libdispatch-913.30.4.tar.gz

[apple/libdispatch.git] / src / inline_internal.h

/*
 * Copyright (c) 2008-2013 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@
 */

/*
 * IMPORTANT: This header file describes INTERNAL interfaces to libdispatch
 * which are subject to change in future releases of Mac OS X. Any applications
 * relying on these interfaces WILL break.
 */

#ifndef __DISPATCH_INLINE_INTERNAL__
#define __DISPATCH_INLINE_INTERNAL__

#ifndef __DISPATCH_INDIRECT__
#error "Please #include <dispatch/dispatch.h> instead of this file directly."
#include <dispatch/base.h> // for HeaderDoc
#endif

#if DISPATCH_USE_CLIENT_CALLOUT

DISPATCH_NOTHROW void
_dispatch_client_callout(void *ctxt, dispatch_function_t f);
DISPATCH_NOTHROW void
_dispatch_client_callout2(void *ctxt, size_t i, void (*f)(void *, size_t));
#if HAVE_MACH
DISPATCH_NOTHROW void
_dispatch_client_callout3(void *ctxt, dispatch_mach_reason_t reason,
                dispatch_mach_msg_t dmsg, dispatch_mach_async_reply_callback_t f);
DISPATCH_NOTHROW void
_dispatch_client_callout4(void *ctxt, dispatch_mach_reason_t reason,
                dispatch_mach_msg_t dmsg, mach_error_t error,
                dispatch_mach_handler_function_t f);
#endif // HAVE_MACH

#else // !DISPATCH_USE_CLIENT_CALLOUT

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_client_callout(void *ctxt, dispatch_function_t f)
{
        return f(ctxt);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_client_callout2(void *ctxt, size_t i, void (*f)(void *, size_t))
{
        return f(ctxt, i);
}

#if HAVE_MACH
DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_client_callout3(void *ctxt, dispatch_mach_reason_t reason,
                dispatch_mach_msg_t dmsg, dispatch_mach_async_reply_callback_t f)
{
        return f(ctxt, reason, dmsg);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_client_callout4(void *ctxt, dispatch_mach_reason_t reason,
                dispatch_mach_msg_t dmsg, mach_error_t error,
                dispatch_mach_handler_function_t f)
{
        return f(ctxt, reason, dmsg, error);
}
#endif // HAVE_MACH

#endif // !DISPATCH_USE_CLIENT_CALLOUT

#pragma mark -
#pragma mark _os_object_t & dispatch_object_t
#if DISPATCH_PURE_C

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_object_has_vtable(dispatch_object_t dou)
{
        uintptr_t dc_flags = dou._dc->dc_flags;

        // vtables are pointers far away from the low page in memory
        return dc_flags > 0xffful;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_object_is_queue(dispatch_object_t dou)
{
        return _dispatch_object_has_vtable(dou) && dx_vtable(dou._do)->do_push;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_object_is_continuation(dispatch_object_t dou)
{
        if (_dispatch_object_has_vtable(dou)) {
                return dx_metatype(dou._do) == _DISPATCH_CONTINUATION_TYPE;
        }
        return true;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_object_has_type(dispatch_object_t dou, unsigned long type)
{
        return _dispatch_object_has_vtable(dou) && dx_type(dou._do) == type;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_object_is_redirection(dispatch_object_t dou)
{
        return _dispatch_object_has_type(dou,
                        DISPATCH_CONTINUATION_TYPE(ASYNC_REDIRECT));
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_object_is_barrier(dispatch_object_t dou)
{
        dispatch_queue_flags_t dq_flags;

        if (!_dispatch_object_has_vtable(dou)) {
                return (dou._dc->dc_flags & DISPATCH_OBJ_BARRIER_BIT);
        }
        switch (dx_metatype(dou._do)) {
        case _DISPATCH_QUEUE_TYPE:
        case _DISPATCH_SOURCE_TYPE:
                dq_flags = os_atomic_load2o(dou._dq, dq_atomic_flags, relaxed);
                return dq_flags & DQF_BARRIER_BIT;
        default:
                return false;
        }
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_object_is_sync_waiter(dispatch_object_t dou)
{
        if (_dispatch_object_has_vtable(dou)) {
                return false;
        }
        return (dou._dc->dc_flags & DISPATCH_OBJ_SYNC_WAITER_BIT);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_object_is_sync_waiter_non_barrier(dispatch_object_t dou)
{
        if (_dispatch_object_has_vtable(dou)) {
                return false;
        }
        return ((dou._dc->dc_flags &
                                (DISPATCH_OBJ_BARRIER_BIT | DISPATCH_OBJ_SYNC_WAITER_BIT)) ==
                                (DISPATCH_OBJ_SYNC_WAITER_BIT));
}

DISPATCH_ALWAYS_INLINE
static inline _os_object_t
_os_object_retain_internal_n_inline(_os_object_t obj, int n)
{
        int ref_cnt = _os_object_refcnt_add_orig(obj, n);
        if (unlikely(ref_cnt < 0)) {
                _OS_OBJECT_CLIENT_CRASH("Resurrection of an object");
        }
        return obj;
}

DISPATCH_ALWAYS_INLINE
static inline void
_os_object_release_internal_n_no_dispose_inline(_os_object_t obj, int n)
{
        int ref_cnt = _os_object_refcnt_sub(obj, n);
        if (likely(ref_cnt >= 0)) {
                return;
        }
        _OS_OBJECT_CLIENT_CRASH("Over-release of an object");
}

DISPATCH_ALWAYS_INLINE
static inline void
_os_object_release_internal_n_inline(_os_object_t obj, int n)
{
        int ref_cnt = _os_object_refcnt_sub(obj, n);
        if (likely(ref_cnt >= 0)) {
                return;
        }
        if (unlikely(ref_cnt < -1)) {
                _OS_OBJECT_CLIENT_CRASH("Over-release of an object");
        }
#if DISPATCH_DEBUG
        int xref_cnt = obj->os_obj_xref_cnt;
        if (unlikely(xref_cnt >= 0)) {
                DISPATCH_INTERNAL_CRASH(xref_cnt,
                                "Release while external references exist");
        }
#endif
        // _os_object_refcnt_dispose_barrier() is in _os_object_dispose()
        return _os_object_dispose(obj);
}

DISPATCH_ALWAYS_INLINE_NDEBUG
static inline void
_dispatch_retain(dispatch_object_t dou)
{
        (void)_os_object_retain_internal_n_inline(dou._os_obj, 1);
}

DISPATCH_ALWAYS_INLINE_NDEBUG
static inline void
_dispatch_retain_2(dispatch_object_t dou)
{
        (void)_os_object_retain_internal_n_inline(dou._os_obj, 2);
}

DISPATCH_ALWAYS_INLINE_NDEBUG
static inline void
_dispatch_retain_n(dispatch_object_t dou, int n)
{
        (void)_os_object_retain_internal_n_inline(dou._os_obj, n);
}

DISPATCH_ALWAYS_INLINE_NDEBUG
static inline void
_dispatch_release(dispatch_object_t dou)
{
        _os_object_release_internal_n_inline(dou._os_obj, 1);
}

DISPATCH_ALWAYS_INLINE_NDEBUG
static inline void
_dispatch_release_2(dispatch_object_t dou)
{
        _os_object_release_internal_n_inline(dou._os_obj, 2);
}

DISPATCH_ALWAYS_INLINE_NDEBUG
static inline void
_dispatch_release_n(dispatch_object_t dou, int n)
{
        _os_object_release_internal_n_inline(dou._os_obj, n);
}

DISPATCH_ALWAYS_INLINE_NDEBUG
static inline void
_dispatch_release_no_dispose(dispatch_object_t dou)
{
        _os_object_release_internal_n_no_dispose_inline(dou._os_obj, 1);
}

DISPATCH_ALWAYS_INLINE_NDEBUG
static inline void
_dispatch_release_2_no_dispose(dispatch_object_t dou)
{
        _os_object_release_internal_n_no_dispose_inline(dou._os_obj, 2);
}

DISPATCH_ALWAYS_INLINE_NDEBUG
static inline void
_dispatch_release_tailcall(dispatch_object_t dou)
{
        _os_object_release_internal(dou._os_obj);
}

DISPATCH_ALWAYS_INLINE_NDEBUG
static inline void
_dispatch_release_2_tailcall(dispatch_object_t dou)
{
        _os_object_release_internal_n(dou._os_obj, 2);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_retain_storage(dispatch_queue_t dq)
{
        int ref_cnt = os_atomic_inc2o(dq, dq_sref_cnt, relaxed);
        if (unlikely(ref_cnt <= 0)) {
                _OS_OBJECT_CLIENT_CRASH("Resurrection of an object");
        }
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_release_storage(dispatch_queue_t dq)
{
        // this refcount only delays the _dispatch_object_dealloc() and there's no
        // need for visibility wrt to the allocation, the internal refcount already
        // gives us that, and the object becomes immutable after the last internal
        // refcount release.
        int ref_cnt = os_atomic_dec2o(dq, dq_sref_cnt, relaxed);
        if (unlikely(ref_cnt >= 0)) {
                return;
        }
        if (unlikely(ref_cnt < -1)) {
                _OS_OBJECT_CLIENT_CRASH("Over-release of an object");
        }
        dq->dq_state = 0xdead000000000000;
        _dispatch_object_dealloc(dq);
}

DISPATCH_ALWAYS_INLINE DISPATCH_NONNULL_ALL
static inline void
_dispatch_object_set_target_queue_inline(dispatch_object_t dou,
                dispatch_queue_t tq)
{
        _dispatch_retain(tq);
        tq = os_atomic_xchg2o(dou._do, do_targetq, tq, release);
        if (tq) _dispatch_release(tq);
        _dispatch_object_debug(dou._do, "%s", __func__);
}

#endif // DISPATCH_PURE_C
#pragma mark -
#pragma mark dispatch_thread
#if DISPATCH_PURE_C

DISPATCH_ALWAYS_INLINE
static inline dispatch_thread_context_t
_dispatch_thread_context_find(const void *key)
{
        dispatch_thread_context_t dtc =
                        _dispatch_thread_getspecific(dispatch_context_key);
        while (dtc) {
                if (dtc->dtc_key == key) {
                        return dtc;
                }
                dtc = dtc->dtc_prev;
        }
        return NULL;
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_thread_context_push(dispatch_thread_context_t ctxt)
{
        ctxt->dtc_prev = _dispatch_thread_getspecific(dispatch_context_key);
        _dispatch_thread_setspecific(dispatch_context_key, ctxt);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_thread_context_pop(dispatch_thread_context_t ctxt)
{
        dispatch_assert(_dispatch_thread_getspecific(dispatch_context_key) == ctxt);
        _dispatch_thread_setspecific(dispatch_context_key, ctxt->dtc_prev);
}

typedef struct dispatch_thread_frame_iterator_s {
        dispatch_queue_t dtfi_queue;
        dispatch_thread_frame_t dtfi_frame;
} *dispatch_thread_frame_iterator_t;

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_thread_frame_iterate_start(dispatch_thread_frame_iterator_t it)
{
        _dispatch_thread_getspecific_pair(
                        dispatch_queue_key, (void **)&it->dtfi_queue,
                        dispatch_frame_key, (void **)&it->dtfi_frame);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_thread_frame_iterate_next(dispatch_thread_frame_iterator_t it)
{
        dispatch_thread_frame_t dtf = it->dtfi_frame;
        dispatch_queue_t dq = it->dtfi_queue;

        if (dtf) {
                dispatch_queue_t tq = dq->do_targetq;
                if (tq) {
                        // redirections, dispatch_sync and dispatch_trysync_f may skip
                        // frames, so we need to simulate seeing the missing links
                        it->dtfi_queue = tq;
                        if (dq == dtf->dtf_queue) {
                                it->dtfi_frame = dtf->dtf_prev;
                        }
                } else {
                        it->dtfi_queue = dtf->dtf_queue;
                        it->dtfi_frame = dtf->dtf_prev;
                }
        } else if (dq) {
                it->dtfi_queue = dq->do_targetq;
        }
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_thread_frame_find_queue(dispatch_queue_t dq)
{
        struct dispatch_thread_frame_iterator_s it;

        _dispatch_thread_frame_iterate_start(&it);
        while (it.dtfi_queue) {
                if (it.dtfi_queue == dq) {
                        return true;
                }
                _dispatch_thread_frame_iterate_next(&it);
        }
        return false;
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_thread_frame_t
_dispatch_thread_frame_get_current(void)
{
        return _dispatch_thread_getspecific(dispatch_frame_key);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_thread_frame_save_state(dispatch_thread_frame_t dtf)
{
        _dispatch_thread_getspecific_packed_pair(
                        dispatch_queue_key, dispatch_frame_key, (void **)&dtf->dtf_queue);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_thread_frame_push(dispatch_thread_frame_t dtf, dispatch_queue_t dq)
{
        _dispatch_thread_frame_save_state(dtf);
        _dispatch_thread_setspecific_pair(dispatch_queue_key, dq,
                        dispatch_frame_key, dtf);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_thread_frame_push_and_rebase(dispatch_thread_frame_t dtf,
                dispatch_queue_t dq, dispatch_thread_frame_t new_base)
{
        _dispatch_thread_frame_save_state(dtf);
        _dispatch_thread_setspecific_pair(dispatch_queue_key, dq,
                        dispatch_frame_key, new_base);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_thread_frame_pop(dispatch_thread_frame_t dtf)
{
        _dispatch_thread_setspecific_packed_pair(
                        dispatch_queue_key, dispatch_frame_key, (void **)&dtf->dtf_queue);
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_queue_t
_dispatch_thread_frame_stash(dispatch_thread_frame_t dtf)
{
        _dispatch_thread_getspecific_pair(
                        dispatch_queue_key, (void **)&dtf->dtf_queue,
                        dispatch_frame_key, (void **)&dtf->dtf_prev);
        _dispatch_thread_frame_pop(dtf->dtf_prev);
        return dtf->dtf_queue;
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_thread_frame_unstash(dispatch_thread_frame_t dtf)
{
        _dispatch_thread_frame_pop(dtf);
}

DISPATCH_ALWAYS_INLINE
static inline int
_dispatch_wqthread_override_start_check_owner(mach_port_t thread,
                dispatch_qos_t qos, mach_port_t *ulock_addr)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        if (!_dispatch_set_qos_class_enabled) return 0;
        return _pthread_workqueue_override_start_direct_check_owner(thread,
                        _dispatch_qos_to_pp(qos), ulock_addr);
#else
        (void)thread; (void)qos; (void)ulock_addr;
        return 0;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_wqthread_override_start(mach_port_t thread, dispatch_qos_t qos)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        if (!_dispatch_set_qos_class_enabled) return;
        (void)_pthread_workqueue_override_start_direct(thread,
                        _dispatch_qos_to_pp(qos));
#else
        (void)thread; (void)qos;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_wqthread_override_reset(void)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        if (!_dispatch_set_qos_class_enabled) return;
        (void)_pthread_workqueue_override_reset();
#endif
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_thread_override_start(mach_port_t thread, pthread_priority_t pp,
                void *resource)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        if (!_dispatch_set_qos_class_enabled) return;
        (void)_pthread_qos_override_start_direct(thread, pp, resource);
#else
        (void)thread; (void)pp; (void)resource;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_thread_override_end(mach_port_t thread, void *resource)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        if (!_dispatch_set_qos_class_enabled) return;
        (void)_pthread_qos_override_end_direct(thread, resource);
#else
        (void)thread; (void)resource;
#endif
}

#endif // DISPATCH_PURE_C
#pragma mark -
#pragma mark dispatch_queue_t state accessors
#if DISPATCH_PURE_C

DISPATCH_ALWAYS_INLINE
static inline dispatch_queue_flags_t
_dispatch_queue_atomic_flags(dispatch_queue_t dq)
{
        return os_atomic_load2o(dq, dq_atomic_flags, relaxed);
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_queue_flags_t
_dispatch_queue_atomic_flags_set(dispatch_queue_t dq,
                dispatch_queue_flags_t bits)
{
        return os_atomic_or2o(dq, dq_atomic_flags, bits, relaxed);
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_queue_flags_t
_dispatch_queue_atomic_flags_set_and_clear_orig(dispatch_queue_t dq,
                dispatch_queue_flags_t add_bits, dispatch_queue_flags_t clr_bits)
{
        dispatch_queue_flags_t oflags, nflags;
        os_atomic_rmw_loop2o(dq, dq_atomic_flags, oflags, nflags, relaxed, {
                nflags = (oflags | add_bits) & ~clr_bits;
        });
        return oflags;
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_queue_flags_t
_dispatch_queue_atomic_flags_set_and_clear(dispatch_queue_t dq,
                dispatch_queue_flags_t add_bits, dispatch_queue_flags_t clr_bits)
{
        dispatch_queue_flags_t oflags, nflags;
        os_atomic_rmw_loop2o(dq, dq_atomic_flags, oflags, nflags, relaxed, {
                nflags = (oflags | add_bits) & ~clr_bits;
        });
        return nflags;
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_queue_flags_t
_dispatch_queue_atomic_flags_set_orig(dispatch_queue_t dq,
                dispatch_queue_flags_t bits)
{
        return os_atomic_or_orig2o(dq, dq_atomic_flags, bits, relaxed);
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_queue_flags_t
_dispatch_queue_atomic_flags_clear(dispatch_queue_t dq,
                dispatch_queue_flags_t bits)
{
        return os_atomic_and2o(dq, dq_atomic_flags, ~bits, relaxed);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_queue_is_thread_bound(dispatch_queue_t dq)
{
        return _dispatch_queue_atomic_flags(dq) & DQF_THREAD_BOUND;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_queue_cannot_trysync(dispatch_queue_t dq)
{
        return _dispatch_queue_atomic_flags(dq) & DQF_CANNOT_TRYSYNC;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_queue_label_needs_free(dispatch_queue_t dq)
{
        return _dispatch_queue_atomic_flags(dq) & DQF_LABEL_NEEDS_FREE;
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_invoke_flags_t
_dispatch_queue_autorelease_frequency(dispatch_queue_t dq)
{
        const unsigned long factor =
                        DISPATCH_INVOKE_AUTORELEASE_ALWAYS / DQF_AUTORELEASE_ALWAYS;
        dispatch_static_assert(factor > 0);

        dispatch_queue_flags_t qaf = _dispatch_queue_atomic_flags(dq);

        qaf &= _DQF_AUTORELEASE_MASK;
        return (dispatch_invoke_flags_t)qaf * factor;
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_invoke_flags_t
_dispatch_queue_merge_autorelease_frequency(dispatch_queue_t dq,
                dispatch_invoke_flags_t flags)
{
        dispatch_invoke_flags_t qaf = _dispatch_queue_autorelease_frequency(dq);

        if (qaf) {
                flags &= ~_DISPATCH_INVOKE_AUTORELEASE_MASK;
                flags |= qaf;
        }
        return flags;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_queue_is_legacy(dispatch_queue_t dq)
{
        return _dispatch_queue_atomic_flags(dq) & DQF_LEGACY;
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_wlh_retain(dispatch_wlh_t wlh)
{
        if (wlh && wlh != DISPATCH_WLH_ANON) {
                _dispatch_queue_retain_storage((dispatch_queue_t)wlh);
        }
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_wlh_release(dispatch_wlh_t wlh)
{
        if (wlh && wlh != DISPATCH_WLH_ANON) {
                _dispatch_queue_release_storage((dispatch_queue_t)wlh);
        }
}

#define DISPATCH_WLH_STORAGE_REF 1ul

DISPATCH_ALWAYS_INLINE DISPATCH_PURE
static inline dispatch_wlh_t
_dispatch_get_wlh(void)
{
        return _dispatch_thread_getspecific(dispatch_wlh_key);
}

DISPATCH_ALWAYS_INLINE DISPATCH_PURE
static inline dispatch_wlh_t
_dispatch_get_wlh_reference(void)
{
        dispatch_wlh_t wlh = _dispatch_thread_getspecific(dispatch_wlh_key);
        if (wlh != DISPATCH_WLH_ANON) {
                wlh = (dispatch_wlh_t)((uintptr_t)wlh & ~DISPATCH_WLH_STORAGE_REF);
        }
        return wlh;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_adopt_wlh_anon_recurse(void)
{
        dispatch_wlh_t cur_wlh = _dispatch_get_wlh_reference();
        if (cur_wlh == DISPATCH_WLH_ANON) return false;
        _dispatch_debug("wlh[anon]: set current (releasing %p)", cur_wlh);
        _dispatch_wlh_release(cur_wlh);
        _dispatch_thread_setspecific(dispatch_wlh_key, (void *)DISPATCH_WLH_ANON);
        return true;
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_adopt_wlh_anon(void)
{
        if (unlikely(!_dispatch_adopt_wlh_anon_recurse())) {
                DISPATCH_INTERNAL_CRASH(0, "Lingering DISPATCH_WLH_ANON");
        }
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_adopt_wlh(dispatch_wlh_t wlh)
{
        dispatch_wlh_t cur_wlh = _dispatch_get_wlh_reference();
        _dispatch_debug("wlh[%p]: adopt current (releasing %p)", wlh, cur_wlh);
        if (cur_wlh == DISPATCH_WLH_ANON) {
                DISPATCH_INTERNAL_CRASH(0, "Lingering DISPATCH_WLH_ANON");
        }
        if (cur_wlh != wlh) {
                dispatch_assert(wlh);
                _dispatch_wlh_release(cur_wlh);
                _dispatch_wlh_retain(wlh);
        }
        _dispatch_thread_setspecific(dispatch_wlh_key, (void *)wlh);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_preserve_wlh_storage_reference(dispatch_wlh_t wlh)
{
        dispatch_assert(wlh != DISPATCH_WLH_ANON);
        dispatch_assert(wlh == _dispatch_get_wlh());
        _dispatch_thread_setspecific(dispatch_wlh_key,
                        (void *)((uintptr_t)wlh | DISPATCH_WLH_STORAGE_REF));
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_reset_wlh(void)
{
        dispatch_assert(_dispatch_get_wlh() == DISPATCH_WLH_ANON);
        _dispatch_debug("wlh[anon]: clear current");
        _dispatch_thread_setspecific(dispatch_wlh_key, NULL);
        _dispatch_clear_return_to_kernel();
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_wlh_should_poll_unote(dispatch_unote_t du)
{
        if (likely(_dispatch_needs_to_return_to_kernel())) {
                dispatch_wlh_t wlh = _dispatch_get_wlh();
                return wlh != DISPATCH_WLH_ANON && du._du->du_wlh == wlh;
        }
        return false;
}

#endif // DISPATCH_PURE_C
#ifndef __cplusplus

DISPATCH_ALWAYS_INLINE
static inline uint32_t
_dq_state_suspend_cnt(uint64_t dq_state)
{
        return (uint32_t)(dq_state / DISPATCH_QUEUE_SUSPEND_INTERVAL);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_has_side_suspend_cnt(uint64_t dq_state)
{
        return dq_state & DISPATCH_QUEUE_HAS_SIDE_SUSPEND_CNT;
}

DISPATCH_ALWAYS_INLINE
static inline int32_t
_dq_state_extract_width_bits(uint64_t dq_state)
{
        dq_state &= DISPATCH_QUEUE_WIDTH_MASK;
        return (int32_t)(dq_state >> DISPATCH_QUEUE_WIDTH_SHIFT);
}

DISPATCH_ALWAYS_INLINE
static inline int32_t
_dq_state_available_width(uint64_t dq_state)
{
        int32_t full = DISPATCH_QUEUE_WIDTH_FULL;
        if (likely(!(dq_state & DISPATCH_QUEUE_WIDTH_FULL_BIT))) {
                return full - _dq_state_extract_width_bits(dq_state);
        }
        return 0;
}

DISPATCH_ALWAYS_INLINE
static inline int32_t
_dq_state_used_width(uint64_t dq_state, uint16_t dq_width)
{
        int32_t full = DISPATCH_QUEUE_WIDTH_FULL;
        int32_t width = _dq_state_extract_width_bits(dq_state);

        if (dq_state & DISPATCH_QUEUE_PENDING_BARRIER) {
                // DISPATCH_QUEUE_PENDING_BARRIER means (dq_width - 1) of the used width
                // is pre-reservation that we want to ignore
                return width - (full - dq_width) - (dq_width - 1);
        }
        return width - (full - dq_width);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_is_suspended(uint64_t dq_state)
{
        return dq_state >= DISPATCH_QUEUE_NEEDS_ACTIVATION;
}
#define DISPATCH_QUEUE_IS_SUSPENDED(x) \
                _dq_state_is_suspended(os_atomic_load2o(x, dq_state, relaxed))

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_is_inactive(uint64_t dq_state)
{
        return dq_state & DISPATCH_QUEUE_INACTIVE;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_needs_activation(uint64_t dq_state)
{
        return dq_state & DISPATCH_QUEUE_NEEDS_ACTIVATION;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_is_in_barrier(uint64_t dq_state)
{
        return dq_state & DISPATCH_QUEUE_IN_BARRIER;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_has_available_width(uint64_t dq_state)
{
        return !(dq_state & DISPATCH_QUEUE_WIDTH_FULL_BIT);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_has_pending_barrier(uint64_t dq_state)
{
        return dq_state & DISPATCH_QUEUE_PENDING_BARRIER;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_is_dirty(uint64_t dq_state)
{
        return dq_state & DISPATCH_QUEUE_DIRTY;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_is_base_wlh(uint64_t dq_state)
{
        return dq_state & DISPATCH_QUEUE_ROLE_BASE_WLH;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_is_base_anon(uint64_t dq_state)
{
        return dq_state & DISPATCH_QUEUE_ROLE_BASE_ANON;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_is_inner_queue(uint64_t dq_state)
{
        return (dq_state & DISPATCH_QUEUE_ROLE_MASK) == DISPATCH_QUEUE_ROLE_INNER;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_is_enqueued(uint64_t dq_state)
{
        return dq_state & (DISPATCH_QUEUE_ENQUEUED|DISPATCH_QUEUE_ENQUEUED_ON_MGR);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_is_enqueued_on_target(uint64_t dq_state)
{
        return dq_state & DISPATCH_QUEUE_ENQUEUED;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_is_enqueued_on_manager(uint64_t dq_state)
{
        return dq_state & DISPATCH_QUEUE_ENQUEUED_ON_MGR;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_in_sync_transfer(uint64_t dq_state)
{
        return dq_state & DISPATCH_QUEUE_SYNC_TRANSFER;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_received_override(uint64_t dq_state)
{
        return _dq_state_is_base_anon(dq_state) &&
                        (dq_state & DISPATCH_QUEUE_RECEIVED_OVERRIDE);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_received_sync_wait(uint64_t dq_state)
{
        return _dq_state_is_base_wlh(dq_state) &&
                        (dq_state & DISPATCH_QUEUE_RECEIVED_SYNC_WAIT);
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_qos_t
_dq_state_max_qos(uint64_t dq_state)
{
        dq_state &= DISPATCH_QUEUE_MAX_QOS_MASK;
        return (dispatch_qos_t)(dq_state >> DISPATCH_QUEUE_MAX_QOS_SHIFT);
}

DISPATCH_ALWAYS_INLINE
static inline uint64_t
_dq_state_from_qos(dispatch_qos_t qos)
{
        return (uint64_t)(qos) << DISPATCH_QUEUE_MAX_QOS_SHIFT;
}

DISPATCH_ALWAYS_INLINE
static inline uint64_t
_dq_state_merge_qos(uint64_t dq_state, dispatch_qos_t qos)
{
        uint64_t qos_bits = _dq_state_from_qos(qos);
        if ((dq_state & DISPATCH_QUEUE_MAX_QOS_MASK) < qos_bits) {
                dq_state &= ~DISPATCH_QUEUE_MAX_QOS_MASK;
                dq_state |= qos_bits;
                if (unlikely(_dq_state_is_base_anon(dq_state))) {
                        dq_state |= DISPATCH_QUEUE_RECEIVED_OVERRIDE;
                }
        }
        return dq_state;
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_tid
_dq_state_drain_owner(uint64_t dq_state)
{
        return _dispatch_lock_owner((dispatch_lock)dq_state);
}
#define DISPATCH_QUEUE_DRAIN_OWNER(dq) \
        _dq_state_drain_owner(os_atomic_load2o(dq, dq_state, relaxed))

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_drain_locked_by(uint64_t dq_state, dispatch_tid tid)
{
        return _dispatch_lock_is_locked_by((dispatch_lock)dq_state, tid);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_drain_locked_by_self(uint64_t dq_state)
{
        return _dispatch_lock_is_locked_by_self((dispatch_lock)dq_state);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_drain_locked(uint64_t dq_state)
{
        return _dispatch_lock_is_locked((dispatch_lock)dq_state);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_is_sync_runnable(uint64_t dq_state)
{
        return dq_state < DISPATCH_QUEUE_IN_BARRIER;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_is_runnable(uint64_t dq_state)
{
        return dq_state < DISPATCH_QUEUE_WIDTH_FULL_BIT;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_should_override(uint64_t dq_state)
{
        if (_dq_state_is_suspended(dq_state) ||
                        _dq_state_is_enqueued_on_manager(dq_state)) {
                return false;
        }
        if (_dq_state_is_enqueued_on_target(dq_state)) {
                return true;
        }
        if (_dq_state_is_base_wlh(dq_state)) {
                return false;
        }
        return _dq_state_drain_locked(dq_state);
}


#endif // __cplusplus
#pragma mark -
#pragma mark dispatch_queue_t state machine

static inline pthread_priority_t _dispatch_get_priority(void);
static inline dispatch_priority_t _dispatch_get_basepri(void);
static inline dispatch_qos_t _dispatch_get_basepri_override_qos_floor(void);
static inline void _dispatch_set_basepri_override_qos(dispatch_qos_t qos);
static inline void _dispatch_reset_basepri(dispatch_priority_t dbp);
static inline dispatch_priority_t _dispatch_set_basepri(dispatch_priority_t dbp);
static inline bool _dispatch_queue_need_override_retain(
                dispatch_queue_class_t dqu, dispatch_qos_t qos);

#if DISPATCH_PURE_C

// Note to later developers: ensure that any initialization changes are
// made for statically allocated queues (i.e. _dispatch_main_q).
static inline void
_dispatch_queue_init(dispatch_queue_t dq, dispatch_queue_flags_t dqf,
                uint16_t width, uint64_t initial_state_bits)
{
        uint64_t dq_state = DISPATCH_QUEUE_STATE_INIT_VALUE(width);

        dispatch_assert((initial_state_bits & ~(DISPATCH_QUEUE_ROLE_MASK |
                        DISPATCH_QUEUE_INACTIVE)) == 0);

        if (initial_state_bits & DISPATCH_QUEUE_INACTIVE) {
                dq_state |= DISPATCH_QUEUE_INACTIVE + DISPATCH_QUEUE_NEEDS_ACTIVATION;
                dq->do_ref_cnt += 2; // rdar://8181908 see _dispatch_queue_resume
        }

        dq_state |= (initial_state_bits & DISPATCH_QUEUE_ROLE_MASK);
        dq->do_next = (struct dispatch_queue_s *)DISPATCH_OBJECT_LISTLESS;
        dqf |= DQF_WIDTH(width);
        os_atomic_store2o(dq, dq_atomic_flags, dqf, relaxed);
        dq->dq_state = dq_state;
        dq->dq_serialnum =
                        os_atomic_inc_orig(&_dispatch_queue_serial_numbers, relaxed);
}

/* Used by:
 * - _dispatch_queue_set_target_queue
 * - changing dispatch source handlers
 *
 * Tries to prevent concurrent wakeup of an inactive queue by suspending it.
 */
DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline bool
_dispatch_queue_try_inactive_suspend(dispatch_queue_t dq)
{
        uint64_t old_state, new_state;

        (void)os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, relaxed, {
                if (unlikely(!_dq_state_is_inactive(old_state))) {
                        os_atomic_rmw_loop_give_up(return false);
                }
                new_state = old_state + DISPATCH_QUEUE_SUSPEND_INTERVAL;
        });
        if (unlikely(!_dq_state_is_suspended(old_state) ||
                        _dq_state_has_side_suspend_cnt(old_state))) {
                // Crashing here means that 128+ dispatch_suspend() calls have been
                // made on an inactive object and then dispatch_set_target_queue() or
                // dispatch_set_*_handler() has been called.
                //
                // We don't want to handle the side suspend count in a codepath that
                // needs to be fast.
                DISPATCH_CLIENT_CRASH(dq, "Too many calls to dispatch_suspend() "
                                "prior to calling dispatch_set_target_queue() "
                                "or dispatch_set_*_handler()");
        }
        return true;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dq_state_needs_lock_override(uint64_t dq_state, dispatch_qos_t qos)
{
        return _dq_state_is_base_anon(dq_state) &&
                        qos < _dq_state_max_qos(dq_state);
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_qos_t
_dispatch_queue_override_self(uint64_t dq_state)
{
        dispatch_qos_t qos = _dq_state_max_qos(dq_state);
        _dispatch_wqthread_override_start(_dispatch_tid_self(), qos);
        // ensure that the root queue sees
        // that this thread was overridden.
        _dispatch_set_basepri_override_qos(qos);
        return qos;
}

DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline uint64_t
_dispatch_queue_drain_try_lock(dispatch_queue_t dq,
                dispatch_invoke_flags_t flags)
{
        uint64_t pending_barrier_width =
                        (dq->dq_width - 1) * DISPATCH_QUEUE_WIDTH_INTERVAL;
        uint64_t set_owner_and_set_full_width =
                        _dispatch_lock_value_for_self() | DISPATCH_QUEUE_WIDTH_FULL_BIT;
        uint64_t lock_fail_mask, old_state, new_state, dequeue_mask;

        // same as !_dq_state_is_runnable()
        lock_fail_mask  = ~(DISPATCH_QUEUE_WIDTH_FULL_BIT - 1);
        // same as _dq_state_drain_locked()
        lock_fail_mask |= DISPATCH_QUEUE_DRAIN_OWNER_MASK;

        if (flags & DISPATCH_INVOKE_STEALING) {
                lock_fail_mask |= DISPATCH_QUEUE_ENQUEUED_ON_MGR;
                dequeue_mask = 0;
        } else if (flags & DISPATCH_INVOKE_MANAGER_DRAIN) {
                dequeue_mask = DISPATCH_QUEUE_ENQUEUED_ON_MGR;
        } else {
                lock_fail_mask |= DISPATCH_QUEUE_ENQUEUED_ON_MGR;
                dequeue_mask = DISPATCH_QUEUE_ENQUEUED;
        }
        dispatch_assert(!(flags & DISPATCH_INVOKE_WLH));

        dispatch_qos_t oq_floor = _dispatch_get_basepri_override_qos_floor();
retry:
        os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, acquire, {
                new_state = old_state;
                if (likely(!(old_state & lock_fail_mask))) {
                        if (unlikely(_dq_state_needs_lock_override(old_state, oq_floor))) {
                                os_atomic_rmw_loop_give_up({
                                        oq_floor = _dispatch_queue_override_self(old_state);
                                        goto retry;
                                });
                        }
                        //
                        // Only keep the HAS_WAITER, MAX_QOS and ENQUEUED bits
                        // In particular acquiring the drain lock clears the DIRTY and
                        // RECEIVED_OVERRIDE bits.
                        //
                        new_state &= DISPATCH_QUEUE_DRAIN_PRESERVED_BITS_MASK;
                        new_state |= set_owner_and_set_full_width;
                        if (_dq_state_has_pending_barrier(old_state) ||
                                        old_state + pending_barrier_width <
                                        DISPATCH_QUEUE_WIDTH_FULL_BIT) {
                                new_state |= DISPATCH_QUEUE_IN_BARRIER;
                        }
                } else if (dequeue_mask) {
                        // dequeue_mask is in a register, xor yields better assembly
                        new_state ^= dequeue_mask;
                } else {
                        os_atomic_rmw_loop_give_up(break);
                }
        });

        dispatch_assert((old_state & dequeue_mask) == dequeue_mask);
        if (likely(!(old_state & lock_fail_mask))) {
                new_state &= DISPATCH_QUEUE_IN_BARRIER | DISPATCH_QUEUE_WIDTH_FULL_BIT |
                                dequeue_mask;
                old_state &= DISPATCH_QUEUE_WIDTH_MASK;
                return new_state - old_state;
        }
        return 0;
}

DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline bool
_dispatch_queue_drain_try_lock_wlh(dispatch_queue_t dq, uint64_t *dq_state)
{
        uint64_t old_state, new_state;
        uint64_t lock_bits = _dispatch_lock_value_for_self() |
                        DISPATCH_QUEUE_WIDTH_FULL_BIT | DISPATCH_QUEUE_IN_BARRIER;

        os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, acquire, {
                new_state = old_state;
                if (unlikely(_dq_state_is_suspended(old_state))) {
                        new_state &= ~DISPATCH_QUEUE_ENQUEUED;
                } else if (unlikely(_dq_state_drain_locked(old_state))) {
                        os_atomic_rmw_loop_give_up(break);
                } else {
                        new_state &= DISPATCH_QUEUE_DRAIN_PRESERVED_BITS_MASK;
                        new_state |= lock_bits;
                }
        });
        if (unlikely(!_dq_state_is_base_wlh(old_state) ||
                        !_dq_state_is_enqueued_on_target(old_state) ||
                        _dq_state_is_enqueued_on_manager(old_state))) {
#if !__LP64__
                old_state >>= 32;
#endif
                DISPATCH_INTERNAL_CRASH(old_state, "Invalid wlh state");
        }

        if (dq_state) *dq_state = new_state;
        return !_dq_state_is_suspended(old_state) &&
                        !_dq_state_drain_locked(old_state);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_mgr_lock(dispatch_queue_t dq)
{
        uint64_t old_state, new_state, set_owner_and_set_full_width =
                        _dispatch_lock_value_for_self() | DISPATCH_QUEUE_SERIAL_DRAIN_OWNED;

        os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, acquire, {
                new_state = old_state;
                if (unlikely(!_dq_state_is_runnable(old_state) ||
                                _dq_state_drain_locked(old_state))) {
                        DISPATCH_INTERNAL_CRASH((uintptr_t)old_state,
                                        "Locking the manager should not fail");
                }
                new_state &= DISPATCH_QUEUE_DRAIN_PRESERVED_BITS_MASK;
                new_state |= set_owner_and_set_full_width;
        });
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_queue_mgr_unlock(dispatch_queue_t dq)
{
        uint64_t old_state, new_state;
        os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, release, {
                new_state = old_state - DISPATCH_QUEUE_SERIAL_DRAIN_OWNED;
                new_state &= ~DISPATCH_QUEUE_DRAIN_UNLOCK_MASK;
                new_state &= ~DISPATCH_QUEUE_MAX_QOS_MASK;
        });
        return _dq_state_is_dirty(old_state);
}

/* Used by _dispatch_barrier_{try,}sync
 *
 * Note, this fails if any of e:1 or dl!=0, but that allows this code to be a
 * simple cmpxchg which is significantly faster on Intel, and makes a
 * significant difference on the uncontended codepath.
 *
 * See discussion for DISPATCH_QUEUE_DIRTY in queue_internal.h
 *
 * Initial state must be `completely idle`
 * Final state forces { ib:1, qf:1, w:0 }
 */
DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline bool
_dispatch_queue_try_acquire_barrier_sync_and_suspend(dispatch_queue_t dq,
                uint32_t tid, uint64_t suspend_count)
{
        uint64_t init  = DISPATCH_QUEUE_STATE_INIT_VALUE(dq->dq_width);
        uint64_t value = DISPATCH_QUEUE_WIDTH_FULL_BIT | DISPATCH_QUEUE_IN_BARRIER |
                        _dispatch_lock_value_from_tid(tid) |
                        (suspend_count * DISPATCH_QUEUE_SUSPEND_INTERVAL);
        uint64_t old_state, new_state;

        return os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, acquire, {
                uint64_t role = old_state & DISPATCH_QUEUE_ROLE_MASK;
                if (old_state != (init | role)) {
                        os_atomic_rmw_loop_give_up(break);
                }
                new_state = value | role;
        });
}

DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline bool
_dispatch_queue_try_acquire_barrier_sync(dispatch_queue_t dq, uint32_t tid)
{
        return _dispatch_queue_try_acquire_barrier_sync_and_suspend(dq, tid, 0);
}

/* Used by _dispatch_sync for root queues and some drain codepaths
 *
 * Root queues have no strict orderning and dispatch_sync() always goes through.
 * Drain is the sole setter of `dl` hence can use this non failing version of
 * _dispatch_queue_try_acquire_sync().
 *
 * Final state: { w += 1 }
 */
DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_reserve_sync_width(dispatch_queue_t dq)
{
        (void)os_atomic_add2o(dq, dq_state,
                        DISPATCH_QUEUE_WIDTH_INTERVAL, relaxed);
}

/* Used by _dispatch_sync on non-serial queues
 *
 * Initial state must be { sc:0, ib:0, pb:0, d:0 }
 * Final state: { w += 1 }
 */
DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline bool
_dispatch_queue_try_reserve_sync_width(dispatch_queue_t dq)
{
        uint64_t old_state, new_state;

        // <rdar://problem/24738102&24743140> reserving non barrier width
        // doesn't fail if only the ENQUEUED bit is set (unlike its barrier width
        // equivalent), so we have to check that this thread hasn't enqueued
        // anything ahead of this call or we can break ordering
        if (unlikely(dq->dq_items_tail)) {
                return false;
        }

        return os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, relaxed, {
                if (unlikely(!_dq_state_is_sync_runnable(old_state)) ||
                                _dq_state_is_dirty(old_state) ||
                                _dq_state_has_pending_barrier(old_state)) {
                        os_atomic_rmw_loop_give_up(return false);
                }
                new_state = old_state + DISPATCH_QUEUE_WIDTH_INTERVAL;
        });
}

/* Used by _dispatch_apply_redirect
 *
 * Try to acquire at most da_width and returns what could be acquired,
 * possibly 0
 */
DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline int32_t
_dispatch_queue_try_reserve_apply_width(dispatch_queue_t dq, int32_t da_width)
{
        uint64_t old_state, new_state;
        int32_t width;

        (void)os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, relaxed, {
                width = (int32_t)_dq_state_available_width(old_state);
                if (unlikely(!width)) {
                        os_atomic_rmw_loop_give_up(return 0);
                }
                if (width > da_width) {
                        width = da_width;
                }
                new_state = old_state + (uint64_t)width * DISPATCH_QUEUE_WIDTH_INTERVAL;
        });
        return width;
}

/* Used by _dispatch_apply_redirect
 *
 * Release width acquired by _dispatch_queue_try_acquire_width
 */
DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_relinquish_width(dispatch_queue_t dq, int32_t da_width)
{
        (void)os_atomic_sub2o(dq, dq_state,
                        (uint64_t)da_width * DISPATCH_QUEUE_WIDTH_INTERVAL, relaxed);
}

/* Used by target-queue recursing code
 *
 * Initial state must be { sc:0, ib:0, qf:0, pb:0, d:0 }
 * Final state: { w += 1 }
 */
DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline bool
_dispatch_queue_try_acquire_async(dispatch_queue_t dq)
{
        uint64_t old_state, new_state;

        return os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, acquire, {
                if (unlikely(!_dq_state_is_runnable(old_state) ||
                                _dq_state_is_dirty(old_state) ||
                                _dq_state_has_pending_barrier(old_state))) {
                        os_atomic_rmw_loop_give_up(return false);
                }
                new_state = old_state + DISPATCH_QUEUE_WIDTH_INTERVAL;
        });
}

/* Used by concurrent drain
 *
 * Either acquires the full barrier width, in which case the Final state is:
 *   { ib:1 qf:1 pb:0 d:0 }
 * Or if there isn't enough width prepare the queue with the PENDING_BARRIER bit
 *   { ib:0 pb:1 d:0}
 *
 * This always clears the dirty bit as we know for sure we shouldn't reevaluate
 * the state machine here
 */
DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline bool
_dispatch_queue_try_upgrade_full_width(dispatch_queue_t dq, uint64_t owned)
{
        uint64_t old_state, new_state;
        uint64_t pending_barrier_width = DISPATCH_QUEUE_PENDING_BARRIER +
                        (dq->dq_width - 1) * DISPATCH_QUEUE_WIDTH_INTERVAL;

        os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, acquire, {
                new_state = old_state - owned;
                if (likely(!_dq_state_has_pending_barrier(old_state))) {
                        new_state += pending_barrier_width;
                }
                if (likely(_dq_state_is_runnable(new_state))) {
                        new_state += DISPATCH_QUEUE_WIDTH_INTERVAL;
                        new_state += DISPATCH_QUEUE_IN_BARRIER;
                        new_state -= DISPATCH_QUEUE_PENDING_BARRIER;
                }
                new_state &= ~DISPATCH_QUEUE_DIRTY;
        });
        return new_state & DISPATCH_QUEUE_IN_BARRIER;
}

/* Used at the end of Drainers
 *
 * This adjusts the `owned` width when the next continuation is already known
 * to account for its barrierness.
 */
DISPATCH_ALWAYS_INLINE
static inline uint64_t
_dispatch_queue_adjust_owned(dispatch_queue_t dq, uint64_t owned,
                struct dispatch_object_s *next_dc)
{
        uint64_t reservation;

        if (unlikely(dq->dq_width > 1)) {
                if (next_dc && _dispatch_object_is_barrier(next_dc)) {
                        reservation  = DISPATCH_QUEUE_PENDING_BARRIER;
                        reservation += (dq->dq_width - 1) * DISPATCH_QUEUE_WIDTH_INTERVAL;
                        owned -= reservation;
                }
        }
        return owned;
}

/* Used at the end of Drainers
 *
 * Unlocking fails if the DIRTY bit is seen (and the queue is not suspended).
 * In that case, only the DIRTY bit is cleared. The DIRTY bit is therefore used
 * as a signal to renew the drain lock instead of releasing it.
 *
 * Successful unlock forces { dl:0, d:!done, qo:0 } and gives back `owned`
 */
DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline bool
_dispatch_queue_drain_try_unlock(dispatch_queue_t dq, uint64_t owned, bool done)
{
        uint64_t old_state, new_state;

        os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, release, {
                new_state  = old_state - owned;
                new_state &= ~DISPATCH_QUEUE_DRAIN_UNLOCK_MASK;
                if (unlikely(_dq_state_is_suspended(old_state))) {
                        // nothing to do
                } else if (unlikely(_dq_state_is_dirty(old_state))) {
                        os_atomic_rmw_loop_give_up({
                                // just renew the drain lock with an acquire barrier, to see
                                // what the enqueuer that set DIRTY has done.
                                // the xor generates better assembly as DISPATCH_QUEUE_DIRTY
                                // is already in a register
                                os_atomic_xor2o(dq, dq_state, DISPATCH_QUEUE_DIRTY, acquire);
                                return false;
                        });
                } else if (likely(done)) {
                        new_state &= ~DISPATCH_QUEUE_MAX_QOS_MASK;
                } else {
                        new_state |= DISPATCH_QUEUE_DIRTY;
                }
        });

        if (_dq_state_received_override(old_state)) {
                // Ensure that the root queue sees that this thread was overridden.
                _dispatch_set_basepri_override_qos(_dq_state_max_qos(old_state));
        }
        return true;
}

#pragma mark -
#pragma mark os_mpsc_queue

// type_t * {volatile,const,_Atomic,...} -> type_t *
// type_t[] -> type_t *
#define os_unqualified_pointer_type(expr) \
                typeof(typeof(*(expr)) *)

#define os_mpsc_node_type(q, _ns)  \
                os_unqualified_pointer_type((q)->_ns##_head)

//
// Multi Producer calls, can be used safely concurrently
//

// Returns true when the queue was empty and the head must be set
#define os_mpsc_push_update_tail_list(q, _ns, head, tail, _o_next)  ({ \
                os_mpsc_node_type(q, _ns) _head = (head), _tail = (tail), _prev; \
                _tail->_o_next = NULL; \
                _prev = os_atomic_xchg2o((q), _ns##_tail, _tail, release); \
                if (likely(_prev)) { \
                        os_atomic_store2o(_prev, _o_next, _head, relaxed); \
                } \
                (_prev == NULL); \
        })

// Returns true when the queue was empty and the head must be set
#define os_mpsc_push_update_tail(q, _ns, o, _o_next)  ({ \
                os_mpsc_node_type(q, _ns) _o = (o); \
                os_mpsc_push_update_tail_list(q, _ns, _o, _o, _o_next); \
        })

#define os_mpsc_push_update_head(q, _ns, o)  ({ \
                os_atomic_store2o((q), _ns##_head, o, relaxed); \
        })

//
// Single Consumer calls, can NOT be used safely concurrently
//

#define os_mpsc_get_head(q, _ns) \
                _dispatch_wait_until(os_atomic_load2o(q, _ns##_head, dependency))

#define os_mpsc_get_next(_n, _o_next) \
                _dispatch_wait_until(os_atomic_load2o(_n, _o_next, dependency))

#define os_mpsc_pop_head(q, _ns, head, _o_next)  ({ \
                typeof(q) _q = (q); \
                os_mpsc_node_type(_q, _ns) _head = (head), _n; \
                _n = os_atomic_load2o(_head, _o_next, dependency); \
                os_atomic_store2o(_q, _ns##_head, _n, relaxed); \
                /* 22708742: set tail to NULL with release, so that NULL write */ \
                /* to head above doesn't clobber head from concurrent enqueuer */ \
                if (unlikely(!_n && \
                                !os_atomic_cmpxchg2o(_q, _ns##_tail, _head, NULL, release))) { \
                        _n = os_mpsc_get_next(_head, _o_next); \
                        os_atomic_store2o(_q, _ns##_head, _n, relaxed); \
                } \
                _n; \
        })

#define os_mpsc_undo_pop_head(q, _ns, head, next, _o_next)  ({ \
                typeof(q) _q = (q); \
                os_mpsc_node_type(_q, _ns) _head = (head), _n = (next); \
                if (unlikely(!_n && \
                                !os_atomic_cmpxchg2o(_q, _ns##_tail, NULL, _head, relaxed))) { \
                        _n = os_mpsc_get_head(q, _ns); \
                        os_atomic_store2o(_head, _o_next, _n, relaxed); \
                } \
                os_atomic_store2o(_q, _ns##_head, _head, relaxed); \
        })

#define os_mpsc_capture_snapshot(q, _ns, tail)  ({ \
                typeof(q) _q = (q); \
                os_mpsc_node_type(_q, _ns) _head = os_mpsc_get_head(q, _ns); \
                os_atomic_store2o(_q, _ns##_head, NULL, relaxed); \
                /* 22708742: set tail to NULL with release, so that NULL write */ \
                /* to head above doesn't clobber head from concurrent enqueuer */ \
                *(tail) = os_atomic_xchg2o(_q, _ns##_tail, NULL, release); \
                _head; \
        })

#define os_mpsc_pop_snapshot_head(head, tail, _o_next) ({ \
                os_unqualified_pointer_type(head) _head = (head), _n = NULL; \
                if (_head != (tail)) { \
                        _n = os_mpsc_get_next(_head, _o_next); \
                }; \
                _n; })

#define os_mpsc_prepend(q, _ns, head, tail, _o_next)  ({ \
                typeof(q) _q = (q); \
                os_mpsc_node_type(_q, _ns) _head = (head), _tail = (tail), _n; \
                os_atomic_store2o(_tail, _o_next, NULL, relaxed); \
                if (unlikely(!os_atomic_cmpxchg2o(_q, _ns##_tail, NULL, _tail, release))) { \
                        _n = os_mpsc_get_head(q, _ns); \
                        os_atomic_store2o(_tail, _o_next, _n, relaxed); \
                } \
                os_atomic_store2o(_q, _ns##_head, _head, relaxed); \
        })

#pragma mark -
#pragma mark dispatch_queue_t tq lock

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_queue_sidelock_trylock(dispatch_queue_t dq, dispatch_qos_t qos)
{
        dispatch_tid owner;
        if (_dispatch_unfair_lock_trylock(&dq->dq_sidelock, &owner)) {
                return true;
        }
        _dispatch_wqthread_override_start_check_owner(owner, qos,
                        &dq->dq_sidelock.dul_lock);
        return false;
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_sidelock_lock(dispatch_queue_t dq)
{
        return _dispatch_unfair_lock_lock(&dq->dq_sidelock);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_queue_sidelock_tryunlock(dispatch_queue_t dq)
{
        if (_dispatch_unfair_lock_tryunlock(&dq->dq_sidelock)) {
                return true;
        }
        // Ensure that the root queue sees that this thread was overridden.
        // Since we don't know which override QoS was used, use MAINTENANCE
        // as a marker for _dispatch_reset_basepri_override()
        _dispatch_set_basepri_override_qos(DISPATCH_QOS_MAINTENANCE);
        return false;
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_sidelock_unlock(dispatch_queue_t dq)
{
        if (_dispatch_unfair_lock_unlock_had_failed_trylock(&dq->dq_sidelock)) {
                // Ensure that the root queue sees that this thread was overridden.
                // Since we don't know which override QoS was used, use MAINTENANCE
                // as a marker for _dispatch_reset_basepri_override()
                _dispatch_set_basepri_override_qos(DISPATCH_QOS_MAINTENANCE);
        }
}

#pragma mark -
#pragma mark dispatch_queue_t misc

DISPATCH_ALWAYS_INLINE
static inline dispatch_queue_t
_dispatch_queue_get_current(void)
{
        return (dispatch_queue_t)_dispatch_thread_getspecific(dispatch_queue_key);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_set_current(dispatch_queue_t dq)
{
        _dispatch_thread_setspecific(dispatch_queue_key, dq);
}

DISPATCH_ALWAYS_INLINE
static inline struct dispatch_object_s*
_dispatch_queue_head(dispatch_queue_t dq)
{
        return os_mpsc_get_head(dq, dq_items);
}

DISPATCH_ALWAYS_INLINE
static inline struct dispatch_object_s*
_dispatch_queue_next(dispatch_queue_t dq, struct dispatch_object_s *dc)
{
        return os_mpsc_pop_head(dq, dq_items, dc, do_next);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_queue_push_update_tail(dispatch_queue_t dq,
                struct dispatch_object_s *tail)
{
        // if we crash here with a value less than 0x1000, then we are
        // at a known bug in client code. for example, see
        // _dispatch_queue_dispose or _dispatch_atfork_child
        return os_mpsc_push_update_tail(dq, dq_items, tail, do_next);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_queue_push_update_tail_list(dispatch_queue_t dq,
                struct dispatch_object_s *head, struct dispatch_object_s *tail)
{
        // if we crash here with a value less than 0x1000, then we are
        // at a known bug in client code. for example, see
        // _dispatch_queue_dispose or _dispatch_atfork_child
        return os_mpsc_push_update_tail_list(dq, dq_items, head, tail, do_next);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_push_update_head(dispatch_queue_t dq,
                struct dispatch_object_s *head)
{
        os_mpsc_push_update_head(dq, dq_items, head);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_root_queue_push_inline(dispatch_queue_t dq, dispatch_object_t _head,
                dispatch_object_t _tail, int n)
{
        struct dispatch_object_s *head = _head._do, *tail = _tail._do;
        if (unlikely(_dispatch_queue_push_update_tail_list(dq, head, tail))) {
                _dispatch_queue_push_update_head(dq, head);
                return _dispatch_global_queue_poke(dq, n, 0);
        }
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_push_inline(dispatch_queue_t dq, dispatch_object_t _tail,
                dispatch_qos_t qos)
{
        struct dispatch_object_s *tail = _tail._do;
        dispatch_wakeup_flags_t flags = 0;
        // If we are going to call dx_wakeup(), the queue must be retained before
        // the item we're pushing can be dequeued, which means:
        // - before we exchange the tail if we may have to override
        // - before we set the head if we made the queue non empty.
        // Otherwise, if preempted between one of these and the call to dx_wakeup()
        // the blocks submitted to the queue may release the last reference to the
        // queue when invoked by _dispatch_queue_drain. <rdar://problem/6932776>
        bool overriding = _dispatch_queue_need_override_retain(dq, qos);
        if (unlikely(_dispatch_queue_push_update_tail(dq, tail))) {
                if (!overriding) _dispatch_retain_2(dq->_as_os_obj);
                _dispatch_queue_push_update_head(dq, tail);
                flags = DISPATCH_WAKEUP_CONSUME_2 | DISPATCH_WAKEUP_MAKE_DIRTY;
        } else if (overriding) {
                flags = DISPATCH_WAKEUP_CONSUME_2;
        } else {
                return;
        }
        return dx_wakeup(dq, qos, flags);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_push_queue(dispatch_queue_t tq, dispatch_queue_t dq,
                uint64_t dq_state)
{
        return dx_push(tq, dq, _dq_state_max_qos(dq_state));
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_priority_t
_dispatch_root_queue_identity_assume(dispatch_queue_t assumed_rq)
{
        dispatch_priority_t old_dbp = _dispatch_get_basepri();
        dispatch_assert(dx_hastypeflag(assumed_rq, QUEUE_ROOT));
        _dispatch_reset_basepri(assumed_rq->dq_priority);
        _dispatch_queue_set_current(assumed_rq);
        return old_dbp;
}

typedef dispatch_queue_wakeup_target_t
_dispatch_queue_class_invoke_handler_t(dispatch_object_t,
                dispatch_invoke_context_t dic, dispatch_invoke_flags_t,
                uint64_t *owned);

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_class_invoke(dispatch_object_t dou,
                dispatch_invoke_context_t dic, dispatch_invoke_flags_t flags,
                dispatch_invoke_flags_t const_restrict_flags,
                _dispatch_queue_class_invoke_handler_t invoke)
{
        dispatch_queue_t dq = dou._dq;
        dispatch_queue_wakeup_target_t tq = DISPATCH_QUEUE_WAKEUP_NONE;
        bool owning = !(flags & DISPATCH_INVOKE_STEALING);
        uint64_t owned = 0;

        // When called from a plain _dispatch_queue_drain:
        //   overriding = false
        //   owning = true
        //
        // When called from an override continuation:
        //   overriding = true
        //   owning depends on whether the override embedded the queue or steals

        if (!(flags & (DISPATCH_INVOKE_STEALING | DISPATCH_INVOKE_WLH))) {
                dq->do_next = DISPATCH_OBJECT_LISTLESS;
        }
        flags |= const_restrict_flags;
        if (likely(flags & DISPATCH_INVOKE_WLH)) {
                owned = DISPATCH_QUEUE_SERIAL_DRAIN_OWNED | DISPATCH_QUEUE_ENQUEUED;
        } else {
                owned = _dispatch_queue_drain_try_lock(dq, flags);
        }
        if (likely(owned)) {
                dispatch_priority_t old_dbp;
                if (!(flags & DISPATCH_INVOKE_MANAGER_DRAIN)) {
                        old_dbp = _dispatch_set_basepri(dq->dq_priority);
                } else {
                        old_dbp = 0;
                }

                flags = _dispatch_queue_merge_autorelease_frequency(dq, flags);
attempt_running_slow_head:
#if DISPATCH_COCOA_COMPAT
                if ((flags & DISPATCH_INVOKE_WLH) &&
                                !(flags & DISPATCH_INVOKE_AUTORELEASE_ALWAYS)) {
                        _dispatch_last_resort_autorelease_pool_push(dic);
                }
#endif // DISPATCH_COCOA_COMPAT
                tq = invoke(dq, dic, flags, &owned);
#if DISPATCH_COCOA_COMPAT
                if ((flags & DISPATCH_INVOKE_WLH) &&
                                !(flags & DISPATCH_INVOKE_AUTORELEASE_ALWAYS)) {
                        dispatch_thread_frame_s dtf;
                        _dispatch_thread_frame_push(&dtf, dq);
                        _dispatch_last_resort_autorelease_pool_pop(dic);
                        _dispatch_thread_frame_pop(&dtf);
                }
#endif // DISPATCH_COCOA_COMPAT
                dispatch_assert(tq != DISPATCH_QUEUE_WAKEUP_TARGET);
                if (unlikely(tq != DISPATCH_QUEUE_WAKEUP_NONE &&
                                tq != DISPATCH_QUEUE_WAKEUP_WAIT_FOR_EVENT)) {
                        // Either dc is set, which is a deferred invoke case
                        //
                        // or only tq is and it means a reenqueue is required, because of:
                        // a retarget, a suspension, or a width change.
                        //
                        // In both cases, we want to bypass the check for DIRTY.
                        // That may cause us to leave DIRTY in place but all drain lock
                        // acquirers clear it
                } else if (!_dispatch_queue_drain_try_unlock(dq, owned,
                                tq == DISPATCH_QUEUE_WAKEUP_NONE)) {
                        tq = _dispatch_queue_get_current();
                        if (dx_hastypeflag(tq, QUEUE_ROOT) || !owning) {
                                goto attempt_running_slow_head;
                        }
                        DISPATCH_COMPILER_CAN_ASSUME(tq != DISPATCH_QUEUE_WAKEUP_NONE);
                } else {
                        owned = 0;
                        tq = NULL;
                }
                if (!(flags & DISPATCH_INVOKE_MANAGER_DRAIN)) {
                        _dispatch_reset_basepri(old_dbp);
                }
        }
        if (likely(owning)) {
                _dispatch_introspection_queue_item_complete(dq);
        }

        if (tq) {
                if (const_restrict_flags & DISPATCH_INVOKE_DISALLOW_SYNC_WAITERS) {
                        dispatch_assert(dic->dic_deferred == NULL);
                } else if (dic->dic_deferred) {
                        return _dispatch_queue_drain_sync_waiter(dq, dic,
                                        flags, owned);
                }

                uint64_t old_state, new_state, enqueued = DISPATCH_QUEUE_ENQUEUED;
                if (tq == DISPATCH_QUEUE_WAKEUP_MGR) {
                        enqueued = DISPATCH_QUEUE_ENQUEUED_ON_MGR;
                }
                os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, release, {
                        new_state  = old_state - owned;
                        new_state &= ~DISPATCH_QUEUE_DRAIN_UNLOCK_MASK;
                        new_state |= DISPATCH_QUEUE_DIRTY;
                        if (_dq_state_is_runnable(new_state) &&
                                        !_dq_state_is_enqueued(new_state)) {
                                // drain was not interupted for suspension
                                // we will reenqueue right away, just put ENQUEUED back
                                new_state |= enqueued;
                        }
                });
                old_state -= owned;
                if (_dq_state_received_override(old_state)) {
                        // Ensure that the root queue sees that this thread was overridden.
                        _dispatch_set_basepri_override_qos(_dq_state_max_qos(new_state));
                }
                if ((old_state ^ new_state) & enqueued) {
                        dispatch_assert(_dq_state_is_enqueued(new_state));
                        return _dispatch_queue_push_queue(tq, dq, new_state);
                }
        }

        _dispatch_release_2_tailcall(dq);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_queue_class_probe(dispatch_queue_class_t dqu)
{
        struct dispatch_object_s *tail;
        // seq_cst wrt atomic store to dq_state <rdar://problem/14637483>
        // seq_cst wrt atomic store to dq_flags <rdar://problem/22623242>
        tail = os_atomic_load2o(dqu._oq, oq_items_tail, ordered);
        return unlikely(tail != NULL);
}

DISPATCH_ALWAYS_INLINE DISPATCH_CONST
static inline bool
_dispatch_is_in_root_queues_array(dispatch_queue_t dq)
{
        return (dq >= _dispatch_root_queues) &&
                        (dq < _dispatch_root_queues + _DISPATCH_ROOT_QUEUE_IDX_COUNT);
}

DISPATCH_ALWAYS_INLINE DISPATCH_CONST
static inline dispatch_queue_t
_dispatch_get_root_queue(dispatch_qos_t qos, bool overcommit)
{
        if (unlikely(qos == DISPATCH_QOS_UNSPECIFIED || qos > DISPATCH_QOS_MAX)) {
                DISPATCH_CLIENT_CRASH(qos, "Corrupted priority");
        }
        return &_dispatch_root_queues[2 * (qos - 1) + overcommit];
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_set_bound_thread(dispatch_queue_t dq)
{
        // Tag thread-bound queues with the owning thread
        dispatch_assert(_dispatch_queue_is_thread_bound(dq));
        uint64_t old_state, new_state;
        os_atomic_rmw_loop2o(dq, dq_state, old_state, new_state, relaxed, {
                new_state = old_state;
                new_state &= ~DISPATCH_QUEUE_DRAIN_OWNER_MASK;
                new_state |= _dispatch_lock_value_for_self();
        });
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_clear_bound_thread(dispatch_queue_t dq)
{
        dispatch_assert(_dispatch_queue_is_thread_bound(dq));
        _dispatch_queue_atomic_flags_clear(dq, DQF_THREAD_BOUND|DQF_CANNOT_TRYSYNC);
        os_atomic_and2o(dq, dq_state, ~DISPATCH_QUEUE_DRAIN_OWNER_MASK, relaxed);
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_pthread_root_queue_observer_hooks_t
_dispatch_get_pthread_root_queue_observer_hooks(void)
{
        return _dispatch_thread_getspecific(
                        dispatch_pthread_root_queue_observer_hooks_key);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_set_pthread_root_queue_observer_hooks(
                dispatch_pthread_root_queue_observer_hooks_t observer_hooks)
{
        _dispatch_thread_setspecific(dispatch_pthread_root_queue_observer_hooks_key,
                        observer_hooks);
}

#pragma mark -
#pragma mark dispatch_priority

DISPATCH_ALWAYS_INLINE
static inline dispatch_priority_t
_dispatch_get_basepri(void)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        return (dispatch_priority_t)(uintptr_t)_dispatch_thread_getspecific(
                        dispatch_basepri_key);
#else
        return 0;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_reset_basepri(dispatch_priority_t dbp)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        dispatch_priority_t old_dbp = _dispatch_get_basepri();
        // If an inner-loop or'd in the override flag to the per-thread priority,
        // it needs to be propagated up the chain.
        dbp &= ~DISPATCH_PRIORITY_OVERRIDE_MASK;
        dbp |= (old_dbp & DISPATCH_PRIORITY_OVERRIDE_MASK);
        _dispatch_thread_setspecific(dispatch_basepri_key, (void*)(uintptr_t)dbp);
#else
        (void)dbp;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_qos_t
_dispatch_get_basepri_override_qos_floor(void)
{
        dispatch_priority_t dbp = _dispatch_get_basepri();
        dispatch_qos_t qos = _dispatch_priority_qos(dbp);
        dispatch_qos_t oqos = _dispatch_priority_override_qos(dbp);
        dispatch_qos_t qos_floor = MAX(qos, oqos);
        return qos_floor ? qos_floor : DISPATCH_QOS_SATURATED;
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_set_basepri_override_qos(dispatch_qos_t qos)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        dispatch_priority_t dbp = _dispatch_get_basepri();
        if (_dispatch_priority_override_qos(dbp) >= qos) return;
        dbp &= ~DISPATCH_PRIORITY_OVERRIDE_MASK;
        dbp |= qos << DISPATCH_PRIORITY_OVERRIDE_SHIFT;
        _dispatch_thread_setspecific(dispatch_basepri_key, (void*)(uintptr_t)dbp);
#else
        (void)qos;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_reset_basepri_override(void)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        dispatch_priority_t dbp = _dispatch_get_basepri();
        dispatch_qos_t oqos = _dispatch_priority_override_qos(dbp);
        if (oqos) {
                dbp &= ~DISPATCH_PRIORITY_OVERRIDE_MASK;
                _dispatch_thread_setspecific(dispatch_basepri_key, (void*)(uintptr_t)dbp);
                return oqos != DISPATCH_QOS_SATURATED;
        }
#endif
        return false;
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_priority_t
_dispatch_set_basepri(dispatch_priority_t dbp)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        const dispatch_priority_t preserved_mask =
                        DISPATCH_PRIORITY_OVERRIDE_MASK | DISPATCH_PRIORITY_FLAG_OVERCOMMIT;
        dispatch_priority_t old_dbp = _dispatch_get_basepri();
        if (old_dbp) {
                dispatch_priority_t flags, defaultqueue, basepri;
                flags = (dbp & DISPATCH_PRIORITY_FLAG_DEFAULTQUEUE);
                defaultqueue = (old_dbp & DISPATCH_PRIORITY_FLAG_DEFAULTQUEUE);
                basepri = old_dbp & DISPATCH_PRIORITY_REQUESTED_MASK;
                dbp &= DISPATCH_PRIORITY_REQUESTED_MASK;
                if (!dbp) {
                        flags = DISPATCH_PRIORITY_FLAG_INHERIT | defaultqueue;
                        dbp = basepri;
                } else if (dbp < basepri && !defaultqueue) { // rdar://16349734
                        dbp = basepri;
                }
                dbp |= flags | (old_dbp & preserved_mask);
        } else {
                dbp &= ~DISPATCH_PRIORITY_OVERRIDE_MASK;
        }
        _dispatch_thread_setspecific(dispatch_basepri_key, (void*)(uintptr_t)dbp);
        return old_dbp;
#else
        (void)dbp;
        return 0;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_priority_t
_dispatch_set_basepri_wlh(dispatch_priority_t dbp)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        dispatch_assert(!_dispatch_get_basepri());
        // _dispatch_set_basepri_override_qos(DISPATCH_QOS_SATURATED)
        dbp |= DISPATCH_QOS_SATURATED << DISPATCH_PRIORITY_OVERRIDE_SHIFT;
        _dispatch_thread_setspecific(dispatch_basepri_key, (void*)(uintptr_t)dbp);
#else
        (void)dbp;
#endif
        return 0;
}

DISPATCH_ALWAYS_INLINE
static inline pthread_priority_t
_dispatch_priority_adopt(pthread_priority_t pp, unsigned long flags)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        dispatch_priority_t inherited, defaultqueue, dbp = _dispatch_get_basepri();
        pthread_priority_t basepp = _dispatch_priority_to_pp_strip_flags(dbp);
        bool enforce = (flags & DISPATCH_PRIORITY_ENFORCE) ||
                        (pp & _PTHREAD_PRIORITY_ENFORCE_FLAG);
        inherited = (dbp & DISPATCH_PRIORITY_FLAG_INHERIT);
        defaultqueue = (dbp & DISPATCH_PRIORITY_FLAG_DEFAULTQUEUE);
        pp &= ~_PTHREAD_PRIORITY_FLAGS_MASK;

        if (!pp) {
                return basepp;
        } else if (defaultqueue) { // rdar://16349734
                return pp;
        } else if (pp < basepp) {
                return basepp;
        } else if (enforce || inherited) {
                return pp;
        } else {
                return basepp;
        }
#else
        (void)pp; (void)flags;
        return 0;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_queue_priority_inherit_from_target(dispatch_queue_t dq,
                dispatch_queue_t tq)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        const dispatch_priority_t rootqueue_flag = DISPATCH_PRIORITY_FLAG_ROOTQUEUE;
        const dispatch_priority_t inherited_flag = DISPATCH_PRIORITY_FLAG_INHERIT;
        const dispatch_priority_t defaultqueue_flag =
            DISPATCH_PRIORITY_FLAG_DEFAULTQUEUE;
        dispatch_priority_t pri = dq->dq_priority, tpri = tq->dq_priority;

        if ((!_dispatch_priority_qos(pri) || (pri & inherited_flag)) &&
                        (tpri & rootqueue_flag)) {
                if (_dispatch_priority_override_qos(pri) == DISPATCH_QOS_SATURATED) {
                        pri &= DISPATCH_PRIORITY_OVERRIDE_MASK;
                } else {
                        pri = 0;
                }
                if (tpri & defaultqueue_flag) {
                        // <rdar://problem/32921639> base queues need to know they target
                        // the default root queue so that _dispatch_queue_override_qos()
                        // in _dispatch_queue_class_wakeup() can fallback to QOS_DEFAULT
                        // if no other priority was provided.
                        pri |= defaultqueue_flag;
                } else {
                        pri |= (tpri & ~rootqueue_flag) | inherited_flag;
                }
                dq->dq_priority = pri;
        } else if (pri & defaultqueue_flag) {
                // the DEFAULTQUEUE flag is only set on queues due to the code above,
                // and must never be kept if we don't target a global root queue.
                dq->dq_priority = (pri & ~defaultqueue_flag);
        }
#else
        (void)dq; (void)tq;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_priority_t
_dispatch_priority_inherit_from_root_queue(dispatch_priority_t pri,
                dispatch_queue_t rq)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        dispatch_priority_t p = pri & DISPATCH_PRIORITY_REQUESTED_MASK;
        dispatch_priority_t rqp = rq->dq_priority & DISPATCH_PRIORITY_REQUESTED_MASK;
        dispatch_priority_t defaultqueue =
                        rq->dq_priority & DISPATCH_PRIORITY_FLAG_DEFAULTQUEUE;

        if (!p || (!defaultqueue && p < rqp)) {
                p = rqp | defaultqueue;
        }
        return p | (rq->dq_priority & DISPATCH_PRIORITY_FLAG_OVERCOMMIT);
#else
        (void)rq; (void)pri;
        return 0;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline pthread_priority_t
_dispatch_get_priority(void)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        pthread_priority_t pp = (uintptr_t)
                        _dispatch_thread_getspecific(dispatch_priority_key);
        return pp;
#else
        return 0;
#endif
}

#if HAVE_PTHREAD_WORKQUEUE_QOS
DISPATCH_ALWAYS_INLINE
static inline pthread_priority_t
_dispatch_priority_compute_update(pthread_priority_t pp)
{
        dispatch_assert(pp != DISPATCH_NO_PRIORITY);
        if (!_dispatch_set_qos_class_enabled) return 0;
        // the priority in _dispatch_get_priority() only tracks manager-ness
        // and overcommit, which is inherited from the current value for each update
        // however if the priority had the NEEDS_UNBIND flag set we need to clear it
        // the first chance we get
        //
        // the manager bit is invalid input, but we keep it to get meaningful
        // assertions in _dispatch_set_priority_and_voucher_slow()
        pp &= _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG | ~_PTHREAD_PRIORITY_FLAGS_MASK;
        pthread_priority_t cur_priority = _dispatch_get_priority();
        pthread_priority_t unbind = _PTHREAD_PRIORITY_NEEDS_UNBIND_FLAG;
        pthread_priority_t overcommit = _PTHREAD_PRIORITY_OVERCOMMIT_FLAG;
        if (unlikely(cur_priority & unbind)) {
                // else we always need an update if the NEEDS_UNBIND flag is set
                // the slow path in _dispatch_set_priority_and_voucher_slow() will
                // adjust the priority further with the proper overcommitness
                return pp ? pp : (cur_priority & ~unbind);
        } else {
                cur_priority &= ~overcommit;
        }
        if (unlikely(pp != cur_priority)) return pp;
        return 0;
}
#endif

DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline voucher_t
_dispatch_set_priority_and_voucher(pthread_priority_t pp,
                voucher_t v, dispatch_thread_set_self_t flags)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        pp = _dispatch_priority_compute_update(pp);
        if (likely(!pp)) {
                if (v == DISPATCH_NO_VOUCHER) {
                        return DISPATCH_NO_VOUCHER;
                }
                if (likely(v == _voucher_get())) {
                        bool retained = flags & DISPATCH_VOUCHER_CONSUME;
                        if (flags & DISPATCH_VOUCHER_REPLACE) {
                                if (retained && v) _voucher_release_no_dispose(v);
                                v = DISPATCH_NO_VOUCHER;
                        } else {
                                if (!retained && v) _voucher_retain(v);
                        }
                        return v;
                }
        }
        return _dispatch_set_priority_and_voucher_slow(pp, v, flags);
#else
        (void)pp; (void)v; (void)flags;
        return DISPATCH_NO_VOUCHER;
#endif
}

DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline voucher_t
_dispatch_adopt_priority_and_set_voucher(pthread_priority_t pp,
                voucher_t v, dispatch_thread_set_self_t flags)
{
        pthread_priority_t p = 0;
        if (pp != DISPATCH_NO_PRIORITY) {
                p = _dispatch_priority_adopt(pp, flags);
        }
        return _dispatch_set_priority_and_voucher(p, v, flags);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_reset_priority_and_voucher(pthread_priority_t pp, voucher_t v)
{
        if (pp == DISPATCH_NO_PRIORITY) pp = 0;
        (void)_dispatch_set_priority_and_voucher(pp, v,
                        DISPATCH_VOUCHER_CONSUME | DISPATCH_VOUCHER_REPLACE);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_reset_voucher(voucher_t v, dispatch_thread_set_self_t flags)
{
        flags |= DISPATCH_VOUCHER_CONSUME | DISPATCH_VOUCHER_REPLACE;
        (void)_dispatch_set_priority_and_voucher(0, v, flags);
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_queue_need_override(dispatch_queue_class_t dqu, dispatch_qos_t qos)
{
        uint64_t dq_state = os_atomic_load2o(dqu._dq, dq_state, relaxed);
        // dq_priority "override qos" contains the priority at which the queue
        // is already running for thread-bound queues.
        // For non thread-bound queues, the qos of the queue may not be observed
        // when the first work item is dispatched synchronously.
        return _dq_state_max_qos(dq_state) < qos &&
                        _dispatch_priority_override_qos(dqu._dq->dq_priority) < qos;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_queue_need_override_retain(dispatch_queue_class_t dqu,
                dispatch_qos_t qos)
{
        if (_dispatch_queue_need_override(dqu, qos)) {
                _os_object_retain_internal_n_inline(dqu._oq->_as_os_obj, 2);
                return true;
        }
        return false;
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_qos_t
_dispatch_queue_override_qos(dispatch_queue_class_t dqu, dispatch_qos_t qos)
{
        if (dqu._oq->oq_priority & DISPATCH_PRIORITY_FLAG_DEFAULTQUEUE) {
                // queues targeting the default root queue use any asynchronous
                // workitem priority available and fallback to QOS_DEFAULT otherwise.
                return qos ? qos : DISPATCH_QOS_DEFAULT;
        }
        // for asynchronous workitems, queue priority is the floor for overrides
        return MAX(qos, _dispatch_priority_qos(dqu._oq->oq_priority));
}

#define DISPATCH_PRIORITY_PROPAGATE_CURRENT 0x1
#define DISPATCH_PRIORITY_PROPAGATE_FOR_SYNC_IPC 0x2

DISPATCH_ALWAYS_INLINE
static inline pthread_priority_t
_dispatch_priority_compute_propagated(pthread_priority_t pp,
                unsigned int flags)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        if (flags & DISPATCH_PRIORITY_PROPAGATE_CURRENT) {
                pp = _dispatch_get_priority();
        }
        pp &= ~_PTHREAD_PRIORITY_FLAGS_MASK;
        if (!(flags & DISPATCH_PRIORITY_PROPAGATE_FOR_SYNC_IPC) &&
                        pp > _dispatch_qos_to_pp(DISPATCH_QOS_USER_INITIATED)) {
                // Cap QOS for propagation at user-initiated <rdar://16681262&16998036>
                return _dispatch_qos_to_pp(DISPATCH_QOS_USER_INITIATED);
        }
        return pp;
#else
        (void)pp; (void)flags;
        return 0;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline pthread_priority_t
_dispatch_priority_propagate(void)
{
        return _dispatch_priority_compute_propagated(0,
                        DISPATCH_PRIORITY_PROPAGATE_CURRENT);
}

// including maintenance
DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_is_background_thread(void)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        pthread_priority_t pp = _dispatch_get_priority();
        return _dispatch_qos_is_background(_dispatch_qos_from_pp(pp));
#else
        return false;
#endif
}

#pragma mark -
#pragma mark dispatch_block_t

#ifdef __BLOCKS__

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_block_has_private_data(const dispatch_block_t block)
{
        extern void (*_dispatch_block_special_invoke)(void*);
        return (_dispatch_Block_invoke(block) == _dispatch_block_special_invoke);
}

DISPATCH_ALWAYS_INLINE DISPATCH_WARN_RESULT
static inline pthread_priority_t
_dispatch_block_invoke_should_set_priority(dispatch_block_flags_t flags,
        pthread_priority_t new_pri)
{
        pthread_priority_t old_pri, p = 0;  // 0 means do not change priority.
        if ((flags & DISPATCH_BLOCK_HAS_PRIORITY)
                        && ((flags & DISPATCH_BLOCK_ENFORCE_QOS_CLASS) ||
                        !(flags & DISPATCH_BLOCK_INHERIT_QOS_CLASS))) {
                old_pri = _dispatch_get_priority();
                new_pri &= ~_PTHREAD_PRIORITY_FLAGS_MASK;
                p = old_pri & ~_PTHREAD_PRIORITY_FLAGS_MASK;
                if (!p || p >= new_pri) p = 0;
        }
        return p;
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_block_private_data_t
_dispatch_block_get_data(const dispatch_block_t db)
{
        if (!_dispatch_block_has_private_data(db)) {
                return NULL;
        }
        // Keep in sync with _dispatch_block_create implementation
        uint8_t *x = (uint8_t *)db;
        // x points to base of struct Block_layout
        x += sizeof(struct Block_layout);
        // x points to base of captured dispatch_block_private_data_s object
        dispatch_block_private_data_t dbpd = (dispatch_block_private_data_t)x;
        if (dbpd->dbpd_magic != DISPATCH_BLOCK_PRIVATE_DATA_MAGIC) {
                DISPATCH_CLIENT_CRASH(dbpd->dbpd_magic,
                                "Corruption of dispatch block object");
        }
        return dbpd;
}

DISPATCH_ALWAYS_INLINE
static inline pthread_priority_t
_dispatch_block_get_priority(const dispatch_block_t db)
{
        dispatch_block_private_data_t dbpd = _dispatch_block_get_data(db);
        return dbpd ? dbpd->dbpd_priority : 0;
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_block_flags_t
_dispatch_block_get_flags(const dispatch_block_t db)
{
        dispatch_block_private_data_t dbpd = _dispatch_block_get_data(db);
        return dbpd ? dbpd->dbpd_flags : 0;
}

#endif

#pragma mark -
#pragma mark dispatch_continuation_t

DISPATCH_ALWAYS_INLINE
static inline dispatch_continuation_t
_dispatch_continuation_alloc_cacheonly(void)
{
        dispatch_continuation_t dc = (dispatch_continuation_t)
                        _dispatch_thread_getspecific(dispatch_cache_key);
        if (likely(dc)) {
                _dispatch_thread_setspecific(dispatch_cache_key, dc->do_next);
        }
        return dc;
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_continuation_t
_dispatch_continuation_alloc(void)
{
        dispatch_continuation_t dc =
                        _dispatch_continuation_alloc_cacheonly();
        if (unlikely(!dc)) {
                return _dispatch_continuation_alloc_from_heap();
        }
        return dc;
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_continuation_t
_dispatch_continuation_free_cacheonly(dispatch_continuation_t dc)
{
        dispatch_continuation_t prev_dc = (dispatch_continuation_t)
                        _dispatch_thread_getspecific(dispatch_cache_key);
        int cnt = prev_dc ? prev_dc->dc_cache_cnt + 1 : 1;
        // Cap continuation cache
        if (unlikely(cnt > _dispatch_continuation_cache_limit)) {
                return dc;
        }
        dc->do_next = prev_dc;
        dc->dc_cache_cnt = cnt;
        _dispatch_thread_setspecific(dispatch_cache_key, dc);
        return NULL;
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_continuation_free(dispatch_continuation_t dc)
{
        dc = _dispatch_continuation_free_cacheonly(dc);
        if (unlikely(dc)) {
                _dispatch_continuation_free_to_cache_limit(dc);
        }
}

#include "trace.h"

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_continuation_with_group_invoke(dispatch_continuation_t dc)
{
        struct dispatch_object_s *dou = dc->dc_data;
        unsigned long type = dx_type(dou);
        if (type == DISPATCH_GROUP_TYPE) {
                _dispatch_client_callout(dc->dc_ctxt, dc->dc_func);
                _dispatch_introspection_queue_item_complete(dou);
                dispatch_group_leave((dispatch_group_t)dou);
        } else {
                DISPATCH_INTERNAL_CRASH(dx_type(dou), "Unexpected object type");
        }
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_continuation_invoke_inline(dispatch_object_t dou, voucher_t ov,
                dispatch_invoke_flags_t flags)
{
        dispatch_continuation_t dc = dou._dc, dc1;
        dispatch_invoke_with_autoreleasepool(flags, {
                uintptr_t dc_flags = dc->dc_flags;
                // Add the item back to the cache before calling the function. This
                // allows the 'hot' continuation to be used for a quick callback.
                //
                // The ccache version is per-thread.
                // Therefore, the object has not been reused yet.
                // This generates better assembly.
                _dispatch_continuation_voucher_adopt(dc, ov, dc_flags);
                if (dc_flags & DISPATCH_OBJ_CONSUME_BIT) {
                        dc1 = _dispatch_continuation_free_cacheonly(dc);
                } else {
                        dc1 = NULL;
                }
                if (unlikely(dc_flags & DISPATCH_OBJ_GROUP_BIT)) {
                        _dispatch_continuation_with_group_invoke(dc);
                } else {
                        _dispatch_client_callout(dc->dc_ctxt, dc->dc_func);
                        _dispatch_introspection_queue_item_complete(dou);
                }
                if (unlikely(dc1)) {
                        _dispatch_continuation_free_to_cache_limit(dc1);
                }
        });
        _dispatch_perfmon_workitem_inc();
}

DISPATCH_ALWAYS_INLINE_NDEBUG
static inline void
_dispatch_continuation_pop_inline(dispatch_object_t dou,
                dispatch_invoke_context_t dic, dispatch_invoke_flags_t flags,
                dispatch_queue_t dq)
{
        dispatch_pthread_root_queue_observer_hooks_t observer_hooks =
                        _dispatch_get_pthread_root_queue_observer_hooks();
        if (observer_hooks) observer_hooks->queue_will_execute(dq);
        _dispatch_trace_continuation_pop(dq, dou);
        flags &= _DISPATCH_INVOKE_PROPAGATE_MASK;
        if (_dispatch_object_has_vtable(dou)) {
                dx_invoke(dou._do, dic, flags);
        } else {
                _dispatch_continuation_invoke_inline(dou, DISPATCH_NO_VOUCHER, flags);
        }
        if (observer_hooks) observer_hooks->queue_did_execute(dq);
}

// used to forward the do_invoke of a continuation with a vtable to its real
// implementation.
#define _dispatch_continuation_pop_forwarded(dc, ov, dc_flags, ...) \
        ({ \
                dispatch_continuation_t _dc = (dc), _dc1; \
                uintptr_t _dc_flags = (dc_flags); \
                _dispatch_continuation_voucher_adopt(_dc, ov, _dc_flags); \
                if (_dc_flags & DISPATCH_OBJ_CONSUME_BIT) { \
                        _dc1 = _dispatch_continuation_free_cacheonly(_dc); \
                } else { \
                        _dc1 = NULL; \
                } \
                __VA_ARGS__; \
                _dispatch_introspection_queue_item_complete(_dc); \
                if (unlikely(_dc1)) { \
                        _dispatch_continuation_free_to_cache_limit(_dc1); \
                } \
        })

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_continuation_priority_set(dispatch_continuation_t dc,
                pthread_priority_t pp, dispatch_block_flags_t flags)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        if (likely(!(flags & DISPATCH_BLOCK_HAS_PRIORITY))) {
                pp = _dispatch_priority_propagate();
        }
        if (flags & DISPATCH_BLOCK_ENFORCE_QOS_CLASS) {
                pp |= _PTHREAD_PRIORITY_ENFORCE_FLAG;
        }
        dc->dc_priority = pp;
#else
        (void)dc; (void)pp; (void)flags;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline dispatch_qos_t
_dispatch_continuation_override_qos(dispatch_queue_t dq,
                dispatch_continuation_t dc)
{
#if HAVE_PTHREAD_WORKQUEUE_QOS
        dispatch_qos_t dc_qos = _dispatch_qos_from_pp(dc->dc_priority);
        bool enforce = dc->dc_priority & _PTHREAD_PRIORITY_ENFORCE_FLAG;
        dispatch_qos_t dq_qos = _dispatch_priority_qos(dq->dq_priority);
        bool defaultqueue = dq->dq_priority & DISPATCH_PRIORITY_FLAG_DEFAULTQUEUE;

        dispatch_assert(dc->dc_priority != DISPATCH_NO_PRIORITY);
        if (dc_qos && (enforce || !dq_qos || defaultqueue)) {
                return dc_qos;
        }
        return dq_qos;
#else
        (void)dq; (void)dc;
        return 0;
#endif
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_continuation_init_f(dispatch_continuation_t dc,
                dispatch_queue_class_t dqu, void *ctxt, dispatch_function_t func,
                pthread_priority_t pp, dispatch_block_flags_t flags, uintptr_t dc_flags)
{
        dc->dc_flags = dc_flags;
        dc->dc_func = func;
        dc->dc_ctxt = ctxt;
        _dispatch_continuation_voucher_set(dc, dqu, flags);
        _dispatch_continuation_priority_set(dc, pp, flags);
}

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_continuation_init(dispatch_continuation_t dc,
                dispatch_queue_class_t dqu, dispatch_block_t work,
                pthread_priority_t pp, dispatch_block_flags_t flags, uintptr_t dc_flags)
{
        dc->dc_flags = dc_flags | DISPATCH_OBJ_BLOCK_BIT;
        dc->dc_ctxt = _dispatch_Block_copy(work);
        _dispatch_continuation_priority_set(dc, pp, flags);

        if (unlikely(_dispatch_block_has_private_data(work))) {
                // always sets dc_func & dc_voucher
                // may update dc_priority & do_vtable
                return _dispatch_continuation_init_slow(dc, dqu, flags);
        }

        if (dc_flags & DISPATCH_OBJ_CONSUME_BIT) {
                dc->dc_func = _dispatch_call_block_and_release;
        } else {
                dc->dc_func = _dispatch_Block_invoke(work);
        }
        _dispatch_continuation_voucher_set(dc, dqu, flags);
}

#if HAVE_MACH
#pragma mark dispatch_mach_reply_refs_t

// assumes low bit of mach port names is always set
#define DISPATCH_MACH_REPLY_PORT_UNOWNED 0x1u

DISPATCH_ALWAYS_INLINE
static inline void
_dispatch_mach_reply_mark_reply_port_owned(dispatch_mach_reply_refs_t dmr)
{
        dmr->du_ident &= ~DISPATCH_MACH_REPLY_PORT_UNOWNED;
}

DISPATCH_ALWAYS_INLINE
static inline bool
_dispatch_mach_reply_is_reply_port_owned(dispatch_mach_reply_refs_t dmr)
{
        mach_port_t reply_port = (mach_port_t)dmr->du_ident;
        return reply_port ? !(reply_port & DISPATCH_MACH_REPLY_PORT_UNOWNED) :false;
}

DISPATCH_ALWAYS_INLINE
static inline mach_port_t
_dispatch_mach_reply_get_reply_port(mach_port_t reply_port)
{
        return reply_port ? (reply_port | DISPATCH_MACH_REPLY_PORT_UNOWNED) : 0;
}

#endif // HAVE_MACH

#endif // DISPATCH_PURE_C

#endif /* __DISPATCH_INLINE_INTERNAL__ */