ruby--ruby/thread_win32.c

/* -*-c-*- */
/**********************************************************************

  thread_win32.c -

  $Author$

  Copyright (C) 2004-2007 Koichi Sasada

**********************************************************************/

#ifdef THREAD_SYSTEM_DEPENDENT_IMPLEMENTATION

#include <process.h>

#define TIME_QUANTUM_USEC (10 * 1000)
#define RB_CONDATTR_CLOCK_MONOTONIC 1 /* no effect */

#undef Sleep

#define native_thread_yield() Sleep(0)
#define unregister_ubf_list(th)
#define ubf_wakeup_all_threads() do {} while (0)
#define ubf_threads_empty() (1)
#define ubf_timer_disarm() do {} while (0)
#define ubf_list_atfork() do {} while (0)

static volatile DWORD ruby_native_thread_key = TLS_OUT_OF_INDEXES;

static int w32_wait_events(HANDLE *events, int count, DWORD timeout, rb_thread_t *th);

static void
w32_error(const char *func)
{
    LPVOID lpMsgBuf;
    DWORD err = GetLastError();
    if (FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
		      FORMAT_MESSAGE_FROM_SYSTEM |
		      FORMAT_MESSAGE_IGNORE_INSERTS,
		      NULL,
		      err,
		      MAKELANGID(LANG_ENGLISH, SUBLANG_ENGLISH_US),
		      (LPTSTR) & lpMsgBuf, 0, NULL) == 0)
	FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
		      FORMAT_MESSAGE_FROM_SYSTEM |
		      FORMAT_MESSAGE_IGNORE_INSERTS,
		      NULL,
		      err,
		      MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
		      (LPTSTR) & lpMsgBuf, 0, NULL);
    rb_bug("%s: %s", func, (char*)lpMsgBuf);
}

static int
w32_mutex_lock(HANDLE lock, bool try)
{
    DWORD result;
    while (1) {
        thread_debug("rb_native_mutex_lock: %p\n", lock);
        result = w32_wait_events(&lock, 1, try ? 0 : INFINITE, 0);
	switch (result) {
	  case WAIT_OBJECT_0:
	    /* get mutex object */
	    thread_debug("acquire mutex: %p\n", lock);
	    return 0;
	  case WAIT_OBJECT_0 + 1:
	    /* interrupt */
	    errno = EINTR;
	    thread_debug("acquire mutex interrupted: %p\n", lock);
	    return 0;
	  case WAIT_TIMEOUT:
	    thread_debug("timeout mutex: %p\n", lock);
            return EBUSY;
	  case WAIT_ABANDONED:
	    rb_bug("win32_mutex_lock: WAIT_ABANDONED");
	    break;
	  default:
	    rb_bug("win32_mutex_lock: unknown result (%ld)", result);
	    break;
	}
    }
    return 0;
}

static HANDLE
w32_mutex_create(void)
{
    HANDLE lock = CreateMutex(NULL, FALSE, NULL);
    if (lock == NULL) {
        w32_error("rb_native_mutex_initialize");
    }
    return lock;
}

#define GVL_DEBUG 0

static void
gvl_acquire(rb_global_vm_lock_t *gvl, rb_thread_t *th)
{
    w32_mutex_lock(gvl->lock, false);
    if (GVL_DEBUG) fprintf(stderr, "gvl acquire (%p): acquire\n", th);
}

static void
gvl_release(rb_global_vm_lock_t *gvl)
{
    ReleaseMutex(gvl->lock);
}

static void
gvl_yield(rb_global_vm_lock_t *gvl, rb_thread_t *th)
{
  gvl_release(gvl);
  native_thread_yield();
  gvl_acquire(gvl, th);
}

void
rb_gvl_init(rb_global_vm_lock_t *gvl)
{
    if (GVL_DEBUG) fprintf(stderr, "gvl init\n");
    gvl->lock = w32_mutex_create();
}

static void
gvl_destroy(rb_global_vm_lock_t *gvl)
{
    if (GVL_DEBUG) fprintf(stderr, "gvl destroy\n");
    CloseHandle(gvl->lock);
}

static rb_thread_t *
ruby_thread_from_native(void)
{
    return TlsGetValue(ruby_native_thread_key);
}

static int
ruby_thread_set_native(rb_thread_t *th)
{
    if (th && th->ec) {
        rb_ractor_set_current_ec(th->ractor, th->ec);
    }
    return TlsSetValue(ruby_native_thread_key, th);
}

void
Init_native_thread(rb_thread_t *th)
{
    if ((ruby_current_ec_key = TlsAlloc()) == TLS_OUT_OF_INDEXES) {
        rb_bug("TlsAlloc() for ruby_current_ec_key fails");
    }
    if ((ruby_native_thread_key = TlsAlloc()) == TLS_OUT_OF_INDEXES) {
        rb_bug("TlsAlloc() for ruby_native_thread_key fails");
    }
    ruby_thread_set_native(th);
    DuplicateHandle(GetCurrentProcess(),
		    GetCurrentThread(),
		    GetCurrentProcess(),
		    &th->thread_id, 0, FALSE, DUPLICATE_SAME_ACCESS);

    th->native_thread_data.interrupt_event = CreateEvent(0, TRUE, FALSE, 0);

    thread_debug("initial thread (th: %p, thid: %p, event: %p)\n",
		 th, GET_THREAD()->thread_id,
		 th->native_thread_data.interrupt_event);
}

static int
w32_wait_events(HANDLE *events, int count, DWORD timeout, rb_thread_t *th)
{
    HANDLE *targets = events;
    HANDLE intr;
    const int initcount = count;
    DWORD ret;

    thread_debug("  w32_wait_events events:%p, count:%d, timeout:%ld, th:%p\n",
		 events, count, timeout, th);
    if (th && (intr = th->native_thread_data.interrupt_event)) {
	if (ResetEvent(intr) && (!RUBY_VM_INTERRUPTED(th->ec) || SetEvent(intr))) {
	    targets = ALLOCA_N(HANDLE, count + 1);
	    memcpy(targets, events, sizeof(HANDLE) * count);

	    targets[count++] = intr;
	    thread_debug("  * handle: %p (count: %d, intr)\n", intr, count);
	}
	else if (intr == th->native_thread_data.interrupt_event) {
	    w32_error("w32_wait_events");
	}
    }

    thread_debug("  WaitForMultipleObjects start (count: %d)\n", count);
    ret = WaitForMultipleObjects(count, targets, FALSE, timeout);
    thread_debug("  WaitForMultipleObjects end (ret: %lu)\n", ret);

    if (ret == (DWORD)(WAIT_OBJECT_0 + initcount) && th) {
	errno = EINTR;
    }
    if (ret == WAIT_FAILED && THREAD_DEBUG) {
	int i;
	DWORD dmy;
	for (i = 0; i < count; i++) {
	    thread_debug("  * error handle %d - %s\n", i,
			 GetHandleInformation(targets[i], &dmy) ? "OK" : "NG");
	}
    }
    return ret;
}

static void ubf_handle(void *ptr);
#define ubf_select ubf_handle

int
rb_w32_wait_events_blocking(HANDLE *events, int num, DWORD timeout)
{
    return w32_wait_events(events, num, timeout, ruby_thread_from_native());
}

int
rb_w32_wait_events(HANDLE *events, int num, DWORD timeout)
{
    int ret;
    rb_thread_t *th = GET_THREAD();

    BLOCKING_REGION(th, ret = rb_w32_wait_events_blocking(events, num, timeout),
		    ubf_handle, ruby_thread_from_native(), FALSE);
    return ret;
}

static void
w32_close_handle(HANDLE handle)
{
    if (CloseHandle(handle) == 0) {
	w32_error("w32_close_handle");
    }
}

static void
w32_resume_thread(HANDLE handle)
{
    if (ResumeThread(handle) == (DWORD)-1) {
	w32_error("w32_resume_thread");
    }
}

#ifdef _MSC_VER
#define HAVE__BEGINTHREADEX 1
#else
#undef HAVE__BEGINTHREADEX
#endif

#ifdef HAVE__BEGINTHREADEX
#define start_thread (HANDLE)_beginthreadex
#define thread_errno errno
typedef unsigned long (__stdcall *w32_thread_start_func)(void*);
#else
#define start_thread CreateThread
#define thread_errno rb_w32_map_errno(GetLastError())
typedef LPTHREAD_START_ROUTINE w32_thread_start_func;
#endif

static HANDLE
w32_create_thread(DWORD stack_size, w32_thread_start_func func, void *val)
{
    return start_thread(0, stack_size, func, val, CREATE_SUSPENDED | STACK_SIZE_PARAM_IS_A_RESERVATION, 0);
}

int
rb_w32_sleep(unsigned long msec)
{
    return w32_wait_events(0, 0, msec, ruby_thread_from_native());
}

int WINAPI
rb_w32_Sleep(unsigned long msec)
{
    int ret;
    rb_thread_t *th = GET_THREAD();

    BLOCKING_REGION(th, ret = rb_w32_sleep(msec),
		    ubf_handle, ruby_thread_from_native(), FALSE);
    return ret;
}

static DWORD
hrtime2msec(rb_hrtime_t hrt)
{
    return (DWORD)hrt / (DWORD)RB_HRTIME_PER_MSEC;
}

static void
native_sleep(rb_thread_t *th, rb_hrtime_t *rel)
{
    const volatile DWORD msec = rel ? hrtime2msec(*rel) : INFINITE;

    GVL_UNLOCK_BEGIN(th);
    {
	DWORD ret;

        rb_native_mutex_lock(&th->interrupt_lock);
	th->unblock.func = ubf_handle;
	th->unblock.arg = th;
        rb_native_mutex_unlock(&th->interrupt_lock);

	if (RUBY_VM_INTERRUPTED(th->ec)) {
	    /* interrupted.  return immediate */
	}
	else {
	    thread_debug("native_sleep start (%lu)\n", msec);
	    ret = w32_wait_events(0, 0, msec, th);
	    thread_debug("native_sleep done (%lu)\n", ret);
	}

        rb_native_mutex_lock(&th->interrupt_lock);
	th->unblock.func = 0;
	th->unblock.arg = 0;
        rb_native_mutex_unlock(&th->interrupt_lock);
    }
    GVL_UNLOCK_END(th);
}

void
rb_native_mutex_lock(rb_nativethread_lock_t *lock)
{
#if USE_WIN32_MUTEX
    w32_mutex_lock(lock->mutex, false);
#else
    EnterCriticalSection(&lock->crit);
#endif
}

int
rb_native_mutex_trylock(rb_nativethread_lock_t *lock)
{
#if USE_WIN32_MUTEX
    return w32_mutex_lock(lock->mutex, true);
#else
    return TryEnterCriticalSection(&lock->crit) == 0 ? EBUSY : 0;
#endif
}

void
rb_native_mutex_unlock(rb_nativethread_lock_t *lock)
{
#if USE_WIN32_MUTEX
    thread_debug("release mutex: %p\n", lock->mutex);
    ReleaseMutex(lock->mutex);
#else
    LeaveCriticalSection(&lock->crit);
#endif
}

void
rb_native_mutex_initialize(rb_nativethread_lock_t *lock)
{
#if USE_WIN32_MUTEX
    lock->mutex = w32_mutex_create();
    /* thread_debug("initialize mutex: %p\n", lock->mutex); */
#else
    InitializeCriticalSection(&lock->crit);
#endif
}

void
rb_native_mutex_destroy(rb_nativethread_lock_t *lock)
{
#if USE_WIN32_MUTEX
    w32_close_handle(lock->mutex);
#else
    DeleteCriticalSection(&lock->crit);
#endif
}

struct cond_event_entry {
    struct cond_event_entry* next;
    struct cond_event_entry* prev;
    HANDLE event;
};

void
rb_native_cond_signal(rb_nativethread_cond_t *cond)
{
    /* cond is guarded by mutex */
    struct cond_event_entry *e = cond->next;
    struct cond_event_entry *head = (struct cond_event_entry*)cond;

    if (e != head) {
	struct cond_event_entry *next = e->next;
	struct cond_event_entry *prev = e->prev;

	prev->next = next;
	next->prev = prev;
	e->next = e->prev = e;

	SetEvent(e->event);
    }
}

void
rb_native_cond_broadcast(rb_nativethread_cond_t *cond)
{
    /* cond is guarded by mutex */
    struct cond_event_entry *e = cond->next;
    struct cond_event_entry *head = (struct cond_event_entry*)cond;

    while (e != head) {
	struct cond_event_entry *next = e->next;
	struct cond_event_entry *prev = e->prev;

	SetEvent(e->event);

	prev->next = next;
	next->prev = prev;
	e->next = e->prev = e;

	e = next;
    }
}

static int
native_cond_timedwait_ms(rb_nativethread_cond_t *cond, rb_nativethread_lock_t *mutex, unsigned long msec)
{
    DWORD r;
    struct cond_event_entry entry;
    struct cond_event_entry *head = (struct cond_event_entry*)cond;

    entry.event = CreateEvent(0, FALSE, FALSE, 0);

    /* cond is guarded by mutex */
    entry.next = head;
    entry.prev = head->prev;
    head->prev->next = &entry;
    head->prev = &entry;

    rb_native_mutex_unlock(mutex);
    {
	r = WaitForSingleObject(entry.event, msec);
	if ((r != WAIT_OBJECT_0) && (r != WAIT_TIMEOUT)) {
            rb_bug("rb_native_cond_wait: WaitForSingleObject returns %lu", r);
	}
    }
    rb_native_mutex_lock(mutex);

    entry.prev->next = entry.next;
    entry.next->prev = entry.prev;

    w32_close_handle(entry.event);
    return (r == WAIT_OBJECT_0) ? 0 : ETIMEDOUT;
}

void
rb_native_cond_wait(rb_nativethread_cond_t *cond, rb_nativethread_lock_t *mutex)
{
    native_cond_timedwait_ms(cond, mutex, INFINITE);
}

static unsigned long
abs_timespec_to_timeout_ms(const struct timespec *ts)
{
    struct timeval tv;
    struct timeval now;

    gettimeofday(&now, NULL);
    tv.tv_sec = ts->tv_sec;
    tv.tv_usec = ts->tv_nsec / 1000;

    if (!rb_w32_time_subtract(&tv, &now))
	return 0;

    return (tv.tv_sec * 1000) + (tv.tv_usec / 1000);
}

static int
native_cond_timedwait(rb_nativethread_cond_t *cond, rb_nativethread_lock_t *mutex, const struct timespec *ts)
{
    unsigned long timeout_ms;

    timeout_ms = abs_timespec_to_timeout_ms(ts);
    if (!timeout_ms)
	return ETIMEDOUT;

    return native_cond_timedwait_ms(cond, mutex, timeout_ms);
}

static struct timespec native_cond_timeout(rb_nativethread_cond_t *cond, struct timespec timeout_rel);

void
rb_native_cond_timedwait(rb_nativethread_cond_t *cond, rb_nativethread_lock_t *mutex, unsigned long msec)
{
    struct timespec rel = {
        .tv_sec = msec / 1000,
        .tv_nsec = (msec % 1000) * 1000 * 1000,
    };
    struct timespec ts = native_cond_timeout(cond, rel);
    native_cond_timedwait(cond, mutex, &ts);
}

static struct timespec
native_cond_timeout(rb_nativethread_cond_t *cond, struct timespec timeout_rel)
{
    int ret;
    struct timeval tv;
    struct timespec timeout;
    struct timespec now;

    ret = gettimeofday(&tv, 0);
    if (ret != 0)
	rb_sys_fail(0);
    now.tv_sec = tv.tv_sec;
    now.tv_nsec = tv.tv_usec * 1000;

    timeout.tv_sec = now.tv_sec;
    timeout.tv_nsec = now.tv_nsec;
    timeout.tv_sec += timeout_rel.tv_sec;
    timeout.tv_nsec += timeout_rel.tv_nsec;

    if (timeout.tv_nsec >= 1000*1000*1000) {
	timeout.tv_sec++;
	timeout.tv_nsec -= 1000*1000*1000;
    }

    if (timeout.tv_sec < now.tv_sec)
	timeout.tv_sec = TIMET_MAX;

    return timeout;
}

void
rb_native_cond_initialize(rb_nativethread_cond_t *cond)
{
    cond->next = (struct cond_event_entry *)cond;
    cond->prev = (struct cond_event_entry *)cond;
}

void
rb_native_cond_destroy(rb_nativethread_cond_t *cond)
{
    /* */
}

void
ruby_init_stack(volatile VALUE *addr)
{
}

#define CHECK_ERR(expr) \
    {if (!(expr)) {rb_bug("err: %lu - %s", GetLastError(), #expr);}}

static void
native_thread_init_stack(rb_thread_t *th)
{
    MEMORY_BASIC_INFORMATION mi;
    char *base, *end;
    DWORD size, space;

    CHECK_ERR(VirtualQuery(&mi, &mi, sizeof(mi)));
    base = mi.AllocationBase;
    end = mi.BaseAddress;
    end += mi.RegionSize;
    size = end - base;
    space = size / 5;
    if (space > 1024*1024) space = 1024*1024;
    th->ec->machine.stack_start = (VALUE *)end - 1;
    th->ec->machine.stack_maxsize = size - space;
}

#ifndef InterlockedExchangePointer
#define InterlockedExchangePointer(t, v) \
    (void *)InterlockedExchange((long *)(t), (long)(v))
#endif
static void
native_thread_destroy(rb_thread_t *th)
{
    HANDLE intr = InterlockedExchangePointer(&th->native_thread_data.interrupt_event, 0);
    thread_debug("close handle - intr: %p, thid: %p\n", intr, th->thread_id);
    w32_close_handle(intr);
}

static unsigned long __stdcall
thread_start_func_1(void *th_ptr)
{
    rb_thread_t *th = th_ptr;
    volatile HANDLE thread_id = th->thread_id;

    native_thread_init_stack(th);
    th->native_thread_data.interrupt_event = CreateEvent(0, TRUE, FALSE, 0);

    /* run */
    thread_debug("thread created (th: %p, thid: %p, event: %p)\n", th,
		 th->thread_id, th->native_thread_data.interrupt_event);

    thread_start_func_2(th, th->ec->machine.stack_start);

    w32_close_handle(thread_id);
    thread_debug("thread deleted (th: %p)\n", th);
    return 0;
}

static int
native_thread_create(rb_thread_t *th)
{
    const size_t stack_size = th->vm->default_params.thread_machine_stack_size + th->vm->default_params.thread_vm_stack_size;
    th->thread_id = w32_create_thread(stack_size, thread_start_func_1, th);

    if ((th->thread_id) == 0) {
	return thread_errno;
    }

    w32_resume_thread(th->thread_id);

    if (THREAD_DEBUG) {
	Sleep(0);
	thread_debug("create: (th: %p, thid: %p, intr: %p), stack size: %"PRIuSIZE"\n",
		     th, th->thread_id,
		     th->native_thread_data.interrupt_event, stack_size);
    }
    return 0;
}

static void
native_thread_join(HANDLE th)
{
    w32_wait_events(&th, 1, INFINITE, 0);
}

#if USE_NATIVE_THREAD_PRIORITY

static void
native_thread_apply_priority(rb_thread_t *th)
{
    int priority = th->priority;
    if (th->priority > 0) {
	priority = THREAD_PRIORITY_ABOVE_NORMAL;
    }
    else if (th->priority < 0) {
	priority = THREAD_PRIORITY_BELOW_NORMAL;
    }
    else {
	priority = THREAD_PRIORITY_NORMAL;
    }

    SetThreadPriority(th->thread_id, priority);
}

#endif /* USE_NATIVE_THREAD_PRIORITY */

int rb_w32_select_with_thread(int, fd_set *, fd_set *, fd_set *, struct timeval *, void *);	/* @internal */

static int
native_fd_select(int n, rb_fdset_t *readfds, rb_fdset_t *writefds, rb_fdset_t *exceptfds, struct timeval *timeout, rb_thread_t *th)
{
    fd_set *r = NULL, *w = NULL, *e = NULL;
    if (readfds) {
        rb_fd_resize(n - 1, readfds);
        r = rb_fd_ptr(readfds);
    }
    if (writefds) {
        rb_fd_resize(n - 1, writefds);
        w = rb_fd_ptr(writefds);
    }
    if (exceptfds) {
        rb_fd_resize(n - 1, exceptfds);
        e = rb_fd_ptr(exceptfds);
    }
    return rb_w32_select_with_thread(n, r, w, e, timeout, th);
}

/* @internal */
int
rb_w32_check_interrupt(rb_thread_t *th)
{
    return w32_wait_events(0, 0, 0, th);
}

static void
ubf_handle(void *ptr)
{
    rb_thread_t *th = (rb_thread_t *)ptr;
    thread_debug("ubf_handle: %p\n", th);

    if (!SetEvent(th->native_thread_data.interrupt_event)) {
	w32_error("ubf_handle");
    }
}

int rb_w32_set_thread_description(HANDLE th, const WCHAR *name);
int rb_w32_set_thread_description_str(HANDLE th, VALUE name);
#define native_set_another_thread_name rb_w32_set_thread_description_str

static struct {
    HANDLE id;
    HANDLE lock;
} timer_thread;
#define TIMER_THREAD_CREATED_P() (timer_thread.id != 0)

static unsigned long __stdcall
timer_thread_func(void *dummy)
{
    rb_vm_t *vm = GET_VM();
    thread_debug("timer_thread\n");
    rb_w32_set_thread_description(GetCurrentThread(), L"ruby-timer-thread");
    while (WaitForSingleObject(timer_thread.lock,
                               TIME_QUANTUM_USEC/1000) == WAIT_TIMEOUT) {
        vm->clock++;
	ruby_sigchld_handler(vm); /* probably no-op */
	rb_threadptr_check_signal(vm->ractor.main_thread);
    }
    thread_debug("timer killed\n");
    return 0;
}

void
rb_thread_wakeup_timer_thread(int sig)
{
    /* do nothing */
}

static VALUE
rb_thread_start_unblock_thread(void)
{
    return Qfalse; /* no-op */
}

static void
rb_thread_create_timer_thread(void)
{
    if (timer_thread.id == 0) {
	if (!timer_thread.lock) {
	    timer_thread.lock = CreateEvent(0, TRUE, FALSE, 0);
	}
	timer_thread.id = w32_create_thread(1024 + (THREAD_DEBUG ? BUFSIZ : 0),
					    timer_thread_func, 0);
	w32_resume_thread(timer_thread.id);
    }
}

static int
native_stop_timer_thread(void)
{
    int stopped = --system_working <= 0;
    if (stopped) {
	SetEvent(timer_thread.lock);
	native_thread_join(timer_thread.id);
	CloseHandle(timer_thread.lock);
	timer_thread.lock = 0;
    }
    return stopped;
}

static void
native_reset_timer_thread(void)
{
    if (timer_thread.id) {
	CloseHandle(timer_thread.id);
	timer_thread.id = 0;
    }
}

int
ruby_stack_overflowed_p(const rb_thread_t *th, const void *addr)
{
    return rb_ec_raised_p(th->ec, RAISED_STACKOVERFLOW);
}

#if defined(__MINGW32__)
LONG WINAPI
rb_w32_stack_overflow_handler(struct _EXCEPTION_POINTERS *exception)
{
    if (exception->ExceptionRecord->ExceptionCode == EXCEPTION_STACK_OVERFLOW) {
	rb_ec_raised_set(GET_EC(), RAISED_STACKOVERFLOW);
	raise(SIGSEGV);
    }
    return EXCEPTION_CONTINUE_SEARCH;
}
#endif

#ifdef RUBY_ALLOCA_CHKSTK
void
ruby_alloca_chkstk(size_t len, void *sp)
{
    if (ruby_stack_length(NULL) * sizeof(VALUE) >= len) {
	rb_execution_context_t *ec = GET_EC();
	if (!rb_ec_raised_p(ec, RAISED_STACKOVERFLOW)) {
	    rb_ec_raised_set(ec, RAISED_STACKOVERFLOW);
	    rb_exc_raise(sysstack_error);
	}
    }
}
#endif
int
rb_reserved_fd_p(int fd)
{
    return 0;
}

int
rb_sigwait_fd_get(rb_thread_t *th)
{
    return -1; /* TODO */
}

NORETURN(void rb_sigwait_fd_put(rb_thread_t *, int));
void
rb_sigwait_fd_put(rb_thread_t *th, int fd)
{
    rb_bug("not implemented, should not be called");
}

NORETURN(void rb_sigwait_sleep(const rb_thread_t *, int, const rb_hrtime_t *));
void
rb_sigwait_sleep(const rb_thread_t *th, int fd, const rb_hrtime_t *rel)
{
    rb_bug("not implemented, should not be called");
}

rb_nativethread_id_t
rb_nativethread_self(void)
{
    return GetCurrentThread();
}

static void
native_set_thread_name(rb_thread_t *th)
{
}

#if USE_MJIT
static unsigned long __stdcall
mjit_worker(void *arg)
{
    void (*worker_func)(void) = arg;
    rb_w32_set_thread_description(GetCurrentThread(), L"ruby-mjitworker");
    worker_func();
    return 0;
}

/* Launch MJIT thread. Returns FALSE if it fails to create thread. */
int
rb_thread_create_mjit_thread(void (*worker_func)(void))
{
    size_t stack_size = 4 * 1024; /* 4KB is the minimum commit size */
    HANDLE thread_id = w32_create_thread(stack_size, mjit_worker, worker_func);
    if (thread_id == 0) {
        return FALSE;
    }

    w32_resume_thread(thread_id);
    return TRUE;
}
#endif

#endif /* THREAD_SYSTEM_DEPENDENT_IMPLEMENTATION */