prior
 * call to park.  This operation is unsafe, as the thread must be
 * guaranteed to be live.
 *
 * @param thread the thread to unblock.
 */
void
ParkHelper::unpark ()
{
  using namespace ::java::lang;
  LONG volatile* ptr = &permit;

  // If this thread is in state RUNNING, give it a permit and return
  // immediately.
  if (compare_and_exchange
      (ptr, Thread::THREAD_PARK_RUNNING, Thread::THREAD_PARK_PERMIT))
    return;
  
  // If this thread is parked, put it into state RUNNING and send it a
  // signal.
  if (compare_and_exchange 
      (ptr, Thread::THREAD_PARK_PARKED, Thread::THREAD_PARK_RUNNING))
    {
      init_event ();
      SetEvent (event);
    }
}

/**
 * Blocks the thread until a matching _Jv_ThreadUnpark() occurs, the
 * thread is interrupted or the optional timeout expires.  If an
 * unpark call has already occurred, this also counts.  A timeout
 * value of zero is defined as no timeout.  When isAbsolute is true,
 * the timeout is in milliseconds relative to the epoch.  Otherwise,
 * the value is the number of nanoseconds which must occur before
 * timeout.  This call may also return spuriously (i.e.  for no
 * apparent reason).
 *
 * @param isAbsolute true if the timeout is specified in milliseconds from
 *                   the epoch.
 * @param time either the number of nanoseconds to wait, or a time in
 *             milliseconds from the epoch to wait for.
 */
void
ParkHelper::park (jboolean isAbsolute, jlong time)
{
  using namespace ::java::lang;
  LONG volatile* ptr = &permit;

  // If we have a permit, return immediately.
  if (compare_and_exchange 
      (ptr, Thread::THREAD_PARK_PERMIT, Thread::THREAD_PARK_RUNNING))
    return;

  // Determine the number of milliseconds to wait.
  jlong millis = 0, nanos = 0;
  
  if (time)
    {
      if (isAbsolute)
	{
	  millis = time - ::java::lang::System::currentTimeMillis();
	  nanos = 0;
	}
      else
	{
	  millis = 0;
	  nanos = time;
	}
	
      if (nanos)
        {
          millis += nanos / 1000000;
          if (millis == 0)
            millis = 1;
            // ...otherwise, we'll block indefinitely.
        }
    }
    
  if (millis < 0) return;
      // Can this ever happen?
      
  if (compare_and_exchange 
      (ptr, Thread::THREAD_PARK_RUNNING, Thread::THREAD_PARK_PARKED))
    {
      init_event();
      
      DWORD timeout = millis==0 ? INFINITE : (DWORD) millis;
      WaitForSingleObject (event, timeout);
      
      // If we were unparked by some other thread, this will already
      // be in state THREAD_PARK_RUNNING.  If we timed out, we have to
      // do it ourself.
      compare_and_exchange 
	(ptr, Thread::THREAD_PARK_PARKED, Thread::THREAD_PARK_RUNNING);
    }
}