text: #include "pycore_interp.h"    // _PyInterpreterState.threads.stacksize
  
  /* This code implemented by Dag.Gruneau@elsa.preseco.comm.se */
  /* Fast NonRecursiveMutex support by Yakov Markovitch, markovitch@iso.ru */
  /* Eliminated some memory leaks, gsw@agere.com */
  
  #include <windows.h>
  #include <limits.h>
  #ifdef HAVE_PROCESS_H
  #include <process.h>
  #endif
  
  /* options */
  #ifndef _PY_USE_CV_LOCKS
  #define _PY_USE_CV_LOCKS 1     /* use locks based on cond vars */
  #endif
  
  /* Now, define a non-recursive mutex using either condition variables
   * and critical sections (fast) or using operating system mutexes
   * (slow)
   */
  
  #if _PY_USE_CV_LOCKS
  
  #include "condvar.h"
  
  typedef struct _NRMUTEX
  {
      PyMUTEX_T cs;
      PyCOND_T cv;
      int locked;
  } NRMUTEX;
  typedef NRMUTEX *PNRMUTEX;
  
  static PNRMUTEX
  AllocNonRecursiveMutex(void)
  {
      PNRMUTEX m = (PNRMUTEX)PyMem_RawMalloc(sizeof(NRMUTEX));
      if (!m)
          return NULL;
      if (PyCOND_INIT(&m->cv))
          goto fail;
      if (PyMUTEX_INIT(&m->cs)) {
          PyCOND_FINI(&m->cv);
          goto fail;
      }
      m->locked = 0;
      return m;
  fail:
      PyMem_RawFree(m);
      return NULL;
  }
  
  static VOID
  FreeNonRecursiveMutex(PNRMUTEX mutex)
  {
      if (mutex) {
          PyCOND_FINI(&mutex->cv);
          PyMUTEX_FINI(&mutex->cs);
          PyMem_RawFree(mutex);
      }
  }
  
  static DWORD
  EnterNonRecursiveMutex(PNRMUTEX mutex, DWORD milliseconds)
  {
      DWORD result = WAIT_OBJECT_0;
      if (PyMUTEX_LOCK(&mutex->cs))
          return WAIT_FAILED;
      if (milliseconds == INFINITE) {
          while (mutex->locked) {
              if (PyCOND_WAIT(&mutex->cv, &mutex->cs)) {
                  result = WAIT_FAILED;
                  break;
              }
          }
      } else if (milliseconds != 0) {
          /* wait at least until the deadline */
          _PyTime_t nanoseconds = _PyTime_FromNanoseconds((_PyTime_t)milliseconds * 1000000);
          _PyTime_t deadline = _PyTime_Add(_PyTime_GetPerfCounter(), nanoseconds);
          while (mutex->locked) {
              _PyTime_t microseconds = _PyTime_AsMicroseconds(nanoseconds,
                                                              _PyTime_ROUND_TIMEOUT);
              if (PyCOND_TIMEDWAIT(&mutex->cv, &mutex->cs, microseconds) < 0) {
                  result = WAIT_FAILED;
                  break;
              }
              nanoseconds = deadline - _PyTime_GetPerfCounter();
              if (nanoseconds <= 0) {
                  break;
              }
          }
      }
      if (!mutex->locked) {
          mutex->locked = 1;
          result = WAIT_OBJECT_0;
      } else if (result == WAIT_OBJECT_0)
          result = WAIT_TIMEOUT;
      /* else, it is WAIT_FAILED */
      PyMUTEX_UNLOCK(&mutex->cs); /* must ignore result here */
      return result;
  }
  
  static BOOL
  LeaveNonRecursiveMutex(PNRMUTEX mutex)
  {
      BOOL result;
      if (PyMUTEX_LOCK(&mutex->cs))
          return FALSE;
      mutex->locked = 0;
      /* condvar APIs return 0 on success. We need to return TRUE on success. */
      result = !PyCOND_SIGNAL(&mutex->cv);
      PyMUTEX_UNLOCK(&mutex->cs);
      return result;
  }
  
  #else /* if ! _PY_USE_CV_LOCKS */
  
  /* NR-locks based on a kernel mutex */
  #define PNRMUTEX HANDLE
  
  static PNRMUTEX
  AllocNonRecursiveMutex(void)
  {
      return CreateSemaphore(NULL, 1, 1, NULL);
  }
  
  static VOID
  FreeNonRecursiveMutex(PNRMUTEX mutex)
  {
      /* No in-use check */
      CloseHandle(mutex);
  }
  
  static DWORD
  EnterNonRecursiveMutex(PNRMUTEX mutex, DWORD milliseconds)
  {
      return WaitForSingleObjectEx(mutex, milliseconds, FALSE);
  }
  
  static BOOL
  LeaveNonRecursiveMutex(PNRMUTEX mutex)
  {
      return ReleaseSemaphore(mutex, 1, NULL);
  }
  #endif /* _PY_USE_CV_LOCKS */
  
  unsigned long PyThread_get_thread_ident(void);
  
  #ifdef PY_HAVE_THREAD_NATIVE_ID
  unsigned long PyThread_get_thread_native_id(void);
  #endif
  
  /*
   * Initialization of the C package, should not be needed.
   */
  static void
  PyThread__init_thread(void)
  {
  }
  
  /*
   * Thread support.
   */
  
  typedef struct {
      void (*func)(void*);
      void *arg;
  } callobj;
  
  /* thunker to call adapt between the function type used by the system's
  thread start function and the internally used one. */
  static unsigned __stdcall
  bootstrap(void *call)
  {
      callobj *obj = (callobj*)call;
      void (*func)(void*) = obj->func;
      void *arg = obj->arg;
      HeapFree(GetProcessHeap(), 0, obj);
      func(arg);
      return 0;
  }
  
  unsigned long
  PyThread_start_new_thread(void (*func)(void *), void *arg)
  {
      HANDLE hThread;
      unsigned threadID;
      callobj *obj;
  
      if (!initialized)
          PyThread_init_thread();
  
      obj = (callobj*)HeapAlloc(GetProcessHeap(), 0, sizeof(*obj));
      if (!obj)
          return PYTHREAD_INVALID_THREAD_ID;
      obj->func = func;
      obj->arg = arg;
      PyThreadState *tstate = _PyThreadState_GET();
      size_t stacksize = tstate ? tstate->interp->threads.stacksize : 0;
      hThread = (HANDLE)_beginthreadex(0,
                        Py_SAFE_DOWNCAST(stacksize, Py_ssize_t, unsigned int),
                        bootstrap, obj,
                        0, &threadID);
      if (hThread == 0) {
          /* I've seen errno == EAGAIN here, which means "there are
           * too many threads".
           */
          int e = errno;
          threadID = (unsigned)-1;
          HeapFree(GetProcessHeap(), 0, obj);
      }
      else {
          CloseHandle(hThread);
      }
      return threadID;
  }
  
  /*
   * Return the thread Id instead of a handle. The Id is said to uniquely identify the
   * thread in the system
   */
  unsigned long
  PyThread_get_thread_ident(void)
  {
      if (!initialized)
          PyThread_init_thread();
  
      return GetCurrentThreadId();
  }
  
  #ifdef PY_HAVE_THREAD_NATIVE_ID
  /*
   * Return the native Thread ID (TID) of the calling thread.
   * The native ID of a thread is valid and guaranteed to be unique system-wide
   * from the time the thread is created until the thread has been terminated.
   */
  unsigned long
  PyThread_get_thread_native_id(void)
  {
      if (!initialized) {
          PyThread_init_thread();
      }
  
      DWORD native_id;
      native_id = GetCurrentThreadId();
      return (unsigned long) native_id;
  }
  #endif
  
  void _Py_NO_RETURN
  PyThread_exit_thread(void)
  {
      if (!initialized)
          exit(0);
      _endthreadex(0);
  }
  
  /*
   * Lock support. It has to be implemented as semaphores.
   * I [Dag] tried to implement it with mutex but I could find a way to
   * tell whether a thread already own the lock or not.
   */
  PyThread_type_lock
  PyThread_allocate_lock(void)
  {
      PNRMUTEX mutex;
  
      if (!initialized)
          PyThread_init_thread();
  
      mutex = AllocNonRecursiveMutex() ;
  
      PyThread_type_lock aLock = (PyThread_type_lock) mutex;
      assert(aLock);
  
      return aLock;
  }
  
  void
  PyThread_free_lock(PyThread_type_lock aLock)
  {
      FreeNonRecursiveMutex(aLock) ;
  }
  
  // WaitForSingleObject() accepts timeout in milliseconds in the range
  // [0; 0xFFFFFFFE] (DWORD type). INFINITE value (0xFFFFFFFF) means no
  // timeout. 0xFFFFFFFE milliseconds is around 49.7 days.
  const DWORD TIMEOUT_MS_MAX = 0xFFFFFFFE;
  
  /*
   * Return 1 on success if the lock was acquired
   *
   * and 0 if the lock was not acquired. This means a 0 is returned
   * if the lock has already been acquired by this thread!
   */
  PyLockStatus
  PyThread_acquire_lock_timed(PyThread_type_lock aLock,
                              PY_TIMEOUT_T microseconds, int intr_flag)
  {
      assert(aLock);
  
      /* Fow now, intr_flag does nothing on Windows, and lock acquires are
       * uninterruptible.  */
      PyLockStatus success;
      PY_TIMEOUT_T milliseconds;
  
      if (microseconds >= 0) {
          milliseconds = microseconds / 1000;
          // Round milliseconds away from zero
          if (microseconds % 1000 > 0) {
              milliseconds++;
          }
          if (milliseconds > (PY_TIMEOUT_T)TIMEOUT_MS_MAX) {
              // bpo-41710: PyThread_acquire_lock_timed() cannot report timeout
              // overflow to the caller, so clamp the timeout to
              // [0, TIMEOUT_MS_MAX] milliseconds.
              //
              // _thread.Lock.acquire() and _thread.RLock.acquire() raise an
              // OverflowError if microseconds is greater than PY_TIMEOUT_MAX.
              milliseconds = TIMEOUT_MS_MAX;
          }
          assert(milliseconds != INFINITE);
      }
      else {
          milliseconds = INFINITE;
      }
  
      if (EnterNonRecursiveMutex((PNRMUTEX)aLock,
                                 (DWORD)milliseconds) == WAIT_OBJECT_0) {
          success = PY_LOCK_ACQUIRED;
      }
      else {
          success = PY_LOCK_FAILURE;
      }
  
      return success;
  }
  int
  PyThread_acquire_lock(PyThread_type_lock aLock, int waitflag)
  {
      return PyThread_acquire_lock_timed(aLock, waitflag ? -1 : 0, 0);
  }
  
  void
  PyThread_release_lock(PyThread_type_lock aLock)
  {
      assert(aLock);
      (void)LeaveNonRecursiveMutex((PNRMUTEX) aLock);
  }
  
  /* minimum/maximum thread stack sizes supported */
  #define THREAD_MIN_STACKSIZE    0x8000          /* 32 KiB */
  #define THREAD_MAX_STACKSIZE    0x10000000      /* 256 MiB */
  
  /* set the thread stack size.
   * Return 0 if size is valid, -1 otherwise.
   */
  static int
  _pythread_nt_set_stacksize(size_t size)
  {
      /* set to default */
      if (size == 0) {
          _PyInterpreterState_GET()->threads.stacksize = 0;
          return 0;
      }
  
      /* valid range? */
      if (size >= THREAD_MIN_STACKSIZE && size < THREAD_MAX_STACKSIZE) {
          _PyInterpreterState_GET()->threads.stacksize = size;
          return 0;
      }
  
      return -1;
  }
  
  #define THREAD_SET_STACKSIZE(x) _pythread_nt_set_stacksize(x)
  
  
  /* Thread Local Storage (TLS) API
  
     This API is DEPRECATED since Python 3.7.  See PEP 539 for details.
  */
  
  int
  PyThread_create_key(void)
  {
      DWORD result = TlsAlloc();
      if (result == TLS_OUT_OF_INDEXES)
          return -1;
      return (int)result;
  }
  
  void
  PyThread_delete_key(int key)
  {
      TlsFree(key);
  }
  
  int
  PyThread_set_key_value(int key, void *value)
  {
      BOOL ok = TlsSetValue(key, value);
      return ok ? 0 : -1;
  }
  
  void *
  PyThread_get_key_value(int key)
  {
      /* because TLS is used in the Py_END_ALLOW_THREAD macro,
       * it is necessary to preserve the windows error state, because
       * it is assumed to be preserved across the call to the macro.
       * Ideally, the macro should be fixed, but it is simpler to
       * do it here.
       */
      DWORD error = GetLastError();
      void *result = TlsGetValue(key);
      SetLastError(error);
      return result;
  }
  
  void
  PyThread_delete_key_value(int key)
  {
      /* NULL is used as "key missing", and it is also the default
       * given by TlsGetValue() if nothing has been set yet.
       */
      TlsSetValue(key, NULL);
  }
  
  
  /* reinitialization of TLS is not necessary after fork when using
   * the native TLS functions.  And forking isn't supported on Windows either.
   */
  void
  PyThread_ReInitTLS(void)
  {
  }
  
  
  /* Thread Specific Storage (TSS) API
  
     Platform-specific components of TSS API implementation.
  */
  
  int
  PyThread_tss_create(Py_tss_t *key)
  {
      assert(key != NULL);
      /* If the key has been created, function is silently skipped. */
      if (key->_is_initialized) {
          return 0;
      }
  
      DWORD result = TlsAlloc();
      if (result == TLS_OUT_OF_INDEXES) {
          return -1;
      }
      /* In Windows, platform-specific key type is DWORD. */
      key->_key = result;
      key->_is_initialized = 1;
      return 0;
  }
  
  void
  PyThread_tss_delete(Py_tss_t *key)
  {
      assert(key != NULL);
      /* If the key has not been created, function is silently skipped. */
      if (!key->_is_initialized) {
          return;
      }
  
      TlsFree(key->_key);
      key->_key = TLS_OUT_OF_INDEXES;
      key->_is_initialized = 0;
  }
  
  int
  PyThread_tss_set(Py_tss_t *key, void *value)
  {
      assert(key != NULL);
      BOOL ok = TlsSetValue(key->_key, value);
      return ok ? 0 : -1;
  }
  
  void *
  PyThread_tss_get(Py_tss_t *key)
  {
      assert(key != NULL);
      /* because TSS is used in the Py_END_ALLOW_THREAD macro,
       * it is necessary to preserve the windows error state, because
       * it is assumed to be preserved across the call to the macro.
       * Ideally, the macro should be fixed, but it is simpler to
       * do it here.
       */
      DWORD error = GetLastError();
      void *result = TlsGetValue(key->_key);
      SetLastError(error);
      return result;
  }
  