thread_sync.c (cb01b9023ec2007c03bddc992416c33f2c59a0e1)

/* included by thread.c */
#include "ccan/list/list.h"
#include "builtin.h"
 
static VALUE rb_cMutex, rb_cQueue, rb_cSizedQueue, rb_cConditionVariable;
static VALUE rb_eClosedQueueError;
 
/* Mutex */
typedef struct rb_mutex_struct {
    rb_serial_t ec_serial;
    rb_thread_t *th; // even if the fiber is collected, we might need access to the thread in mutex_free
    struct rb_mutex_struct *next_mutex;
    struct ccan_list_head waitq; /* protected by GVL */
} rb_mutex_t;
 
/* sync_waiter is always on-stack */
struct sync_waiter {
    VALUE self;
    rb_thread_t *th;
    rb_fiber_t *fiber;
    struct ccan_list_node node;
};
 
static inline rb_fiber_t*
nonblocking_fiber(rb_fiber_t *fiber)
{
    if (rb_fiberptr_blocking(fiber)) {
        return NULL;
    }
 
    return fiber;
}
 
struct queue_sleep_arg {
    VALUE self;
    VALUE timeout;
    rb_hrtime_t end;
};
 
#define MUTEX_ALLOW_TRAP FL_USER1
 
static void
sync_wakeup(struct ccan_list_head *head, long max)
{
    RUBY_DEBUG_LOG("max:%ld", max);
 
    struct sync_waiter *cur = 0, *next;
 
    ccan_list_for_each_safe(head, cur, next, node) {
        ccan_list_del_init(&cur->node);
 
        if (cur->th->status != THREAD_KILLED) {
            if (cur->th->scheduler != Qnil && cur->fiber) {
                rb_fiber_scheduler_unblock(cur->th->scheduler, cur->self, rb_fiberptr_self(cur->fiber));
            }
            else {
                RUBY_DEBUG_LOG("target_th:%u", rb_th_serial(cur->th));
                rb_threadptr_interrupt(cur->th);
                cur->th->status = THREAD_RUNNABLE;
            }
 
            if (--max == 0) return;
        }
    }
}
 
static void
wakeup_one(struct ccan_list_head *head)
{
    sync_wakeup(head, 1);
}
 
static void
wakeup_all(struct ccan_list_head *head)
{
    sync_wakeup(head, LONG_MAX);
}
 
#if defined(HAVE_WORKING_FORK)
static void rb_mutex_abandon_all(rb_mutex_t *mutexes);
static void rb_mutex_abandon_keeping_mutexes(rb_thread_t *th);
static void rb_mutex_abandon_locking_mutex(rb_thread_t *th);
#endif
static const char* rb_mutex_unlock_th(rb_mutex_t *mutex, rb_thread_t *th, rb_serial_t ec_serial);
 
/*
 *  Document-class: Thread::Mutex
 *
 *  Thread::Mutex implements a simple semaphore that can be used to
 *  coordinate access to shared data from multiple concurrent threads.
 *
 *  Example:
 *
 *    semaphore = Thread::Mutex.new
 *
 *    a = Thread.new {
 *      semaphore.synchronize {
 *        # access shared resource
 *      }
 *    }
 *
 *    b = Thread.new {
 *      semaphore.synchronize {
 *        # access shared resource
 *      }
 *    }
 *
 */
 
static size_t
rb_mutex_num_waiting(rb_mutex_t *mutex)
{
    struct sync_waiter *w = 0;
    size_t n = 0;
 
    ccan_list_for_each(&mutex->waitq, w, node) {
        n++;
    }
 
    return n;
}
 
rb_thread_t* rb_fiber_threadptr(const rb_fiber_t *fiber);
 
static bool
mutex_locked_p(rb_mutex_t *mutex)
{
    return mutex->ec_serial != 0;
}
 
static void
mutex_free(void *ptr)
{
    rb_mutex_t *mutex = ptr;
    if (mutex_locked_p(mutex)) {
        const char *err = rb_mutex_unlock_th(mutex, mutex->th, 0);
        if (err) rb_bug("%s", err);
    }
    ruby_xfree(ptr);
}
 
static size_t
mutex_memsize(const void *ptr)
{
    return sizeof(rb_mutex_t);
}
 
static const rb_data_type_t mutex_data_type = {
    "mutex",
    {NULL, mutex_free, mutex_memsize,},
    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
};
 
static rb_mutex_t *
mutex_ptr(VALUE obj)
{
    rb_mutex_t *mutex;
 
    TypedData_Get_Struct(obj, rb_mutex_t, &mutex_data_type, mutex);
 
    return mutex;
}
 
VALUE
rb_obj_is_mutex(VALUE obj)
{
    return RBOOL(rb_typeddata_is_kind_of(obj, &mutex_data_type));
}
 
static VALUE
mutex_alloc(VALUE klass)
{
    VALUE obj;
    rb_mutex_t *mutex;
 
    obj = TypedData_Make_Struct(klass, rb_mutex_t, &mutex_data_type, mutex);
 
    ccan_list_head_init(&mutex->waitq);
    return obj;
}
 
VALUE
rb_mutex_new(void)
{
    return mutex_alloc(rb_cMutex);
}
 
VALUE
rb_mutex_locked_p(VALUE self)
{
    rb_mutex_t *mutex = mutex_ptr(self);
 
    return RBOOL(mutex_locked_p(mutex));
}
 
static void
thread_mutex_insert(rb_thread_t *thread, rb_mutex_t *mutex)
{
    RUBY_ASSERT(!mutex->next_mutex);
    if (thread->keeping_mutexes) {
        mutex->next_mutex = thread->keeping_mutexes;
    }
 
    thread->keeping_mutexes = mutex;
}
 
static void
thread_mutex_remove(rb_thread_t *thread, rb_mutex_t *mutex)
{
    rb_mutex_t **keeping_mutexes = &thread->keeping_mutexes;
 
    while (*keeping_mutexes && *keeping_mutexes != mutex) {
        // Move to the next mutex in the list:
        keeping_mutexes = &(*keeping_mutexes)->next_mutex;
    }
 
    if (*keeping_mutexes) {
        *keeping_mutexes = mutex->next_mutex;
        mutex->next_mutex = NULL;
    }
}
 
static void
mutex_set_owner(rb_mutex_t *mutex, rb_thread_t *th, rb_serial_t ec_serial)
{
    mutex->th = th;
    mutex->ec_serial = ec_serial;
}
 
static void
mutex_locked(rb_mutex_t *mutex, rb_thread_t *th, rb_serial_t ec_serial)
{
    mutex_set_owner(mutex, th, ec_serial);
    thread_mutex_insert(th, mutex);
}
 
static inline bool
do_mutex_trylock(rb_mutex_t *mutex, rb_thread_t *th, rb_serial_t ec_serial)
{
    if (mutex->ec_serial == 0) {
        RUBY_DEBUG_LOG("%p ok", mutex);
 
        mutex_locked(mutex, th, ec_serial);
        return true;
    }
    else {
        RUBY_DEBUG_LOG("%p ng", mutex);
        return false;
    }
}
 
static VALUE
rb_mut_trylock(rb_execution_context_t *ec, VALUE self)
{
    return RBOOL(do_mutex_trylock(mutex_ptr(self), ec->thread_ptr, rb_ec_serial(ec)));
}
 
VALUE
rb_mutex_trylock(VALUE self)
{
    return rb_mut_trylock(GET_EC(), self);
}
 
static VALUE
mutex_owned_p(rb_serial_t ec_serial, rb_mutex_t *mutex)
{
    return RBOOL(mutex->ec_serial == ec_serial);
}
 
static VALUE
call_rb_fiber_scheduler_block(VALUE mutex)
{
    return rb_fiber_scheduler_block(rb_fiber_scheduler_current(), mutex, Qnil);
}
 
static VALUE
delete_from_waitq(VALUE value)
{
    struct sync_waiter *sync_waiter = (void *)value;
    ccan_list_del(&sync_waiter->node);
 
    return Qnil;
}
 
static inline rb_atomic_t threadptr_get_interrupts(rb_thread_t *th);
 
struct mutex_args {
    VALUE self;
    rb_mutex_t *mutex;
    rb_execution_context_t *ec;
};
 
static inline void
mutex_args_init(struct mutex_args *args, VALUE mutex)
{
    args->self = mutex;
    args->mutex = mutex_ptr(mutex);
    args->ec = GET_EC();
}
 
static VALUE
do_mutex_lock(struct mutex_args *args, int interruptible_p)
{
    VALUE self = args->self;
    rb_execution_context_t *ec = args->ec;
    rb_thread_t *th = ec->thread_ptr;
    rb_fiber_t *fiber = ec->fiber_ptr;
    rb_serial_t ec_serial = rb_ec_serial(ec);
    rb_mutex_t *mutex = args->mutex;
    rb_atomic_t saved_ints = 0;
 
    /* When running trap handler */
    if (!FL_TEST_RAW(self, MUTEX_ALLOW_TRAP) &&
        th->ec->interrupt_mask & TRAP_INTERRUPT_MASK) {
        rb_raise(rb_eThreadError, "can't be called from trap context");
    }
 
    if (!do_mutex_trylock(mutex, th, ec_serial)) {
        if (mutex->ec_serial == ec_serial) {
            rb_raise(rb_eThreadError, "deadlock; recursive locking");
        }
 
        while (mutex->ec_serial != ec_serial) {
            VM_ASSERT(mutex->ec_serial != 0);
 
            VALUE scheduler = rb_fiber_scheduler_current();
            if (scheduler != Qnil) {
                struct sync_waiter sync_waiter = {
                    .self = self,
                    .th = th,
                    .fiber = nonblocking_fiber(fiber)
                };
 
                ccan_list_add_tail(&mutex->waitq, &sync_waiter.node);
 
                rb_ensure(call_rb_fiber_scheduler_block, self, delete_from_waitq, (VALUE)&sync_waiter);
 
                if (!mutex->ec_serial) {
                    mutex_set_owner(mutex, th, ec_serial);
                }
            }
            else {
                if (!th->vm->thread_ignore_deadlock && mutex->th == th) {
                    rb_raise(rb_eThreadError, "deadlock; lock already owned by another fiber belonging to the same thread");
                }
 
                struct sync_waiter sync_waiter = {
                    .self = self,
                    .th = th,
                    .fiber = nonblocking_fiber(fiber),
                };
 
                RUBY_DEBUG_LOG("%p wait", mutex);
 
                // similar code with `sleep_forever`, but
                // sleep_forever(SLEEP_DEADLOCKABLE) raises an exception.
                // Ensure clause is needed like but `rb_ensure` a bit slow.
                //
                //   begin
                //     sleep_forever(th, SLEEP_DEADLOCKABLE);
                //   ensure
                //     ccan_list_del(&sync_waiter.node);
                //   end
                enum rb_thread_status prev_status = th->status;
                th->status = THREAD_STOPPED_FOREVER;
                rb_ractor_sleeper_threads_inc(th->ractor);
                rb_check_deadlock(th->ractor);
 
                RUBY_ASSERT(!th->locking_mutex);
                th->locking_mutex = self;
 
                ccan_list_add_tail(&mutex->waitq, &sync_waiter.node);
                {
                    native_sleep(th, NULL);
                }
                ccan_list_del(&sync_waiter.node);
 
                // unlocked by another thread while sleeping
                if (!mutex->ec_serial) {
                    mutex_set_owner(mutex, th, ec_serial);
                }
 
                rb_ractor_sleeper_threads_dec(th->ractor);
                th->status = prev_status;
                th->locking_mutex = Qfalse;
 
                RUBY_DEBUG_LOG("%p wakeup", mutex);
            }
 
            if (interruptible_p) {
                /* release mutex before checking for interrupts...as interrupt checking
                 * code might call rb_raise() */
                if (mutex->ec_serial == ec_serial) {
                    mutex->th = NULL;
                    mutex->ec_serial = 0;
                }
                RUBY_VM_CHECK_INTS_BLOCKING(th->ec); /* may release mutex */
                if (!mutex->ec_serial) {
                    mutex_set_owner(mutex, th, ec_serial);
                }
            }
            else {
                // clear interrupt information
                if (RUBY_VM_INTERRUPTED(th->ec)) {
                    // reset interrupts
                    if (saved_ints == 0) {
                        saved_ints = threadptr_get_interrupts(th);
                    }
                    else {
                        // ignore additional interrupts
                        threadptr_get_interrupts(th);
                    }
                }
            }
        }
 
        if (saved_ints) th->ec->interrupt_flag = saved_ints;
        if (mutex->ec_serial == ec_serial) mutex_locked(mutex, th, ec_serial);
    }
 
    RUBY_DEBUG_LOG("%p locked", mutex);
 
    // assertion
    if (mutex_owned_p(ec_serial, mutex) == Qfalse) rb_bug("do_mutex_lock: mutex is not owned.");
 
    return self;
}
 
static VALUE
mutex_lock_uninterruptible(VALUE self)
{
    struct mutex_args args;
    mutex_args_init(&args, self);
    return do_mutex_lock(&args, 0);
}
 
static VALUE
rb_mut_lock(rb_execution_context_t *ec, VALUE self)
{
    struct mutex_args args = {
        .self = self,
        .mutex = mutex_ptr(self),
        .ec = ec,
    };
    return do_mutex_lock(&args, 1);
}
 
VALUE
rb_mutex_lock(VALUE self)
{
    struct mutex_args args;
    mutex_args_init(&args, self);
    return do_mutex_lock(&args, 1);
}
 
static VALUE
rb_mut_owned_p(rb_execution_context_t *ec, VALUE self)
{
    return mutex_owned_p(rb_ec_serial(ec), mutex_ptr(self));
}
 
VALUE
rb_mutex_owned_p(VALUE self)
{
    return rb_mut_owned_p(GET_EC(), self);
}
 
static const char *
rb_mutex_unlock_th(rb_mutex_t *mutex, rb_thread_t *th, rb_serial_t ec_serial)
{
    RUBY_DEBUG_LOG("%p", mutex);
 
    if (mutex->ec_serial == 0) {
        return "Attempt to unlock a mutex which is not locked";
    }
    else if (ec_serial && mutex->ec_serial != ec_serial) {
        return "Attempt to unlock a mutex which is locked by another thread/fiber";
    }
 
    struct sync_waiter *cur = 0, *next;
 
    mutex->ec_serial = 0;
    thread_mutex_remove(th, mutex);
 
    ccan_list_for_each_safe(&mutex->waitq, cur, next, node) {
        ccan_list_del_init(&cur->node);
 
        if (cur->th->scheduler != Qnil && cur->fiber) {
            rb_fiber_scheduler_unblock(cur->th->scheduler, cur->self, rb_fiberptr_self(cur->fiber));
            return NULL;
        }
        else {
            switch (cur->th->status) {
              case THREAD_RUNNABLE: /* from someone else calling Thread#run */
              case THREAD_STOPPED_FOREVER: /* likely (rb_mutex_lock) */
                RUBY_DEBUG_LOG("wakeup th:%u", rb_th_serial(cur->th));
                rb_threadptr_interrupt(cur->th);
                return NULL;
              case THREAD_STOPPED: /* probably impossible */
                rb_bug("unexpected THREAD_STOPPED");
              case THREAD_KILLED:
                /* not sure about this, possible in exit GC? */
                rb_bug("unexpected THREAD_KILLED");
                continue;
            }
        }
    }
 
    // We did not find any threads to wake up, so we can just return with no error:
    return NULL;
}
 
static void
do_mutex_unlock(struct mutex_args *args)
{
    const char *err;
    rb_mutex_t *mutex = args->mutex;
    rb_thread_t *th = rb_ec_thread_ptr(args->ec);
 
    err = rb_mutex_unlock_th(mutex, th, rb_ec_serial(args->ec));
    if (err) rb_raise(rb_eThreadError, "%s", err);
}
 
static VALUE
do_mutex_unlock_safe(VALUE args)
{
    do_mutex_unlock((struct mutex_args *)args);
    return Qnil;
}
 
/*
 * 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)
{
    struct mutex_args args;
    mutex_args_init(&args, self);
    do_mutex_unlock(&args);
    return self;
}
 
static VALUE
rb_mut_unlock(rb_execution_context_t *ec, VALUE self)
{
    struct mutex_args args = {
        .self = self,
        .mutex = mutex_ptr(self),
        .ec = ec,
    };
    do_mutex_unlock(&args);
    return self;
}
 
#if defined(HAVE_WORKING_FORK)
static void
rb_mutex_abandon_keeping_mutexes(rb_thread_t *th)
{
    rb_mutex_abandon_all(th->keeping_mutexes);
    th->keeping_mutexes = NULL;
}
 
static void
rb_mutex_abandon_locking_mutex(rb_thread_t *th)
{
    if (th->locking_mutex) {
        rb_mutex_t *mutex = mutex_ptr(th->locking_mutex);
 
        ccan_list_head_init(&mutex->waitq);
        th->locking_mutex = Qfalse;
    }
}
 
static void
rb_mutex_abandon_all(rb_mutex_t *mutexes)
{
    rb_mutex_t *mutex;
 
    while (mutexes) {
        mutex = mutexes;
        mutexes = mutex->next_mutex;
        mutex->ec_serial = 0;
        mutex->next_mutex = 0;
        ccan_list_head_init(&mutex->waitq);
    }
}
#endif
 
struct rb_mutex_sleep_arguments {
    VALUE self;
    VALUE timeout;
};
 
static VALUE
mutex_sleep_begin(VALUE _arguments)
{
    struct rb_mutex_sleep_arguments *arguments = (struct rb_mutex_sleep_arguments *)_arguments;
    VALUE timeout = arguments->timeout;
    VALUE woken = Qtrue;
 
    VALUE scheduler = rb_fiber_scheduler_current();
    if (scheduler != Qnil) {
        rb_fiber_scheduler_kernel_sleep(scheduler, timeout);
    }
    else {
        if (NIL_P(timeout)) {
            rb_thread_sleep_deadly_allow_spurious_wakeup(arguments->self, Qnil, 0);
        }
        else {
            struct timeval timeout_value = rb_time_interval(timeout);
            rb_hrtime_t relative_timeout = rb_timeval2hrtime(&timeout_value);
            /* permit spurious check */
            woken = RBOOL(sleep_hrtime(GET_THREAD(), relative_timeout, 0));
        }
    }
 
    return woken;
}
 
static VALUE
rb_mut_sleep(rb_execution_context_t *ec, VALUE self, VALUE timeout)
{
    if (!NIL_P(timeout)) {
        // Validate the argument:
        rb_time_interval(timeout);
    }
 
    rb_mut_unlock(ec, self);
    time_t beg = time(0);
 
    struct rb_mutex_sleep_arguments arguments = {
        .self = self,
        .timeout = timeout,
    };
 
    VALUE woken = rb_ec_ensure(ec, mutex_sleep_begin, (VALUE)&arguments, mutex_lock_uninterruptible, self);
 
    RUBY_VM_CHECK_INTS_BLOCKING(ec);
    if (!woken) return Qnil;
    time_t end = time(0) - beg;
    return TIMET2NUM(end);
}
 
VALUE
rb_mutex_sleep(VALUE self, VALUE timeout)
{
    return rb_mut_sleep(GET_EC(), self, timeout);
}
 
VALUE
rb_mutex_synchronize(VALUE self, VALUE (*func)(VALUE arg), VALUE arg)
{
    struct mutex_args args;
    mutex_args_init(&args, self);
    do_mutex_lock(&args, 1);
    return rb_ec_ensure(args.ec, func, arg, do_mutex_unlock_safe, (VALUE)&args);
}
 
static VALUE
do_ec_yield(VALUE _ec)
{
    return rb_ec_yield((rb_execution_context_t *)_ec, Qundef);
}
 
VALUE
rb_mut_synchronize(rb_execution_context_t *ec, VALUE self)
{
    struct mutex_args args = {
        .self = self,
        .mutex = mutex_ptr(self),
        .ec = ec,
    };
    do_mutex_lock(&args, 1);
    return rb_ec_ensure(args.ec, do_ec_yield, (VALUE)ec, do_mutex_unlock_safe, (VALUE)&args);
}
 
void
rb_mutex_allow_trap(VALUE self, int val)
{
    Check_TypedStruct(self, &mutex_data_type);
 
    if (val)
        FL_SET_RAW(self, MUTEX_ALLOW_TRAP);
    else
        FL_UNSET_RAW(self, MUTEX_ALLOW_TRAP);
}
 
/* Queue */
 
#define queue_waitq(q) UNALIGNED_MEMBER_PTR(q, waitq)
#define queue_list(q) UNALIGNED_MEMBER_PTR(q, que)
RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_BEGIN()
struct rb_queue {
    struct ccan_list_head waitq;
    rb_serial_t fork_gen;
    const VALUE que;
    int num_waiting;
} RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_END();
 
#define szqueue_waitq(sq) UNALIGNED_MEMBER_PTR(sq, q.waitq)
#define szqueue_list(sq) UNALIGNED_MEMBER_PTR(sq, q.que)
#define szqueue_pushq(sq) UNALIGNED_MEMBER_PTR(sq, pushq)
RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_BEGIN()
struct rb_szqueue {
    struct rb_queue q;
    int num_waiting_push;
    struct ccan_list_head pushq;
    long max;
} RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_END();
 
static void
queue_mark_and_move(void *ptr)
{
    struct rb_queue *q = ptr;
 
    /* no need to mark threads in waitq, they are on stack */
    rb_gc_mark_and_move((VALUE *)UNALIGNED_MEMBER_PTR(q, que));
}
 
static size_t
queue_memsize(const void *ptr)
{
    return sizeof(struct rb_queue);
}
 
static const rb_data_type_t queue_data_type = {
    .wrap_struct_name = "Thread::Queue",
    .function = {
        .dmark = queue_mark_and_move,
        .dfree = RUBY_TYPED_DEFAULT_FREE,
        .dsize = queue_memsize,
        .dcompact = queue_mark_and_move,
    },
    .flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
};
 
static VALUE
queue_alloc(VALUE klass)
{
    VALUE obj;
    struct rb_queue *q;
 
    obj = TypedData_Make_Struct(klass, struct rb_queue, &queue_data_type, q);
    ccan_list_head_init(queue_waitq(q));
    return obj;
}
 
static int
queue_fork_check(struct rb_queue *q)
{
    rb_serial_t fork_gen = GET_VM()->fork_gen;
 
    if (q->fork_gen == fork_gen) {
        return 0;
    }
    /* forked children can't reach into parent thread stacks */
    q->fork_gen = fork_gen;
    ccan_list_head_init(queue_waitq(q));
    q->num_waiting = 0;
    return 1;
}
 
static struct rb_queue *
queue_ptr(VALUE obj)
{
    struct rb_queue *q;
 
    TypedData_Get_Struct(obj, struct rb_queue, &queue_data_type, q);
    queue_fork_check(q);
 
    return q;
}
 
#define QUEUE_CLOSED          FL_USER5
 
static rb_hrtime_t
queue_timeout2hrtime(VALUE timeout)
{
    if (NIL_P(timeout)) {
        return (rb_hrtime_t)0;
    }
    rb_hrtime_t rel = 0;
    if (FIXNUM_P(timeout)) {
        rel = rb_sec2hrtime(NUM2TIMET(timeout));
    }
    else {
        double2hrtime(&rel, rb_num2dbl(timeout));
    }
    return rb_hrtime_add(rel, rb_hrtime_now());
}
 
static void
szqueue_mark_and_move(void *ptr)
{
    struct rb_szqueue *sq = ptr;
 
    queue_mark_and_move(&sq->q);
}
 
static size_t
szqueue_memsize(const void *ptr)
{
    return sizeof(struct rb_szqueue);
}
 
static const rb_data_type_t szqueue_data_type = {
    .wrap_struct_name = "Thread::SizedQueue",
    .function = {
        .dmark = szqueue_mark_and_move,
        .dfree = RUBY_TYPED_DEFAULT_FREE,
        .dsize = szqueue_memsize,
        .dcompact = szqueue_mark_and_move,
    },
    .parent = &queue_data_type,
    .flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
};
 
static VALUE
szqueue_alloc(VALUE klass)
{
    struct rb_szqueue *sq;
    VALUE obj = TypedData_Make_Struct(klass, struct rb_szqueue,
                                        &szqueue_data_type, sq);
    ccan_list_head_init(szqueue_waitq(sq));
    ccan_list_head_init(szqueue_pushq(sq));
    return obj;
}
 
static struct rb_szqueue *
szqueue_ptr(VALUE obj)
{
    struct rb_szqueue *sq;
 
    TypedData_Get_Struct(obj, struct rb_szqueue, &szqueue_data_type, sq);
    if (queue_fork_check(&sq->q)) {
        ccan_list_head_init(szqueue_pushq(sq));
        sq->num_waiting_push = 0;
    }
 
    return sq;
}
 
static VALUE
ary_buf_new(void)
{
    return rb_ary_hidden_new(1);
}
 
static inline VALUE
check_array(VALUE obj, VALUE ary)
{
    if (RB_LIKELY(ary)) {
        return ary;
    }
    rb_raise(rb_eTypeError, "%+"PRIsVALUE" not initialized", obj);
}
 
static long
queue_length(VALUE self, struct rb_queue *q)
{
    return RARRAY_LEN(check_array(self, q->que));
}
 
static int
queue_closed_p(VALUE self)
{
    return FL_TEST_RAW(self, QUEUE_CLOSED) != 0;
}
 
/*
 *  Document-class: ClosedQueueError
 *
 *  The exception class which will be raised when pushing into a closed
 *  Queue.  See Thread::Queue#close and Thread::SizedQueue#close.
 */
 
NORETURN(static void raise_closed_queue_error(VALUE self));
 
static void
raise_closed_queue_error(VALUE self)
{
    rb_raise(rb_eClosedQueueError, "queue closed");
}
 
static VALUE
queue_closed_result(VALUE self, struct rb_queue *q)
{
    RUBY_ASSERT(queue_length(self, q) == 0);
    return Qnil;
}
 
/*
 *  Document-class: Thread::Queue
 *
 *  The Thread::Queue class implements multi-producer, multi-consumer
 *  queues.  It is especially useful in threaded programming when
 *  information must be exchanged safely between multiple threads. The
 *  Thread::Queue class implements all the required locking semantics.
 *
 *  The class implements FIFO (first in, first out) type of queue.
 *  In a FIFO queue, the first tasks added are the first retrieved.
 *
 *  Example:
 *
 *      queue = Thread::Queue.new
 *
 *      producer = Thread.new do
 *        5.times do |i|
 *          sleep rand(i) # simulate expense
 *          queue << i
 *          puts "#{i} produced"
 *        end
 *      end
 *
 *      consumer = Thread.new do
 *        5.times do |i|
 *          value = queue.pop
 *          sleep rand(i/2) # simulate expense
 *          puts "consumed #{value}"
 *        end
 *      end
 *
 *      consumer.join
 *
 */
 
/*
 * Document-method: Queue::new
 *
 * call-seq:
 *   Thread::Queue.new -> empty_queue
 *   Thread::Queue.new(enumerable) -> queue
 *
 * Creates a new queue instance, optionally using the contents of an +enumerable+
 * for its initial state.
 *
 * Example:
 *
 *      q = Thread::Queue.new
 *      #=> #<Thread::Queue:0x00007ff7501110d0>
 *      q.empty?
 *      #=> true
 *
 *      q = Thread::Queue.new([1, 2, 3])
 *      #=> #<Thread::Queue:0x00007ff7500ec500>
 *      q.empty?
 *      #=> false
 *      q.pop
 *      #=> 1
 */
 
static VALUE
rb_queue_initialize(int argc, VALUE *argv, VALUE self)
{
    VALUE initial;
    struct rb_queue *q = queue_ptr(self);
    if ((argc = rb_scan_args(argc, argv, "01", &initial)) == 1) {
        initial = rb_to_array(initial);
    }
    RB_OBJ_WRITE(self, queue_list(q), ary_buf_new());
    ccan_list_head_init(queue_waitq(q));
    if (argc == 1) {
        rb_ary_concat(q->que, initial);
    }
    return self;
}
 
static VALUE
queue_do_push(VALUE self, struct rb_queue *q, VALUE obj)
{
    if (queue_closed_p(self)) {
        raise_closed_queue_error(self);
    }
    rb_ary_push(check_array(self, q->que), obj);
    wakeup_one(queue_waitq(q));
    return self;
}
 
/*
 * Document-method: Thread::Queue#close
 * call-seq:
 *   close
 *
 * Closes the queue. A closed queue cannot be re-opened.
 *
 * After the call to close completes, the following are true:
 *
 * - +closed?+ will return true
 *
 * - +close+ will be ignored.
 *
 * - calling enq/push/<< will raise a +ClosedQueueError+.
 *
 * - when +empty?+ is false, calling deq/pop/shift will return an object
 *   from the queue as usual.
 * - when +empty?+ is true, deq(false) will not suspend the thread and will return nil.
 *   deq(true) will raise a +ThreadError+.
 *
 * ClosedQueueError is inherited from StopIteration, so that you can break loop block.
 *
 * Example:
 *
 *      q = Thread::Queue.new
 *      Thread.new{
 *        while e = q.deq # wait for nil to break loop
 *          # ...
 *        end
 *      }
 *      q.close
 */
 
static VALUE
rb_queue_close(VALUE self)
{
    struct rb_queue *q = queue_ptr(self);
 
    if (!queue_closed_p(self)) {
        FL_SET(self, QUEUE_CLOSED);
 
        wakeup_all(queue_waitq(q));
    }
 
    return self;
}
 
/*
 * Document-method: Thread::Queue#closed?
 * call-seq: closed?
 *
 * Returns +true+ if the queue is closed.
 */
 
static VALUE
rb_queue_closed_p(VALUE self)
{
    return RBOOL(queue_closed_p(self));
}
 
/*
 * Document-method: Thread::Queue#push
 * call-seq:
 *   push(object)
 *   enq(object)
 *   <<(object)
 *
 * Pushes the given +object+ to the queue.
 */
 
static VALUE
rb_queue_push(VALUE self, VALUE obj)
{
    return queue_do_push(self, queue_ptr(self), obj);
}
 
static VALUE
queue_sleep(VALUE _args)
{
    struct queue_sleep_arg *args = (struct queue_sleep_arg *)_args;
    rb_thread_sleep_deadly_allow_spurious_wakeup(args->self, args->timeout, args->end);
    return Qnil;
}
 
struct queue_waiter {
    struct sync_waiter w;
    union {
        struct rb_queue *q;
        struct rb_szqueue *sq;
    } as;
};
 
static VALUE
queue_sleep_done(VALUE p)
{
    struct queue_waiter *qw = (struct queue_waiter *)p;
 
    ccan_list_del(&qw->w.node);
    qw->as.q->num_waiting--;
 
    return Qfalse;
}
 
static VALUE
szqueue_sleep_done(VALUE p)
{
    struct queue_waiter *qw = (struct queue_waiter *)p;
 
    ccan_list_del(&qw->w.node);
    qw->as.sq->num_waiting_push--;
 
    return Qfalse;
}
 
static inline VALUE
queue_do_pop(rb_execution_context_t *ec, VALUE self, struct rb_queue *q, VALUE non_block, VALUE timeout)
{
    check_array(self, q->que);
    if (RARRAY_LEN(q->que) == 0) {
        if (RTEST(non_block)) {
            rb_raise(rb_eThreadError, "queue empty");
        }
 
        if (RTEST(rb_equal(INT2FIX(0), timeout))) {
            return Qnil;
        }
    }
 
    rb_hrtime_t end = queue_timeout2hrtime(timeout);
    while (RARRAY_LEN(q->que) == 0) {
        if (queue_closed_p(self)) {
            return queue_closed_result(self, q);
        }
        else {
            RUBY_ASSERT(RARRAY_LEN(q->que) == 0);
            RUBY_ASSERT(queue_closed_p(self) == 0);
 
            struct queue_waiter queue_waiter = {
                .w = {.self = self, .th = ec->thread_ptr, .fiber = nonblocking_fiber(ec->fiber_ptr)},
                .as = {.q = q}
            };
 
            struct ccan_list_head *waitq = queue_waitq(q);
 
            ccan_list_add_tail(waitq, &queue_waiter.w.node);
            queue_waiter.as.q->num_waiting++;
 
            struct queue_sleep_arg queue_sleep_arg = {
                .self = self,
                .timeout = timeout,
                .end = end
            };
 
            rb_ensure(queue_sleep, (VALUE)&queue_sleep_arg, queue_sleep_done, (VALUE)&queue_waiter);
            if (!NIL_P(timeout) && (rb_hrtime_now() >= end))
                break;
        }
    }
 
    return rb_ary_shift(q->que);
}
 
static VALUE
rb_queue_pop(rb_execution_context_t *ec, VALUE self, VALUE non_block, VALUE timeout)
{
    return queue_do_pop(ec, self, queue_ptr(self), non_block, timeout);
}
 
/*
 * Document-method: Thread::Queue#empty?
 * call-seq: empty?
 *
 * Returns +true+ if the queue is empty.
 */
 
static VALUE
rb_queue_empty_p(VALUE self)
{
    return RBOOL(queue_length(self, queue_ptr(self)) == 0);
}
 
/*
 * Document-method: Thread::Queue#clear
 *
 * Removes all objects from the queue.
 */
 
static VALUE
rb_queue_clear(VALUE self)
{
    struct rb_queue *q = queue_ptr(self);
 
    rb_ary_clear(check_array(self, q->que));
    return self;
}
 
/*
 * Document-method: Thread::Queue#length
 * call-seq:
 *   length
 *   size
 *
 * Returns the length of the queue.
 */
 
static VALUE
rb_queue_length(VALUE self)
{
    return LONG2NUM(queue_length(self, queue_ptr(self)));
}
 
NORETURN(static VALUE rb_queue_freeze(VALUE self));
/*
 * call-seq:
 *   freeze
 *
 * The queue can't be frozen, so this method raises an exception:
 *   Thread::Queue.new.freeze # Raises TypeError (cannot freeze #<Thread::Queue:0x...>)
 *
 */
static VALUE
rb_queue_freeze(VALUE self)
{
    rb_raise(rb_eTypeError, "cannot freeze " "%+"PRIsVALUE, self);
    UNREACHABLE_RETURN(self);
}
 
/*
 * Document-method: Thread::Queue#num_waiting
 *
 * Returns the number of threads waiting on the queue.
 */
 
static VALUE
rb_queue_num_waiting(VALUE self)
{
    struct rb_queue *q = queue_ptr(self);
 
    return INT2NUM(q->num_waiting);
}
 
/*
 *  Document-class: Thread::SizedQueue
 *
 * This class represents queues of specified size capacity.  The push operation
 * may be blocked if the capacity is full.
 *
 * See Thread::Queue for an example of how a Thread::SizedQueue works.
 */
 
/*
 * Document-method: SizedQueue::new
 * call-seq: new(max)
 *
 * Creates a fixed-length queue with a maximum size of +max+.
 */
 
static VALUE
rb_szqueue_initialize(VALUE self, VALUE vmax)
{
    long max;
    struct rb_szqueue *sq = szqueue_ptr(self);
 
    max = NUM2LONG(vmax);
    if (max <= 0) {
        rb_raise(rb_eArgError, "queue size must be positive");
    }
 
    RB_OBJ_WRITE(self, szqueue_list(sq), ary_buf_new());
    ccan_list_head_init(szqueue_waitq(sq));
    ccan_list_head_init(szqueue_pushq(sq));
    sq->max = max;
 
    return self;
}
 
/*
 * Document-method: Thread::SizedQueue#close
 * call-seq:
 *   close
 *
 * Similar to Thread::Queue#close.
 *
 * The difference is behavior with waiting enqueuing threads.
 *
 * If there are waiting enqueuing threads, they are interrupted by
 * raising ClosedQueueError('queue closed').
 */
static VALUE
rb_szqueue_close(VALUE self)
{
    if (!queue_closed_p(self)) {
        struct rb_szqueue *sq = szqueue_ptr(self);
 
        FL_SET(self, QUEUE_CLOSED);
        wakeup_all(szqueue_waitq(sq));
        wakeup_all(szqueue_pushq(sq));
    }
    return self;
}
 
/*
 * Document-method: Thread::SizedQueue#max
 *
 * Returns the maximum size of the queue.
 */
 
static VALUE
rb_szqueue_max_get(VALUE self)
{
    return LONG2NUM(szqueue_ptr(self)->max);
}
 
/*
 * Document-method: Thread::SizedQueue#max=
 * call-seq: max=(number)
 *
 * Sets the maximum size of the queue to the given +number+.
 */
 
static VALUE
rb_szqueue_max_set(VALUE self, VALUE vmax)
{
    long max = NUM2LONG(vmax);
    long diff = 0;
    struct rb_szqueue *sq = szqueue_ptr(self);
 
    if (max <= 0) {
        rb_raise(rb_eArgError, "queue size must be positive");
    }
    if (max > sq->max) {
        diff = max - sq->max;
    }
    sq->max = max;
    sync_wakeup(szqueue_pushq(sq), diff);
    return vmax;
}
 
static VALUE
rb_szqueue_push(rb_execution_context_t *ec, VALUE self, VALUE object, VALUE non_block, VALUE timeout)
{
    struct rb_szqueue *sq = szqueue_ptr(self);
 
    if (queue_length(self, &sq->q) >= sq->max) {
        if (RTEST(non_block)) {
            rb_raise(rb_eThreadError, "queue full");
        }
 
        if (RTEST(rb_equal(INT2FIX(0), timeout))) {
            return Qnil;
        }
    }
 
    rb_hrtime_t end = queue_timeout2hrtime(timeout);
    while (queue_length(self, &sq->q) >= sq->max) {
        if (queue_closed_p(self)) {
            raise_closed_queue_error(self);
        }
        else {
            struct queue_waiter queue_waiter = {
                .w = {.self = self, .th = ec->thread_ptr, .fiber = nonblocking_fiber(ec->fiber_ptr)},
                .as = {.sq = sq}
            };
 
            struct ccan_list_head *pushq = szqueue_pushq(sq);
 
            ccan_list_add_tail(pushq, &queue_waiter.w.node);
            sq->num_waiting_push++;
 
            struct queue_sleep_arg queue_sleep_arg = {
                .self = self,
                .timeout = timeout,
                .end = end
            };
            rb_ensure(queue_sleep, (VALUE)&queue_sleep_arg, szqueue_sleep_done, (VALUE)&queue_waiter);
            if (!NIL_P(timeout) && rb_hrtime_now() >= end) {
                return Qnil;
            }
        }
    }
 
    return queue_do_push(self, &sq->q, object);
}
 
static VALUE
rb_szqueue_pop(rb_execution_context_t *ec, VALUE self, VALUE non_block, VALUE timeout)
{
    struct rb_szqueue *sq = szqueue_ptr(self);
    VALUE retval = queue_do_pop(ec, self, &sq->q, non_block, timeout);
 
    if (queue_length(self, &sq->q) < sq->max) {
        wakeup_one(szqueue_pushq(sq));
    }
 
    return retval;
}
 
/*
 * Document-method: Thread::SizedQueue#clear
 *
 * Removes all objects from the queue.
 */
 
static VALUE
rb_szqueue_clear(VALUE self)
{
    struct rb_szqueue *sq = szqueue_ptr(self);
 
    rb_ary_clear(check_array(self, sq->q.que));
    wakeup_all(szqueue_pushq(sq));
    return self;
}
 
/*
 * Document-method: Thread::SizedQueue#num_waiting
 *
 * Returns the number of threads waiting on the queue.
 */
 
static VALUE
rb_szqueue_num_waiting(VALUE self)
{
    struct rb_szqueue *sq = szqueue_ptr(self);
 
    return INT2NUM(sq->q.num_waiting + sq->num_waiting_push);
}
 
 
/* ConditionalVariable */
struct rb_condvar {
    struct ccan_list_head waitq;
    rb_serial_t fork_gen;
};
 
/*
 *  Document-class: Thread::ConditionVariable
 *
 *  ConditionVariable objects augment class Mutex. Using condition variables,
 *  it is possible to suspend while in the middle of a critical section until a
 *  condition is met, such as a resource becomes available.
 *
 *  Due to non-deterministic scheduling and spurious wake-ups, users of
 *  condition variables should always use a separate boolean predicate (such as
 *  reading from a boolean variable) to check if the condition is actually met
 *  before starting to wait, and should wait in a loop, re-checking the
 *  condition every time the ConditionVariable is waken up.  The idiomatic way
 *  of using condition variables is calling the +wait+ method in an +until+
 *  loop with the predicate as the loop condition.
 *
 *    condvar.wait(mutex) until condition_is_met
 *
 *  In the example below, we use the boolean variable +resource_available+
 *  (which is protected by +mutex+) to indicate the availability of the
 *  resource, and use +condvar+ to wait for that variable to become true.  Note
 *  that:
 *
 *  1.  Thread +b+ may be scheduled before thread +a1+ and +a2+, and may run so
 *      fast that it have already made the resource available before either
 *      +a1+ or +a2+ starts. Therefore, +a1+ and +a2+ should check if
 *      +resource_available+ is already true before starting to wait.
 *  2.  The +wait+ method may spuriously wake up without signalling. Therefore,
 *      thread +a1+ and +a2+ should recheck +resource_available+ after the
 *      +wait+ method returns, and go back to wait if the condition is not
 *      actually met.
 *  3.  It is possible that thread +a2+ starts right after thread +a1+ is waken
 *      up by +b+.  Thread +a2+ may have acquired the +mutex+ and consumed the
 *      resource before thread +a1+ acquires the +mutex+.  This necessitates
 *      rechecking after +wait+, too.
 *
 *  Example:
 *
 *    mutex = Thread::Mutex.new
 *
 *    resource_available = false
 *    condvar = Thread::ConditionVariable.new
 *
 *    a1 = Thread.new {
 *      # Thread 'a1' waits for the resource to become available and consumes
 *      # the resource.
 *      mutex.synchronize {
 *        condvar.wait(mutex) until resource_available
 *        # After the loop, 'resource_available' is guaranteed to be true.
 *
 *        resource_available = false
 *        puts "a1 consumed the resource"
 *      }
 *    }
 *
 *    a2 = Thread.new {
 *      # Thread 'a2' behaves like 'a1'.
 *      mutex.synchronize {
 *        condvar.wait(mutex) until resource_available
 *        resource_available = false
 *        puts "a2 consumed the resource"
 *      }
 *    }
 *
 *    b = Thread.new {
 *      # Thread 'b' periodically makes the resource available.
 *      loop {
 *        mutex.synchronize {
 *          resource_available = true
 *
 *          # Notify one waiting thread if any.  It is possible that neither
 *          # 'a1' nor 'a2 is waiting on 'condvar' at this moment.  That's OK.
 *          condvar.signal
 *        }
 *        sleep 1
 *      }
 *    }
 *
 *    # Eventually both 'a1' and 'a2' will have their resources, albeit in an
 *    # unspecified order.
 *    [a1, a2].each {|th| th.join}
 */
 
static size_t
condvar_memsize(const void *ptr)
{
    return sizeof(struct rb_condvar);
}
 
static const rb_data_type_t cv_data_type = {
    "condvar",
    {0, RUBY_TYPED_DEFAULT_FREE, condvar_memsize,},
    0, 0, RUBY_TYPED_FREE_IMMEDIATELY|RUBY_TYPED_WB_PROTECTED
};
 
static struct rb_condvar *
condvar_ptr(VALUE self)
{
    struct rb_condvar *cv;
    rb_serial_t fork_gen = GET_VM()->fork_gen;
 
    TypedData_Get_Struct(self, struct rb_condvar, &cv_data_type, cv);
 
    /* forked children can't reach into parent thread stacks */
    if (cv->fork_gen != fork_gen) {
        cv->fork_gen = fork_gen;
        ccan_list_head_init(&cv->waitq);
    }
 
    return cv;
}
 
static VALUE
condvar_alloc(VALUE klass)
{
    struct rb_condvar *cv;
    VALUE obj;
 
    obj = TypedData_Make_Struct(klass, struct rb_condvar, &cv_data_type, cv);
    ccan_list_head_init(&cv->waitq);
 
    return obj;
}
 
struct sleep_call {
    rb_execution_context_t *ec;
    VALUE mutex;
    VALUE timeout;
};
 
static ID id_sleep;
 
static VALUE
do_sleep(VALUE args)
{
    struct sleep_call *p = (struct sleep_call *)args;
    if (CLASS_OF(p->mutex) == rb_cMutex) {
        return rb_mut_sleep(p->ec, p->mutex, p->timeout);
    }
    else {
        return rb_funcallv(p->mutex, id_sleep, 1, &p->timeout);
    }
}
 
static VALUE
rb_condvar_wait(rb_execution_context_t *ec, VALUE self, VALUE mutex, VALUE timeout)
{
    struct rb_condvar *cv = condvar_ptr(self);
    struct sleep_call args = {
        .ec = ec,
        .mutex = mutex,
        .timeout = timeout,
    };
 
    struct sync_waiter sync_waiter = {
        .self = mutex,
        .th = ec->thread_ptr,
        .fiber = nonblocking_fiber(ec->fiber_ptr)
    };
 
    ccan_list_add_tail(&cv->waitq, &sync_waiter.node);
    return rb_ec_ensure(ec, do_sleep, (VALUE)&args, delete_from_waitq, (VALUE)&sync_waiter);
}
 
static VALUE
rb_condvar_signal(rb_execution_context_t *ec, VALUE self)
{
    struct rb_condvar *cv = condvar_ptr(self);
    wakeup_one(&cv->waitq);
    return self;
}
 
static VALUE
rb_condvar_broadcast(rb_execution_context_t *ec, VALUE self)
{
    struct rb_condvar *cv = condvar_ptr(self);
    wakeup_all(&cv->waitq);
    return self;
}
 
NORETURN(static VALUE undumpable(VALUE obj));
/* :nodoc: */
static VALUE
undumpable(VALUE obj)
{
    rb_raise(rb_eTypeError, "can't dump %"PRIsVALUE, rb_obj_class(obj));
    UNREACHABLE_RETURN(Qnil);
}
 
static VALUE
define_thread_class(VALUE outer, const ID name, VALUE super)
{
    VALUE klass = rb_define_class_id_under(outer, name, super);
    rb_const_set(rb_cObject, name, klass);
    return klass;
}
 
static void
Init_thread_sync(void)
{
#undef rb_intern
#if defined(TEACH_RDOC) && TEACH_RDOC == 42
    rb_cMutex = rb_define_class_under(rb_cThread, "Mutex", rb_cObject);
    rb_cConditionVariable = rb_define_class_under(rb_cThread, "ConditionVariable", rb_cObject);
    rb_cQueue = rb_define_class_under(rb_cThread, "Queue", rb_cObject);
    rb_cSizedQueue = rb_define_class_under(rb_cThread, "SizedQueue", rb_cObject);
#endif
 
#define DEFINE_CLASS(name, super) \
    rb_c##name = define_thread_class(rb_cThread, rb_intern(#name), rb_c##super)
 
    /* Mutex */
    DEFINE_CLASS(Mutex, Object);
    rb_define_alloc_func(rb_cMutex, mutex_alloc);
 
    /* Queue */
    DEFINE_CLASS(Queue, Object);
    rb_define_alloc_func(rb_cQueue, queue_alloc);
 
    rb_eClosedQueueError = rb_define_class("ClosedQueueError", rb_eStopIteration);
 
    rb_define_method(rb_cQueue, "initialize", rb_queue_initialize, -1);
    rb_undef_method(rb_cQueue, "initialize_copy");
    rb_define_method(rb_cQueue, "marshal_dump", undumpable, 0);
    rb_define_method(rb_cQueue, "close", rb_queue_close, 0);
    rb_define_method(rb_cQueue, "closed?", rb_queue_closed_p, 0);
    rb_define_method(rb_cQueue, "push", rb_queue_push, 1);
    rb_define_method(rb_cQueue, "empty?", rb_queue_empty_p, 0);
    rb_define_method(rb_cQueue, "clear", rb_queue_clear, 0);
    rb_define_method(rb_cQueue, "length", rb_queue_length, 0);
    rb_define_method(rb_cQueue, "num_waiting", rb_queue_num_waiting, 0);
    rb_define_method(rb_cQueue, "freeze", rb_queue_freeze, 0);
 
    rb_define_alias(rb_cQueue, "enq", "push");
    rb_define_alias(rb_cQueue, "<<", "push");
    rb_define_alias(rb_cQueue, "size", "length");
 
    DEFINE_CLASS(SizedQueue, Queue);
    rb_define_alloc_func(rb_cSizedQueue, szqueue_alloc);
 
    rb_define_method(rb_cSizedQueue, "initialize", rb_szqueue_initialize, 1);
    rb_define_method(rb_cSizedQueue, "close", rb_szqueue_close, 0);
    rb_define_method(rb_cSizedQueue, "max", rb_szqueue_max_get, 0);
    rb_define_method(rb_cSizedQueue, "max=", rb_szqueue_max_set, 1);
    rb_define_method(rb_cSizedQueue, "clear", rb_szqueue_clear, 0);
    rb_define_method(rb_cSizedQueue, "num_waiting", rb_szqueue_num_waiting, 0);
 
    /* CVar */
    DEFINE_CLASS(ConditionVariable, Object);
    rb_define_alloc_func(rb_cConditionVariable, condvar_alloc);
 
    id_sleep = rb_intern("sleep");
 
    rb_provide("thread.rb");
}
 
#include "thread_sync.rbinc"