libdispatch-187.5.tar.gz

[apple/libdispatch.git] / src / source.c

/*
 * Copyright (c) 2008-2011 Apple Inc. All rights reserved.
 *
 * @APPLE_APACHE_LICENSE_HEADER_START@
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @APPLE_APACHE_LICENSE_HEADER_END@
 */

#include "internal.h"
#if HAVE_MACH
#include "protocol.h"
#include "protocolServer.h"
#endif
#include <sys/mount.h>

static void _dispatch_source_dispose(dispatch_source_t ds);
static dispatch_queue_t _dispatch_source_invoke(dispatch_source_t ds);
static bool _dispatch_source_probe(dispatch_source_t ds);
static void _dispatch_source_merge_kevent(dispatch_source_t ds,
                const struct kevent *ke);
static void _dispatch_kevent_register(dispatch_source_t ds);
static void _dispatch_kevent_unregister(dispatch_source_t ds);
static bool _dispatch_kevent_resume(dispatch_kevent_t dk, uint32_t new_flags,
                uint32_t del_flags);
static inline void _dispatch_source_timer_init(void);
static void _dispatch_timer_list_update(dispatch_source_t ds);
static inline unsigned long _dispatch_source_timer_data(
                dispatch_source_refs_t dr, unsigned long prev);
#if HAVE_MACH
static kern_return_t _dispatch_kevent_machport_resume(dispatch_kevent_t dk,
                uint32_t new_flags, uint32_t del_flags);
static void _dispatch_drain_mach_messages(struct kevent *ke);
#endif
static size_t _dispatch_source_kevent_debug(dispatch_source_t ds,
                char* buf, size_t bufsiz);
#if DISPATCH_DEBUG
static void _dispatch_kevent_debugger(void *context);
#endif

#pragma mark -
#pragma mark dispatch_source_t

const struct dispatch_source_vtable_s _dispatch_source_kevent_vtable = {
        .do_type = DISPATCH_SOURCE_KEVENT_TYPE,
        .do_kind = "kevent-source",
        .do_invoke = _dispatch_source_invoke,
        .do_dispose = _dispatch_source_dispose,
        .do_probe = _dispatch_source_probe,
        .do_debug = _dispatch_source_kevent_debug,
};

dispatch_source_t
dispatch_source_create(dispatch_source_type_t type,
        uintptr_t handle,
        unsigned long mask,
        dispatch_queue_t q)
{
        const struct kevent *proto_kev = &type->ke;
        dispatch_source_t ds = NULL;
        dispatch_kevent_t dk = NULL;

        // input validation
        if (type == NULL || (mask & ~type->mask)) {
                goto out_bad;
        }

        switch (type->ke.filter) {
        case EVFILT_SIGNAL:
                if (handle >= NSIG) {
                        goto out_bad;
                }
                break;
        case EVFILT_FS:
#if DISPATCH_USE_VM_PRESSURE
        case EVFILT_VM:
#endif
        case DISPATCH_EVFILT_CUSTOM_ADD:
        case DISPATCH_EVFILT_CUSTOM_OR:
        case DISPATCH_EVFILT_TIMER:
                if (handle) {
                        goto out_bad;
                }
                break;
        default:
                break;
        }

        ds = calloc(1ul, sizeof(struct dispatch_source_s));
        if (slowpath(!ds)) {
                goto out_bad;
        }
        dk = calloc(1ul, sizeof(struct dispatch_kevent_s));
        if (slowpath(!dk)) {
                goto out_bad;
        }

        dk->dk_kevent = *proto_kev;
        dk->dk_kevent.ident = handle;
        dk->dk_kevent.flags |= EV_ADD|EV_ENABLE;
        dk->dk_kevent.fflags |= (uint32_t)mask;
        dk->dk_kevent.udata = dk;
        TAILQ_INIT(&dk->dk_sources);

        // Initialize as a queue first, then override some settings below.
        _dispatch_queue_init((dispatch_queue_t)ds);
        strlcpy(ds->dq_label, "source", sizeof(ds->dq_label));

        // Dispatch Object
        ds->do_vtable = &_dispatch_source_kevent_vtable;
        ds->do_ref_cnt++; // the reference the manger queue holds
        ds->do_ref_cnt++; // since source is created suspended
        ds->do_suspend_cnt = DISPATCH_OBJECT_SUSPEND_INTERVAL;
        // The initial target queue is the manager queue, in order to get
        // the source installed. <rdar://problem/8928171>
        ds->do_targetq = &_dispatch_mgr_q;

        // Dispatch Source
        ds->ds_ident_hack = dk->dk_kevent.ident;
        ds->ds_dkev = dk;
        ds->ds_pending_data_mask = dk->dk_kevent.fflags;
        if ((EV_DISPATCH|EV_ONESHOT) & proto_kev->flags) {
                ds->ds_is_level = true;
                ds->ds_needs_rearm = true;
        } else if (!(EV_CLEAR & proto_kev->flags)) {
                // we cheat and use EV_CLEAR to mean a "flag thingy"
                ds->ds_is_adder = true;
        }

        // Some sources require special processing
        if (type->init != NULL) {
                type->init(ds, type, handle, mask, q);
        }
        if (fastpath(!ds->ds_refs)) {
                ds->ds_refs = calloc(1ul, sizeof(struct dispatch_source_refs_s));
                if (slowpath(!ds->ds_refs)) {
                        goto out_bad;
                }
        }
        ds->ds_refs->dr_source_wref = _dispatch_ptr2wref(ds);
        dispatch_assert(!(ds->ds_is_level && ds->ds_is_adder));

        // First item on the queue sets the user-specified target queue
        dispatch_set_target_queue(ds, q);
#if DISPATCH_DEBUG
        dispatch_debug(ds, "%s", __FUNCTION__);
#endif
        return ds;

out_bad:
        free(ds);
        free(dk);
        return NULL;
}

static void
_dispatch_source_dispose(dispatch_source_t ds)
{
        free(ds->ds_refs);
        _dispatch_queue_dispose((dispatch_queue_t)ds);
}

void
_dispatch_source_xref_release(dispatch_source_t ds)
{
        if (slowpath(DISPATCH_OBJECT_SUSPENDED(ds))) {
                // Arguments for and against this assert are within 6705399
                DISPATCH_CLIENT_CRASH("Release of a suspended object");
        }
        _dispatch_wakeup(ds);
        _dispatch_release(ds);
}

void
dispatch_source_cancel(dispatch_source_t ds)
{
#if DISPATCH_DEBUG
        dispatch_debug(ds, "%s", __FUNCTION__);
#endif
        // Right after we set the cancel flag, someone else
        // could potentially invoke the source, do the cancelation,
        // unregister the source, and deallocate it. We would
        // need to therefore retain/release before setting the bit

        _dispatch_retain(ds);
        (void)dispatch_atomic_or2o(ds, ds_atomic_flags, DSF_CANCELED);
        _dispatch_wakeup(ds);
        _dispatch_release(ds);
}

long
dispatch_source_testcancel(dispatch_source_t ds)
{
        return (bool)(ds->ds_atomic_flags & DSF_CANCELED);
}


unsigned long
dispatch_source_get_mask(dispatch_source_t ds)
{
        return ds->ds_pending_data_mask;
}

uintptr_t
dispatch_source_get_handle(dispatch_source_t ds)
{
        return (int)ds->ds_ident_hack;
}

unsigned long
dispatch_source_get_data(dispatch_source_t ds)
{
        return ds->ds_data;
}

void
dispatch_source_merge_data(dispatch_source_t ds, unsigned long val)
{
        struct kevent kev = {
                .fflags = (typeof(kev.fflags))val,
                .data = val,
        };

        dispatch_assert(
                        ds->ds_dkev->dk_kevent.filter == DISPATCH_EVFILT_CUSTOM_ADD ||
                        ds->ds_dkev->dk_kevent.filter == DISPATCH_EVFILT_CUSTOM_OR);

        _dispatch_source_merge_kevent(ds, &kev);
}

#pragma mark -
#pragma mark dispatch_source_handler

#ifdef __BLOCKS__
// 6618342 Contact the team that owns the Instrument DTrace probe before
//         renaming this symbol
static void
_dispatch_source_set_event_handler2(void *context)
{
        struct Block_layout *bl = context;

        dispatch_source_t ds = (dispatch_source_t)_dispatch_queue_get_current();
        dispatch_assert(ds->do_vtable == &_dispatch_source_kevent_vtable);
        dispatch_source_refs_t dr = ds->ds_refs;

        if (ds->ds_handler_is_block && dr->ds_handler_ctxt) {
                Block_release(dr->ds_handler_ctxt);
        }
        dr->ds_handler_func = bl ? (void *)bl->invoke : NULL;
        dr->ds_handler_ctxt = bl;
        ds->ds_handler_is_block = true;
}

void
dispatch_source_set_event_handler(dispatch_source_t ds,
                dispatch_block_t handler)
{
        handler = _dispatch_Block_copy(handler);
        dispatch_barrier_async_f((dispatch_queue_t)ds, handler,
                        _dispatch_source_set_event_handler2);
}
#endif /* __BLOCKS__ */

static void
_dispatch_source_set_event_handler_f(void *context)
{
        dispatch_source_t ds = (dispatch_source_t)_dispatch_queue_get_current();
        dispatch_assert(ds->do_vtable == &_dispatch_source_kevent_vtable);
        dispatch_source_refs_t dr = ds->ds_refs;

#ifdef __BLOCKS__
        if (ds->ds_handler_is_block && dr->ds_handler_ctxt) {
                Block_release(dr->ds_handler_ctxt);
        }
#endif
        dr->ds_handler_func = context;
        dr->ds_handler_ctxt = ds->do_ctxt;
        ds->ds_handler_is_block = false;
}

void
dispatch_source_set_event_handler_f(dispatch_source_t ds,
        dispatch_function_t handler)
{
        dispatch_barrier_async_f((dispatch_queue_t)ds, handler,
                        _dispatch_source_set_event_handler_f);
}

#ifdef __BLOCKS__
// 6618342 Contact the team that owns the Instrument DTrace probe before
//         renaming this symbol
static void
_dispatch_source_set_cancel_handler2(void *context)
{
        dispatch_source_t ds = (dispatch_source_t)_dispatch_queue_get_current();
        dispatch_assert(ds->do_vtable == &_dispatch_source_kevent_vtable);
        dispatch_source_refs_t dr = ds->ds_refs;

        if (ds->ds_cancel_is_block && dr->ds_cancel_handler) {
                Block_release(dr->ds_cancel_handler);
        }
        dr->ds_cancel_handler = context;
        ds->ds_cancel_is_block = true;
}

void
dispatch_source_set_cancel_handler(dispatch_source_t ds,
        dispatch_block_t handler)
{
        handler = _dispatch_Block_copy(handler);
        dispatch_barrier_async_f((dispatch_queue_t)ds, handler,
                        _dispatch_source_set_cancel_handler2);
}
#endif /* __BLOCKS__ */

static void
_dispatch_source_set_cancel_handler_f(void *context)
{
        dispatch_source_t ds = (dispatch_source_t)_dispatch_queue_get_current();
        dispatch_assert(ds->do_vtable == &_dispatch_source_kevent_vtable);
        dispatch_source_refs_t dr = ds->ds_refs;

#ifdef __BLOCKS__
        if (ds->ds_cancel_is_block && dr->ds_cancel_handler) {
                Block_release(dr->ds_cancel_handler);
        }
#endif
        dr->ds_cancel_handler = context;
        ds->ds_cancel_is_block = false;
}

void
dispatch_source_set_cancel_handler_f(dispatch_source_t ds,
        dispatch_function_t handler)
{
        dispatch_barrier_async_f((dispatch_queue_t)ds, handler,
                        _dispatch_source_set_cancel_handler_f);
}

#ifdef __BLOCKS__
static void
_dispatch_source_set_registration_handler2(void *context)
{
        dispatch_source_t ds = (dispatch_source_t)_dispatch_queue_get_current();
        dispatch_assert(ds->do_vtable == &_dispatch_source_kevent_vtable);
        dispatch_source_refs_t dr = ds->ds_refs;

        if (ds->ds_registration_is_block && dr->ds_registration_handler) {
                Block_release(dr->ds_registration_handler);
        }
        dr->ds_registration_handler = context;
        ds->ds_registration_is_block = true;
}

void
dispatch_source_set_registration_handler(dispatch_source_t ds,
        dispatch_block_t handler)
{
        handler = _dispatch_Block_copy(handler);
        dispatch_barrier_async_f((dispatch_queue_t)ds, handler,
                        _dispatch_source_set_registration_handler2);
}
#endif /* __BLOCKS__ */

static void
_dispatch_source_set_registration_handler_f(void *context)
{
        dispatch_source_t ds = (dispatch_source_t)_dispatch_queue_get_current();
        dispatch_assert(ds->do_vtable == &_dispatch_source_kevent_vtable);
        dispatch_source_refs_t dr = ds->ds_refs;

#ifdef __BLOCKS__
        if (ds->ds_registration_is_block && dr->ds_registration_handler) {
                Block_release(dr->ds_registration_handler);
        }
#endif
        dr->ds_registration_handler = context;
        ds->ds_registration_is_block = false;
}

void
dispatch_source_set_registration_handler_f(dispatch_source_t ds,
        dispatch_function_t handler)
{
        dispatch_barrier_async_f((dispatch_queue_t)ds, handler,
                        _dispatch_source_set_registration_handler_f);
}

#pragma mark -
#pragma mark dispatch_source_invoke

static void
_dispatch_source_registration_callout(dispatch_source_t ds)
{
        dispatch_source_refs_t dr = ds->ds_refs;

        if ((ds->ds_atomic_flags & DSF_CANCELED) || (ds->do_xref_cnt == 0)) {
                // no registration callout if source is canceled rdar://problem/8955246
#ifdef __BLOCKS__
                if (ds->ds_registration_is_block) {
                        Block_release(dr->ds_registration_handler);
                }
        } else if (ds->ds_registration_is_block) {
                dispatch_block_t b = dr->ds_registration_handler;
                _dispatch_client_callout_block(b);
                Block_release(dr->ds_registration_handler);
#endif
        } else {
                dispatch_function_t f = dr->ds_registration_handler;
                _dispatch_client_callout(ds->do_ctxt, f);
        }
        ds->ds_registration_is_block = false;
        dr->ds_registration_handler = NULL;
}

static void
_dispatch_source_cancel_callout(dispatch_source_t ds)
{
        dispatch_source_refs_t dr = ds->ds_refs;

        ds->ds_pending_data_mask = 0;
        ds->ds_pending_data = 0;
        ds->ds_data = 0;

#ifdef __BLOCKS__
        if (ds->ds_handler_is_block) {
                Block_release(dr->ds_handler_ctxt);
                ds->ds_handler_is_block = false;
                dr->ds_handler_func = NULL;
                dr->ds_handler_ctxt = NULL;
        }
        if (ds->ds_registration_is_block) {
                Block_release(dr->ds_registration_handler);
                ds->ds_registration_is_block = false;
                dr->ds_registration_handler = NULL;
        }
#endif

        if (!dr->ds_cancel_handler) {
                return;
        }
        if (ds->ds_cancel_is_block) {
#ifdef __BLOCKS__
                dispatch_block_t b = dr->ds_cancel_handler;
                if (ds->ds_atomic_flags & DSF_CANCELED) {
                        _dispatch_client_callout_block(b);
                }
                Block_release(dr->ds_cancel_handler);
                ds->ds_cancel_is_block = false;
#endif
        } else {
                dispatch_function_t f = dr->ds_cancel_handler;
                if (ds->ds_atomic_flags & DSF_CANCELED) {
                        _dispatch_client_callout(ds->do_ctxt, f);
                }
        }
        dr->ds_cancel_handler = NULL;
}

static void
_dispatch_source_latch_and_call(dispatch_source_t ds)
{
        unsigned long prev;

        if ((ds->ds_atomic_flags & DSF_CANCELED) || (ds->do_xref_cnt == 0)) {
                return;
        }
        dispatch_source_refs_t dr = ds->ds_refs;
        prev = dispatch_atomic_xchg2o(ds, ds_pending_data, 0);
        if (ds->ds_is_level) {
                ds->ds_data = ~prev;
        } else if (ds->ds_is_timer && ds_timer(dr).target && prev) {
                ds->ds_data = _dispatch_source_timer_data(dr, prev);
        } else {
                ds->ds_data = prev;
        }
        if (dispatch_assume(prev) && dr->ds_handler_func) {
                _dispatch_client_callout(dr->ds_handler_ctxt, dr->ds_handler_func);
        }
}

static void
_dispatch_source_kevent_resume(dispatch_source_t ds, uint32_t new_flags)
{
        switch (ds->ds_dkev->dk_kevent.filter) {
        case DISPATCH_EVFILT_TIMER:
                // called on manager queue only
                return _dispatch_timer_list_update(ds);
        case EVFILT_MACHPORT:
                if (ds->ds_pending_data_mask & DISPATCH_MACH_RECV_MESSAGE) {
                        new_flags |= DISPATCH_MACH_RECV_MESSAGE; // emulate EV_DISPATCH
                }
                break;
        }
        if (_dispatch_kevent_resume(ds->ds_dkev, new_flags, 0)) {
                _dispatch_kevent_unregister(ds);
        }
}

static dispatch_queue_t
_dispatch_source_invoke(dispatch_source_t ds)
{
        // This function performs all source actions. Each action is responsible
        // for verifying that it takes place on the appropriate queue. If the
        // current queue is not the correct queue for this action, the correct queue
        // will be returned and the invoke will be re-driven on that queue.

        // The order of tests here in invoke and in probe should be consistent.

        dispatch_queue_t dq = _dispatch_queue_get_current();
        dispatch_source_refs_t dr = ds->ds_refs;

        if (!ds->ds_is_installed) {
                // The source needs to be installed on the manager queue.
                if (dq != &_dispatch_mgr_q) {
                        return &_dispatch_mgr_q;
                }
                _dispatch_kevent_register(ds);
                if (dr->ds_registration_handler) {
                        return ds->do_targetq;
                }
                if (slowpath(ds->do_xref_cnt == 0)) {
                        return &_dispatch_mgr_q; // rdar://problem/9558246
                }
        } else if (slowpath(DISPATCH_OBJECT_SUSPENDED(ds))) {
                // Source suspended by an item drained from the source queue.
                return NULL;
        } else if (dr->ds_registration_handler) {
                // The source has been registered and the registration handler needs
                // to be delivered on the target queue.
                if (dq != ds->do_targetq) {
                        return ds->do_targetq;
                }
                // clears ds_registration_handler
                _dispatch_source_registration_callout(ds);
                if (slowpath(ds->do_xref_cnt == 0)) {
                        return &_dispatch_mgr_q; // rdar://problem/9558246
                }
        } else if ((ds->ds_atomic_flags & DSF_CANCELED) || (ds->do_xref_cnt == 0)) {
                // The source has been cancelled and needs to be uninstalled from the
                // manager queue. After uninstallation, the cancellation handler needs
                // to be delivered to the target queue.
                if (ds->ds_dkev) {
                        if (dq != &_dispatch_mgr_q) {
                                return &_dispatch_mgr_q;
                        }
                        _dispatch_kevent_unregister(ds);
                        return ds->do_targetq;
                } else if (dr->ds_cancel_handler) {
                        if (dq != ds->do_targetq) {
                                return ds->do_targetq;
                        }
                }
                _dispatch_source_cancel_callout(ds);
        } else if (ds->ds_pending_data) {
                // The source has pending data to deliver via the event handler callback
                // on the target queue. Some sources need to be rearmed on the manager
                // queue after event delivery.
                if (dq != ds->do_targetq) {
                        return ds->do_targetq;
                }
                _dispatch_source_latch_and_call(ds);
                if (ds->ds_needs_rearm) {
                        return &_dispatch_mgr_q;
                }
        } else if (ds->ds_needs_rearm && !(ds->ds_atomic_flags & DSF_ARMED)) {
                // The source needs to be rearmed on the manager queue.
                if (dq != &_dispatch_mgr_q) {
                        return &_dispatch_mgr_q;
                }
                _dispatch_source_kevent_resume(ds, 0);
                (void)dispatch_atomic_or2o(ds, ds_atomic_flags, DSF_ARMED);
        }

        return NULL;
}

static bool
_dispatch_source_probe(dispatch_source_t ds)
{
        // This function determines whether the source needs to be invoked.
        // The order of tests here in probe and in invoke should be consistent.

        dispatch_source_refs_t dr = ds->ds_refs;
        if (!ds->ds_is_installed) {
                // The source needs to be installed on the manager queue.
                return true;
        } else if (dr->ds_registration_handler) {
                // The registration handler needs to be delivered to the target queue.
                return true;
        } else if ((ds->ds_atomic_flags & DSF_CANCELED) || (ds->do_xref_cnt == 0)) {
                // The source needs to be uninstalled from the manager queue, or the
                // cancellation handler needs to be delivered to the target queue.
                // Note: cancellation assumes installation.
                if (ds->ds_dkev || dr->ds_cancel_handler) {
                        return true;
                }
        } else if (ds->ds_pending_data) {
                // The source has pending data to deliver to the target queue.
                return true;
        } else if (ds->ds_needs_rearm && !(ds->ds_atomic_flags & DSF_ARMED)) {
                // The source needs to be rearmed on the manager queue.
                return true;
        }
        // Nothing to do.
        return false;
}

#pragma mark -
#pragma mark dispatch_source_kevent

static void
_dispatch_source_merge_kevent(dispatch_source_t ds, const struct kevent *ke)
{
        struct kevent fake;

        if ((ds->ds_atomic_flags & DSF_CANCELED) || (ds->do_xref_cnt == 0)) {
                return;
        }

        // EVFILT_PROC may fail with ESRCH when the process exists but is a zombie
        // <rdar://problem/5067725>. As a workaround, we simulate an exit event for
        // any EVFILT_PROC with an invalid pid <rdar://problem/6626350>.
        if (ke->flags & EV_ERROR) {
                if (ke->filter == EVFILT_PROC && ke->data == ESRCH) {
                        fake = *ke;
                        fake.flags &= ~EV_ERROR;
                        fake.fflags = NOTE_EXIT;
                        fake.data = 0;
                        ke = &fake;
#if DISPATCH_USE_VM_PRESSURE
                } else if (ke->filter == EVFILT_VM && ke->data == ENOTSUP) {
                        // Memory pressure kevent is not supported on all platforms
                        // <rdar://problem/8636227>
                        return;
#endif
                } else {
                        // log the unexpected error
                        (void)dispatch_assume_zero(ke->data);
                        return;
                }
        }

        if (ds->ds_is_level) {
                // ke->data is signed and "negative available data" makes no sense
                // zero bytes happens when EV_EOF is set
                // 10A268 does not fail this assert with EVFILT_READ and a 10 GB file
                dispatch_assert(ke->data >= 0l);
                ds->ds_pending_data = ~ke->data;
        } else if (ds->ds_is_adder) {
                (void)dispatch_atomic_add2o(ds, ds_pending_data, ke->data);
        } else if (ke->fflags & ds->ds_pending_data_mask) {
                (void)dispatch_atomic_or2o(ds, ds_pending_data,
                                ke->fflags & ds->ds_pending_data_mask);
        }

        // EV_DISPATCH and EV_ONESHOT sources are no longer armed after delivery
        if (ds->ds_needs_rearm) {
                (void)dispatch_atomic_and2o(ds, ds_atomic_flags, ~DSF_ARMED);
        }

        _dispatch_wakeup(ds);
}

void
_dispatch_source_drain_kevent(struct kevent *ke)
{
        dispatch_kevent_t dk = ke->udata;
        dispatch_source_refs_t dri;

#if DISPATCH_DEBUG
        static dispatch_once_t pred;
        dispatch_once_f(&pred, NULL, _dispatch_kevent_debugger);
#endif

        dispatch_debug_kevents(ke, 1, __func__);

#if HAVE_MACH
        if (ke->filter == EVFILT_MACHPORT) {
                return _dispatch_drain_mach_messages(ke);
        }
#endif
        dispatch_assert(dk);

        if (ke->flags & EV_ONESHOT) {
                dk->dk_kevent.flags |= EV_ONESHOT;
        }

        TAILQ_FOREACH(dri, &dk->dk_sources, dr_list) {
                _dispatch_source_merge_kevent(_dispatch_source_from_refs(dri), ke);
        }
}

#pragma mark -
#pragma mark dispatch_kevent_t

static struct dispatch_kevent_s _dispatch_kevent_data_or = {
        .dk_kevent = {
                .filter = DISPATCH_EVFILT_CUSTOM_OR,
                .flags = EV_CLEAR,
                .udata = &_dispatch_kevent_data_or,
        },
        .dk_sources = TAILQ_HEAD_INITIALIZER(_dispatch_kevent_data_or.dk_sources),
};
static struct dispatch_kevent_s _dispatch_kevent_data_add = {
        .dk_kevent = {
                .filter = DISPATCH_EVFILT_CUSTOM_ADD,
                .udata = &_dispatch_kevent_data_add,
        },
        .dk_sources = TAILQ_HEAD_INITIALIZER(_dispatch_kevent_data_add.dk_sources),
};

#if TARGET_OS_EMBEDDED
#define DSL_HASH_SIZE  64u // must be a power of two
#else
#define DSL_HASH_SIZE 256u // must be a power of two
#endif
#define DSL_HASH(x) ((x) & (DSL_HASH_SIZE - 1))

DISPATCH_CACHELINE_ALIGN
static TAILQ_HEAD(, dispatch_kevent_s) _dispatch_sources[DSL_HASH_SIZE];

static dispatch_once_t __dispatch_kevent_init_pred;

static void
_dispatch_kevent_init(void *context DISPATCH_UNUSED)
{
        unsigned int i;
        for (i = 0; i < DSL_HASH_SIZE; i++) {
                TAILQ_INIT(&_dispatch_sources[i]);
        }

        TAILQ_INSERT_TAIL(&_dispatch_sources[0],
                        &_dispatch_kevent_data_or, dk_list);
        TAILQ_INSERT_TAIL(&_dispatch_sources[0],
                        &_dispatch_kevent_data_add, dk_list);

        _dispatch_source_timer_init();
}

static inline uintptr_t
_dispatch_kevent_hash(uintptr_t ident, short filter)
{
        uintptr_t value;
#if HAVE_MACH
        value = (filter == EVFILT_MACHPORT ? MACH_PORT_INDEX(ident) : ident);
#else
        value = ident;
#endif
        return DSL_HASH(value);
}

static dispatch_kevent_t
_dispatch_kevent_find(uintptr_t ident, short filter)
{
        uintptr_t hash = _dispatch_kevent_hash(ident, filter);
        dispatch_kevent_t dki;

        TAILQ_FOREACH(dki, &_dispatch_sources[hash], dk_list) {
                if (dki->dk_kevent.ident == ident && dki->dk_kevent.filter == filter) {
                        break;
                }
        }
        return dki;
}

static void
_dispatch_kevent_insert(dispatch_kevent_t dk)
{
        uintptr_t hash = _dispatch_kevent_hash(dk->dk_kevent.ident,
                        dk->dk_kevent.filter);

        TAILQ_INSERT_TAIL(&_dispatch_sources[hash], dk, dk_list);
}

// Find existing kevents, and merge any new flags if necessary
static void
_dispatch_kevent_register(dispatch_source_t ds)
{
        dispatch_kevent_t dk;
        typeof(dk->dk_kevent.fflags) new_flags;
        bool do_resume = false;

        if (ds->ds_is_installed) {
                return;
        }
        ds->ds_is_installed = true;

        dispatch_once_f(&__dispatch_kevent_init_pred,
                        NULL, _dispatch_kevent_init);

        dk = _dispatch_kevent_find(ds->ds_dkev->dk_kevent.ident,
                        ds->ds_dkev->dk_kevent.filter);

        if (dk) {
                // If an existing dispatch kevent is found, check to see if new flags
                // need to be added to the existing kevent
                new_flags = ~dk->dk_kevent.fflags & ds->ds_dkev->dk_kevent.fflags;
                dk->dk_kevent.fflags |= ds->ds_dkev->dk_kevent.fflags;
                free(ds->ds_dkev);
                ds->ds_dkev = dk;
                do_resume = new_flags;
        } else {
                dk = ds->ds_dkev;
                _dispatch_kevent_insert(dk);
                new_flags = dk->dk_kevent.fflags;
                do_resume = true;
        }

        TAILQ_INSERT_TAIL(&dk->dk_sources, ds->ds_refs, dr_list);

        // Re-register the kevent with the kernel if new flags were added
        // by the dispatch kevent
        if (do_resume) {
                dk->dk_kevent.flags |= EV_ADD;
        }
        if (do_resume || ds->ds_needs_rearm) {
                _dispatch_source_kevent_resume(ds, new_flags);
        }
        (void)dispatch_atomic_or2o(ds, ds_atomic_flags, DSF_ARMED);
}

static bool
_dispatch_kevent_resume(dispatch_kevent_t dk, uint32_t new_flags,
                uint32_t del_flags)
{
        long r;
        switch (dk->dk_kevent.filter) {
        case DISPATCH_EVFILT_TIMER:
        case DISPATCH_EVFILT_CUSTOM_ADD:
        case DISPATCH_EVFILT_CUSTOM_OR:
                // these types not registered with kevent
                return 0;
#if HAVE_MACH
        case EVFILT_MACHPORT:
                return _dispatch_kevent_machport_resume(dk, new_flags, del_flags);
#endif
        case EVFILT_PROC:
                if (dk->dk_kevent.flags & EV_ONESHOT) {
                        return 0;
                }
                // fall through
        default:
                r = _dispatch_update_kq(&dk->dk_kevent);
                if (dk->dk_kevent.flags & EV_DISPATCH) {
                        dk->dk_kevent.flags &= ~EV_ADD;
                }
                return r;
        }
}

static void
_dispatch_kevent_dispose(dispatch_kevent_t dk)
{
        uintptr_t hash;

        switch (dk->dk_kevent.filter) {
        case DISPATCH_EVFILT_TIMER:
        case DISPATCH_EVFILT_CUSTOM_ADD:
        case DISPATCH_EVFILT_CUSTOM_OR:
                // these sources live on statically allocated lists
                return;
#if HAVE_MACH
        case EVFILT_MACHPORT:
                _dispatch_kevent_machport_resume(dk, 0, dk->dk_kevent.fflags);
                break;
#endif
        case EVFILT_PROC:
                if (dk->dk_kevent.flags & EV_ONESHOT) {
                        break; // implicitly deleted
                }
                // fall through
        default:
                if (~dk->dk_kevent.flags & EV_DELETE) {
                        dk->dk_kevent.flags |= EV_DELETE;
                        _dispatch_update_kq(&dk->dk_kevent);
                }
                break;
        }

        hash = _dispatch_kevent_hash(dk->dk_kevent.ident,
                        dk->dk_kevent.filter);
        TAILQ_REMOVE(&_dispatch_sources[hash], dk, dk_list);
        free(dk);
}

static void
_dispatch_kevent_unregister(dispatch_source_t ds)
{
        dispatch_kevent_t dk = ds->ds_dkev;
        dispatch_source_refs_t dri;
        uint32_t del_flags, fflags = 0;

        ds->ds_dkev = NULL;

        TAILQ_REMOVE(&dk->dk_sources, ds->ds_refs, dr_list);

        if (TAILQ_EMPTY(&dk->dk_sources)) {
                _dispatch_kevent_dispose(dk);
        } else {
                TAILQ_FOREACH(dri, &dk->dk_sources, dr_list) {
                        dispatch_source_t dsi = _dispatch_source_from_refs(dri);
                        fflags |= (uint32_t)dsi->ds_pending_data_mask;
                }
                del_flags = (uint32_t)ds->ds_pending_data_mask & ~fflags;
                if (del_flags) {
                        dk->dk_kevent.flags |= EV_ADD;
                        dk->dk_kevent.fflags = fflags;
                        _dispatch_kevent_resume(dk, 0, del_flags);
                }
        }

        (void)dispatch_atomic_and2o(ds, ds_atomic_flags, ~DSF_ARMED);
        ds->ds_needs_rearm = false; // re-arm is pointless and bad now
        _dispatch_release(ds); // the retain is done at creation time
}

#pragma mark -
#pragma mark dispatch_timer

DISPATCH_CACHELINE_ALIGN
static struct dispatch_kevent_s _dispatch_kevent_timer[] = {
        [DISPATCH_TIMER_INDEX_WALL] = {
                .dk_kevent = {
                        .ident = DISPATCH_TIMER_INDEX_WALL,
                        .filter = DISPATCH_EVFILT_TIMER,
                        .udata = &_dispatch_kevent_timer[DISPATCH_TIMER_INDEX_WALL],
                },
                .dk_sources = TAILQ_HEAD_INITIALIZER(
                                _dispatch_kevent_timer[DISPATCH_TIMER_INDEX_WALL].dk_sources),
        },
        [DISPATCH_TIMER_INDEX_MACH] = {
                .dk_kevent = {
                        .ident = DISPATCH_TIMER_INDEX_MACH,
                        .filter = DISPATCH_EVFILT_TIMER,
                        .udata = &_dispatch_kevent_timer[DISPATCH_TIMER_INDEX_MACH],
                },
                .dk_sources = TAILQ_HEAD_INITIALIZER(
                                _dispatch_kevent_timer[DISPATCH_TIMER_INDEX_MACH].dk_sources),
        },
        [DISPATCH_TIMER_INDEX_DISARM] = {
                .dk_kevent = {
                        .ident = DISPATCH_TIMER_INDEX_DISARM,
                        .filter = DISPATCH_EVFILT_TIMER,
                        .udata = &_dispatch_kevent_timer[DISPATCH_TIMER_INDEX_DISARM],
                },
                .dk_sources = TAILQ_HEAD_INITIALIZER(
                                _dispatch_kevent_timer[DISPATCH_TIMER_INDEX_DISARM].dk_sources),
        },
};
// Don't count disarmed timer list
#define DISPATCH_TIMER_COUNT ((sizeof(_dispatch_kevent_timer) \
                / sizeof(_dispatch_kevent_timer[0])) - 1)

static inline void
_dispatch_source_timer_init(void)
{
        TAILQ_INSERT_TAIL(&_dispatch_sources[DSL_HASH(DISPATCH_TIMER_INDEX_WALL)],
                        &_dispatch_kevent_timer[DISPATCH_TIMER_INDEX_WALL], dk_list);
        TAILQ_INSERT_TAIL(&_dispatch_sources[DSL_HASH(DISPATCH_TIMER_INDEX_MACH)],
                        &_dispatch_kevent_timer[DISPATCH_TIMER_INDEX_MACH], dk_list);
        TAILQ_INSERT_TAIL(&_dispatch_sources[DSL_HASH(DISPATCH_TIMER_INDEX_DISARM)],
                        &_dispatch_kevent_timer[DISPATCH_TIMER_INDEX_DISARM], dk_list);
}

DISPATCH_ALWAYS_INLINE
static inline unsigned int
_dispatch_source_timer_idx(dispatch_source_refs_t dr)
{
        return ds_timer(dr).flags & DISPATCH_TIMER_WALL_CLOCK ?
                DISPATCH_TIMER_INDEX_WALL : DISPATCH_TIMER_INDEX_MACH;
}

DISPATCH_ALWAYS_INLINE
static inline uint64_t
_dispatch_source_timer_now2(unsigned int timer)
{
        switch (timer) {
        case DISPATCH_TIMER_INDEX_MACH:
                return _dispatch_absolute_time();
        case DISPATCH_TIMER_INDEX_WALL:
                return _dispatch_get_nanoseconds();
        default:
                DISPATCH_CRASH("Invalid timer");
        }
}

DISPATCH_ALWAYS_INLINE
static inline uint64_t
_dispatch_source_timer_now(dispatch_source_refs_t dr)
{
        return _dispatch_source_timer_now2(_dispatch_source_timer_idx(dr));
}

// Updates the ordered list of timers based on next fire date for changes to ds.
// Should only be called from the context of _dispatch_mgr_q.
static void
_dispatch_timer_list_update(dispatch_source_t ds)
{
        dispatch_source_refs_t dr = ds->ds_refs, dri = NULL;

        dispatch_assert(_dispatch_queue_get_current() == &_dispatch_mgr_q);

        // do not reschedule timers unregistered with _dispatch_kevent_unregister()
        if (!ds->ds_dkev) {
                return;
        }

        // Ensure the source is on the global kevent lists before it is removed and
        // readded below.
        _dispatch_kevent_register(ds);

        TAILQ_REMOVE(&ds->ds_dkev->dk_sources, dr, dr_list);

        // Move timers that are disabled, suspended or have missed intervals to the
        // disarmed list, rearm after resume resp. source invoke will reenable them
        if (!ds_timer(dr).target || DISPATCH_OBJECT_SUSPENDED(ds) ||
                        ds->ds_pending_data) {
                (void)dispatch_atomic_and2o(ds, ds_atomic_flags, ~DSF_ARMED);
                ds->ds_dkev = &_dispatch_kevent_timer[DISPATCH_TIMER_INDEX_DISARM];
                TAILQ_INSERT_TAIL(&ds->ds_dkev->dk_sources, (dispatch_source_refs_t)dr,
                                dr_list);
                return;
        }

        // change the list if the clock type has changed
        ds->ds_dkev = &_dispatch_kevent_timer[_dispatch_source_timer_idx(dr)];

        TAILQ_FOREACH(dri, &ds->ds_dkev->dk_sources, dr_list) {
                if (ds_timer(dri).target == 0 ||
                                ds_timer(dr).target < ds_timer(dri).target) {
                        break;
                }
        }

        if (dri) {
                TAILQ_INSERT_BEFORE(dri, dr, dr_list);
        } else {
                TAILQ_INSERT_TAIL(&ds->ds_dkev->dk_sources, dr, dr_list);
        }
}

static inline void
_dispatch_run_timers2(unsigned int timer)
{
        dispatch_source_refs_t dr;
        dispatch_source_t ds;
        uint64_t now, missed;

        now = _dispatch_source_timer_now2(timer);
        while ((dr = TAILQ_FIRST(&_dispatch_kevent_timer[timer].dk_sources))) {
                ds = _dispatch_source_from_refs(dr);
                // We may find timers on the wrong list due to a pending update from
                // dispatch_source_set_timer. Force an update of the list in that case.
                if (timer != ds->ds_ident_hack) {
                        _dispatch_timer_list_update(ds);
                        continue;
                }
                if (!ds_timer(dr).target) {
                        // no configured timers on the list
                        break;
                }
                if (ds_timer(dr).target > now) {
                        // Done running timers for now.
                        break;
                }
                // Remove timers that are suspended or have missed intervals from the
                // list, rearm after resume resp. source invoke will reenable them
                if (DISPATCH_OBJECT_SUSPENDED(ds) || ds->ds_pending_data) {
                        _dispatch_timer_list_update(ds);
                        continue;
                }
                // Calculate number of missed intervals.
                missed = (now - ds_timer(dr).target) / ds_timer(dr).interval;
                if (++missed > INT_MAX) {
                        missed = INT_MAX;
                }
                ds_timer(dr).target += missed * ds_timer(dr).interval;
                _dispatch_timer_list_update(ds);
                ds_timer(dr).last_fire = now;
                (void)dispatch_atomic_add2o(ds, ds_pending_data, (int)missed);
                _dispatch_wakeup(ds);
        }
}

void
_dispatch_run_timers(void)
{
        dispatch_once_f(&__dispatch_kevent_init_pred,
                        NULL, _dispatch_kevent_init);

        unsigned int i;
        for (i = 0; i < DISPATCH_TIMER_COUNT; i++) {
                if (!TAILQ_EMPTY(&_dispatch_kevent_timer[i].dk_sources)) {
                        _dispatch_run_timers2(i);
                }
        }
}

static inline unsigned long
_dispatch_source_timer_data(dispatch_source_refs_t dr, unsigned long prev)
{
        // calculate the number of intervals since last fire
        unsigned long data, missed;
        uint64_t now = _dispatch_source_timer_now(dr);
        missed = (unsigned long)((now - ds_timer(dr).last_fire) /
                        ds_timer(dr).interval);
        // correct for missed intervals already delivered last time
        data = prev - ds_timer(dr).missed + missed;
        ds_timer(dr).missed = missed;
        return data;
}

// approx 1 year (60s * 60m * 24h * 365d)
#define FOREVER_NSEC 31536000000000000ull

struct timespec *
_dispatch_get_next_timer_fire(struct timespec *howsoon)
{
        // <rdar://problem/6459649>
        // kevent(2) does not allow large timeouts, so we use a long timeout
        // instead (approximately 1 year).
        dispatch_source_refs_t dr = NULL;
        unsigned int timer;
        uint64_t now, delta_tmp, delta = UINT64_MAX;

        for (timer = 0; timer < DISPATCH_TIMER_COUNT; timer++) {
                // Timers are kept in order, first one will fire next
                dr = TAILQ_FIRST(&_dispatch_kevent_timer[timer].dk_sources);
                if (!dr || !ds_timer(dr).target) {
                        // Empty list or disabled timer
                        continue;
                }
                now = _dispatch_source_timer_now(dr);
                if (ds_timer(dr).target <= now) {
                        howsoon->tv_sec = 0;
                        howsoon->tv_nsec = 0;
                        return howsoon;
                }
                // the subtraction cannot go negative because the previous "if"
                // verified that the target is greater than now.
                delta_tmp = ds_timer(dr).target - now;
                if (!(ds_timer(dr).flags & DISPATCH_TIMER_WALL_CLOCK)) {
                        delta_tmp = _dispatch_time_mach2nano(delta_tmp);
                }
                if (delta_tmp < delta) {
                        delta = delta_tmp;
                }
        }
        if (slowpath(delta > FOREVER_NSEC)) {
                return NULL;
        } else {
                howsoon->tv_sec = (time_t)(delta / NSEC_PER_SEC);
                howsoon->tv_nsec = (long)(delta % NSEC_PER_SEC);
        }
        return howsoon;
}

struct dispatch_set_timer_params {
        dispatch_source_t ds;
        uintptr_t ident;
        struct dispatch_timer_source_s values;
};

static void
_dispatch_source_set_timer3(void *context)
{
        // Called on the _dispatch_mgr_q
        struct dispatch_set_timer_params *params = context;
        dispatch_source_t ds = params->ds;
        ds->ds_ident_hack = params->ident;
        ds_timer(ds->ds_refs) = params->values;
        // Clear any pending data that might have accumulated on
        // older timer params <rdar://problem/8574886>
        ds->ds_pending_data = 0;
        _dispatch_timer_list_update(ds);
        dispatch_resume(ds);
        dispatch_release(ds);
        free(params);
}

static void
_dispatch_source_set_timer2(void *context)
{
        // Called on the source queue
        struct dispatch_set_timer_params *params = context;
        dispatch_suspend(params->ds);
        dispatch_barrier_async_f(&_dispatch_mgr_q, params,
                        _dispatch_source_set_timer3);
}

void
dispatch_source_set_timer(dispatch_source_t ds,
        dispatch_time_t start,
        uint64_t interval,
        uint64_t leeway)
{
        if (slowpath(!ds->ds_is_timer)) {
                DISPATCH_CLIENT_CRASH("Attempt to set timer on a non-timer source");
        }

        struct dispatch_set_timer_params *params;

        // we use zero internally to mean disabled
        if (interval == 0) {
                interval = 1;
        } else if ((int64_t)interval < 0) {
                // 6866347 - make sure nanoseconds won't overflow
                interval = INT64_MAX;
        }
        if ((int64_t)leeway < 0) {
                leeway = INT64_MAX;
        }

        if (start == DISPATCH_TIME_NOW) {
                start = _dispatch_absolute_time();
        } else if (start == DISPATCH_TIME_FOREVER) {
                start = INT64_MAX;
        }

        while (!(params = calloc(1ul, sizeof(struct dispatch_set_timer_params)))) {
                sleep(1);
        }

        params->ds = ds;
        params->values.flags = ds_timer(ds->ds_refs).flags;

        if ((int64_t)start < 0) {
                // wall clock
                params->ident = DISPATCH_TIMER_INDEX_WALL;
                params->values.target = -((int64_t)start);
                params->values.interval = interval;
                params->values.leeway = leeway;
                params->values.flags |= DISPATCH_TIMER_WALL_CLOCK;
        } else {
                // absolute clock
                params->ident = DISPATCH_TIMER_INDEX_MACH;
                params->values.target = start;
                params->values.interval = _dispatch_time_nano2mach(interval);

                // rdar://problem/7287561 interval must be at least one in
                // in order to avoid later division by zero when calculating
                // the missed interval count. (NOTE: the wall clock's
                // interval is already "fixed" to be 1 or more)
                if (params->values.interval < 1) {
                        params->values.interval = 1;
                }

                params->values.leeway = _dispatch_time_nano2mach(leeway);
                params->values.flags &= ~DISPATCH_TIMER_WALL_CLOCK;
        }
        // Suspend the source so that it doesn't fire with pending changes
        // The use of suspend/resume requires the external retain/release
        dispatch_retain(ds);
        dispatch_barrier_async_f((dispatch_queue_t)ds, params,
                        _dispatch_source_set_timer2);
}

#pragma mark -
#pragma mark dispatch_mach

#if HAVE_MACH

#if DISPATCH_DEBUG && DISPATCH_MACHPORT_DEBUG
#define _dispatch_debug_machport(name) \
                dispatch_debug_machport((name), __func__)
#else
#define _dispatch_debug_machport(name)
#endif

// Flags for all notifications that are registered/unregistered when a
// send-possible notification is requested/delivered
#define _DISPATCH_MACH_SP_FLAGS (DISPATCH_MACH_SEND_POSSIBLE| \
                DISPATCH_MACH_SEND_DEAD|DISPATCH_MACH_SEND_DELETED)

#define _DISPATCH_IS_POWER_OF_TWO(v) (!(v & (v - 1)) && v)
#define _DISPATCH_HASH(x, y) (_DISPATCH_IS_POWER_OF_TWO(y) ? \
                (MACH_PORT_INDEX(x) & ((y) - 1)) : (MACH_PORT_INDEX(x) % (y)))

#define _DISPATCH_MACHPORT_HASH_SIZE 32
#define _DISPATCH_MACHPORT_HASH(x) \
                _DISPATCH_HASH((x), _DISPATCH_MACHPORT_HASH_SIZE)

static dispatch_source_t _dispatch_mach_notify_source;
static mach_port_t _dispatch_port_set;
static mach_port_t _dispatch_event_port;

static kern_return_t _dispatch_mach_notify_update(dispatch_kevent_t dk,
        uint32_t new_flags, uint32_t del_flags, uint32_t mask,
        mach_msg_id_t notify_msgid, mach_port_mscount_t notify_sync);

static void
_dispatch_port_set_init(void *context DISPATCH_UNUSED)
{
        struct kevent kev = {
                .filter = EVFILT_MACHPORT,
                .flags = EV_ADD,
        };
        kern_return_t kr;

        kr = mach_port_allocate(mach_task_self(), MACH_PORT_RIGHT_PORT_SET,
                        &_dispatch_port_set);
        DISPATCH_VERIFY_MIG(kr);
        if (kr) {
                _dispatch_bug_mach_client(
                                "_dispatch_port_set_init: mach_port_allocate() failed", kr);
                DISPATCH_CLIENT_CRASH(
                                "mach_port_allocate() failed: cannot create port set");
        }
        kr = mach_port_allocate(mach_task_self(), MACH_PORT_RIGHT_RECEIVE,
                        &_dispatch_event_port);
        DISPATCH_VERIFY_MIG(kr);
        if (kr) {
                _dispatch_bug_mach_client(
                                "_dispatch_port_set_init: mach_port_allocate() failed", kr);
                DISPATCH_CLIENT_CRASH(
                                "mach_port_allocate() failed: cannot create receive right");
        }
        kr = mach_port_move_member(mach_task_self(), _dispatch_event_port,
                        _dispatch_port_set);
        DISPATCH_VERIFY_MIG(kr);
        if (kr) {
                _dispatch_bug_mach_client(
                                "_dispatch_port_set_init: mach_port_move_member() failed", kr);
                DISPATCH_CLIENT_CRASH("mach_port_move_member() failed");
        }

        kev.ident = _dispatch_port_set;

        _dispatch_update_kq(&kev);
}

static mach_port_t
_dispatch_get_port_set(void)
{
        static dispatch_once_t pred;

        dispatch_once_f(&pred, NULL, _dispatch_port_set_init);

        return _dispatch_port_set;
}

static kern_return_t
_dispatch_kevent_machport_enable(dispatch_kevent_t dk)
{
        mach_port_t mp = (mach_port_t)dk->dk_kevent.ident;
        kern_return_t kr;

        _dispatch_debug_machport(mp);
        kr = mach_port_move_member(mach_task_self(), mp, _dispatch_get_port_set());
        if (slowpath(kr)) {
                DISPATCH_VERIFY_MIG(kr);
                switch (kr) {
                case KERN_INVALID_NAME:
#if DISPATCH_DEBUG
                        _dispatch_log("Corruption: Mach receive right 0x%x destroyed "
                                        "prematurely", mp);
#endif
                        break;
                case KERN_INVALID_RIGHT:
                        _dispatch_bug_mach_client("_dispatch_kevent_machport_enable: "
                                        "mach_port_move_member() failed ", kr);
                        break;
                default:
                        (void)dispatch_assume_zero(kr);
                        break;
                }
        }
        return kr;
}

static void
_dispatch_kevent_machport_disable(dispatch_kevent_t dk)
{
        mach_port_t mp = (mach_port_t)dk->dk_kevent.ident;
        kern_return_t kr;

        _dispatch_debug_machport(mp);
        kr = mach_port_move_member(mach_task_self(), mp, 0);
        if (slowpath(kr)) {
                DISPATCH_VERIFY_MIG(kr);
                switch (kr) {
                case KERN_INVALID_RIGHT:
                case KERN_INVALID_NAME:
#if DISPATCH_DEBUG
                        _dispatch_log("Corruption: Mach receive right 0x%x destroyed "
                                        "prematurely", mp);
#endif
                        break;
                default:
                        (void)dispatch_assume_zero(kr);
                        break;
                }
        }
}

kern_return_t
_dispatch_kevent_machport_resume(dispatch_kevent_t dk, uint32_t new_flags,
                uint32_t del_flags)
{
        kern_return_t kr_recv = 0, kr_sp = 0;

        dispatch_assert_zero(new_flags & del_flags);
        if (new_flags & DISPATCH_MACH_RECV_MESSAGE) {
                kr_recv = _dispatch_kevent_machport_enable(dk);
        } else if (del_flags & DISPATCH_MACH_RECV_MESSAGE) {
                _dispatch_kevent_machport_disable(dk);
        }
        if ((new_flags & _DISPATCH_MACH_SP_FLAGS) ||
                        (del_flags & _DISPATCH_MACH_SP_FLAGS)) {
                // Requesting a (delayed) non-sync send-possible notification
                // registers for both immediate dead-name notification and delayed-arm
                // send-possible notification for the port.
                // The send-possible notification is armed when a mach_msg() with the
                // the MACH_SEND_NOTIFY to the port times out.
                // If send-possible is unavailable, fall back to immediate dead-name
                // registration rdar://problem/2527840&9008724
                kr_sp = _dispatch_mach_notify_update(dk, new_flags, del_flags,
                                _DISPATCH_MACH_SP_FLAGS, MACH_NOTIFY_SEND_POSSIBLE,
                                MACH_NOTIFY_SEND_POSSIBLE == MACH_NOTIFY_DEAD_NAME ? 1 : 0);
        }

        return (kr_recv ? kr_recv : kr_sp);
}

void
_dispatch_drain_mach_messages(struct kevent *ke)
{
        mach_port_t name = (mach_port_name_t)ke->data;
        dispatch_source_refs_t dri;
        dispatch_kevent_t dk;
        struct kevent kev;

        if (!dispatch_assume(name)) {
                return;
        }
        _dispatch_debug_machport(name);
        dk = _dispatch_kevent_find(name, EVFILT_MACHPORT);
        if (!dispatch_assume(dk)) {
                return;
        }
        _dispatch_kevent_machport_disable(dk); // emulate EV_DISPATCH

        EV_SET(&kev, name, EVFILT_MACHPORT, EV_ADD|EV_ENABLE|EV_DISPATCH,
                        DISPATCH_MACH_RECV_MESSAGE, 0, dk);

        TAILQ_FOREACH(dri, &dk->dk_sources, dr_list) {
                _dispatch_source_merge_kevent(_dispatch_source_from_refs(dri), &kev);
        }
}

static inline void
_dispatch_mach_notify_merge(mach_port_t name, uint32_t flag, uint32_t unreg,
                bool final)
{
        dispatch_source_refs_t dri;
        dispatch_kevent_t dk;
        struct kevent kev;

        dk = _dispatch_kevent_find(name, EVFILT_MACHPORT);
        if (!dk) {
                return;
        }

        // Update notification registration state.
        dk->dk_kevent.data &= ~unreg;
        if (!final) {
                // Re-register for notification before delivery
                _dispatch_kevent_resume(dk, flag, 0);
        }

        EV_SET(&kev, name, EVFILT_MACHPORT, EV_ADD|EV_ENABLE, flag, 0, dk);

        TAILQ_FOREACH(dri, &dk->dk_sources, dr_list) {
                _dispatch_source_merge_kevent(_dispatch_source_from_refs(dri), &kev);
                if (final) {
                        // this can never happen again
                        // this must happen after the merge
                        // this may be racy in the future, but we don't provide a 'setter'
                        // API for the mask yet
                        _dispatch_source_from_refs(dri)->ds_pending_data_mask &= ~unreg;
                }
        }

        if (final) {
                // no more sources have these flags
                dk->dk_kevent.fflags &= ~unreg;
        }
}

static kern_return_t
_dispatch_mach_notify_update(dispatch_kevent_t dk, uint32_t new_flags,
                uint32_t del_flags, uint32_t mask, mach_msg_id_t notify_msgid,
                mach_port_mscount_t notify_sync)
{
        mach_port_t previous, port = (mach_port_t)dk->dk_kevent.ident;
        typeof(dk->dk_kevent.data) prev = dk->dk_kevent.data;
        kern_return_t kr, krr = 0;

        // Update notification registration state.
        dk->dk_kevent.data |= (new_flags | dk->dk_kevent.fflags) & mask;
        dk->dk_kevent.data &= ~(del_flags & mask);

        _dispatch_debug_machport(port);
        if ((dk->dk_kevent.data & mask) && !(prev & mask)) {
                previous = MACH_PORT_NULL;
                krr = mach_port_request_notification(mach_task_self(), port,
                                notify_msgid, notify_sync, _dispatch_event_port,
                                MACH_MSG_TYPE_MAKE_SEND_ONCE, &previous);
                DISPATCH_VERIFY_MIG(krr);

                switch(krr) {
                case KERN_INVALID_NAME:
                case KERN_INVALID_RIGHT:
                        // Supress errors & clear registration state
                        dk->dk_kevent.data &= ~mask;
                        break;
                default:
                        // Else, we dont expect any errors from mach. Log any errors
                        if (dispatch_assume_zero(krr)) {
                                // log the error & clear registration state
                                dk->dk_kevent.data &= ~mask;
                        } else if (dispatch_assume_zero(previous)) {
                                // Another subsystem has beat libdispatch to requesting the
                                // specified Mach notification on this port. We should
                                // technically cache the previous port and message it when the
                                // kernel messages our port. Or we can just say screw those
                                // subsystems and deallocate the previous port.
                                // They should adopt libdispatch :-P
                                kr = mach_port_deallocate(mach_task_self(), previous);
                                DISPATCH_VERIFY_MIG(kr);
                                (void)dispatch_assume_zero(kr);
                                previous = MACH_PORT_NULL;
                        }
                }
        } else if (!(dk->dk_kevent.data & mask) && (prev & mask)) {
                previous = MACH_PORT_NULL;
                kr = mach_port_request_notification(mach_task_self(), port,
                                notify_msgid, notify_sync, MACH_PORT_NULL,
                                MACH_MSG_TYPE_MOVE_SEND_ONCE, &previous);
                DISPATCH_VERIFY_MIG(kr);

                switch (kr) {
                case KERN_INVALID_NAME:
                case KERN_INVALID_RIGHT:
                case KERN_INVALID_ARGUMENT:
                        break;
                default:
                        if (dispatch_assume_zero(kr)) {
                                // log the error
                        }
                }
        } else {
                return 0;
        }
        if (slowpath(previous)) {
                // the kernel has not consumed the send-once right yet
                (void)dispatch_assume_zero(
                                _dispatch_send_consume_send_once_right(previous));
        }
        return krr;
}

static void
_dispatch_mach_notify_source2(void *context)
{
        dispatch_source_t ds = context;
        size_t maxsz = MAX(sizeof(union
                __RequestUnion___dispatch_send_libdispatch_internal_protocol_subsystem),
                sizeof(union
                __ReplyUnion___dispatch_libdispatch_internal_protocol_subsystem));

        dispatch_mig_server(ds, maxsz, libdispatch_internal_protocol_server);
}

void
_dispatch_mach_notify_source_init(void *context DISPATCH_UNUSED)
{
        _dispatch_get_port_set();

        _dispatch_mach_notify_source = dispatch_source_create(
                        DISPATCH_SOURCE_TYPE_MACH_RECV, _dispatch_event_port, 0,
                        &_dispatch_mgr_q);
        dispatch_assert(_dispatch_mach_notify_source);
        dispatch_set_context(_dispatch_mach_notify_source,
                        _dispatch_mach_notify_source);
        dispatch_source_set_event_handler_f(_dispatch_mach_notify_source,
                        _dispatch_mach_notify_source2);
        dispatch_resume(_dispatch_mach_notify_source);
}

kern_return_t
_dispatch_mach_notify_port_deleted(mach_port_t notify DISPATCH_UNUSED,
                mach_port_name_t name)
{
#if DISPATCH_DEBUG
        _dispatch_log("Corruption: Mach send/send-once/dead-name right 0x%x "
                        "deleted prematurely", name);
#endif

        _dispatch_debug_machport(name);
        _dispatch_mach_notify_merge(name, DISPATCH_MACH_SEND_DELETED,
                                _DISPATCH_MACH_SP_FLAGS, true);

        return KERN_SUCCESS;
}

kern_return_t
_dispatch_mach_notify_dead_name(mach_port_t notify DISPATCH_UNUSED,
                mach_port_name_t name)
{
        kern_return_t kr;

#if DISPATCH_DEBUG
        _dispatch_log("machport[0x%08x]: dead-name notification: %s",
                        name, __func__);
#endif
        _dispatch_debug_machport(name);
        _dispatch_mach_notify_merge(name, DISPATCH_MACH_SEND_DEAD,
                                _DISPATCH_MACH_SP_FLAGS, true);

        // the act of receiving a dead name notification allocates a dead-name
        // right that must be deallocated
        kr = mach_port_deallocate(mach_task_self(), name);
        DISPATCH_VERIFY_MIG(kr);
        //(void)dispatch_assume_zero(kr);

        return KERN_SUCCESS;
}

kern_return_t
_dispatch_mach_notify_send_possible(mach_port_t notify DISPATCH_UNUSED,
                mach_port_name_t name)
{
#if DISPATCH_DEBUG
        _dispatch_log("machport[0x%08x]: send-possible notification: %s",
                        name, __func__);
#endif
        _dispatch_debug_machport(name);
        _dispatch_mach_notify_merge(name, DISPATCH_MACH_SEND_POSSIBLE,
                                _DISPATCH_MACH_SP_FLAGS, false);

        return KERN_SUCCESS;
}

mach_msg_return_t
dispatch_mig_server(dispatch_source_t ds, size_t maxmsgsz,
                dispatch_mig_callback_t callback)
{
        mach_msg_options_t options = MACH_RCV_MSG | MACH_RCV_TIMEOUT
                | MACH_RCV_TRAILER_ELEMENTS(MACH_RCV_TRAILER_CTX)
                | MACH_RCV_TRAILER_TYPE(MACH_MSG_TRAILER_FORMAT_0);
        mach_msg_options_t tmp_options;
        mig_reply_error_t *bufTemp, *bufRequest, *bufReply;
        mach_msg_return_t kr = 0;
        unsigned int cnt = 1000; // do not stall out serial queues
        int demux_success;
        bool received = false;
        size_t rcv_size = maxmsgsz + MAX_TRAILER_SIZE;

        // XXX FIXME -- allocate these elsewhere
        bufRequest = alloca(rcv_size);
        bufReply = alloca(rcv_size);
        bufReply->Head.msgh_size = 0; // make CLANG happy
        bufRequest->RetCode = 0;

#if DISPATCH_DEBUG
        options |= MACH_RCV_LARGE; // rdar://problem/8422992
#endif
        tmp_options = options;
        // XXX FIXME -- change this to not starve out the target queue
        for (;;) {
                if (DISPATCH_OBJECT_SUSPENDED(ds) || (--cnt == 0)) {
                        options &= ~MACH_RCV_MSG;
                        tmp_options &= ~MACH_RCV_MSG;

                        if (!(tmp_options & MACH_SEND_MSG)) {
                                break;
                        }
                }
                kr = mach_msg(&bufReply->Head, tmp_options, bufReply->Head.msgh_size,
                                (mach_msg_size_t)rcv_size, (mach_port_t)ds->ds_ident_hack, 0,0);

                tmp_options = options;

                if (slowpath(kr)) {
                        switch (kr) {
                        case MACH_SEND_INVALID_DEST:
                        case MACH_SEND_TIMED_OUT:
                                if (bufReply->Head.msgh_bits & MACH_MSGH_BITS_COMPLEX) {
                                        mach_msg_destroy(&bufReply->Head);
                                }
                                break;
                        case MACH_RCV_TIMED_OUT:
                                // Don't return an error if a message was sent this time or
                                // a message was successfully received previously
                                // rdar://problems/7363620&7791738
                                if(bufReply->Head.msgh_remote_port || received) {
                                        kr = MACH_MSG_SUCCESS;
                                }
                                break;
                        case MACH_RCV_INVALID_NAME:
                                break;
#if DISPATCH_DEBUG
                        case MACH_RCV_TOO_LARGE:
                                // receive messages that are too large and log their id and size
                                // rdar://problem/8422992
                                tmp_options &= ~MACH_RCV_LARGE;
                                size_t large_size = bufReply->Head.msgh_size + MAX_TRAILER_SIZE;
                                void *large_buf = malloc(large_size);
                                if (large_buf) {
                                        rcv_size = large_size;
                                        bufReply = large_buf;
                                }
                                if (!mach_msg(&bufReply->Head, tmp_options, 0,
                                                (mach_msg_size_t)rcv_size,
                                                (mach_port_t)ds->ds_ident_hack, 0, 0)) {
                                        _dispatch_log("BUG in libdispatch client: "
                                                        "dispatch_mig_server received message larger than "
                                                        "requested size %zd: id = 0x%x, size = %d",
                                                        maxmsgsz, bufReply->Head.msgh_id,
                                                        bufReply->Head.msgh_size);
                                }
                                if (large_buf) {
                                        free(large_buf);
                                }
                                // fall through
#endif
                        default:
                                _dispatch_bug_mach_client(
                                                "dispatch_mig_server: mach_msg() failed", kr);
                                break;
                        }
                        break;
                }

                if (!(tmp_options & MACH_RCV_MSG)) {
                        break;
                }
                received = true;

                bufTemp = bufRequest;
                bufRequest = bufReply;
                bufReply = bufTemp;

                demux_success = callback(&bufRequest->Head, &bufReply->Head);

                if (!demux_success) {
                        // destroy the request - but not the reply port
                        bufRequest->Head.msgh_remote_port = 0;
                        mach_msg_destroy(&bufRequest->Head);
                } else if (!(bufReply->Head.msgh_bits & MACH_MSGH_BITS_COMPLEX)) {
                        // if MACH_MSGH_BITS_COMPLEX is _not_ set, then bufReply->RetCode
                        // is present
                        if (slowpath(bufReply->RetCode)) {
                                if (bufReply->RetCode == MIG_NO_REPLY) {
                                        continue;
                                }

                                // destroy the request - but not the reply port
                                bufRequest->Head.msgh_remote_port = 0;
                                mach_msg_destroy(&bufRequest->Head);
                        }
                }

                if (bufReply->Head.msgh_remote_port) {
                        tmp_options |= MACH_SEND_MSG;
                        if (MACH_MSGH_BITS_REMOTE(bufReply->Head.msgh_bits) !=
                                        MACH_MSG_TYPE_MOVE_SEND_ONCE) {
                                tmp_options |= MACH_SEND_TIMEOUT;
                        }
                }
        }

        return kr;
}

#endif /* HAVE_MACH */

#pragma mark -
#pragma mark dispatch_source_debug

DISPATCH_NOINLINE
static const char *
_evfiltstr(short filt)
{
        switch (filt) {
#define _evfilt2(f) case (f): return #f
        _evfilt2(EVFILT_READ);
        _evfilt2(EVFILT_WRITE);
        _evfilt2(EVFILT_AIO);
        _evfilt2(EVFILT_VNODE);
        _evfilt2(EVFILT_PROC);
        _evfilt2(EVFILT_SIGNAL);
        _evfilt2(EVFILT_TIMER);
#ifdef EVFILT_VM
        _evfilt2(EVFILT_VM);
#endif
#if HAVE_MACH
        _evfilt2(EVFILT_MACHPORT);
#endif
        _evfilt2(EVFILT_FS);
        _evfilt2(EVFILT_USER);

        _evfilt2(DISPATCH_EVFILT_TIMER);
        _evfilt2(DISPATCH_EVFILT_CUSTOM_ADD);
        _evfilt2(DISPATCH_EVFILT_CUSTOM_OR);
        default:
                return "EVFILT_missing";
        }
}

static size_t
_dispatch_source_debug_attr(dispatch_source_t ds, char* buf, size_t bufsiz)
{
        dispatch_queue_t target = ds->do_targetq;
        return snprintf(buf, bufsiz, "target = %s[%p], pending_data = 0x%lx, "
                        "pending_data_mask = 0x%lx, ",
                        target ? target->dq_label : "", target,
                        ds->ds_pending_data, ds->ds_pending_data_mask);
}

static size_t
_dispatch_timer_debug_attr(dispatch_source_t ds, char* buf, size_t bufsiz)
{
        dispatch_source_refs_t dr = ds->ds_refs;
        return snprintf(buf, bufsiz, "timer = { target = 0x%llx, "
                        "last_fire = 0x%llx, interval = 0x%llx, flags = 0x%llx }, ",
                        ds_timer(dr).target, ds_timer(dr).last_fire, ds_timer(dr).interval,
                        ds_timer(dr).flags);
}

static size_t
_dispatch_source_debug(dispatch_source_t ds, char* buf, size_t bufsiz)
{
        size_t offset = 0;
        offset += snprintf(&buf[offset], bufsiz - offset, "%s[%p] = { ",
                        dx_kind(ds), ds);
        offset += _dispatch_object_debug_attr(ds, &buf[offset], bufsiz - offset);
        offset += _dispatch_source_debug_attr(ds, &buf[offset], bufsiz - offset);
        if (ds->ds_is_timer) {
                offset += _dispatch_timer_debug_attr(ds, &buf[offset], bufsiz - offset);
        }
        return offset;
}

static size_t
_dispatch_source_kevent_debug(dispatch_source_t ds, char* buf, size_t bufsiz)
{
        size_t offset = _dispatch_source_debug(ds, buf, bufsiz);
        offset += snprintf(&buf[offset], bufsiz - offset, "filter = %s }",
                        ds->ds_dkev ? _evfiltstr(ds->ds_dkev->dk_kevent.filter) : "????");
        return offset;
}

#if DISPATCH_DEBUG
void
dispatch_debug_kevents(struct kevent* kev, size_t count, const char* str)
{
        size_t i;
        for (i = 0; i < count; ++i) {
                _dispatch_log("kevent[%lu] = { ident = %p, filter = %s, flags = 0x%x, "
                                "fflags = 0x%x, data = %p, udata = %p }: %s",
                                i, (void*)kev[i].ident, _evfiltstr(kev[i].filter), kev[i].flags,
                                kev[i].fflags, (void*)kev[i].data, (void*)kev[i].udata, str);
        }
}

static void
_dispatch_kevent_debugger2(void *context)
{
        struct sockaddr sa;
        socklen_t sa_len = sizeof(sa);
        int c, fd = (int)(long)context;
        unsigned int i;
        dispatch_kevent_t dk;
        dispatch_source_t ds;
        dispatch_source_refs_t dr;
        FILE *debug_stream;

        c = accept(fd, &sa, &sa_len);
        if (c == -1) {
                if (errno != EAGAIN) {
                        (void)dispatch_assume_zero(errno);
                }
                return;
        }
#if 0
        int r = fcntl(c, F_SETFL, 0); // disable non-blocking IO
        if (r == -1) {
                (void)dispatch_assume_zero(errno);
        }
#endif
        debug_stream = fdopen(c, "a");
        if (!dispatch_assume(debug_stream)) {
                close(c);
                return;
        }

        fprintf(debug_stream, "HTTP/1.0 200 OK\r\n");
        fprintf(debug_stream, "Content-type: text/html\r\n");
        fprintf(debug_stream, "Pragma: nocache\r\n");
        fprintf(debug_stream, "\r\n");
        fprintf(debug_stream, "<html>\n");
        fprintf(debug_stream, "<head><title>PID %u</title></head>\n", getpid());
        fprintf(debug_stream, "<body>\n<ul>\n");

        //fprintf(debug_stream, "<tr><td>DK</td><td>DK</td><td>DK</td><td>DK</td>"
        //              "<td>DK</td><td>DK</td><td>DK</td></tr>\n");

        for (i = 0; i < DSL_HASH_SIZE; i++) {
                if (TAILQ_EMPTY(&_dispatch_sources[i])) {
                        continue;
                }
                TAILQ_FOREACH(dk, &_dispatch_sources[i], dk_list) {
                        fprintf(debug_stream, "\t<br><li>DK %p ident %lu filter %s flags "
                                        "0x%hx fflags 0x%x data 0x%lx udata %p\n",
                                        dk, (unsigned long)dk->dk_kevent.ident,
                                        _evfiltstr(dk->dk_kevent.filter), dk->dk_kevent.flags,
                                        dk->dk_kevent.fflags, (unsigned long)dk->dk_kevent.data,
                                        dk->dk_kevent.udata);
                        fprintf(debug_stream, "\t\t<ul>\n");
                        TAILQ_FOREACH(dr, &dk->dk_sources, dr_list) {
                                ds = _dispatch_source_from_refs(dr);
                                fprintf(debug_stream, "\t\t\t<li>DS %p refcnt 0x%x suspend "
                                                "0x%x data 0x%lx mask 0x%lx flags 0x%x</li>\n",
                                                ds, ds->do_ref_cnt, ds->do_suspend_cnt,
                                                ds->ds_pending_data, ds->ds_pending_data_mask,
                                                ds->ds_atomic_flags);
                                if (ds->do_suspend_cnt == DISPATCH_OBJECT_SUSPEND_LOCK) {
                                        dispatch_queue_t dq = ds->do_targetq;
                                        fprintf(debug_stream, "\t\t<br>DQ: %p refcnt 0x%x suspend "
                                                        "0x%x label: %s\n", dq, dq->do_ref_cnt,
                                                        dq->do_suspend_cnt, dq->dq_label);
                                }
                        }
                        fprintf(debug_stream, "\t\t</ul>\n");
                        fprintf(debug_stream, "\t</li>\n");
                }
        }
        fprintf(debug_stream, "</ul>\n</body>\n</html>\n");
        fflush(debug_stream);
        fclose(debug_stream);
}

static void
_dispatch_kevent_debugger2_cancel(void *context)
{
        int ret, fd = (int)(long)context;

        ret = close(fd);
        if (ret != -1) {
                (void)dispatch_assume_zero(errno);
        }
}

static void
_dispatch_kevent_debugger(void *context DISPATCH_UNUSED)
{
        union {
                struct sockaddr_in sa_in;
                struct sockaddr sa;
        } sa_u = {
                .sa_in = {
                        .sin_family = AF_INET,
                        .sin_addr = { htonl(INADDR_LOOPBACK), },
                },
        };
        dispatch_source_t ds;
        const char *valstr;
        int val, r, fd, sock_opt = 1;
        socklen_t slen = sizeof(sa_u);

        if (issetugid()) {
                return;
        }
        valstr = getenv("LIBDISPATCH_DEBUGGER");
        if (!valstr) {
                return;
        }
        val = atoi(valstr);
        if (val == 2) {
                sa_u.sa_in.sin_addr.s_addr = 0;
        }
        fd = socket(PF_INET, SOCK_STREAM, 0);
        if (fd == -1) {
                (void)dispatch_assume_zero(errno);
                return;
        }
        r = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (void *)&sock_opt,
                        (socklen_t) sizeof sock_opt);
        if (r == -1) {
                (void)dispatch_assume_zero(errno);
                goto out_bad;
        }
#if 0
        r = fcntl(fd, F_SETFL, O_NONBLOCK);
        if (r == -1) {
                (void)dispatch_assume_zero(errno);
                goto out_bad;
        }
#endif
        r = bind(fd, &sa_u.sa, sizeof(sa_u));
        if (r == -1) {
                (void)dispatch_assume_zero(errno);
                goto out_bad;
        }
        r = listen(fd, SOMAXCONN);
        if (r == -1) {
                (void)dispatch_assume_zero(errno);
                goto out_bad;
        }
        r = getsockname(fd, &sa_u.sa, &slen);
        if (r == -1) {
                (void)dispatch_assume_zero(errno);
                goto out_bad;
        }

        ds = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, fd, 0,
                        &_dispatch_mgr_q);
        if (dispatch_assume(ds)) {
                _dispatch_log("LIBDISPATCH: debug port: %hu",
                                (in_port_t)ntohs(sa_u.sa_in.sin_port));

                /* ownership of fd transfers to ds */
                dispatch_set_context(ds, (void *)(long)fd);
                dispatch_source_set_event_handler_f(ds, _dispatch_kevent_debugger2);
                dispatch_source_set_cancel_handler_f(ds,
                                _dispatch_kevent_debugger2_cancel);
                dispatch_resume(ds);

                return;
        }
out_bad:
        close(fd);
}

#if HAVE_MACH

#ifndef MACH_PORT_TYPE_SPREQUEST
#define MACH_PORT_TYPE_SPREQUEST 0x40000000
#endif

void
dispatch_debug_machport(mach_port_t name, const char* str)
{
        mach_port_type_t type;
        mach_msg_bits_t ns = 0, nr = 0, nso = 0, nd = 0;
        unsigned int dnreqs = 0, dnrsiz;
        kern_return_t kr = mach_port_type(mach_task_self(), name, &type);
        if (kr) {
                _dispatch_log("machport[0x%08x] = { error(0x%x) \"%s\" }: %s", name,
                                kr, mach_error_string(kr), str);
                return;
        }
        if (type & MACH_PORT_TYPE_SEND) {
                (void)dispatch_assume_zero(mach_port_get_refs(mach_task_self(), name,
                                MACH_PORT_RIGHT_SEND, &ns));
        }
        if (type & MACH_PORT_TYPE_SEND_ONCE) {
                (void)dispatch_assume_zero(mach_port_get_refs(mach_task_self(), name,
                                MACH_PORT_RIGHT_SEND_ONCE, &nso));
        }
        if (type & MACH_PORT_TYPE_DEAD_NAME) {
                (void)dispatch_assume_zero(mach_port_get_refs(mach_task_self(), name,
                                MACH_PORT_RIGHT_DEAD_NAME, &nd));
        }
        if (type & (MACH_PORT_TYPE_RECEIVE|MACH_PORT_TYPE_SEND|
                        MACH_PORT_TYPE_SEND_ONCE)) {
                (void)dispatch_assume_zero(mach_port_dnrequest_info(mach_task_self(),
                                name, &dnrsiz, &dnreqs));
                }
        if (type & MACH_PORT_TYPE_RECEIVE) {
                mach_port_status_t status = { .mps_pset = 0, };
                mach_msg_type_number_t cnt = MACH_PORT_RECEIVE_STATUS_COUNT;
                (void)dispatch_assume_zero(mach_port_get_refs(mach_task_self(), name,
                                MACH_PORT_RIGHT_RECEIVE, &nr));
                (void)dispatch_assume_zero(mach_port_get_attributes(mach_task_self(),
                                name, MACH_PORT_RECEIVE_STATUS, (void*)&status, &cnt));
                _dispatch_log("machport[0x%08x] = { R(%03u) S(%03u) SO(%03u) D(%03u) "
                                "dnreqs(%03u) spreq(%s) nsreq(%s) pdreq(%s) srights(%s) "
                                "sorights(%03u) qlim(%03u) msgcount(%03u) mkscount(%03u) "
                                "seqno(%03u) }: %s", name, nr, ns, nso, nd, dnreqs,
                                type & MACH_PORT_TYPE_SPREQUEST ? "Y":"N",
                                status.mps_nsrequest ? "Y":"N", status.mps_pdrequest ? "Y":"N",
                                status.mps_srights ? "Y":"N", status.mps_sorights,
                                status.mps_qlimit, status.mps_msgcount, status.mps_mscount,
                                status.mps_seqno, str);
        } else if (type & (MACH_PORT_TYPE_SEND|MACH_PORT_TYPE_SEND_ONCE|
                        MACH_PORT_TYPE_DEAD_NAME)) {
                _dispatch_log("machport[0x%08x] = { R(%03u) S(%03u) SO(%03u) D(%03u) "
                                "dnreqs(%03u) spreq(%s) }: %s", name, nr, ns, nso, nd, dnreqs,
                                type & MACH_PORT_TYPE_SPREQUEST ? "Y":"N", str);
        } else {
                _dispatch_log("machport[0x%08x] = { type(0x%08x) }: %s", name, type,
                                str);
        }
}

#endif // HAVE_MACH

#endif // DISPATCH_DEBUG