ruby--ruby/thread.c

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

  thread.c -

  $Author$

  Copyright (C) 2004-2007 Koichi Sasada

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

/*
  YARV Thread Desgin

  model 1: Userlevel Thread
    Same as traditional ruby thread.

  model 2: Native Thread with Giant VM lock
    Using pthread (or Windows thread) and Ruby threads run concurrent.

  model 3: Native Thread with fine grain lock
    Using pthread and Ruby threads run concurrent or parallel.

------------------------------------------------------------------------

  model 2:
    A thread has mutex (GVL: Global VM Lock) can run.  When thread
    scheduling, running thread release GVL.  If running thread
    try blocking operation, this thread must release GVL and another
    thread can continue this flow.  After blocking operation, thread
    must check interrupt (RUBY_VM_CHECK_INTS).

    Every VM can run parallel.

    Ruby threads are scheduled by OS thread scheduler.

------------------------------------------------------------------------

  model 3:
    Every threads run concurrent or parallel and to access shared object
    exclusive access control is needed.  For example, to access String
    object or Array object, fine grain lock must be locked every time.
 */


/* for model 2 */

#include "eval_intern.h"
#include "gc.h"

#ifndef USE_NATIVE_THREAD_PRIORITY
#define USE_NATIVE_THREAD_PRIORITY 0
#define RUBY_THREAD_PRIORITY_MAX 3
#define RUBY_THREAD_PRIORITY_MIN -3
#endif

#ifndef THREAD_DEBUG
#define THREAD_DEBUG 0
#endif

VALUE rb_cMutex;
VALUE rb_cBarrier;

static void sleep_timeval(rb_thread_t *th, struct timeval time);
static void sleep_wait_for_interrupt(rb_thread_t *th, double sleepsec);
static void sleep_forever(rb_thread_t *th, int nodeadlock);
static double timeofday(void);
struct timeval rb_time_interval(VALUE);
static int rb_thread_dead(rb_thread_t *th);

static void rb_check_deadlock(rb_vm_t *vm);

void rb_signal_exec(rb_thread_t *th, int sig);
void rb_disable_interrupt(void);
void rb_thread_stop_timer_thread(void);

static const VALUE eKillSignal = INT2FIX(0);
static const VALUE eTerminateSignal = INT2FIX(1);
static volatile int system_working = 1;

inline static void
st_delete_wrap(st_table *table, st_data_t key)
{
    st_delete(table, &key, 0);
}

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

#define THREAD_SYSTEM_DEPENDENT_IMPLEMENTATION

struct rb_blocking_region_buffer {
    enum rb_thread_status prev_status;
    struct rb_unblock_callback oldubf;
};

static void set_unblock_function(rb_thread_t *th, rb_unblock_function_t *func, void *arg,
				 struct rb_unblock_callback *old);
static void reset_unblock_function(rb_thread_t *th, const struct rb_unblock_callback *old);

static void inline blocking_region_begin(rb_thread_t *th, struct rb_blocking_region_buffer *region,
					 rb_unblock_function_t *func, void *arg);
static void inline blocking_region_end(rb_thread_t *th, struct rb_blocking_region_buffer *region);

#define GVL_UNLOCK_BEGIN() do { \
  rb_thread_t *_th_stored = GET_THREAD(); \
  rb_gc_save_machine_context(_th_stored); \
  native_mutex_unlock(&_th_stored->vm->global_vm_lock)

#define GVL_UNLOCK_END() \
  native_mutex_lock(&_th_stored->vm->global_vm_lock); \
  rb_thread_set_current(_th_stored); \
} while(0)

#define BLOCKING_REGION_CORE(exec) do { \
    GVL_UNLOCK_BEGIN(); {\
	    exec; \
    } \
    GVL_UNLOCK_END(); \
} while(0);

#define BLOCKING_REGION(exec, ubf, ubfarg) do { \
    rb_thread_t *__th = GET_THREAD(); \
    struct rb_blocking_region_buffer __region; \
    blocking_region_begin(__th, &__region, ubf, ubfarg); \
    exec; \
    blocking_region_end(__th, &__region); \
    RUBY_VM_CHECK_INTS(); \
} while(0)

#if THREAD_DEBUG
#ifdef HAVE_VA_ARGS_MACRO
void rb_thread_debug(const char *file, int line, const char *fmt, ...);
#define thread_debug(fmt, ...) rb_thread_debug(__FILE__, __LINE__, fmt, ##__VA_ARGS__)
#define POSITION_FORMAT "%s:%d:"
#define POSITION_ARGS ,file, line
#else
void rb_thread_debug(const char *fmt, ...);
#define thread_debug rb_thread_debug
#define POSITION_FORMAT
#define POSITION_ARGS
#endif

# if THREAD_DEBUG < 0
static int rb_thread_debug_enabled;

static VALUE
rb_thread_s_debug(void)
{
    return INT2NUM(rb_thread_debug_enabled);
}

static VALUE
rb_thread_s_debug_set(VALUE self, VALUE val)
{
    rb_thread_debug_enabled = RTEST(val);
    return val;
}
# else
# define rb_thread_debug_enabled THREAD_DEBUG
# endif
#else
#define thread_debug if(0)printf
#endif

#ifndef __ia64
#define thread_start_func_2(th, st, rst) thread_start_func_2(th, st)
#endif
NOINLINE(static int thread_start_func_2(rb_thread_t *th, VALUE *stack_start,
					VALUE *register_stack_start));
static void timer_thread_function(void *);

#if   defined(_WIN32)
#include "thread_win32.c"

#define DEBUG_OUT() \
  WaitForSingleObject(&debug_mutex, INFINITE); \
  printf(POSITION_FORMAT"%p - %s" POSITION_ARGS, GetCurrentThreadId(), buf); \
  fflush(stdout); \
  ReleaseMutex(&debug_mutex);

#elif defined(HAVE_PTHREAD_H)
#include "thread_pthread.c"

#define DEBUG_OUT() \
  pthread_mutex_lock(&debug_mutex); \
  printf(POSITION_FORMAT"%#"PRIxVALUE" - %s" POSITION_ARGS, (VALUE)pthread_self(), buf); \
  fflush(stdout); \
  pthread_mutex_unlock(&debug_mutex);

#else
#error "unsupported thread type"
#endif

#if THREAD_DEBUG
static int debug_mutex_initialized = 1;
static rb_thread_lock_t debug_mutex;

void
rb_thread_debug(
#ifdef HAVE_VA_ARGS_MACRO
    const char *file, int line,
#endif
    const char *fmt, ...)
{
    va_list args;
    char buf[BUFSIZ];

    if (!rb_thread_debug_enabled) return;

    if (debug_mutex_initialized == 1) {
	debug_mutex_initialized = 0;
	native_mutex_initialize(&debug_mutex);
    }

    va_start(args, fmt);
    vsnprintf(buf, BUFSIZ, fmt, args);
    va_end(args);

    DEBUG_OUT();
}
#endif


static void
set_unblock_function(rb_thread_t *th, rb_unblock_function_t *func, void *arg,
		     struct rb_unblock_callback *old)
{
  check_ints:
    RUBY_VM_CHECK_INTS(); /* check signal or so */
    native_mutex_lock(&th->interrupt_lock);
    if (th->interrupt_flag) {
	native_mutex_unlock(&th->interrupt_lock);
	goto check_ints;
    }
    else {
	if (old) *old = th->unblock;
	th->unblock.func = func;
	th->unblock.arg = arg;
    }
    native_mutex_unlock(&th->interrupt_lock);
}

static void
reset_unblock_function(rb_thread_t *th, const struct rb_unblock_callback *old)
{
    native_mutex_lock(&th->interrupt_lock);
    th->unblock = *old;
    native_mutex_unlock(&th->interrupt_lock);
}

static void
rb_thread_interrupt(rb_thread_t *th)
{
    native_mutex_lock(&th->interrupt_lock);
    RUBY_VM_SET_INTERRUPT(th);
    if (th->unblock.func) {
	(th->unblock.func)(th->unblock.arg);
    }
    else {
	/* none */
    }
    native_mutex_unlock(&th->interrupt_lock);
}


static int
terminate_i(st_data_t key, st_data_t val, rb_thread_t *main_thread)
{
    VALUE thval = key;
    rb_thread_t *th;
    GetThreadPtr(thval, th);

    if (th != main_thread) {
	thread_debug("terminate_i: %p\n", th);
	rb_thread_interrupt(th);
	th->thrown_errinfo = eTerminateSignal;
	th->status = THREAD_TO_KILL;
    }
    else {
	thread_debug("terminate_i: main thread (%p)\n", th);
    }
    return ST_CONTINUE;
}

typedef struct rb_mutex_struct
{
    rb_thread_lock_t lock;
    rb_thread_cond_t cond;
    struct rb_thread_struct volatile *th;
    volatile int cond_waiting, cond_notified;
    struct rb_mutex_struct *next_mutex;
} mutex_t;

static void rb_mutex_unlock_all(mutex_t *mutex);

void
rb_thread_terminate_all(void)
{
    rb_thread_t *th = GET_THREAD(); /* main thread */
    rb_vm_t *vm = th->vm;
    if (vm->main_thread != th) {
	rb_bug("rb_thread_terminate_all: called by child thread (%p, %p)", vm->main_thread, th);
    }

    /* unlock all locking mutexes */
    if (th->keeping_mutexes) {
	rb_mutex_unlock_all(th->keeping_mutexes);
    }

    thread_debug("rb_thread_terminate_all (main thread: %p)\n", th);
    st_foreach(vm->living_threads, terminate_i, (st_data_t)th);

    while (!rb_thread_alone()) {
	PUSH_TAG();
	if (EXEC_TAG() == 0) {
	    rb_thread_schedule();
	}
	else {
	    /* ignore exception */
	}
	POP_TAG();
    }
    rb_thread_stop_timer_thread();
}

static void
thread_cleanup_func_before_exec(void *th_ptr)
{
    rb_thread_t *th = th_ptr;
    th->status = THREAD_KILLED;
    th->machine_stack_start = th->machine_stack_end = 0;
#ifdef __ia64
    th->machine_register_stack_start = th->machine_register_stack_end = 0;
#endif
}

static void
thread_cleanup_func(void *th_ptr)
{
    rb_thread_t *th = th_ptr;
    thread_cleanup_func_before_exec(th_ptr);
    native_thread_destroy(th);
}

extern void ruby_error_print(void);
static VALUE rb_thread_raise(int, VALUE *, rb_thread_t *);
void rb_thread_recycle_stack_release(VALUE *);

void
ruby_thread_init_stack(rb_thread_t *th)
{
    native_thread_init_stack(th);
}

static int
thread_start_func_2(rb_thread_t *th, VALUE *stack_start, VALUE *register_stack_start)
{
    int state;
    VALUE args = th->first_args;
    rb_proc_t *proc;
    rb_thread_t *join_th;
    rb_thread_t *main_th;
    VALUE errinfo = Qnil;

    th->machine_stack_start = stack_start;
#ifdef __ia64
    th->machine_register_stack_start = register_stack_start;
#endif
    thread_debug("thread start: %p\n", th);

    native_mutex_lock(&th->vm->global_vm_lock);
    {
	thread_debug("thread start (get lock): %p\n", th);
	rb_thread_set_current(th);

	TH_PUSH_TAG(th);
	if ((state = EXEC_TAG()) == 0) {
	    SAVE_ROOT_JMPBUF(th, {
		if (th->first_proc) {
		    GetProcPtr(th->first_proc, proc);
		    th->errinfo = Qnil;
		    th->local_lfp = proc->block.lfp;
		    th->local_svar = Qnil;
		    th->value = vm_invoke_proc(th, proc, proc->block.self,
					       RARRAY_LEN(args), RARRAY_PTR(args), 0);
		}
		else {
		    th->value = (*th->first_func)((void *)th->first_args);
		}
	    });
	}
	else {
	    errinfo = th->errinfo;
	    if (NIL_P(errinfo)) errinfo = rb_errinfo();
	    if (state == TAG_FATAL) {
		/* fatal error within this thread, need to stop whole script */
	    }
	    else if (rb_obj_is_kind_of(errinfo, rb_eSystemExit)) {
		if (th->safe_level >= 4) {
		    th->errinfo = rb_exc_new3(rb_eSecurityError,
					      rb_sprintf("Insecure exit at level %d", th->safe_level));
		    errinfo = Qnil;
		}
	    }
	    else if (th->safe_level < 4 &&
		     (th->vm->thread_abort_on_exception ||
		      th->abort_on_exception || RTEST(ruby_debug))) {
		/* exit on main_thread */
	    }
	    else {
		errinfo = Qnil;
	    }
	    th->value = Qnil;
	}

	th->status = THREAD_KILLED;
	thread_debug("thread end: %p\n", th);

	main_th = th->vm->main_thread;
	if (th != main_th) {
	    if (TYPE(errinfo) == T_OBJECT) {
		/* treat with normal error object */
		rb_thread_raise(1, &errinfo, main_th);
	    }
	}
	TH_POP_TAG();

	/* locking_mutex must be Qfalse */
	if (th->locking_mutex != Qfalse) {
	    rb_bug("thread_start_func_2: locking_mutex must not be set (%p:%"PRIxVALUE")",
		   th, th->locking_mutex);
	}

	/* unlock all locking mutexes */
	if (th->keeping_mutexes) {
	    rb_mutex_unlock_all(th->keeping_mutexes);
	    th->keeping_mutexes = NULL;
	}

	/* delete self from living_threads */
	st_delete_wrap(th->vm->living_threads, th->self);

	/* wake up joinning threads */
	join_th = th->join_list_head;
	while (join_th) {
	    if (join_th == main_th) errinfo = Qnil;
	    rb_thread_interrupt(join_th);
	    switch (join_th->status) {
	      case THREAD_STOPPED: case THREAD_STOPPED_FOREVER:
		join_th->status = THREAD_RUNNABLE;
	      default: break;
	    }
	    join_th = join_th->join_list_next;
	}
	if (th != main_th) rb_check_deadlock(th->vm);

	if (!th->root_fiber) {
	    rb_thread_recycle_stack_release(th->stack);
	    th->stack = 0;
	}
    }
    thread_cleanup_func(th);
    native_mutex_unlock(&th->vm->global_vm_lock);

    return 0;
}

static VALUE
thread_create_core(VALUE thval, VALUE args, VALUE (*fn)(ANYARGS))
{
    rb_thread_t *th;

    if (OBJ_FROZEN(GET_THREAD()->thgroup)) {
	rb_raise(rb_eThreadError,
		 "can't start a new thread (frozen ThreadGroup)");
    }
    GetThreadPtr(thval, th);

    /* setup thread environment */
    th->first_func = fn;
    th->first_proc = fn ? Qfalse : rb_block_proc();
    th->first_args = args; /* GC: shouldn't put before above line */

    th->priority = GET_THREAD()->priority;
    th->thgroup = GET_THREAD()->thgroup;

    native_mutex_initialize(&th->interrupt_lock);
    /* kick thread */
    st_insert(th->vm->living_threads, thval, (st_data_t) th->thread_id);
    native_thread_create(th);
    return thval;
}

static VALUE
thread_s_new(int argc, VALUE *argv, VALUE klass)
{
    rb_thread_t *th;
    VALUE thread = rb_thread_alloc(klass);
    rb_obj_call_init(thread, argc, argv);
    GetThreadPtr(thread, th);
    if (!th->first_args) {
	rb_raise(rb_eThreadError, "uninitialized thread - check `%s#initialize'",
		 rb_class2name(klass));
    }
    return thread;
}

/*
 *  call-seq:
 *     Thread.start([args]*) {|args| block }   => thread
 *     Thread.fork([args]*) {|args| block }    => thread
 *
 *  Basically the same as <code>Thread::new</code>. However, if class
 *  <code>Thread</code> is subclassed, then calling <code>start</code> in that
 *  subclass will not invoke the subclass's <code>initialize</code> method.
 */

static VALUE
thread_start(VALUE klass, VALUE args)
{
    return thread_create_core(rb_thread_alloc(klass), args, 0);
}

static VALUE
thread_initialize(VALUE thread, VALUE args)
{
    rb_thread_t *th;
    if (!rb_block_given_p()) {
	rb_raise(rb_eThreadError, "must be called with a block");
    }
    GetThreadPtr(thread, th);
    if (th->first_args) {
	VALUE rb_proc_location(VALUE self);
	VALUE proc = th->first_proc, line, loc;
	const char *file;
        if (!proc || !RTEST(loc = rb_proc_location(proc))) {
            rb_raise(rb_eThreadError, "already initialized thread");
        }
	file = RSTRING_PTR(RARRAY_PTR(loc)[0]);
	if (NIL_P(line = RARRAY_PTR(loc)[1])) {
	    rb_raise(rb_eThreadError, "already initialized thread - %s",
		     file);
	}
        rb_raise(rb_eThreadError, "already initialized thread - %s:%d",
                 file, NUM2INT(line));
    }
    return thread_create_core(thread, args, 0);
}

VALUE
rb_thread_create(VALUE (*fn)(ANYARGS), void *arg)
{
    return thread_create_core(rb_thread_alloc(rb_cThread), (VALUE)arg, fn);
}


/* +infty, for this purpose */
#define DELAY_INFTY 1E30

struct join_arg {
    rb_thread_t *target, *waiting;
    double limit;
    int forever;
};

static VALUE
remove_from_join_list(VALUE arg)
{
    struct join_arg *p = (struct join_arg *)arg;
    rb_thread_t *target_th = p->target, *th = p->waiting;

    if (target_th->status != THREAD_KILLED) {
	rb_thread_t **pth = &target_th->join_list_head;

	while (*pth) {
	    if (*pth == th) {
		*pth = th->join_list_next;
		break;
	    }
	    pth = &(*pth)->join_list_next;
	}
    }

    return Qnil;
}

static VALUE
thread_join_sleep(VALUE arg)
{
    struct join_arg *p = (struct join_arg *)arg;
    rb_thread_t *target_th = p->target, *th = p->waiting;
    double now, limit = p->limit;

    while (target_th->status != THREAD_KILLED) {
	if (p->forever) {
	    sleep_forever(th, 1);
	}
	else {
	    now = timeofday();
	    if (now > limit) {
		thread_debug("thread_join: timeout (thid: %p)\n",
			     (void *)target_th->thread_id);
		return Qfalse;
	    }
	    sleep_wait_for_interrupt(th, limit - now);
	}
	thread_debug("thread_join: interrupted (thid: %p)\n",
		     (void *)target_th->thread_id);
    }
    return Qtrue;
}

static VALUE
thread_join(rb_thread_t *target_th, double delay)
{
    rb_thread_t *th = GET_THREAD();
    struct join_arg arg;

    arg.target = target_th;
    arg.waiting = th;
    arg.limit = timeofday() + delay;
    arg.forever = delay == DELAY_INFTY;

    thread_debug("thread_join (thid: %p)\n", (void *)target_th->thread_id);

    if (target_th->status != THREAD_KILLED) {
	th->join_list_next = target_th->join_list_head;
	target_th->join_list_head = th;
	if (!rb_ensure(thread_join_sleep, (VALUE)&arg,
		       remove_from_join_list, (VALUE)&arg)) {
	    return Qnil;
	}
    }

    thread_debug("thread_join: success (thid: %p)\n",
		 (void *)target_th->thread_id);

    if (target_th->errinfo != Qnil) {
	VALUE err = target_th->errinfo;

	if (FIXNUM_P(err)) {
	    /* */
	}
	else if (TYPE(target_th->errinfo) == T_NODE) {
	    rb_exc_raise(vm_make_jump_tag_but_local_jump(
		GET_THROWOBJ_STATE(err), GET_THROWOBJ_VAL(err)));
	}
	else {
	    /* normal exception */
	    rb_exc_raise(err);
	}
    }
    return target_th->self;
}

/*
 *  call-seq:
 *     thr.join          => thr
 *     thr.join(limit)   => thr
 *
 *  The calling thread will suspend execution and run <i>thr</i>. Does not
 *  return until <i>thr</i> exits or until <i>limit</i> seconds have passed. If
 *  the time limit expires, <code>nil</code> will be returned, otherwise
 *  <i>thr</i> is returned.
 *
 *  Any threads not joined will be killed when the main program exits.  If
 *  <i>thr</i> had previously raised an exception and the
 *  <code>abort_on_exception</code> and <code>$DEBUG</code> flags are not set
 *  (so the exception has not yet been processed) it will be processed at this
 *  time.
 *
 *     a = Thread.new { print "a"; sleep(10); print "b"; print "c" }
 *     x = Thread.new { print "x"; Thread.pass; print "y"; print "z" }
 *     x.join # Let x thread finish, a will be killed on exit.
 *
 *  <em>produces:</em>
 *
 *     axyz
 *
 *  The following example illustrates the <i>limit</i> parameter.
 *
 *     y = Thread.new { 4.times { sleep 0.1; puts 'tick... ' }}
 *     puts "Waiting" until y.join(0.15)
 *
 *  <em>produces:</em>
 *
 *     tick...
 *     Waiting
 *     tick...
 *     Waitingtick...
 *
 *
 *     tick...
 */

static VALUE
thread_join_m(int argc, VALUE *argv, VALUE self)
{
    rb_thread_t *target_th;
    double delay = DELAY_INFTY;
    VALUE limit;

    GetThreadPtr(self, target_th);

    rb_scan_args(argc, argv, "01", &limit);
    if (!NIL_P(limit)) {
	delay = rb_num2dbl(limit);
    }

    return thread_join(target_th, delay);
}

/*
 *  call-seq:
 *     thr.value   => obj
 *
 *  Waits for <i>thr</i> to complete (via <code>Thread#join</code>) and returns
 *  its value.
 *
 *     a = Thread.new { 2 + 2 }
 *     a.value   #=> 4
 */

static VALUE
thread_value(VALUE self)
{
    rb_thread_t *th;
    GetThreadPtr(self, th);
    thread_join(th, DELAY_INFTY);
    return th->value;
}

/*
 * Thread Scheduling
 */

static struct timeval
double2timeval(double d)
{
    struct timeval time;

    time.tv_sec = (int)d;
    time.tv_usec = (int)((d - (int)d) * 1e6);
    if (time.tv_usec < 0) {
	time.tv_usec += (long)1e6;
	time.tv_sec -= 1;
    }
    return time;
}

static void
sleep_forever(rb_thread_t *th, int deadlockable)
{
    enum rb_thread_status prev_status = th->status;

    th->status = deadlockable ? THREAD_STOPPED_FOREVER : THREAD_STOPPED;
    do {
	if (deadlockable) {
	    th->vm->sleeper++;
	    rb_check_deadlock(th->vm);
	}
	native_sleep(th, 0);
	if (deadlockable) {
	    th->vm->sleeper--;
	}
	RUBY_VM_CHECK_INTS();
    } while (th->status == THREAD_STOPPED_FOREVER);
    th->status = prev_status;
}

static void
getclockofday(struct timeval *tp)
{
#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
    struct timespec ts;

    if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0) {
	tp->tv_sec = ts.tv_sec;
	tp->tv_usec = ts.tv_nsec / 1000;
    } else
#endif
    {
        gettimeofday(tp, NULL);
    }
}

static void
sleep_timeval(rb_thread_t *th, struct timeval tv)
{
    struct timeval to, tvn;
    enum rb_thread_status prev_status = th->status;

    getclockofday(&to);
    to.tv_sec += tv.tv_sec;
    if ((to.tv_usec += tv.tv_usec) >= 1000000) {
	to.tv_sec++;
	to.tv_usec -= 1000000;
    }

    th->status = THREAD_STOPPED;
    do {
	native_sleep(th, &tv);
	RUBY_VM_CHECK_INTS();
	getclockofday(&tvn);
	if (to.tv_sec < tvn.tv_sec) break;
	if (to.tv_sec == tvn.tv_sec && to.tv_usec <= tvn.tv_usec) break;
	thread_debug("sleep_timeval: %ld.%.6ld > %ld.%.6ld\n",
		     (long)to.tv_sec, to.tv_usec,
		     (long)tvn.tv_sec, tvn.tv_usec);
	tv.tv_sec = to.tv_sec - tvn.tv_sec;
	if ((tv.tv_usec = to.tv_usec - tvn.tv_usec) < 0) {
	    --tv.tv_sec;
	    tv.tv_usec += 1000000;
	}
    } while (th->status == THREAD_STOPPED);
    th->status = prev_status;
}

void
rb_thread_sleep_forever()
{
    thread_debug("rb_thread_sleep_forever\n");
    sleep_forever(GET_THREAD(), 0);
}

static void
rb_thread_sleep_deadly()
{
    thread_debug("rb_thread_sleep_deadly\n");
    sleep_forever(GET_THREAD(), 1);
}

static double
timeofday(void)
{
#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
    struct timespec tp;

    if (clock_gettime(CLOCK_MONOTONIC, &tp) == 0) {
        return (double)tp.tv_sec + (double)tp.tv_nsec * 1e-9;
    } else
#endif
    {
        struct timeval tv;
        gettimeofday(&tv, NULL);
        return (double)tv.tv_sec + (double)tv.tv_usec * 1e-6;
    }
}

static void
sleep_wait_for_interrupt(rb_thread_t *th, double sleepsec)
{
    sleep_timeval(th, double2timeval(sleepsec));
}

static void
sleep_for_polling(rb_thread_t *th)
{
    struct timeval time;
    time.tv_sec = 0;
    time.tv_usec = 100 * 1000;	/* 0.1 sec */
    sleep_timeval(th, time);
}

void
rb_thread_wait_for(struct timeval time)
{
    rb_thread_t *th = GET_THREAD();
    sleep_timeval(th, time);
}

void
rb_thread_polling(void)
{
    RUBY_VM_CHECK_INTS();
    if (!rb_thread_alone()) {
	rb_thread_t *th = GET_THREAD();
	sleep_for_polling(th);
    }
}

/*
 * CAUTION: This function causes thread switching.
 *          rb_thread_check_ints() check ruby's interrupts.
 *          some interrupt needs thread switching/invoke handlers,
 *          and so on.
 */

void
rb_thread_check_ints(void)
{
    RUBY_VM_CHECK_INTS();
}

/*
 * Hidden API for tcl/tk wrapper.
 * There is no guarantee to perpetuate it.
 */
int
rb_thread_check_trap_pending(void)
{
    return GET_THREAD()->exec_signal != 0;
}

/* This function can be called in blocking region. */
int
rb_thread_interrupted(VALUE thval)
{
    rb_thread_t *th;
    GetThreadPtr(thval, th);
    return RUBY_VM_INTERRUPTED(th);
}

struct timeval rb_time_timeval();

void
rb_thread_sleep(int sec)
{
    rb_thread_wait_for(rb_time_timeval(INT2FIX(sec)));
}

void
rb_thread_schedule(void)
{
    thread_debug("rb_thread_schedule\n");
    if (!rb_thread_alone()) {
	rb_thread_t *th = GET_THREAD();

	thread_debug("rb_thread_schedule/switch start\n");

	rb_gc_save_machine_context(th);
	native_mutex_unlock(&th->vm->global_vm_lock);
	{
	    native_thread_yield();
	}
	native_mutex_lock(&th->vm->global_vm_lock);

	rb_thread_set_current(th);
	thread_debug("rb_thread_schedule/switch done\n");

	RUBY_VM_CHECK_INTS();
    }
}

/* blocking region */
static inline void
blocking_region_begin(rb_thread_t *th, struct rb_blocking_region_buffer *region,
		      rb_unblock_function_t *func, void *arg)
{
    region->prev_status = th->status;
    set_unblock_function(th, func, arg, &region->oldubf);
    th->status = THREAD_STOPPED;
    thread_debug("enter blocking region (%p)\n", th);
    rb_gc_save_machine_context(th);
    native_mutex_unlock(&th->vm->global_vm_lock);
}

static inline void
blocking_region_end(rb_thread_t *th, struct rb_blocking_region_buffer *region)
{
    native_mutex_lock(&th->vm->global_vm_lock);
    rb_thread_set_current(th);
    thread_debug("leave blocking region (%p)\n", th);
    remove_signal_thread_list(th);
    reset_unblock_function(th, &region->oldubf);
    if (th->status == THREAD_STOPPED) {
	th->status = region->prev_status;
    }
}

struct rb_blocking_region_buffer *
rb_thread_blocking_region_begin(void)
{
    rb_thread_t *th = GET_THREAD();
    struct rb_blocking_region_buffer *region = ALLOC(struct rb_blocking_region_buffer);
    blocking_region_begin(th, region, ubf_select, th);
    return region;
}

void
rb_thread_blocking_region_end(struct rb_blocking_region_buffer *region)
{
    rb_thread_t *th = GET_THREAD();
    blocking_region_end(th, region);
    xfree(region);
    RUBY_VM_CHECK_INTS();
}

/*
 * rb_thread_blocking_region - permit concurrent/parallel execution.
 *
 * This function does:
 *   (1) release GVL.
 *       Other Ruby threads may run in parallel.
 *   (2) call func with data1.
 *   (3) aquire GVL.
 *       Other Ruby threads can not run in parallel any more.
 *
 *   If another thread interrupts this thread (Thread#kill, signal deliverly,
 *   VM-shutdown request, and so on), `ubf()' is called (`ubf()' means
 *   "un-blocking function").  `ubf()' should interrupt `func()' execution.
 *
 *   There are built-in ubfs and you can specify these ubfs.
 *   However, we can not guarantee our built-in ubfs interrupt
 *   your `func()' correctly.  Be careful to use rb_thread_blocking_region().
 *
 *     * RUBY_UBF_IO: ubf for IO operation
 *     * RUBY_UBF_PROCESS: ubf for process operation
 *
 *   NOTE: You can not execute most of Ruby C API and touch Ruby objects
 *         in `func()' and `ubf()' because current thread doesn't acquire
 *         GVL (cause synchronization problem).  If you need to do it,
 *         read source code of C APIs and confirm by yourself.
 *
 *   Safe C API:
 *     * rb_thread_interrupted() - check interrupt flag
 */
VALUE
rb_thread_blocking_region(
    rb_blocking_function_t *func, void *data1,
    rb_unblock_function_t *ubf, void *data2)
{
    VALUE val;
    rb_thread_t *th = GET_THREAD();

    if (ubf == RUBY_UBF_IO || ubf == RUBY_UBF_PROCESS) {
	ubf = ubf_select;
	data2 = th;
    }

    BLOCKING_REGION({
	val = func(data1);
    }, ubf, data2);

    return val;
}

/*
 *  call-seq:
 *     Thread.pass   => nil
 *
 *  Invokes the thread scheduler to pass execution to another thread.
 *
 *     a = Thread.new { print "a"; Thread.pass;
 *                      print "b"; Thread.pass;
 *                      print "c" }
 *     b = Thread.new { print "x"; Thread.pass;
 *                      print "y"; Thread.pass;
 *                      print "z" }
 *     a.join
 *     b.join
 *
 *  <em>produces:</em>
 *
 *     axbycz
 */

static VALUE
thread_s_pass(VALUE klass)
{
    rb_thread_schedule();
    return Qnil;
}

/*
 *
 */

void
rb_thread_execute_interrupts(rb_thread_t *th)
{
    if (th->raised_flag) return;

    while (th->interrupt_flag) {
	enum rb_thread_status status = th->status;
	int timer_interrupt = th->interrupt_flag & 0x01;
	int finalizer_interrupt = th->interrupt_flag & 0x04;

	th->status = THREAD_RUNNABLE;
	th->interrupt_flag = 0;

	/* signal handling */
	if (th->exec_signal) {
	    int sig = th->exec_signal;
	    th->exec_signal = 0;
	    rb_signal_exec(th, sig);
	}

	/* exception from another thread */
	if (th->thrown_errinfo) {
	    VALUE err = th->thrown_errinfo;
	    th->thrown_errinfo = 0;
	    thread_debug("rb_thread_execute_interrupts: %ld\n", err);

	    if (err == eKillSignal || err == eTerminateSignal) {
		th->errinfo = INT2FIX(TAG_FATAL);
		TH_JUMP_TAG(th, TAG_FATAL);
	    }
	    else {
		rb_exc_raise(err);
	    }
	}
	th->status = status;

	if (finalizer_interrupt) {
	    rb_gc_finalize_deferred();
	}

	if (timer_interrupt) {
	    EXEC_EVENT_HOOK(th, RUBY_EVENT_SWITCH, th->cfp->self, 0, 0);

	    if (th->slice > 0) {
		th->slice--;
	    }
	    else {
	      reschedule:
		rb_thread_schedule();
		if (th->slice < 0) {
		    th->slice++;
		    goto reschedule;
		}
		else {
		    th->slice = th->priority;
		}
	    }
	}
    }
}


void
rb_gc_mark_threads(void)
{
    /* TODO: remove */
}

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

static void
rb_thread_ready(rb_thread_t *th)
{
    rb_thread_interrupt(th);
}

static VALUE
rb_thread_raise(int argc, VALUE *argv, rb_thread_t *th)
{
    VALUE exc;

  again:
    if (rb_thread_dead(th)) {
	return Qnil;
    }

    if (th->thrown_errinfo != 0 || th->raised_flag) {
	rb_thread_schedule();
	goto again;
    }

    exc = rb_make_exception(argc, argv);
    th->thrown_errinfo = exc;
    rb_thread_ready(th);
    return Qnil;
}

void
rb_thread_signal_raise(void *thptr, int sig)
{
    VALUE argv[2];
    rb_thread_t *th = thptr;

    argv[0] = rb_eSignal;
    argv[1] = INT2FIX(sig);
    rb_thread_raise(2, argv, th->vm->main_thread);
}

void
rb_thread_signal_exit(void *thptr)
{
    VALUE argv[2];
    rb_thread_t *th = thptr;

    argv[0] = rb_eSystemExit;
    argv[1] = rb_str_new2("exit");
    rb_thread_raise(2, argv, th->vm->main_thread);
}

int
rb_thread_set_raised(rb_thread_t *th)
{
    if (th->raised_flag & RAISED_EXCEPTION) {
	return 1;
    }
    th->raised_flag |= RAISED_EXCEPTION;
    return 0;
}

int
rb_thread_reset_raised(rb_thread_t *th)
{
    if (!(th->raised_flag & RAISED_EXCEPTION)) {
	return 0;
    }
    th->raised_flag &= ~RAISED_EXCEPTION;
    return 1;
}

void
rb_thread_fd_close(int fd)
{
    /* TODO: fix me */
}

/*
 *  call-seq:
 *     thr.raise(exception)
 *
 *  Raises an exception (see <code>Kernel::raise</code>) from <i>thr</i>. The
 *  caller does not have to be <i>thr</i>.
 *
 *     Thread.abort_on_exception = true
 *     a = Thread.new { sleep(200) }
 *     a.raise("Gotcha")
 *
 *  <em>produces:</em>
 *
 *     prog.rb:3: Gotcha (RuntimeError)
 *     	from prog.rb:2:in `initialize'
 *     	from prog.rb:2:in `new'
 *     	from prog.rb:2
 */

static VALUE
thread_raise_m(int argc, VALUE *argv, VALUE self)
{
    rb_thread_t *th;
    GetThreadPtr(self, th);
    rb_thread_raise(argc, argv, th);
    return Qnil;
}


/*
 *  call-seq:
 *     thr.exit        => thr or nil
 *     thr.kill        => thr or nil
 *     thr.terminate   => thr or nil
 *
 *  Terminates <i>thr</i> and schedules another thread to be run. If this thread
 *  is already marked to be killed, <code>exit</code> returns the
 *  <code>Thread</code>. If this is the main thread, or the last thread, exits
 *  the process.
 */

VALUE
rb_thread_kill(VALUE thread)
{
    rb_thread_t *th;

    GetThreadPtr(thread, th);

    if (th != GET_THREAD() && th->safe_level < 4) {
	rb_secure(4);
    }
    if (th->status == THREAD_TO_KILL || th->status == THREAD_KILLED) {
	return thread;
    }
    if (th == th->vm->main_thread) {
	rb_exit(EXIT_SUCCESS);
    }

    thread_debug("rb_thread_kill: %p (%p)\n", th, (void *)th->thread_id);

    rb_thread_interrupt(th);
    th->thrown_errinfo = eKillSignal;
    th->status = THREAD_TO_KILL;

    return thread;
}


/*
 *  call-seq:
 *     Thread.kill(thread)   => thread
 *
 *  Causes the given <em>thread</em> to exit (see <code>Thread::exit</code>).
 *
 *     count = 0
 *     a = Thread.new { loop { count += 1 } }
 *     sleep(0.1)       #=> 0
 *     Thread.kill(a)   #=> #<Thread:0x401b3d30 dead>
 *     count            #=> 93947
 *     a.alive?         #=> false
 */

static VALUE
rb_thread_s_kill(VALUE obj, VALUE th)
{
    return rb_thread_kill(th);
}


/*
 *  call-seq:
 *     Thread.exit   => thread
 *
 *  Terminates the currently running thread and schedules another thread to be
 *  run. If this thread is already marked to be killed, <code>exit</code>
 *  returns the <code>Thread</code>. If this is the main thread, or the last
 *  thread, exit the process.
 */

static VALUE
rb_thread_exit(void)
{
    return rb_thread_kill(GET_THREAD()->self);
}


/*
 *  call-seq:
 *     thr.wakeup   => thr
 *
 *  Marks <i>thr</i> as eligible for scheduling (it may still remain blocked on
 *  I/O, however). Does not invoke the scheduler (see <code>Thread#run</code>).
 *
 *     c = Thread.new { Thread.stop; puts "hey!" }
 *     c.wakeup
 *
 *  <em>produces:</em>
 *
 *     hey!
 */

VALUE
rb_thread_wakeup(VALUE thread)
{
    rb_thread_t *th;
    GetThreadPtr(thread, th);

    if (th->status == THREAD_KILLED) {
	rb_raise(rb_eThreadError, "killed thread");
    }
    rb_thread_ready(th);
    if (th->status != THREAD_TO_KILL) {
	th->status = THREAD_RUNNABLE;
    }
    return thread;
}


/*
 *  call-seq:
 *     thr.run   => thr
 *
 *  Wakes up <i>thr</i>, making it eligible for scheduling.
 *
 *     a = Thread.new { puts "a"; Thread.stop; puts "c" }
 *     Thread.pass
 *     puts "Got here"
 *     a.run
 *     a.join
 *
 *  <em>produces:</em>
 *
 *     a
 *     Got here
 *     c
 */

VALUE
rb_thread_run(VALUE thread)
{
    rb_thread_wakeup(thread);
    rb_thread_schedule();
    return thread;
}


/*
 *  call-seq:
 *     Thread.stop   => nil
 *
 *  Stops execution of the current thread, putting it into a ``sleep'' state,
 *  and schedules execution of another thread.
 *
 *     a = Thread.new { print "a"; Thread.stop; print "c" }
 *     Thread.pass
 *     print "b"
 *     a.run
 *     a.join
 *
 *  <em>produces:</em>
 *
 *     abc
 */

VALUE
rb_thread_stop(void)
{
    if (rb_thread_alone()) {
	rb_raise(rb_eThreadError,
		 "stopping only thread\n\tnote: use sleep to stop forever");
    }
    rb_thread_sleep_deadly();
    return Qnil;
}

static int
thread_list_i(st_data_t key, st_data_t val, void *data)
{
    VALUE ary = (VALUE)data;
    rb_thread_t *th;
    GetThreadPtr((VALUE)key, th);

    switch (th->status) {
      case THREAD_RUNNABLE:
      case THREAD_STOPPED:
      case THREAD_STOPPED_FOREVER:
      case THREAD_TO_KILL:
	rb_ary_push(ary, th->self);
      default:
	break;
    }
    return ST_CONTINUE;
}

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

/*
 *  call-seq:
 *     Thread.list   => array
 *
 *  Returns an array of <code>Thread</code> objects for all threads that are
 *  either runnable or stopped.
 *
 *     Thread.new { sleep(200) }
 *     Thread.new { 1000000.times {|i| i*i } }
 *     Thread.new { Thread.stop }
 *     Thread.list.each {|t| p t}
 *
 *  <em>produces:</em>
 *
 *     #<Thread:0x401b3e84 sleep>
 *     #<Thread:0x401b3f38 run>
 *     #<Thread:0x401b3fb0 sleep>
 *     #<Thread:0x401bdf4c run>
 */

VALUE
rb_thread_list(void)
{
    VALUE ary = rb_ary_new();
    st_foreach(GET_THREAD()->vm->living_threads, thread_list_i, ary);
    return ary;
}

VALUE
rb_thread_current(void)
{
    return GET_THREAD()->self;
}

/*
 *  call-seq:
 *     Thread.current   => thread
 *
 *  Returns the currently executing thread.
 *
 *     Thread.current   #=> #<Thread:0x401bdf4c run>
 */

static VALUE
thread_s_current(VALUE klass)
{
    return rb_thread_current();
}

VALUE
rb_thread_main(void)
{
    return GET_THREAD()->vm->main_thread->self;
}

static VALUE
rb_thread_s_main(VALUE klass)
{
    return rb_thread_main();
}


/*
 *  call-seq:
 *     Thread.abort_on_exception   => true or false
 *
 *  Returns the status of the global ``abort on exception'' condition.  The
 *  default is <code>false</code>. When set to <code>true</code>, or if the
 *  global <code>$DEBUG</code> flag is <code>true</code> (perhaps because the
 *  command line option <code>-d</code> was specified) all threads will abort
 *  (the process will <code>exit(0)</code>) if an exception is raised in any
 *  thread. See also <code>Thread::abort_on_exception=</code>.
 */

static VALUE
rb_thread_s_abort_exc(void)
{
    return GET_THREAD()->vm->thread_abort_on_exception ? Qtrue : Qfalse;
}


/*
 *  call-seq:
 *     Thread.abort_on_exception= boolean   => true or false
 *
 *  When set to <code>true</code>, all threads will abort if an exception is
 *  raised. Returns the new state.
 *
 *     Thread.abort_on_exception = true
 *     t1 = Thread.new do
 *       puts  "In new thread"
 *       raise "Exception from thread"
 *     end
 *     sleep(1)
 *     puts "not reached"
 *
 *  <em>produces:</em>
 *
 *     In new thread
 *     prog.rb:4: Exception from thread (RuntimeError)
 *     	from prog.rb:2:in `initialize'
 *     	from prog.rb:2:in `new'
 *     	from prog.rb:2
 */

static VALUE
rb_thread_s_abort_exc_set(VALUE self, VALUE val)
{
    rb_secure(4);
    GET_THREAD()->vm->thread_abort_on_exception = RTEST(val);
    return val;
}


/*
 *  call-seq:
 *     thr.abort_on_exception   => true or false
 *
 *  Returns the status of the thread-local ``abort on exception'' condition for
 *  <i>thr</i>. The default is <code>false</code>. See also
 *  <code>Thread::abort_on_exception=</code>.
 */

static VALUE
rb_thread_abort_exc(VALUE thread)
{
    rb_thread_t *th;
    GetThreadPtr(thread, th);
    return th->abort_on_exception ? Qtrue : Qfalse;
}


/*
 *  call-seq:
 *     thr.abort_on_exception= boolean   => true or false
 *
 *  When set to <code>true</code>, causes all threads (including the main
 *  program) to abort if an exception is raised in <i>thr</i>. The process will
 *  effectively <code>exit(0)</code>.
 */

static VALUE
rb_thread_abort_exc_set(VALUE thread, VALUE val)
{
    rb_thread_t *th;
    rb_secure(4);

    GetThreadPtr(thread, th);
    th->abort_on_exception = RTEST(val);
    return val;
}


/*
 *  call-seq:
 *     thr.group   => thgrp or nil
 *
 *  Returns the <code>ThreadGroup</code> which contains <i>thr</i>, or nil if
 *  the thread is not a member of any group.
 *
 *     Thread.main.group   #=> #<ThreadGroup:0x4029d914>
 */

VALUE
rb_thread_group(VALUE thread)
{
    rb_thread_t *th;
    VALUE group;
    GetThreadPtr(thread, th);
    group = th->thgroup;

    if (!group) {
	group = Qnil;
    }
    return group;
}

static const char *
thread_status_name(enum rb_thread_status status)
{
    switch (status) {
      case THREAD_RUNNABLE:
	return "run";
      case THREAD_STOPPED:
      case THREAD_STOPPED_FOREVER:
	return "sleep";
      case THREAD_TO_KILL:
	return "aborting";
      case THREAD_KILLED:
	return "dead";
      default:
	return "unknown";
    }
}

static int
rb_thread_dead(rb_thread_t *th)
{
    return th->status == THREAD_KILLED;
}


/*
 *  call-seq:
 *     thr.status   => string, false or nil
 *
 *  Returns the status of <i>thr</i>: ``<code>sleep</code>'' if <i>thr</i> is
 *  sleeping or waiting on I/O, ``<code>run</code>'' if <i>thr</i> is executing,
 *  ``<code>aborting</code>'' if <i>thr</i> is aborting, <code>false</code> if
 *  <i>thr</i> terminated normally, and <code>nil</code> if <i>thr</i>
 *  terminated with an exception.
 *
 *     a = Thread.new { raise("die now") }
 *     b = Thread.new { Thread.stop }
 *     c = Thread.new { Thread.exit }
 *     d = Thread.new { sleep }
 *     d.kill                  #=> #<Thread:0x401b3678 aborting>
 *     a.status                #=> nil
 *     b.status                #=> "sleep"
 *     c.status                #=> false
 *     d.status                #=> "aborting"
 *     Thread.current.status   #=> "run"
 */

static VALUE
rb_thread_status(VALUE thread)
{
    rb_thread_t *th;
    GetThreadPtr(thread, th);

    if (rb_thread_dead(th)) {
	if (!NIL_P(th->errinfo) && !FIXNUM_P(th->errinfo)
	    /* TODO */ ) {
	    return Qnil;
	}
	return Qfalse;
    }
    return rb_str_new2(thread_status_name(th->status));
}


/*
 *  call-seq:
 *     thr.alive?   => true or false
 *
 *  Returns <code>true</code> if <i>thr</i> is running or sleeping.
 *
 *     thr = Thread.new { }
 *     thr.join                #=> #<Thread:0x401b3fb0 dead>
 *     Thread.current.alive?   #=> true
 *     thr.alive?              #=> false
 */

static VALUE
rb_thread_alive_p(VALUE thread)
{
    rb_thread_t *th;
    GetThreadPtr(thread, th);

    if (rb_thread_dead(th))
	return Qfalse;
    return Qtrue;
}

/*
 *  call-seq:
 *     thr.stop?   => true or false
 *
 *  Returns <code>true</code> if <i>thr</i> is dead or sleeping.
 *
 *     a = Thread.new { Thread.stop }
 *     b = Thread.current
 *     a.stop?   #=> true
 *     b.stop?   #=> false
 */

static VALUE
rb_thread_stop_p(VALUE thread)
{
    rb_thread_t *th;
    GetThreadPtr(thread, th);

    if (rb_thread_dead(th))
	return Qtrue;
    if (th->status == THREAD_STOPPED || th->status == THREAD_STOPPED_FOREVER)
	return Qtrue;
    return Qfalse;
}

/*
 *  call-seq:
 *     thr.safe_level   => integer
 *
 *  Returns the safe level in effect for <i>thr</i>. Setting thread-local safe
 *  levels can help when implementing sandboxes which run insecure code.
 *
 *     thr = Thread.new { $SAFE = 3; sleep }
 *     Thread.current.safe_level   #=> 0
 *     thr.safe_level              #=> 3
 */

static VALUE
rb_thread_safe_level(VALUE thread)
{
    rb_thread_t *th;
    GetThreadPtr(thread, th);

    return INT2NUM(th->safe_level);
}

/*
 * call-seq:
 *   thr.inspect   => string
 *
 * Dump the name, id, and status of _thr_ to a string.
 */

static VALUE
rb_thread_inspect(VALUE thread)
{
    const char *cname = rb_obj_classname(thread);
    rb_thread_t *th;
    const char *status;
    VALUE str;

    GetThreadPtr(thread, th);
    status = thread_status_name(th->status);
    str = rb_sprintf("#<%s:%p %s>", cname, (void *)thread, status);
    OBJ_INFECT(str, thread);

    return str;
}

VALUE
rb_thread_local_aref(VALUE thread, ID id)
{
    rb_thread_t *th;
    VALUE val;

    GetThreadPtr(thread, th);
    if (rb_safe_level() >= 4 && th != GET_THREAD()) {
	rb_raise(rb_eSecurityError, "Insecure: thread locals");
    }
    if (!th->local_storage) {
	return Qnil;
    }
    if (st_lookup(th->local_storage, id, &val)) {
	return val;
    }
    return Qnil;
}

/*
 *  call-seq:
 *      thr[sym]   => obj or nil
 *
 *  Attribute Reference---Returns the value of a thread-local variable, using
 *  either a symbol or a string name. If the specified variable does not exist,
 *  returns <code>nil</code>.
 *
 *     a = Thread.new { Thread.current["name"] = "A"; Thread.stop }
 *     b = Thread.new { Thread.current[:name]  = "B"; Thread.stop }
 *     c = Thread.new { Thread.current["name"] = "C"; Thread.stop }
 *     Thread.list.each {|x| puts "#{x.inspect}: #{x[:name]}" }
 *
 *  <em>produces:</em>
 *
 *     #<Thread:0x401b3b3c sleep>: C
 *     #<Thread:0x401b3bc8 sleep>: B
 *     #<Thread:0x401b3c68 sleep>: A
 *     #<Thread:0x401bdf4c run>:
 */

static VALUE
rb_thread_aref(VALUE thread, VALUE id)
{
    return rb_thread_local_aref(thread, rb_to_id(id));
}

VALUE
rb_thread_local_aset(VALUE thread, ID id, VALUE val)
{
    rb_thread_t *th;
    GetThreadPtr(thread, th);

    if (rb_safe_level() >= 4 && th != GET_THREAD()) {
	rb_raise(rb_eSecurityError, "Insecure: can't modify thread locals");
    }
    if (OBJ_FROZEN(thread)) {
	rb_error_frozen("thread locals");
    }
    if (!th->local_storage) {
	th->local_storage = st_init_numtable();
    }
    if (NIL_P(val)) {
	st_delete_wrap(th->local_storage, id);
	return Qnil;
    }
    st_insert(th->local_storage, id, val);
    return val;
}

/*
 *  call-seq:
 *      thr[sym] = obj   => obj
 *
 *  Attribute Assignment---Sets or creates the value of a thread-local variable,
 *  using either a symbol or a string. See also <code>Thread#[]</code>.
 */

static VALUE
rb_thread_aset(VALUE self, ID id, VALUE val)
{
    return rb_thread_local_aset(self, rb_to_id(id), val);
}

/*
 *  call-seq:
 *     thr.key?(sym)   => true or false
 *
 *  Returns <code>true</code> if the given string (or symbol) exists as a
 *  thread-local variable.
 *
 *     me = Thread.current
 *     me[:oliver] = "a"
 *     me.key?(:oliver)    #=> true
 *     me.key?(:stanley)   #=> false
 */

static VALUE
rb_thread_key_p(VALUE self, VALUE key)
{
    rb_thread_t *th;
    ID id = rb_to_id(key);

    GetThreadPtr(self, th);

    if (!th->local_storage) {
	return Qfalse;
    }
    if (st_lookup(th->local_storage, id, 0)) {
	return Qtrue;
    }
    return Qfalse;
}

static int
thread_keys_i(ID key, VALUE value, VALUE ary)
{
    rb_ary_push(ary, ID2SYM(key));
    return ST_CONTINUE;
}

static int
vm_living_thread_num(rb_vm_t *vm)
{
    return vm->living_threads->num_entries;
}

int
rb_thread_alone()
{
    int num = 1;
    if (GET_THREAD()->vm->living_threads) {
	num = vm_living_thread_num(GET_THREAD()->vm);
	thread_debug("rb_thread_alone: %d\n", num);
    }
    return num == 1;
}

/*
 *  call-seq:
 *     thr.keys   => array
 *
 *  Returns an an array of the names of the thread-local variables (as Symbols).
 *
 *     thr = Thread.new do
 *       Thread.current[:cat] = 'meow'
 *       Thread.current["dog"] = 'woof'
 *     end
 *     thr.join   #=> #<Thread:0x401b3f10 dead>
 *     thr.keys   #=> [:dog, :cat]
 */

static VALUE
rb_thread_keys(VALUE self)
{
    rb_thread_t *th;
    VALUE ary = rb_ary_new();
    GetThreadPtr(self, th);

    if (th->local_storage) {
	st_foreach(th->local_storage, thread_keys_i, ary);
    }
    return ary;
}

/*
 *  call-seq:
 *     thr.priority   => integer
 *
 *  Returns the priority of <i>thr</i>. Default is inherited from the
 *  current thread which creating the new thread, or zero for the
 *  initial main thread; higher-priority threads will run before
 *  lower-priority threads.
 *
 *     Thread.current.priority   #=> 0
 */

static VALUE
rb_thread_priority(VALUE thread)
{
    rb_thread_t *th;
    GetThreadPtr(thread, th);
    return INT2NUM(th->priority);
}


/*
 *  call-seq:
 *     thr.priority= integer   => thr
 *
 *  Sets the priority of <i>thr</i> to <i>integer</i>. Higher-priority threads
 *  will run before lower-priority threads.
 *
 *     count1 = count2 = 0
 *     a = Thread.new do
 *           loop { count1 += 1 }
 *         end
 *     a.priority = -1
 *
 *     b = Thread.new do
 *           loop { count2 += 1 }
 *         end
 *     b.priority = -2
 *     sleep 1   #=> 1
 *     count1    #=> 622504
 *     count2    #=> 5832
 */

static VALUE
rb_thread_priority_set(VALUE thread, VALUE prio)
{
    rb_thread_t *th;
    int priority;
    GetThreadPtr(thread, th);

    rb_secure(4);

#if USE_NATIVE_THREAD_PRIORITY
    th->priority = NUM2INT(prio);
    native_thread_apply_priority(th);
#else
    priority = NUM2INT(prio);
    if (priority > RUBY_THREAD_PRIORITY_MAX) {
	priority = RUBY_THREAD_PRIORITY_MAX;
    }
    else if (priority < RUBY_THREAD_PRIORITY_MIN) {
	priority = RUBY_THREAD_PRIORITY_MIN;
    }
    th->priority = priority;
    th->slice = priority;
#endif
    return INT2NUM(th->priority);
}

/* for IO */

#if defined(NFDBITS) && defined(HAVE_RB_FD_INIT)
void
rb_fd_init(volatile rb_fdset_t *fds)
{
    fds->maxfd = 0;
    fds->fdset = ALLOC(fd_set);
    FD_ZERO(fds->fdset);
}

void
rb_fd_term(rb_fdset_t *fds)
{
    if (fds->fdset) xfree(fds->fdset);
    fds->maxfd = 0;
    fds->fdset = 0;
}

void
rb_fd_zero(rb_fdset_t *fds)
{
    if (fds->fdset) {
	MEMZERO(fds->fdset, fd_mask, howmany(fds->maxfd, NFDBITS));
	FD_ZERO(fds->fdset);
    }
}

static void
rb_fd_resize(int n, rb_fdset_t *fds)
{
    int m = howmany(n + 1, NFDBITS) * sizeof(fd_mask);
    int o = howmany(fds->maxfd, NFDBITS) * sizeof(fd_mask);

    if (m < sizeof(fd_set)) m = sizeof(fd_set);
    if (o < sizeof(fd_set)) o = sizeof(fd_set);

    if (m > o) {
	fds->fdset = realloc(fds->fdset, m);
	memset((char *)fds->fdset + o, 0, m - o);
    }
    if (n >= fds->maxfd) fds->maxfd = n + 1;
}

void
rb_fd_set(int n, rb_fdset_t *fds)
{
    rb_fd_resize(n, fds);
    FD_SET(n, fds->fdset);
}

void
rb_fd_clr(int n, rb_fdset_t *fds)
{
    if (n >= fds->maxfd) return;
    FD_CLR(n, fds->fdset);
}

int
rb_fd_isset(int n, const rb_fdset_t *fds)
{
    if (n >= fds->maxfd) return 0;
    return FD_ISSET(n, fds->fdset) != 0; /* "!= 0" avoids FreeBSD PR 91421 */
}

void
rb_fd_copy(rb_fdset_t *dst, const fd_set *src, int max)
{
    int size = howmany(max, NFDBITS) * sizeof(fd_mask);

    if (size < sizeof(fd_set)) size = sizeof(fd_set);
    dst->maxfd = max;
    dst->fdset = realloc(dst->fdset, size);
    memcpy(dst->fdset, src, size);
}

int
rb_fd_select(int n, rb_fdset_t *readfds, rb_fdset_t *writefds, rb_fdset_t *exceptfds, struct timeval *timeout)
{
    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 select(n, r, w, e, timeout);
}

#undef FD_ZERO
#undef FD_SET
#undef FD_CLR
#undef FD_ISSET

#define FD_ZERO(f)	rb_fd_zero(f)
#define FD_SET(i, f)	rb_fd_set(i, f)
#define FD_CLR(i, f)	rb_fd_clr(i, f)
#define FD_ISSET(i, f)	rb_fd_isset(i, f)

#endif

#if defined(__CYGWIN__) || defined(_WIN32)
static long
cmp_tv(const struct timeval *a, const struct timeval *b)
{
    long d = (a->tv_sec - b->tv_sec);
    return (d != 0) ? d : (a->tv_usec - b->tv_usec);
}

static int
subtract_tv(struct timeval *rest, const struct timeval *wait)
{
    while (rest->tv_usec < wait->tv_usec) {
	if (rest->tv_sec <= wait->tv_sec) {
	    return 0;
	}
	rest->tv_sec -= 1;
	rest->tv_usec += 1000 * 1000;
    }
    rest->tv_sec -= wait->tv_sec;
    rest->tv_usec -= wait->tv_usec;
    return 1;
}
#endif

static int
do_select(int n, fd_set *read, fd_set *write, fd_set *except,
	  struct timeval *timeout)
{
    int result, lerrno;
    fd_set orig_read, orig_write, orig_except;

#ifndef linux
    double limit = 0;
    struct timeval wait_rest;
# if defined(__CYGWIN__) || defined(_WIN32)
    struct timeval start_time;
# endif

    if (timeout) {
# if defined(__CYGWIN__) || defined(_WIN32)
	gettimeofday(&start_time, NULL);
	limit = (double)start_time.tv_sec + (double)start_time.tv_usec*1e-6;
# else
	limit = timeofday();
# endif
	limit += (double)timeout->tv_sec+(double)timeout->tv_usec*1e-6;
	wait_rest = *timeout;
	timeout = &wait_rest;
    }
#endif

    if (read) orig_read = *read;
    if (write) orig_write = *write;
    if (except) orig_except = *except;

  retry:
    lerrno = 0;

#if defined(__CYGWIN__) || defined(_WIN32)
    {
	int finish = 0;
	/* polling duration: 100ms */
	struct timeval wait_100ms, *wait;
	wait_100ms.tv_sec = 0;
	wait_100ms.tv_usec = 100 * 1000; /* 100 ms */

	do {
	    wait = (timeout == 0 || cmp_tv(&wait_100ms, timeout) > 0) ? &wait_100ms : timeout;
	    BLOCKING_REGION({
		do {
		    result = select(n, read, write, except, wait);
		    if (result < 0) lerrno = errno;
		    if (result != 0) break;

		    if (read) *read = orig_read;
		    if (write) *write = orig_write;
		    if (except) *except = orig_except;
		    wait = &wait_100ms;
		    if (timeout) {
			struct timeval elapsed;
			gettimeofday(&elapsed, NULL);
			subtract_tv(&elapsed, &start_time);
			if (!subtract_tv(timeout, &elapsed)) {
			    finish = 1;
			    break;
			}
			if (cmp_tv(&wait_100ms, timeout) < 0) wait = timeout;
		    }
		} while (__th->interrupt_flag == 0);
	    }, 0, 0);
	} while (result == 0 && !finish);
    }
#else
    BLOCKING_REGION({
	result = select(n, read, write, except, timeout);
	if (result < 0) lerrno = errno;
    }, ubf_select, GET_THREAD());
#endif

    errno = lerrno;

    if (result < 0) {
	switch (errno) {
	  case EINTR:
#ifdef ERESTART
	  case ERESTART:
#endif
	    if (read) *read = orig_read;
	    if (write) *write = orig_write;
	    if (except) *except = orig_except;
#ifndef linux
	    if (timeout) {
		double d = limit - timeofday();

		wait_rest.tv_sec = (unsigned int)d;
		wait_rest.tv_usec = (long)((d-(double)wait_rest.tv_sec)*1e6);
		if (wait_rest.tv_sec < 0)  wait_rest.tv_sec = 0;
		if (wait_rest.tv_usec < 0) wait_rest.tv_usec = 0;
	    }
#endif
	    goto retry;
	  default:
	    break;
	}
    }
    return result;
}

static void
rb_thread_wait_fd_rw(int fd, int read)
{
    int result = 0;
    thread_debug("rb_thread_wait_fd_rw(%d, %s)\n", fd, read ? "read" : "write");

    if (fd < 0) {
	rb_raise(rb_eIOError, "closed stream");
    }
    if (rb_thread_alone()) return;
    while (result <= 0) {
	rb_fdset_t set;
	rb_fd_init(&set);
	FD_SET(fd, &set);

	if (read) {
	    result = do_select(fd + 1, rb_fd_ptr(&set), 0, 0, 0);
	}
	else {
	    result = do_select(fd + 1, 0, rb_fd_ptr(&set), 0, 0);
	}

	rb_fd_term(&set);

	if (result < 0) {
	    rb_sys_fail(0);
	}
    }

    thread_debug("rb_thread_wait_fd_rw(%d, %s): done\n", fd, read ? "read" : "write");
}

void
rb_thread_wait_fd(int fd)
{
    rb_thread_wait_fd_rw(fd, 1);
}

int
rb_thread_fd_writable(int fd)
{
    rb_thread_wait_fd_rw(fd, 0);
    return Qtrue;
}

int
rb_thread_select(int max, fd_set * read, fd_set * write, fd_set * except,
		 struct timeval *timeout)
{
    if (!read && !write && !except) {
	if (!timeout) {
	    rb_thread_sleep_forever();
	    return 0;
	}
	rb_thread_wait_for(*timeout);
	return 0;
    }
    else {
	return do_select(max, read, write, except, timeout);
    }
}


/*
 * for GC
 */

#ifdef USE_CONSERVATIVE_STACK_END
void
rb_gc_set_stack_end(VALUE **stack_end_p)
{
    VALUE stack_end;
    *stack_end_p = &stack_end;
}
#endif

void
rb_gc_save_machine_context(rb_thread_t *th)
{
    SET_MACHINE_STACK_END(&th->machine_stack_end);
    FLUSH_REGISTER_WINDOWS;
#ifdef __ia64
    th->machine_register_stack_end = rb_ia64_bsp();
#endif
    setjmp(th->machine_regs);
}

/*
 *
 */

int rb_get_next_signal(void);

static void
timer_thread_function(void *arg)
{
    rb_vm_t *vm = GET_VM(); /* TODO: fix me for Multi-VM */
    int sig;

    /* for time slice */
    RUBY_VM_SET_TIMER_INTERRUPT(vm->running_thread);

    /* check signal */
    if ((sig = rb_get_next_signal()) > 0) {
	rb_thread_t *mth = vm->main_thread;
	enum rb_thread_status prev_status = mth->status;
	thread_debug("main_thread: %s, sig: %d\n",
		     thread_status_name(prev_status), sig);
	mth->exec_signal = sig;
	if (mth->status != THREAD_KILLED) mth->status = THREAD_RUNNABLE;
	rb_thread_interrupt(mth);
	mth->status = prev_status;
    }

#if 0
    /* prove profiler */
    if (vm->prove_profile.enable) {
	rb_thread_t *th = vm->running_thread;

	if (vm->during_gc) {
	    /* GC prove profiling */
	}
    }
#endif
}

void
rb_thread_stop_timer_thread(void)
{
    if (timer_thread_id && native_stop_timer_thread()) {
	native_thread_join(timer_thread_id);
	timer_thread_id = 0;
    }
}

void
rb_thread_reset_timer_thread(void)
{
    timer_thread_id = 0;
}

void
rb_thread_start_timer_thread(void)
{
    system_working = 1;
    rb_thread_create_timer_thread();
}

static int
clear_coverage_i(st_data_t key, st_data_t val, st_data_t dummy)
{
    int i;
    VALUE lines = (VALUE)val;

    for (i = 0; i < RARRAY_LEN(lines); i++) {
	if (RARRAY_PTR(lines)[i] != Qnil) {
	    RARRAY_PTR(lines)[i] = INT2FIX(0);
	}
    }
    return ST_CONTINUE;
}

static void
clear_coverage(void)
{
    extern VALUE rb_get_coverages(void);
    VALUE coverages = rb_get_coverages();
    if (RTEST(coverages)) {
	st_foreach(RHASH_TBL(coverages), clear_coverage_i, 0);
    }
}

static int
terminate_atfork_i(st_data_t key, st_data_t val, rb_thread_t *current_th)
{
    VALUE thval = key;
    rb_thread_t *th;
    GetThreadPtr(thval, th);

    if (th != current_th) {
	thread_cleanup_func(th);
    }
    return ST_CONTINUE;
}

void
rb_thread_atfork(void)
{
    rb_thread_t *th = GET_THREAD();
    rb_vm_t *vm = th->vm;
    VALUE thval = th->self;
    vm->main_thread = th;

    st_foreach(vm->living_threads, terminate_atfork_i, (st_data_t)th);
    st_clear(vm->living_threads);
    st_insert(vm->living_threads, thval, (st_data_t) th->thread_id);
    vm->sleeper = 0;
    clear_coverage();
    rb_reset_random_seed();
}

static int
terminate_atfork_before_exec_i(st_data_t key, st_data_t val, rb_thread_t *current_th)
{
    VALUE thval = key;
    rb_thread_t *th;
    GetThreadPtr(thval, th);

    if (th != current_th) {
	thread_cleanup_func_before_exec(th);
    }
    return ST_CONTINUE;
}

void
rb_thread_atfork_before_exec(void)
{
    rb_thread_t *th = GET_THREAD();
    rb_vm_t *vm = th->vm;
    VALUE thval = th->self;
    vm->main_thread = th;

    st_foreach(vm->living_threads, terminate_atfork_before_exec_i, (st_data_t)th);
    st_clear(vm->living_threads);
    st_insert(vm->living_threads, thval, (st_data_t) th->thread_id);
    vm->sleeper = 0;
    clear_coverage();
}

struct thgroup {
    int enclosed;
    VALUE group;
};

/*
 * Document-class: ThreadGroup
 *
 *  <code>ThreadGroup</code> provides a means of keeping track of a number of
 *  threads as a group. A <code>Thread</code> can belong to only one
 *  <code>ThreadGroup</code> at a time; adding a thread to a new group will
 *  remove it from any previous group.
 *
 *  Newly created threads belong to the same group as the thread from which they
 *  were created.
 */

static VALUE thgroup_s_alloc(VALUE);
static VALUE
thgroup_s_alloc(VALUE klass)
{
    VALUE group;
    struct thgroup *data;

    group = Data_Make_Struct(klass, struct thgroup, 0, -1, data);
    data->enclosed = 0;
    data->group = group;

    return group;
}

struct thgroup_list_params {
    VALUE ary;
    VALUE group;
};

static int
thgroup_list_i(st_data_t key, st_data_t val, st_data_t data)
{
    VALUE thread = (VALUE)key;
    VALUE ary = ((struct thgroup_list_params *)data)->ary;
    VALUE group = ((struct thgroup_list_params *)data)->group;
    rb_thread_t *th;
    GetThreadPtr(thread, th);

    if (th->thgroup == group) {
	rb_ary_push(ary, thread);
    }
    return ST_CONTINUE;
}

/*
 *  call-seq:
 *     thgrp.list   => array
 *
 *  Returns an array of all existing <code>Thread</code> objects that belong to
 *  this group.
 *
 *     ThreadGroup::Default.list   #=> [#<Thread:0x401bdf4c run>]
 */

static VALUE
thgroup_list(VALUE group)
{
    VALUE ary = rb_ary_new();
    struct thgroup_list_params param;
    
    param.ary = ary;
    param.group = group;
    st_foreach(GET_THREAD()->vm->living_threads, thgroup_list_i, (st_data_t) & param);
    return ary;
}


/*
 *  call-seq:
 *     thgrp.enclose   => thgrp
 *
 *  Prevents threads from being added to or removed from the receiving
 *  <code>ThreadGroup</code>. New threads can still be started in an enclosed
 *  <code>ThreadGroup</code>.
 *
 *     ThreadGroup::Default.enclose        #=> #<ThreadGroup:0x4029d914>
 *     thr = Thread::new { Thread.stop }   #=> #<Thread:0x402a7210 sleep>
 *     tg = ThreadGroup::new               #=> #<ThreadGroup:0x402752d4>
 *     tg.add thr
 *
 *  <em>produces:</em>
 *
 *     ThreadError: can't move from the enclosed thread group
 */

static VALUE
thgroup_enclose(VALUE group)
{
    struct thgroup *data;

    Data_Get_Struct(group, struct thgroup, data);
    data->enclosed = 1;

    return group;
}


/*
 *  call-seq:
 *     thgrp.enclosed?   => true or false
 *
 *  Returns <code>true</code> if <em>thgrp</em> is enclosed. See also
 *  ThreadGroup#enclose.
 */

static VALUE
thgroup_enclosed_p(VALUE group)
{
    struct thgroup *data;

    Data_Get_Struct(group, struct thgroup, data);
    if (data->enclosed)
	return Qtrue;
    return Qfalse;
}


/*
 *  call-seq:
 *     thgrp.add(thread)   => thgrp
 *
 *  Adds the given <em>thread</em> to this group, removing it from any other
 *  group to which it may have previously belonged.
 *
 *     puts "Initial group is #{ThreadGroup::Default.list}"
 *     tg = ThreadGroup.new
 *     t1 = Thread.new { sleep }
 *     t2 = Thread.new { sleep }
 *     puts "t1 is #{t1}"
 *     puts "t2 is #{t2}"
 *     tg.add(t1)
 *     puts "Initial group now #{ThreadGroup::Default.list}"
 *     puts "tg group now #{tg.list}"
 *
 *  <em>produces:</em>
 *
 *     Initial group is #<Thread:0x401bdf4c>
 *     t1 is #<Thread:0x401b3c90>
 *     t2 is #<Thread:0x401b3c18>
 *     Initial group now #<Thread:0x401b3c18>#<Thread:0x401bdf4c>
 *     tg group now #<Thread:0x401b3c90>
 */

static VALUE
thgroup_add(VALUE group, VALUE thread)
{
    rb_thread_t *th;
    struct thgroup *data;

    rb_secure(4);
    GetThreadPtr(thread, th);

    if (OBJ_FROZEN(group)) {
	rb_raise(rb_eThreadError, "can't move to the frozen thread group");
    }
    Data_Get_Struct(group, struct thgroup, data);
    if (data->enclosed) {
	rb_raise(rb_eThreadError, "can't move to the enclosed thread group");
    }

    if (!th->thgroup) {
	return Qnil;
    }

    if (OBJ_FROZEN(th->thgroup)) {
	rb_raise(rb_eThreadError, "can't move from the frozen thread group");
    }
    Data_Get_Struct(th->thgroup, struct thgroup, data);
    if (data->enclosed) {
	rb_raise(rb_eThreadError,
		 "can't move from the enclosed thread group");
    }

    th->thgroup = group;
    return group;
}


/*
 *  Document-class: Mutex
 *
 *  Mutex implements a simple semaphore that can be used to coordinate access to
 *  shared data from multiple concurrent threads.
 *
 *  Example:
 *
 *    require 'thread'
 *    semaphore = Mutex.new
 *
 *    a = Thread.new {
 *      semaphore.synchronize {
 *        # access shared resource
 *      }
 *    }
 *
 *    b = Thread.new {
 *      semaphore.synchronize {
 *        # access shared resource
 *      }
 *    }
 *
 */

#define GetMutexPtr(obj, tobj) \
  Data_Get_Struct(obj, mutex_t, tobj)

static const char *mutex_unlock(mutex_t *mutex);

static void
mutex_free(void *ptr)
{
    if (ptr) {
	mutex_t *mutex = ptr;
	if (mutex->th) {
	    /* rb_warn("free locked mutex"); */
	    mutex_unlock(mutex);
	}
	native_mutex_destroy(&mutex->lock);
	native_cond_destroy(&mutex->cond);
    }
    ruby_xfree(ptr);
}

static VALUE
mutex_alloc(VALUE klass)
{
    VALUE volatile obj;
    mutex_t *mutex;

    obj = Data_Make_Struct(klass, mutex_t, NULL, mutex_free, mutex);
    native_mutex_initialize(&mutex->lock);
    native_cond_initialize(&mutex->cond);
    return obj;
}

/*
 *  call-seq:
 *     Mutex.new   => mutex
 *
 *  Creates a new Mutex
 */
static VALUE
mutex_initialize(VALUE self)
{
    return self;
}

VALUE
rb_mutex_new(void)
{
    return mutex_alloc(rb_cMutex);
}

/*
 * call-seq:
 *    mutex.locked?  => true or false
 *
 * Returns +true+ if this lock is currently held by some thread.
 */
VALUE
rb_mutex_locked_p(VALUE self)
{
    mutex_t *mutex;
    GetMutexPtr(self, mutex);
    return mutex->th ? Qtrue : Qfalse;
}

static void
mutex_locked(rb_thread_t *th, VALUE self)
{
    mutex_t *mutex;
    GetMutexPtr(self, mutex);

    if (th->keeping_mutexes) {
	mutex->next_mutex = th->keeping_mutexes;
    }
    th->keeping_mutexes = mutex;
}

/*
 * call-seq:
 *    mutex.try_lock  => true or false
 *
 * Attempts to obtain the lock and returns immediately. Returns +true+ if the
 * lock was granted.
 */
VALUE
rb_mutex_trylock(VALUE self)
{
    mutex_t *mutex;
    VALUE locked = Qfalse;
    GetMutexPtr(self, mutex);

    if (mutex->th == GET_THREAD()) {
	rb_raise(rb_eThreadError, "deadlock; recursive locking");
    }

    native_mutex_lock(&mutex->lock);
    if (mutex->th == 0) {
	mutex->th = GET_THREAD();
	locked = Qtrue;

	mutex_locked(GET_THREAD(), self);
    }
    native_mutex_unlock(&mutex->lock);

    return locked;
}

static int
lock_func(rb_thread_t *th, mutex_t *mutex, int last_thread)
{
    int interrupted = 0;
#if 0 /* for debug */
    native_thread_yield();
#endif

    native_mutex_lock(&mutex->lock);
    th->transition_for_lock = 0;
    while (mutex->th || (mutex->th = th, 0)) {
	if (last_thread) {
	    interrupted = 2;
	    break;
	}

	mutex->cond_waiting++;
	native_cond_wait(&mutex->cond, &mutex->lock);
	mutex->cond_notified--;

	if (RUBY_VM_INTERRUPTED(th)) {
	    interrupted = 1;
	    break;
	}
    }
    th->transition_for_lock = 1;
    native_mutex_unlock(&mutex->lock);

    if (interrupted == 2) native_thread_yield();
#if 0 /* for debug */
    native_thread_yield();
#endif

    return interrupted;
}

static void
lock_interrupt(void *ptr)
{
    mutex_t *mutex = (mutex_t *)ptr;
    native_mutex_lock(&mutex->lock);
    if (mutex->cond_waiting > 0) {
	native_cond_broadcast(&mutex->cond);
	mutex->cond_notified = mutex->cond_waiting;
	mutex->cond_waiting = 0;
    }
    native_mutex_unlock(&mutex->lock);
}

/*
 * call-seq:
 *    mutex.lock  => true or false
 *
 * Attempts to grab the lock and waits if it isn't available.
 * Raises +ThreadError+ if +mutex+ was locked by the current thread.
 */
VALUE
rb_mutex_lock(VALUE self)
{
    if (rb_mutex_trylock(self) == Qfalse) {
	mutex_t *mutex;
	rb_thread_t *th = GET_THREAD();
	GetMutexPtr(self, mutex);

	while (mutex->th != th) {
	    int interrupted;
	    enum rb_thread_status prev_status = th->status;
	    int last_thread = 0;
	    struct rb_unblock_callback oldubf;

	    set_unblock_function(th, lock_interrupt, mutex, &oldubf);
	    th->status = THREAD_STOPPED_FOREVER;
	    th->vm->sleeper++;
	    th->locking_mutex = self;
	    if (vm_living_thread_num(th->vm) == th->vm->sleeper) {
		last_thread = 1;
	    }

	    th->transition_for_lock = 1;
	    BLOCKING_REGION_CORE({
		interrupted = lock_func(th, mutex, last_thread);
	    });
	    th->transition_for_lock = 0;
	    remove_signal_thread_list(th);
	    reset_unblock_function(th, &oldubf);

	    th->locking_mutex = Qfalse;
	    if (mutex->th && interrupted == 2) {
		rb_check_deadlock(th->vm);
	    }
	    if (th->status == THREAD_STOPPED_FOREVER) {
		th->status = prev_status;
	    }
	    th->vm->sleeper--;

	    if (mutex->th == th) mutex_locked(th, self);

	    if (interrupted) {
		RUBY_VM_CHECK_INTS();
	    }
	}
    }
    return self;
}

static const char *
mutex_unlock(mutex_t *mutex)
{
    const char *err = NULL;
    rb_thread_t *th = GET_THREAD();
    mutex_t *th_mutex;

    native_mutex_lock(&mutex->lock);

    if (mutex->th == 0) {
	err = "Attempt to unlock a mutex which is not locked";
    }
    else if (mutex->th != GET_THREAD()) {
	err = "Attempt to unlock a mutex which is locked by another thread";
    }
    else {
	mutex->th = 0;
	if (mutex->cond_waiting > 0) {
	    /* waiting thread */
	    native_cond_signal(&mutex->cond);
	    mutex->cond_waiting--;
	    mutex->cond_notified++;
	}
    }

    native_mutex_unlock(&mutex->lock);

    if (!err) {
	th_mutex = th->keeping_mutexes;
	if (th_mutex == mutex) {
	    th->keeping_mutexes = mutex->next_mutex;
	}
	else {
	    while (1) {
		mutex_t *tmp_mutex;
		tmp_mutex = th_mutex->next_mutex;
		if (tmp_mutex == mutex) {
		    th_mutex->next_mutex = tmp_mutex->next_mutex;
		    break;
		}
		th_mutex = tmp_mutex;
	    }
	}
	mutex->next_mutex = NULL;
    }

    return err;
}

/*
 * call-seq:
 *    mutex.unlock    => self
 *
 * Releases the lock.
 * Raises +ThreadError+ if +mutex+ wasn't locked by the current thread.
 */
VALUE
rb_mutex_unlock(VALUE self)
{
    const char *err;
    mutex_t *mutex;
    GetMutexPtr(self, mutex);

    err = mutex_unlock(mutex);
    if (err) rb_raise(rb_eThreadError, err);

    return self;
}

static void
rb_mutex_unlock_all(mutex_t *mutexes)
{
    const char *err;
    mutex_t *mutex;

    while (mutexes) {
	mutex = mutexes;
	/* rb_warn("mutex #<%p> remains to be locked by terminated thread",
		mutexes); */
	mutexes = mutex->next_mutex;
	err = mutex_unlock(mutex);
	if (err) rb_bug("invalid keeping_mutexes: %s", err);
    }
}

static VALUE
rb_mutex_sleep_forever(VALUE time)
{
    rb_thread_sleep_deadly();
    return Qnil;
}

static VALUE
rb_mutex_wait_for(VALUE time)
{
    const struct timeval *t = (struct timeval *)time;
    rb_thread_wait_for(*t);
    return Qnil;
}

VALUE
rb_mutex_sleep(VALUE self, VALUE timeout)
{
    time_t beg, end;
    struct timeval t;

    if (!NIL_P(timeout)) {
        t = rb_time_interval(timeout);
    }
    rb_mutex_unlock(self);
    beg = time(0);
    if (NIL_P(timeout)) {
	rb_ensure(rb_mutex_sleep_forever, Qnil, rb_mutex_lock, self);
    }
    else {
	rb_ensure(rb_mutex_wait_for, (VALUE)&t, rb_mutex_lock, self);
    }
    end = time(0) - beg;
    return INT2FIX(end);
}

/*
 * call-seq:
 *    mutex.sleep(timeout = nil)    => number
 *
 * Releases the lock and sleeps +timeout+ seconds if it is given and
 * non-nil or forever.  Raises +ThreadError+ if +mutex+ wasn't locked by
 * the current thread.
 */
static VALUE
mutex_sleep(int argc, VALUE *argv, VALUE self)
{
    VALUE timeout;

    rb_scan_args(argc, argv, "01", &timeout);
    return rb_mutex_sleep(self, timeout);
}

/*
 * call-seq:
 *    mutex.synchronize { ... }    => result of the block
 *
 * Obtains a lock, runs the block, and releases the lock when the block
 * completes.  See the example under +Mutex+.
 */

VALUE
rb_mutex_synchronize(VALUE mutex, VALUE (*func)(VALUE arg), VALUE arg)
{
    rb_mutex_lock(mutex);
    return rb_ensure(func, arg, rb_mutex_unlock, mutex);
}

/*
 * Document-class: Barrier
 */
static VALUE
barrier_alloc(VALUE klass)
{
    return Data_Wrap_Struct(klass, rb_gc_mark, 0, (void *)mutex_alloc(0));
}

VALUE
rb_barrier_new(void)
{
    VALUE barrier = barrier_alloc(rb_cBarrier);
    rb_mutex_lock((VALUE)DATA_PTR(barrier));
    return barrier;
}

VALUE
rb_barrier_wait(VALUE self)
{
    VALUE mutex = (VALUE)DATA_PTR(self);
    mutex_t *m;

    if (!mutex) return Qfalse;
    GetMutexPtr(mutex, m);
    if (m->th == GET_THREAD()) return Qfalse;
    rb_mutex_lock(mutex);
    if (DATA_PTR(self)) return Qtrue;
    rb_mutex_unlock(mutex);
    return Qfalse;
}

VALUE
rb_barrier_release(VALUE self)
{
    return rb_mutex_unlock((VALUE)DATA_PTR(self));
}

VALUE
rb_barrier_destroy(VALUE self)
{
    VALUE mutex = (VALUE)DATA_PTR(self);
    DATA_PTR(self) = 0;
    return rb_mutex_unlock(mutex);
}

/* variables for recursive traversals */
static ID recursive_key;

static VALUE
recursive_check(VALUE hash, VALUE obj)
{
    if (NIL_P(hash) || TYPE(hash) != T_HASH) {
	return Qfalse;
    }
    else {
	VALUE list = rb_hash_aref(hash, ID2SYM(rb_frame_this_func()));

	if (NIL_P(list) || TYPE(list) != T_HASH)
	    return Qfalse;
	if (NIL_P(rb_hash_lookup(list, obj)))
	    return Qfalse;
	return Qtrue;
    }
}

static VALUE
recursive_push(VALUE hash, VALUE obj)
{
    VALUE list, sym;

    sym = ID2SYM(rb_frame_this_func());
    if (NIL_P(hash) || TYPE(hash) != T_HASH) {
	hash = rb_hash_new();
	rb_thread_local_aset(rb_thread_current(), recursive_key, hash);
	list = Qnil;
    }
    else {
	list = rb_hash_aref(hash, sym);
    }
    if (NIL_P(list) || TYPE(list) != T_HASH) {
	list = rb_hash_new();
	rb_hash_aset(hash, sym, list);
    }
    rb_hash_aset(list, obj, Qtrue);
    return hash;
}

static void
recursive_pop(VALUE hash, VALUE obj)
{
    VALUE list, sym;

    sym = ID2SYM(rb_frame_this_func());
    if (NIL_P(hash) || TYPE(hash) != T_HASH) {
	VALUE symname;
	VALUE thrname;
	symname = rb_inspect(sym);
	thrname = rb_inspect(rb_thread_current());

	rb_raise(rb_eTypeError, "invalid inspect_tbl hash for %s in %s",
		 StringValuePtr(symname), StringValuePtr(thrname));
    }
    list = rb_hash_aref(hash, sym);
    if (NIL_P(list) || TYPE(list) != T_HASH) {
	VALUE symname = rb_inspect(sym);
	VALUE thrname = rb_inspect(rb_thread_current());
	rb_raise(rb_eTypeError, "invalid inspect_tbl list for %s in %s",
		 StringValuePtr(symname), StringValuePtr(thrname));
    }
    rb_hash_delete(list, obj);
}

VALUE
rb_exec_recursive(VALUE (*func) (VALUE, VALUE, int), VALUE obj, VALUE arg)
{
    VALUE hash = rb_thread_local_aref(rb_thread_current(), recursive_key);
    VALUE objid = rb_obj_id(obj);

    if (recursive_check(hash, objid)) {
	return (*func) (obj, arg, Qtrue);
    }
    else {
	VALUE result = Qundef;
	int state;

	hash = recursive_push(hash, objid);
	PUSH_TAG();
	if ((state = EXEC_TAG()) == 0) {
	    result = (*func) (obj, arg, Qfalse);
	}
	POP_TAG();
	recursive_pop(hash, objid);
	if (state)
	    JUMP_TAG(state);
	return result;
    }
}

/* tracer */

static rb_event_hook_t *
alloc_event_hook(rb_event_hook_func_t func, rb_event_flag_t events, VALUE data)
{
    rb_event_hook_t *hook = ALLOC(rb_event_hook_t);
    hook->func = func;
    hook->flag = events;
    hook->data = data;
    return hook;
}

static void
thread_reset_event_flags(rb_thread_t *th)
{
    rb_event_hook_t *hook = th->event_hooks;
    rb_event_flag_t flag = th->event_flags & RUBY_EVENT_VM;

    while (hook) {
	flag |= hook->flag;
	hook = hook->next;
    }
}

void
rb_thread_add_event_hook(rb_thread_t *th,
			 rb_event_hook_func_t func, rb_event_flag_t events, VALUE data)
{
    rb_event_hook_t *hook = alloc_event_hook(func, events, data);
    hook->next = th->event_hooks;
    th->event_hooks = hook;
    thread_reset_event_flags(th);
}

static int
set_threads_event_flags_i(st_data_t key, st_data_t val, st_data_t flag)
{
    VALUE thval = key;
    rb_thread_t *th;
    GetThreadPtr(thval, th);

    if (flag) {
	th->event_flags |= RUBY_EVENT_VM;
    }
    else {
	th->event_flags &= (~RUBY_EVENT_VM);
    }
    return ST_CONTINUE;
}

static void
set_threads_event_flags(int flag)
{
    st_foreach(GET_VM()->living_threads, set_threads_event_flags_i, (st_data_t) flag);
}

void
rb_add_event_hook(rb_event_hook_func_t func, rb_event_flag_t events, VALUE data)
{
    rb_event_hook_t *hook = alloc_event_hook(func, events, data);
    rb_vm_t *vm = GET_VM();

    hook->next = vm->event_hooks;
    vm->event_hooks = hook;

    set_threads_event_flags(1);
}

static int
remove_event_hook(rb_event_hook_t **root, rb_event_hook_func_t func)
{
    rb_event_hook_t *prev = NULL, *hook = *root, *next;

    while (hook) {
	next = hook->next;
	if (func == 0 || hook->func == func) {
	    if (prev) {
		prev->next = hook->next;
	    }
	    else {
		*root = hook->next;
	    }
	    xfree(hook);
	}
	else {
	    prev = hook;
	}
	hook = next;
    }
    return -1;
}

int
rb_thread_remove_event_hook(rb_thread_t *th, rb_event_hook_func_t func)
{
    int ret = remove_event_hook(&th->event_hooks, func);
    thread_reset_event_flags(th);
    return ret;
}

int
rb_remove_event_hook(rb_event_hook_func_t func)
{
    rb_vm_t *vm = GET_VM();
    rb_event_hook_t *hook = vm->event_hooks;
    int ret = remove_event_hook(&vm->event_hooks, func);

    if (hook != NULL && vm->event_hooks == NULL) {
	set_threads_event_flags(0);
    }

    return ret;
}

static int
clear_trace_func_i(st_data_t key, st_data_t val, st_data_t flag)
{
    rb_thread_t *th;
    GetThreadPtr((VALUE)key, th);
    rb_thread_remove_event_hook(th, 0);
    return ST_CONTINUE;
}

void
rb_clear_trace_func(void)
{
    st_foreach(GET_VM()->living_threads, clear_trace_func_i, (st_data_t) 0);
    rb_remove_event_hook(0);
}

static void call_trace_func(rb_event_flag_t, VALUE data, VALUE self, ID id, VALUE klass);

/*
 *  call-seq:
 *     set_trace_func(proc)    => proc
 *     set_trace_func(nil)     => nil
 *
 *  Establishes _proc_ as the handler for tracing, or disables
 *  tracing if the parameter is +nil+. _proc_ takes up
 *  to six parameters: an event name, a filename, a line number, an
 *  object id, a binding, and the name of a class. _proc_ is
 *  invoked whenever an event occurs. Events are: <code>c-call</code>
 *  (call a C-language routine), <code>c-return</code> (return from a
 *  C-language routine), <code>call</code> (call a Ruby method),
 *  <code>class</code> (start a class or module definition),
 *  <code>end</code> (finish a class or module definition),
 *  <code>line</code> (execute code on a new line), <code>raise</code>
 *  (raise an exception), and <code>return</code> (return from a Ruby
 *  method). Tracing is disabled within the context of _proc_.
 *
 *      class Test
 *	def test
 *	  a = 1
 *	  b = 2
 *	end
 *      end
 *
 *      set_trace_func proc { |event, file, line, id, binding, classname|
 *	   printf "%8s %s:%-2d %10s %8s\n", event, file, line, id, classname
 *      }
 *      t = Test.new
 *      t.test
 *
 *	  line prog.rb:11               false
 *      c-call prog.rb:11        new    Class
 *      c-call prog.rb:11 initialize   Object
 *    c-return prog.rb:11 initialize   Object
 *    c-return prog.rb:11        new    Class
 *	  line prog.rb:12               false
 *  	  call prog.rb:2        test     Test
 *	  line prog.rb:3        test     Test
 *	  line prog.rb:4        test     Test
 *      return prog.rb:4        test     Test
 */

static VALUE
set_trace_func(VALUE obj, VALUE trace)
{
    rb_remove_event_hook(call_trace_func);

    if (NIL_P(trace)) {
	return Qnil;
    }

    if (!rb_obj_is_proc(trace)) {
	rb_raise(rb_eTypeError, "trace_func needs to be Proc");
    }

    rb_add_event_hook(call_trace_func, RUBY_EVENT_ALL, trace);
    return trace;
}

static void
thread_add_trace_func(rb_thread_t *th, VALUE trace)
{
    if (!rb_obj_is_proc(trace)) {
	rb_raise(rb_eTypeError, "trace_func needs to be Proc");
    }

    rb_thread_add_event_hook(th, call_trace_func, RUBY_EVENT_ALL, trace);
}

static VALUE
thread_add_trace_func_m(VALUE obj, VALUE trace)
{
    rb_thread_t *th;
    GetThreadPtr(obj, th);
    thread_add_trace_func(th, trace);
    return trace;
}

static VALUE
thread_set_trace_func_m(VALUE obj, VALUE trace)
{
    rb_thread_t *th;
    GetThreadPtr(obj, th);
    rb_thread_remove_event_hook(th, call_trace_func);

    if (NIL_P(trace)) {
	return Qnil;
    }
    thread_add_trace_func(th, trace);
    return trace;
}

static const char *
get_event_name(rb_event_flag_t event)
{
    switch (event) {
      case RUBY_EVENT_LINE:
	return "line";
      case RUBY_EVENT_CLASS:
	return "class";
      case RUBY_EVENT_END:
	return "end";
      case RUBY_EVENT_CALL:
	return "call";
      case RUBY_EVENT_RETURN:
	return "return";
      case RUBY_EVENT_C_CALL:
	return "c-call";
      case RUBY_EVENT_C_RETURN:
	return "c-return";
      case RUBY_EVENT_RAISE:
	return "raise";
      default:
	return "unknown";
    }
}

VALUE ruby_suppress_tracing(VALUE (*func)(VALUE, int), VALUE arg, int always);

struct call_trace_func_args {
    rb_event_flag_t event;
    VALUE proc;
    VALUE self;
    ID id;
    VALUE klass;
};

static VALUE
call_trace_proc(VALUE args, int tracing)
{
    struct call_trace_func_args *p = (struct call_trace_func_args *)args;
    VALUE eventname = rb_str_new2(get_event_name(p->event));
    VALUE filename = rb_str_new2(rb_sourcefile());
    VALUE argv[6];
    int line = rb_sourceline();
    ID id = 0;
    VALUE klass = 0;

    if (p->event == RUBY_EVENT_C_CALL ||
	p->event == RUBY_EVENT_C_RETURN) {
	id = p->id;
	klass = p->klass;
    }
    else {
	rb_thread_method_id_and_class(GET_THREAD(), &id, &klass);
    }
    if (id == ID_ALLOCATOR)
      return Qnil;
    if (klass) {
	if (TYPE(klass) == T_ICLASS) {
	    klass = RBASIC(klass)->klass;
	}
	else if (FL_TEST(klass, FL_SINGLETON)) {
	    klass = rb_iv_get(klass, "__attached__");
	}
    }

    argv[0] = eventname;
    argv[1] = filename;
    argv[2] = INT2FIX(line);
    argv[3] = id ? ID2SYM(id) : Qnil;
    argv[4] = p->self ? rb_binding_new() : Qnil;
    argv[5] = klass ? klass : Qnil;

    return rb_proc_call_with_block(p->proc, 6, argv, Qnil);
}

static void
call_trace_func(rb_event_flag_t event, VALUE proc, VALUE self, ID id, VALUE klass)
{
    struct call_trace_func_args args;
    
    args.event = event;
    args.proc = proc;
    args.self = self;
    args.id = id;
    args.klass = klass;
    ruby_suppress_tracing(call_trace_proc, (VALUE)&args, Qfalse);
}

VALUE
ruby_suppress_tracing(VALUE (*func)(VALUE, int), VALUE arg, int always)
{
    rb_thread_t *th = GET_THREAD();
    int state, raised, tracing;
    VALUE result = Qnil;

    if ((tracing = th->tracing) != 0 && !always) {
	return Qnil;
    }
    else {
	th->tracing = 1;
    }

    raised = rb_thread_reset_raised(th);

    PUSH_TAG();
    if ((state = EXEC_TAG()) == 0) {
	result = (*func)(arg, tracing);
    }

    if (raised) {
	rb_thread_set_raised(th);
    }
    POP_TAG();

    th->tracing = tracing;
    if (state) {
	JUMP_TAG(state);
    }

    return result;
}

/*
 *  +Thread+ encapsulates the behavior of a thread of
 *  execution, including the main thread of the Ruby script.
 *
 *  In the descriptions of the methods in this class, the parameter _sym_
 *  refers to a symbol, which is either a quoted string or a
 *  +Symbol+ (such as <code>:name</code>).
 */

void
Init_Thread(void)
{
#undef rb_intern
#define rb_intern(str) rb_intern_const(str)

    VALUE cThGroup;

    rb_define_singleton_method(rb_cThread, "new", thread_s_new, -1);
    rb_define_singleton_method(rb_cThread, "start", thread_start, -2);
    rb_define_singleton_method(rb_cThread, "fork", thread_start, -2);
    rb_define_singleton_method(rb_cThread, "main", rb_thread_s_main, 0);
    rb_define_singleton_method(rb_cThread, "current", thread_s_current, 0);
    rb_define_singleton_method(rb_cThread, "stop", rb_thread_stop, 0);
    rb_define_singleton_method(rb_cThread, "kill", rb_thread_s_kill, 1);
    rb_define_singleton_method(rb_cThread, "exit", rb_thread_exit, 0);
    rb_define_singleton_method(rb_cThread, "pass", thread_s_pass, 0);
    rb_define_singleton_method(rb_cThread, "list", rb_thread_list, 0);
    rb_define_singleton_method(rb_cThread, "abort_on_exception", rb_thread_s_abort_exc, 0);
    rb_define_singleton_method(rb_cThread, "abort_on_exception=", rb_thread_s_abort_exc_set, 1);
#if THREAD_DEBUG < 0
    rb_define_singleton_method(rb_cThread, "DEBUG", rb_thread_s_debug, 0);
    rb_define_singleton_method(rb_cThread, "DEBUG=", rb_thread_s_debug_set, 1);
#endif

    rb_define_method(rb_cThread, "initialize", thread_initialize, -2);
    rb_define_method(rb_cThread, "raise", thread_raise_m, -1);
    rb_define_method(rb_cThread, "join", thread_join_m, -1);
    rb_define_method(rb_cThread, "value", thread_value, 0);
    rb_define_method(rb_cThread, "kill", rb_thread_kill, 0);
    rb_define_method(rb_cThread, "terminate", rb_thread_kill, 0);
    rb_define_method(rb_cThread, "exit", rb_thread_kill, 0);
    rb_define_method(rb_cThread, "run", rb_thread_run, 0);
    rb_define_method(rb_cThread, "wakeup", rb_thread_wakeup, 0);
    rb_define_method(rb_cThread, "[]", rb_thread_aref, 1);
    rb_define_method(rb_cThread, "[]=", rb_thread_aset, 2);
    rb_define_method(rb_cThread, "key?", rb_thread_key_p, 1);
    rb_define_method(rb_cThread, "keys", rb_thread_keys, 0);
    rb_define_method(rb_cThread, "priority", rb_thread_priority, 0);
    rb_define_method(rb_cThread, "priority=", rb_thread_priority_set, 1);
    rb_define_method(rb_cThread, "status", rb_thread_status, 0);
    rb_define_method(rb_cThread, "alive?", rb_thread_alive_p, 0);
    rb_define_method(rb_cThread, "stop?", rb_thread_stop_p, 0);
    rb_define_method(rb_cThread, "abort_on_exception", rb_thread_abort_exc, 0);
    rb_define_method(rb_cThread, "abort_on_exception=", rb_thread_abort_exc_set, 1);
    rb_define_method(rb_cThread, "safe_level", rb_thread_safe_level, 0);
    rb_define_method(rb_cThread, "group", rb_thread_group, 0);

    rb_define_method(rb_cThread, "inspect", rb_thread_inspect, 0);

    cThGroup = rb_define_class("ThreadGroup", rb_cObject);
    rb_define_alloc_func(cThGroup, thgroup_s_alloc);
    rb_define_method(cThGroup, "list", thgroup_list, 0);
    rb_define_method(cThGroup, "enclose", thgroup_enclose, 0);
    rb_define_method(cThGroup, "enclosed?", thgroup_enclosed_p, 0);
    rb_define_method(cThGroup, "add", thgroup_add, 1);

    {
	rb_thread_t *th = GET_THREAD();
	th->thgroup = th->vm->thgroup_default = rb_obj_alloc(cThGroup);
	rb_define_const(cThGroup, "Default", th->thgroup);
    }

    rb_cMutex = rb_define_class("Mutex", rb_cObject);
    rb_define_alloc_func(rb_cMutex, mutex_alloc);
    rb_define_method(rb_cMutex, "initialize", mutex_initialize, 0);
    rb_define_method(rb_cMutex, "locked?", rb_mutex_locked_p, 0);
    rb_define_method(rb_cMutex, "try_lock", rb_mutex_trylock, 0);
    rb_define_method(rb_cMutex, "lock", rb_mutex_lock, 0);
    rb_define_method(rb_cMutex, "unlock", rb_mutex_unlock, 0);
    rb_define_method(rb_cMutex, "sleep", mutex_sleep, -1);

    recursive_key = rb_intern("__recursive_key__");
    rb_eThreadError = rb_define_class("ThreadError", rb_eStandardError);

    /* trace */
    rb_define_global_function("set_trace_func", set_trace_func, 1);
    rb_define_method(rb_cThread, "set_trace_func", thread_set_trace_func_m, 1);
    rb_define_method(rb_cThread, "add_trace_func", thread_add_trace_func_m, 1);

    /* init thread core */
    Init_native_thread();
    {
	/* main thread setting */
	{
	    /* acquire global interpreter lock */
	    rb_thread_lock_t *lp = &GET_THREAD()->vm->global_vm_lock;
	    native_mutex_initialize(lp);
	    native_mutex_lock(lp);
	    native_mutex_initialize(&GET_THREAD()->interrupt_lock);
	}
    }

    rb_thread_create_timer_thread();

    (void)native_mutex_trylock;
    (void)ruby_thread_set_native;
}

int
ruby_native_thread_p(void)
{
    rb_thread_t *th = ruby_thread_from_native();

    return th ? Qtrue : Qfalse;
}

static int
check_deadlock_i(st_data_t key, st_data_t val, int *found)
{
    VALUE thval = key;
    rb_thread_t *th;
    GetThreadPtr(thval, th);

    if (th->status != THREAD_STOPPED_FOREVER || RUBY_VM_INTERRUPTED(th) || th->transition_for_lock) {
	*found = 1;
    }
    else if (th->locking_mutex) {
	mutex_t *mutex;
	GetMutexPtr(th->locking_mutex, mutex);

	native_mutex_lock(&mutex->lock);
	if (mutex->th == th || (!mutex->th && mutex->cond_notified)) {
	    *found = 1;
	}
	native_mutex_unlock(&mutex->lock);
    }

    return (*found) ? ST_STOP : ST_CONTINUE;
}

#if 0 /* for debug */
static int
debug_i(st_data_t key, st_data_t val, int *found)
{
    VALUE thval = key;
    rb_thread_t *th;
    GetThreadPtr(thval, th);

    printf("th:%p %d %d %d", th, th->status, th->interrupt_flag, th->transition_for_lock);
    if (th->locking_mutex) {
	mutex_t *mutex;
	GetMutexPtr(th->locking_mutex, mutex);

	native_mutex_lock(&mutex->lock);
	printf(" %p %d\n", mutex->th, mutex->cond_notified);
	native_mutex_unlock(&mutex->lock);
    }
    else puts("");

    return ST_CONTINUE;
}
#endif

static void
rb_check_deadlock(rb_vm_t *vm)
{
    int found = 0;

    if (vm_living_thread_num(vm) > vm->sleeper) return;
    if (vm_living_thread_num(vm) < vm->sleeper) rb_bug("sleeper must not be more than vm_living_thread_num(vm)");

    st_foreach(vm->living_threads, check_deadlock_i, (st_data_t)&found);

    if (!found) {
	VALUE argv[2];
	argv[0] = rb_eFatal;
	argv[1] = rb_str_new2("deadlock detected");
#if 0 /* for debug */
	printf("%d %d %p %p\n", vm->living_threads->num_entries, vm->sleeper, GET_THREAD(), vm->main_thread);
	st_foreach(vm->living_threads, debug_i, (st_data_t)0);
#endif
	rb_thread_raise(2, argv, vm->main_thread);
    }
}

static void
update_coverage(rb_event_flag_t event, VALUE proc, VALUE self, ID id, VALUE klass)
{
    VALUE coverage = GET_THREAD()->cfp->iseq->coverage;
    if (coverage && RBASIC(coverage)->klass == 0) {
	long line = rb_sourceline() - 1;
	long count;
	if (RARRAY_PTR(coverage)[line] == Qnil) {
	    rb_bug("bug");
	}
	count = FIX2LONG(RARRAY_PTR(coverage)[line]) + 1;
	if (POSFIXABLE(count)) {
	    RARRAY_PTR(coverage)[line] = LONG2FIX(count);
	}
    }
}

VALUE
rb_get_coverages(void)
{
    return GET_VM()->coverages;
}

void
rb_set_coverages(VALUE coverages)
{
    GET_VM()->coverages = coverages;
    rb_add_event_hook(update_coverage, RUBY_EVENT_COVERAGE, Qnil);
}

void
rb_reset_coverages(void)
{
    GET_VM()->coverages = Qfalse;
    rb_remove_event_hook(update_coverage);
}