[apple/libpthread.git] / src / pthread.c

/*
 * Copyright (c) 2000-2013 Apple Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * Copyright 1996 1995 by Open Software Foundation, Inc. 1997 1996 1995 1994 1993 1992 1991
 *              All Rights Reserved
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation for any purpose and without fee is hereby granted,
 * provided that the above copyright notice appears in all copies and
 * that both the copyright notice and this permission notice appear in
 * supporting documentation.
 *
 * OSF DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE.
 *
 * IN NO EVENT SHALL OSF BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
 * NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */
/*
 * MkLinux
 */

/*
 * POSIX Pthread Library
 */

#include "resolver.h"
#include "internal.h"
#include "private.h"
#include "workqueue_private.h"
#include "introspection_private.h"
#include "qos_private.h"
#include "tsd_private.h"
#include "pthread/stack_np.h"
#include "offsets.h" // included to validate the offsets at build time

#include <stdlib.h>
#include <errno.h>
#include <signal.h>
#include <unistd.h>
#include <mach/mach_init.h>
#include <mach/mach_vm.h>
#include <mach/mach_sync_ipc.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/sysctl.h>
#include <sys/queue.h>
#include <sys/ulock.h>
#include <sys/mman.h>
#include <machine/vmparam.h>
#define __APPLE_API_PRIVATE
#include <machine/cpu_capabilities.h>

#include <_simple.h>
#include <platform/string.h>
#include <platform/compat.h>

extern int __sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
                void *newp, size_t newlen);
extern void __exit(int) __attribute__((noreturn));
extern int __pthread_kill(mach_port_t, int);

extern void _pthread_joiner_wake(pthread_t thread);

#if !VARIANT_DYLD
PTHREAD_NOEXPORT extern struct _pthread *_main_thread_ptr;
#define main_thread() (_main_thread_ptr)
#endif // VARIANT_DYLD

// Default stack size is 512KB; independent of the main thread's stack size.
#define DEFAULT_STACK_SIZE (size_t)(512 * 1024)


//
// Global constants
//

/*
 * The pthread may be offset into a page.  In that event, by contract
 * with the kernel, the allocation will extend PTHREAD_SIZE from the
 * start of the next page.  There's also one page worth of allocation
 * below stacksize for the guard page. <rdar://problem/19941744>
 */
#define PTHREAD_SIZE ((size_t)mach_vm_round_page(sizeof(struct _pthread)))
#define PTHREAD_ALLOCADDR(stackaddr, stacksize) ((stackaddr - stacksize) - vm_page_size)
#define PTHREAD_ALLOCSIZE(stackaddr, stacksize) ((round_page((uintptr_t)stackaddr) + PTHREAD_SIZE) - (uintptr_t)PTHREAD_ALLOCADDR(stackaddr, stacksize))

static const pthread_attr_t _pthread_attr_default = {
        .sig       = _PTHREAD_ATTR_SIG,
        .stacksize = 0,
        .detached  = PTHREAD_CREATE_JOINABLE,
        .inherit   = _PTHREAD_DEFAULT_INHERITSCHED,
        .policy    = _PTHREAD_DEFAULT_POLICY,
        .defaultguardpage = true,
        // compile time constant for _pthread_default_priority(0)
        .qosclass  = (1U << (THREAD_QOS_LEGACY - 1 + _PTHREAD_PRIORITY_QOS_CLASS_SHIFT)) |
                        ((uint8_t)-1 & _PTHREAD_PRIORITY_PRIORITY_MASK),
};

#if PTHREAD_LAYOUT_SPI

const struct pthread_layout_offsets_s pthread_layout_offsets = {
        .plo_version = 1,
        .plo_pthread_tsd_base_offset = offsetof(struct _pthread, tsd),
        .plo_pthread_tsd_base_address_offset = 0,
        .plo_pthread_tsd_entry_size = sizeof(((struct _pthread *)NULL)->tsd[0]),
};

#endif // PTHREAD_LAYOUT_SPI

//
// Global exported variables
//

// This global should be used (carefully) by anyone needing to know if a
// pthread (other than the main thread) has been created.
int __is_threaded = 0;
int __unix_conforming = 0;

//
// Global internal variables
//

// _pthread_list_lock protects _pthread_count, access to the __pthread_head
// list. Externally imported by pthread_cancelable.c.
struct __pthread_list __pthread_head = TAILQ_HEAD_INITIALIZER(__pthread_head);
_pthread_lock _pthread_list_lock = _PTHREAD_LOCK_INITIALIZER;

uint32_t _main_qos;

#if VARIANT_DYLD
// The main thread's pthread_t
struct _pthread _main_thread __attribute__((aligned(64))) = { };
#define main_thread() (&_main_thread)
#else // VARIANT_DYLD
struct _pthread *_main_thread_ptr;
#endif // VARIANT_DYLD

#if PTHREAD_DEBUG_LOG
#include <fcntl.h>
int _pthread_debuglog;
uint64_t _pthread_debugstart;
#endif

//
// Global static variables
//
static bool __workq_newapi;
static uint8_t default_priority;
#if !VARIANT_DYLD
static uint8_t max_priority;
static uint8_t min_priority;
#endif // !VARIANT_DYLD
static int _pthread_count = 1;
static int pthread_concurrency;
static uintptr_t _pthread_ptr_munge_token;

static void (*exitf)(int) = __exit;
#if !VARIANT_DYLD
static void *(*_pthread_malloc)(size_t) = NULL;
static void (*_pthread_free)(void *) = NULL;
#endif // !VARIANT_DYLD

// work queue support data
PTHREAD_NORETURN
static void
__pthread_invalid_keventfunction(void **events, int *nevents)
{
        PTHREAD_CLIENT_CRASH(0, "Invalid kqworkq setup");
}

PTHREAD_NORETURN
static void
__pthread_invalid_workloopfunction(uint64_t *workloop_id, void **events, int *nevents)
{
        PTHREAD_CLIENT_CRASH(0, "Invalid kqwl setup");
}
static pthread_workqueue_function2_t __libdispatch_workerfunction;
static pthread_workqueue_function_kevent_t __libdispatch_keventfunction = &__pthread_invalid_keventfunction;
static pthread_workqueue_function_workloop_t __libdispatch_workloopfunction = &__pthread_invalid_workloopfunction;
static int __libdispatch_offset;
static int __pthread_supported_features; // supported feature set

#if defined(__i386__) || defined(__x86_64__)
static mach_vm_address_t __pthread_stack_hint = 0xB0000000;
#else
#error no __pthread_stack_hint for this architecture
#endif

//
// Function prototypes
//

// pthread primitives
static inline void _pthread_struct_init(pthread_t t, const pthread_attr_t *attrs,
                void *stack, size_t stacksize, void *freeaddr, size_t freesize);

#if VARIANT_DYLD
static void _pthread_set_self_dyld(void);
#endif // VARIANT_DYLD
static inline void _pthread_set_self_internal(pthread_t, bool needs_tsd_base_set);

static void _pthread_dealloc_reply_port(pthread_t t);
static void _pthread_dealloc_special_reply_port(pthread_t t);

static inline void __pthread_started_thread(pthread_t t);

static void _pthread_exit(pthread_t self, void *value_ptr) __dead2;

static inline void _pthread_introspection_thread_create(pthread_t t);
static inline void _pthread_introspection_thread_start(pthread_t t);
static inline void _pthread_introspection_thread_terminate(pthread_t t);
static inline void _pthread_introspection_thread_destroy(pthread_t t);

extern void _pthread_set_self(pthread_t);
extern void start_wqthread(pthread_t self, mach_port_t kport, void *stackaddr, void *unused, int reuse); // trampoline into _pthread_wqthread
extern void thread_start(pthread_t self, mach_port_t kport, void *(*fun)(void *), void * funarg, size_t stacksize, unsigned int flags); // trampoline into _pthread_start

/*
 * Flags filed passed to bsdthread_create and back in pthread_start
 * 31  <---------------------------------> 0
 * _________________________________________
 * | flags(8) | policy(8) | importance(16) |
 * -----------------------------------------
 */
#define PTHREAD_START_CUSTOM            0x01000000 // <rdar://problem/34501401>
#define PTHREAD_START_SETSCHED          0x02000000
// was PTHREAD_START_DETACHED           0x04000000
#define PTHREAD_START_QOSCLASS          0x08000000
#define PTHREAD_START_TSD_BASE_SET      0x10000000
#define PTHREAD_START_SUSPENDED         0x20000000
#define PTHREAD_START_QOSCLASS_MASK 0x00ffffff
#define PTHREAD_START_POLICY_BITSHIFT 16
#define PTHREAD_START_POLICY_MASK 0xff
#define PTHREAD_START_IMPORTANCE_MASK 0xffff

#if (!defined(__OPEN_SOURCE__) && TARGET_OS_OSX) || OS_VARIANT_RESOLVED // 40703288
static int pthread_setschedparam_internal(pthread_t, mach_port_t, int,
                const struct sched_param *);
#endif

extern pthread_t __bsdthread_create(void *(*func)(void *), void * func_arg, void * stack, pthread_t  thread, unsigned int flags);
extern int __bsdthread_register(void (*)(pthread_t, mach_port_t, void *(*)(void *), void *, size_t, unsigned int), void (*)(pthread_t, mach_port_t, void *, void *, int), int,void (*)(pthread_t, mach_port_t, void *(*)(void *), void *, size_t, unsigned int), int32_t *,__uint64_t);
extern int __bsdthread_terminate(void * freeaddr, size_t freesize, mach_port_t kport, mach_port_t joinsem);
extern __uint64_t __thread_selfid( void );

#if __LP64__
_Static_assert(offsetof(struct _pthread, tsd) == 224, "TSD LP64 offset");
#else
_Static_assert(offsetof(struct _pthread, tsd) == 176, "TSD ILP32 offset");
#endif
_Static_assert(offsetof(struct _pthread, tsd) + _PTHREAD_STRUCT_DIRECT_THREADID_OFFSET
                == offsetof(struct _pthread, thread_id),
                "_PTHREAD_STRUCT_DIRECT_THREADID_OFFSET is correct");

#pragma mark pthread attrs

_Static_assert(sizeof(struct _pthread_attr_t) == sizeof(__darwin_pthread_attr_t),
                "internal pthread_attr_t == external pthread_attr_t");

int
pthread_attr_destroy(pthread_attr_t *attr)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG) {
                attr->sig = 0;
                ret = 0;
        }
        return ret;
}

int
pthread_attr_getdetachstate(const pthread_attr_t *attr, int *detachstate)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG) {
                *detachstate = attr->detached;
                ret = 0;
        }
        return ret;
}

int
pthread_attr_getinheritsched(const pthread_attr_t *attr, int *inheritsched)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG) {
                *inheritsched = attr->inherit;
                ret = 0;
        }
        return ret;
}

static PTHREAD_ALWAYS_INLINE void
_pthread_attr_get_schedparam(const pthread_attr_t *attr,
                struct sched_param *param)
{
        if (attr->schedset) {
                *param = attr->param;
        } else {
                param->sched_priority = default_priority;
                param->quantum = 10; /* quantum isn't public yet */
        }
}

int
pthread_attr_getschedparam(const pthread_attr_t *attr, struct sched_param *param)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG) {
                _pthread_attr_get_schedparam(attr, param);
                ret = 0;
        }
        return ret;
}

int
pthread_attr_getschedpolicy(const pthread_attr_t *attr, int *policy)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG) {
                *policy = attr->policy;
                ret = 0;
        }
        return ret;
}

int
pthread_attr_init(pthread_attr_t *attr)
{
        *attr = _pthread_attr_default;
        return 0;
}

int
pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG &&
                        (detachstate == PTHREAD_CREATE_JOINABLE ||
                        detachstate == PTHREAD_CREATE_DETACHED)) {
                attr->detached = detachstate;
                ret = 0;
        }
        return ret;
}

int
pthread_attr_setinheritsched(pthread_attr_t *attr, int inheritsched)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG &&
                        (inheritsched == PTHREAD_INHERIT_SCHED ||
                        inheritsched == PTHREAD_EXPLICIT_SCHED)) {
                attr->inherit = inheritsched;
                ret = 0;
        }
        return ret;
}

int
pthread_attr_setschedparam(pthread_attr_t *attr, const struct sched_param *param)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG) {
                /* TODO: Validate sched_param fields */
                attr->param = *param;
                attr->schedset = 1;
                ret = 0;
        }
        return ret;
}

int
pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG && (policy == SCHED_OTHER ||
                        policy == SCHED_RR || policy == SCHED_FIFO)) {
                if (!_PTHREAD_POLICY_IS_FIXEDPRI(policy)) {
                        /* non-fixedpri policy should remove cpupercent */
                        attr->cpupercentset = 0;
                }
                attr->policy = policy;
                attr->policyset = 1;
                ret = 0;
        }
        return ret;
}

int
pthread_attr_setscope(pthread_attr_t *attr, int scope)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG) {
                if (scope == PTHREAD_SCOPE_SYSTEM) {
                        // No attribute yet for the scope.
                        ret = 0;
                } else if (scope == PTHREAD_SCOPE_PROCESS) {
                        ret = ENOTSUP;
                }
        }
        return ret;
}

int
pthread_attr_getscope(const pthread_attr_t *attr, int *scope)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG) {
                *scope = PTHREAD_SCOPE_SYSTEM;
                ret = 0;
        }
        return ret;
}

int
pthread_attr_getstackaddr(const pthread_attr_t *attr, void **stackaddr)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG) {
                *stackaddr = attr->stackaddr;
                ret = 0;
        }
        return ret;
}

int
pthread_attr_setstackaddr(pthread_attr_t *attr, void *stackaddr)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG &&
                        ((uintptr_t)stackaddr % vm_page_size) == 0) {
                attr->stackaddr = stackaddr;
                attr->defaultguardpage = false;
                attr->guardsize = 0;
                ret = 0;
        }
        return ret;
}

static inline size_t
_pthread_attr_stacksize(const pthread_attr_t *attr)
{
        return attr->stacksize ? attr->stacksize : DEFAULT_STACK_SIZE;
}

int
pthread_attr_getstacksize(const pthread_attr_t *attr, size_t *stacksize)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG) {
                *stacksize = _pthread_attr_stacksize(attr);
                ret = 0;
        }
        return ret;
}

int
pthread_attr_setstacksize(pthread_attr_t *attr, size_t stacksize)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG &&
                        (stacksize % vm_page_size) == 0 &&
                        stacksize >= PTHREAD_STACK_MIN) {
                attr->stacksize = stacksize;
                ret = 0;
        }
        return ret;
}

int
pthread_attr_getstack(const pthread_attr_t *attr, void **stackaddr, size_t * stacksize)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG) {
                *stackaddr = (void *)((uintptr_t)attr->stackaddr - attr->stacksize);
                *stacksize = _pthread_attr_stacksize(attr);
                ret = 0;
        }
        return ret;
}

// Per SUSv3, the stackaddr is the base address, the lowest addressable byte
// address. This is not the same as in pthread_attr_setstackaddr.
int
pthread_attr_setstack(pthread_attr_t *attr, void *stackaddr, size_t stacksize)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG &&
                        ((uintptr_t)stackaddr % vm_page_size) == 0 &&
                        (stacksize % vm_page_size) == 0 &&
                        stacksize >= PTHREAD_STACK_MIN) {
                attr->stackaddr = (void *)((uintptr_t)stackaddr + stacksize);
                attr->stacksize = stacksize;
                ret = 0;
        }
        return ret;
}

int
pthread_attr_setguardsize(pthread_attr_t *attr, size_t guardsize)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG && (guardsize % vm_page_size) == 0) {
                /* Guardsize of 0 is valid, means no guard */
                attr->defaultguardpage = false;
                attr->guardsize = guardsize;
                ret = 0;
        }
        return ret;
}

static inline size_t
_pthread_attr_guardsize(const pthread_attr_t *attr)
{
        return attr->defaultguardpage ? vm_page_size : attr->guardsize;
}

int
pthread_attr_getguardsize(const pthread_attr_t *attr, size_t *guardsize)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG) {
                *guardsize = _pthread_attr_guardsize(attr);
                ret = 0;
        }
        return ret;
}

int
pthread_attr_setcpupercent_np(pthread_attr_t *attr, int percent,
                unsigned long refillms)
{
        int ret = EINVAL;
        if (attr->sig == _PTHREAD_ATTR_SIG && percent < UINT8_MAX &&
                        refillms < _PTHREAD_ATTR_REFILLMS_MAX && attr->policyset &&
                        _PTHREAD_POLICY_IS_FIXEDPRI(attr->policy)) {
                attr->cpupercent = percent;
                attr->refillms = (uint32_t)(refillms & 0x00ffffff);
                attr->cpupercentset = 1;
                ret = 0;
        }
        return ret;
}

#pragma mark pthread lifetime

// Allocate a thread structure, stack and guard page.
//
// The thread structure may optionally be placed in the same allocation as the
// stack, residing above the top of the stack. This cannot be done if a
// custom stack address is provided.
//
// Similarly the guard page cannot be allocated if a custom stack address is
// provided.
//
// The allocated thread structure is initialized with values that indicate how
// it should be freed.

static pthread_t
_pthread_allocate(const pthread_attr_t *attrs, void **stack)
{
        mach_vm_address_t allocaddr = __pthread_stack_hint;
        size_t allocsize, guardsize, stacksize, pthreadoff;
        kern_return_t kr;
        pthread_t t;

        PTHREAD_ASSERT(attrs->stacksize == 0 ||
                        attrs->stacksize >= PTHREAD_STACK_MIN);

        // Allocate a pthread structure if necessary

        if (attrs->stackaddr != NULL) {
                PTHREAD_ASSERT(((uintptr_t)attrs->stackaddr % vm_page_size) == 0);
                allocsize = PTHREAD_SIZE;
                guardsize = 0;
                pthreadoff = 0;
                // <rdar://problem/42588315> if the attrs struct specifies a custom
                // stack address but not a custom size, using ->stacksize here instead
                // of _pthread_attr_stacksize stores stacksize as zero, indicating
                // that the stack size is unknown.
                stacksize = attrs->stacksize;
        } else {
                guardsize = _pthread_attr_guardsize(attrs);
                stacksize = _pthread_attr_stacksize(attrs) + PTHREAD_T_OFFSET;
                pthreadoff = stacksize + guardsize;
                allocsize = pthreadoff + PTHREAD_SIZE;
                allocsize = mach_vm_round_page(allocsize);
        }

        kr = mach_vm_map(mach_task_self(), &allocaddr, allocsize, vm_page_size - 1,
                         VM_MAKE_TAG(VM_MEMORY_STACK)| VM_FLAGS_ANYWHERE, MEMORY_OBJECT_NULL,
                         0, FALSE, VM_PROT_DEFAULT, VM_PROT_ALL, VM_INHERIT_DEFAULT);

        if (kr != KERN_SUCCESS) {
                kr = mach_vm_allocate(mach_task_self(), &allocaddr, allocsize,
                                 VM_MAKE_TAG(VM_MEMORY_STACK)| VM_FLAGS_ANYWHERE);
        }
        if (kr != KERN_SUCCESS) {
                *stack  = NULL;
                return NULL;
        }

        // The stack grows down.
        // Set the guard page at the lowest address of the
        // newly allocated stack. Return the highest address
        // of the stack.
        if (guardsize) {
                (void)mach_vm_protect(mach_task_self(), allocaddr, guardsize,
                                FALSE, VM_PROT_NONE);
        }

        // Thread structure resides at the top of the stack (when using a
        // custom stack, allocsize == PTHREAD_SIZE, so places the pthread_t
        // at allocaddr).
        t = (pthread_t)(allocaddr + pthreadoff);
        if (attrs->stackaddr) {
                *stack = attrs->stackaddr;
        } else {
                *stack = t;
        }

        _pthread_struct_init(t, attrs, *stack, stacksize, allocaddr, allocsize);
        return t;
}

PTHREAD_NOINLINE
void
_pthread_deallocate(pthread_t t, bool from_mach_thread)
{
        kern_return_t ret;

        // Don't free the main thread.
        if (t != main_thread()) {
                if (!from_mach_thread) { // see __pthread_add_thread
                        _pthread_introspection_thread_destroy(t);
                }
                ret = mach_vm_deallocate(mach_task_self(), t->freeaddr, t->freesize);
                PTHREAD_ASSERT(ret == KERN_SUCCESS);
        }
}

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wreturn-stack-address"

PTHREAD_NOINLINE
static void*
_pthread_current_stack_address(void)
{
        int a;
        return &a;
}

#pragma clang diagnostic pop

void
_pthread_joiner_wake(pthread_t thread)
{
        uint32_t *exit_gate = &thread->tl_exit_gate;

        for (;;) {
                int ret = __ulock_wake(UL_UNFAIR_LOCK | ULF_NO_ERRNO, exit_gate, 0);
                if (ret == 0 || ret == -ENOENT) {
                        return;
                }
                if (ret != -EINTR) {
                        PTHREAD_INTERNAL_CRASH(-ret, "pthread_join() wake failure");
                }
        }
}

// Terminates the thread if called from the currently running thread.
PTHREAD_NORETURN PTHREAD_NOINLINE PTHREAD_NOT_TAIL_CALLED
static void
_pthread_terminate(pthread_t t, void *exit_value)
{
        PTHREAD_ASSERT(t == pthread_self());

        _pthread_introspection_thread_terminate(t);

        uintptr_t freeaddr = (uintptr_t)t->freeaddr;
        size_t freesize = t->freesize;
        bool should_exit;

        // the size of just the stack
        size_t freesize_stack = t->freesize;

        // We usually pass our structure+stack to bsdthread_terminate to free, but
        // if we get told to keep the pthread_t structure around then we need to
        // adjust the free size and addr in the pthread_t to just refer to the
        // structure and not the stack.  If we do end up deallocating the
        // structure, this is useless work since no one can read the result, but we
        // can't do it after the call to pthread_remove_thread because it isn't
        // safe to dereference t after that.
        if ((void*)t > t->freeaddr && (void*)t < t->freeaddr + t->freesize){
                // Check to ensure the pthread structure itself is part of the
                // allocation described by freeaddr/freesize, in which case we split and
                // only deallocate the area below the pthread structure.  In the event of a
                // custom stack, the freeaddr/size will be the pthread structure itself, in
                // which case we shouldn't free anything (the final else case).
                freesize_stack = trunc_page((uintptr_t)t - (uintptr_t)freeaddr);

                // describe just the remainder for deallocation when the pthread_t goes away
                t->freeaddr += freesize_stack;
                t->freesize -= freesize_stack;
        } else if (t == main_thread()) {
                freeaddr = t->stackaddr - pthread_get_stacksize_np(t);
                uintptr_t stackborder = trunc_page((uintptr_t)_pthread_current_stack_address());
                freesize_stack = stackborder - freeaddr;
        } else {
                freesize_stack = 0;
        }

        mach_port_t kport = _pthread_kernel_thread(t);
        bool keep_thread_struct = false, needs_wake = false;
        semaphore_t custom_stack_sema = MACH_PORT_NULL;

        _pthread_dealloc_special_reply_port(t);
        _pthread_dealloc_reply_port(t);

        _PTHREAD_LOCK(_pthread_list_lock);

        // This piece of code interacts with pthread_join. It will always:
        // - set tl_exit_gate to MACH_PORT_DEAD (thread exited)
        // - set tl_exit_value to the value passed to pthread_exit()
        // - decrement _pthread_count, so that we can exit the process when all
        //   threads exited even if not all of them were joined.
        t->tl_exit_gate = MACH_PORT_DEAD;
        t->tl_exit_value = exit_value;
        should_exit = (--_pthread_count <= 0);

        // If we see a joiner, we prepost that the join has to succeed,
        // and the joiner is committed to finish (even if it was canceled)
        if (t->tl_join_ctx) {
                custom_stack_sema = _pthread_joiner_prepost_wake(t); // unsets tl_joinable
                needs_wake = true;
        }

        // Joinable threads that have no joiner yet are kept on the thread list
        // so that pthread_join() can later discover the thread when it is joined,
        // and will have to do the pthread_t cleanup.
        if (t->tl_joinable) {
                t->tl_joiner_cleans_up = keep_thread_struct = true;
        } else {
                TAILQ_REMOVE(&__pthread_head, t, tl_plist);
        }

        _PTHREAD_UNLOCK(_pthread_list_lock);

        if (needs_wake) {
                // When we found a waiter, we want to drop the very contended list lock
                // before we do the syscall in _pthread_joiner_wake(). Then, we decide
                // who gets to cleanup the pthread_t between the joiner and the exiting
                // thread:
                // - the joiner tries to set tl_join_ctx to NULL
                // - the exiting thread tries to set tl_joiner_cleans_up to true
                // Whoever does it first commits the other guy to cleanup the pthread_t
                _pthread_joiner_wake(t);
                _PTHREAD_LOCK(_pthread_list_lock);
                if (t->tl_join_ctx) {
                        t->tl_joiner_cleans_up = true;
                        keep_thread_struct = true;
                }
                _PTHREAD_UNLOCK(_pthread_list_lock);
        }

        //
        // /!\ dereferencing `t` past this point is not safe /!\
        //

        if (keep_thread_struct || t == main_thread()) {
                // Use the adjusted freesize of just the stack that we computed above.
                freesize = freesize_stack;
        } else {
                _pthread_introspection_thread_destroy(t);
        }

        // Check if there is nothing to free because the thread has a custom
        // stack allocation and is joinable.
        if (freesize == 0) {
                freeaddr = 0;
        }
        if (should_exit) {
                exitf(0);
        }
        __bsdthread_terminate((void *)freeaddr, freesize, kport, custom_stack_sema);
        PTHREAD_INTERNAL_CRASH(t, "thread didn't terminate");
}

PTHREAD_NORETURN
static void
_pthread_terminate_invoke(pthread_t t, void *exit_value)
{
#if PTHREAD_T_OFFSET
        void *p = NULL;
        // <rdar://problem/25688492> During pthread termination there is a race
        // between pthread_join and pthread_terminate; if the joiner is responsible
        // for cleaning up the pthread_t struct, then it may destroy some part of the
        // stack with it on 16k OSes. So that this doesn't cause _pthread_terminate()
        // to crash because its stack has been removed from under its feet, just make
        // sure termination happens in a part of the stack that is not on the same
        // page as the pthread_t.
        if (trunc_page((uintptr_t)__builtin_frame_address(0)) ==
                        trunc_page((uintptr_t)t)) {
                p = alloca(PTHREAD_T_OFFSET);
        }
        // And this __asm__ volatile is needed to stop the compiler from optimising
        // away the alloca() completely.
        __asm__ volatile ("" : : "r"(p) );
#endif
        _pthread_terminate(t, exit_value);
}

#pragma mark pthread start / body

/*
 * Create and start execution of a new thread.
 */
PTHREAD_NOINLINE PTHREAD_NORETURN
static void
_pthread_body(pthread_t self, bool needs_tsd_base_set)
{
        _pthread_set_self_internal(self, needs_tsd_base_set);
        __pthread_started_thread(self);
        _pthread_exit(self, (self->fun)(self->arg));
}

PTHREAD_NORETURN
void
_pthread_start(pthread_t self, mach_port_t kport,
                __unused void *(*fun)(void *), __unused void *arg,
                __unused size_t stacksize, unsigned int pflags)
{
        bool thread_tsd_bsd_set = (bool)(pflags & PTHREAD_START_TSD_BASE_SET);

        if (os_unlikely(pflags & PTHREAD_START_SUSPENDED)) {
                PTHREAD_INTERNAL_CRASH(0,
                                "kernel without PTHREAD_START_SUSPENDED support");
        }
#if DEBUG
        PTHREAD_ASSERT(MACH_PORT_VALID(kport));
        PTHREAD_ASSERT(_pthread_kernel_thread(self) == kport);
#endif
        // will mark the thread initialized
        _pthread_markcancel_if_canceled(self, kport);

        _pthread_body(self, !thread_tsd_bsd_set);
}

PTHREAD_ALWAYS_INLINE
static inline void
_pthread_struct_init(pthread_t t, const pthread_attr_t *attrs,
                void *stackaddr, size_t stacksize, void *freeaddr, size_t freesize)
{
#if DEBUG
        PTHREAD_ASSERT(t->sig != _PTHREAD_SIG);
#endif

        t->sig = _PTHREAD_SIG;
        t->tsd[_PTHREAD_TSD_SLOT_PTHREAD_SELF] = t;
        t->tsd[_PTHREAD_TSD_SLOT_ERRNO] = &t->err_no;
        if (attrs->schedset == 0) {
                t->tsd[_PTHREAD_TSD_SLOT_PTHREAD_QOS_CLASS] = attrs->qosclass;
        } else {
                t->tsd[_PTHREAD_TSD_SLOT_PTHREAD_QOS_CLASS] =
                                _pthread_unspecified_priority();
        }
        t->tsd[_PTHREAD_TSD_SLOT_PTR_MUNGE] = _pthread_ptr_munge_token;
        t->tl_has_custom_stack = (attrs->stackaddr != NULL);

        _PTHREAD_LOCK_INIT(t->lock);

        t->stackaddr = stackaddr;
        t->stackbottom = stackaddr - stacksize;
        t->freeaddr = freeaddr;
        t->freesize = freesize;

        t->guardsize = _pthread_attr_guardsize(attrs);
        t->tl_joinable = (attrs->detached == PTHREAD_CREATE_JOINABLE);
        t->inherit = attrs->inherit;
        t->tl_policy = attrs->policy;
        t->schedset = attrs->schedset;
        _pthread_attr_get_schedparam(attrs, &t->tl_param);
        t->cancel_state = PTHREAD_CANCEL_ENABLE | PTHREAD_CANCEL_DEFERRED;
}

#pragma mark pthread public interface

/* Need to deprecate this in future */
int
_pthread_is_threaded(void)
{
        return __is_threaded;
}

/* Non portable public api to know whether this process has(had) atleast one thread
 * apart from main thread. There could be race if there is a thread in the process of
 * creation at the time of call . It does not tell whether there are more than one thread
 * at this point of time.
 */
int
pthread_is_threaded_np(void)
{
        return __is_threaded;
}


PTHREAD_NOEXPORT_VARIANT
mach_port_t
pthread_mach_thread_np(pthread_t t)
{
        mach_port_t kport = MACH_PORT_NULL;
        (void)_pthread_is_valid(t, &kport);
        return kport;
}

PTHREAD_NOEXPORT_VARIANT
pthread_t
pthread_from_mach_thread_np(mach_port_t kernel_thread)
{
        struct _pthread *p = NULL;

        /* No need to wait as mach port is already known */
        _PTHREAD_LOCK(_pthread_list_lock);

        TAILQ_FOREACH(p, &__pthread_head, tl_plist) {
                if (_pthread_kernel_thread(p) == kernel_thread) {
                        break;
                }
        }

        _PTHREAD_UNLOCK(_pthread_list_lock);

        return p;
}

PTHREAD_NOEXPORT_VARIANT
size_t
pthread_get_stacksize_np(pthread_t t)
{
        size_t size = 0;
        size_t stacksize = t->stackaddr - t->stackbottom;

        if (t == NULL) {
                return ESRCH; // XXX bug?
        }

#if !defined(__arm__) && !defined(__arm64__)
        // The default rlimit based allocations will be provided with a stacksize
        // of the current limit and a freesize of the max.  However, custom
        // allocations will just have the guard page to free.  If we aren't in the
        // latter case, call into rlimit to determine the current stack size.  In
        // the event that the current limit == max limit then we'll fall down the
        // fast path, but since it's unlikely that the limit is going to be lowered
        // after it's been change to the max, we should be fine.
        //
        // Of course, on arm rlim_cur == rlim_max and there's only the one guard
        // page.  So, we can skip all this there.
        if (t == main_thread() && stacksize + vm_page_size != t->freesize) {
                // We want to call getrlimit() just once, as it's relatively expensive
                static size_t rlimit_stack;

                if (rlimit_stack == 0) {
                        struct rlimit limit;
                        int ret = getrlimit(RLIMIT_STACK, &limit);

                        if (ret == 0) {
                                rlimit_stack = (size_t) limit.rlim_cur;
                        }
                }

                if (rlimit_stack == 0 || rlimit_stack > t->freesize) {
                        return stacksize;
                } else {
                        return rlimit_stack;
                }
        }
#endif /* !defined(__arm__) && !defined(__arm64__) */

        if (t == pthread_self() || t == main_thread()) {
                size = stacksize;
                goto out;
        }

        if (_pthread_validate_thread_and_list_lock(t)) {
                size = stacksize;
                _PTHREAD_UNLOCK(_pthread_list_lock);
        } else {
                size = ESRCH; // XXX bug?
        }

out:
        // <rdar://problem/42588315> binary compatibility issues force us to return
        // DEFAULT_STACK_SIZE here when we do not know the size of the stack
        return size ? size : DEFAULT_STACK_SIZE;
}

PTHREAD_NOEXPORT_VARIANT
void *
pthread_get_stackaddr_np(pthread_t t)
{
        // since the main thread will not get de-allocated from underneath us
        if (t == pthread_self() || t == main_thread()) {
                return t->stackaddr;
        }

        if (!_pthread_validate_thread_and_list_lock(t)) {
                return (void *)(uintptr_t)ESRCH; // XXX bug?
        }

        void *addr = t->stackaddr;
        _PTHREAD_UNLOCK(_pthread_list_lock);
        return addr;
}


static mach_port_t
_pthread_reply_port(pthread_t t)
{
        void *p;
        if (t == NULL) {
                p = _pthread_getspecific_direct(_PTHREAD_TSD_SLOT_MIG_REPLY);
        } else {
                p = t->tsd[_PTHREAD_TSD_SLOT_MIG_REPLY];
        }
        return (mach_port_t)(uintptr_t)p;
}

static void
_pthread_set_reply_port(pthread_t t, mach_port_t reply_port)
{
        void *p = (void *)(uintptr_t)reply_port;
        if (t == NULL) {
                _pthread_setspecific_direct(_PTHREAD_TSD_SLOT_MIG_REPLY, p);
        } else {
                t->tsd[_PTHREAD_TSD_SLOT_MIG_REPLY] = p;
        }
}

static void
_pthread_dealloc_reply_port(pthread_t t)
{
        mach_port_t reply_port = _pthread_reply_port(t);
        if (reply_port != MACH_PORT_NULL) {
                mig_dealloc_reply_port(reply_port);
        }
}

static mach_port_t
_pthread_special_reply_port(pthread_t t)
{
        void *p;
        if (t == NULL) {
                p = _pthread_getspecific_direct(_PTHREAD_TSD_SLOT_MACH_SPECIAL_REPLY);
        } else {
                p = t->tsd[_PTHREAD_TSD_SLOT_MACH_SPECIAL_REPLY];
        }
        return (mach_port_t)(uintptr_t)p;
}

static void
_pthread_dealloc_special_reply_port(pthread_t t)
{
        mach_port_t special_reply_port = _pthread_special_reply_port(t);
        if (special_reply_port != MACH_PORT_NULL) {
                thread_destruct_special_reply_port(special_reply_port,
                                THREAD_SPECIAL_REPLY_PORT_ALL);
        }
}

pthread_t
pthread_main_thread_np(void)
{
        return main_thread();
}

/* returns non-zero if the current thread is the main thread */
int
pthread_main_np(void)
{
        return pthread_self() == main_thread();
}


/*
 * if we are passed in a pthread_t that is NULL, then we return the current
 * thread's thread_id. So folks don't have to call pthread_self, in addition to
 * us doing it, if they just want their thread_id.
 */
PTHREAD_NOEXPORT_VARIANT
int
pthread_threadid_np(pthread_t thread, uint64_t *thread_id)
{
        int res = 0;
        pthread_t self = pthread_self();

        if (thread_id == NULL) {
                return EINVAL;
        }

        if (thread == NULL || thread == self) {
                *thread_id = self->thread_id;
        } else if (!_pthread_validate_thread_and_list_lock(thread)) {
                res = ESRCH;
        } else {
                if (thread->thread_id == 0) {
                        res = EINVAL;
                } else {
                        *thread_id = thread->thread_id;
                }
                _PTHREAD_UNLOCK(_pthread_list_lock);
        }
        return res;
}

PTHREAD_NOEXPORT_VARIANT
int
pthread_getname_np(pthread_t thread, char *threadname, size_t len)
{
        if (thread == pthread_self()) {
                strlcpy(threadname, thread->pthread_name, len);
                return 0;
        }

        if (!_pthread_validate_thread_and_list_lock(thread)) {
                return ESRCH;
        }

        strlcpy(threadname, thread->pthread_name, len);
        _PTHREAD_UNLOCK(_pthread_list_lock);
        return 0;
}


int
pthread_setname_np(const char *name)
{
        int res;
        pthread_t self = pthread_self();

        size_t len = 0;
        if (name != NULL) {
                len = strlen(name);
        }

        /* protytype is in pthread_internals.h */
        res = __proc_info(5, getpid(), 2, (uint64_t)0, (void*)name, (int)len);
        if (res == 0) {
                if (len > 0) {
                        strlcpy(self->pthread_name, name, MAXTHREADNAMESIZE);
                } else {
                        bzero(self->pthread_name, MAXTHREADNAMESIZE);
                }
        }
        return res;

}

PTHREAD_ALWAYS_INLINE
static inline void
__pthread_add_thread(pthread_t t, bool from_mach_thread)
{
        if (from_mach_thread) {
                _PTHREAD_LOCK_FROM_MACH_THREAD(_pthread_list_lock);
        } else {
                _PTHREAD_LOCK(_pthread_list_lock);
        }

        TAILQ_INSERT_TAIL(&__pthread_head, t, tl_plist);
        _pthread_count++;

        if (from_mach_thread) {
                _PTHREAD_UNLOCK_FROM_MACH_THREAD(_pthread_list_lock);
        } else {
                _PTHREAD_UNLOCK(_pthread_list_lock);
        }

        if (!from_mach_thread) {
                // PR-26275485: Mach threads will likely crash trying to run
                // introspection code.  Since the fall out from the introspection
                // code not seeing the injected thread is likely less than crashing
                // in the introspection code, just don't make the call.
                _pthread_introspection_thread_create(t);
        }
}

PTHREAD_ALWAYS_INLINE
static inline void
__pthread_undo_add_thread(pthread_t t, bool from_mach_thread)
{
        if (from_mach_thread) {
                _PTHREAD_LOCK_FROM_MACH_THREAD(_pthread_list_lock);
        } else {
                _PTHREAD_LOCK(_pthread_list_lock);
        }

        TAILQ_REMOVE(&__pthread_head, t, tl_plist);
        _pthread_count--;

        if (from_mach_thread) {
                _PTHREAD_UNLOCK_FROM_MACH_THREAD(_pthread_list_lock);
        } else {
                _PTHREAD_UNLOCK(_pthread_list_lock);
        }
}

PTHREAD_ALWAYS_INLINE
static inline void
__pthread_started_thread(pthread_t t)
{
        mach_port_t kport = _pthread_kernel_thread(t);
        if (os_slowpath(!MACH_PORT_VALID(kport))) {
                PTHREAD_CLIENT_CRASH(kport,
                                "Unable to allocate thread port, possible port leak");
        }
        _pthread_introspection_thread_start(t);
}

#define _PTHREAD_CREATE_NONE              0x0
#define _PTHREAD_CREATE_FROM_MACH_THREAD  0x1
#define _PTHREAD_CREATE_SUSPENDED         0x2

static int
_pthread_create(pthread_t *thread, const pthread_attr_t *attrs,
                void *(*start_routine)(void *), void *arg, unsigned int create_flags)
{
        pthread_t t = NULL;
        void *stack = NULL;
        bool from_mach_thread = (create_flags & _PTHREAD_CREATE_FROM_MACH_THREAD);

        if (attrs == NULL) {
                attrs = &_pthread_attr_default;
        } else if (attrs->sig != _PTHREAD_ATTR_SIG) {
                return EINVAL;
        }

        unsigned int flags = PTHREAD_START_CUSTOM;
        if (attrs->schedset != 0) {
                struct sched_param p;
                _pthread_attr_get_schedparam(attrs, &p);
                flags |= PTHREAD_START_SETSCHED;
                flags |= ((attrs->policy & PTHREAD_START_POLICY_MASK) << PTHREAD_START_POLICY_BITSHIFT);
                flags |= (p.sched_priority & PTHREAD_START_IMPORTANCE_MASK);
        } else if (attrs->qosclass != 0) {
                flags |= PTHREAD_START_QOSCLASS;
                flags |= (attrs->qosclass & PTHREAD_START_QOSCLASS_MASK);
        }
        if (create_flags & _PTHREAD_CREATE_SUSPENDED) {
                flags |= PTHREAD_START_SUSPENDED;
        }

        __is_threaded = 1;

        t =_pthread_allocate(attrs, &stack);
        if (t == NULL) {
                return EAGAIN;
        }

        t->arg = arg;
        t->fun = start_routine;
        __pthread_add_thread(t, from_mach_thread);

        if (__bsdthread_create(start_routine, arg, stack, t, flags) ==
                        (pthread_t)-1) {
                if (errno == EMFILE) {
                        PTHREAD_CLIENT_CRASH(0,
                                        "Unable to allocate thread port, possible port leak");
                }
                __pthread_undo_add_thread(t, from_mach_thread);
                _pthread_deallocate(t, from_mach_thread);
                return EAGAIN;
        }

        if (create_flags & _PTHREAD_CREATE_SUSPENDED) {
                _pthread_markcancel_if_canceled(t, _pthread_kernel_thread(t));
        }

        // n.b. if a thread is created detached and exits, t will be invalid
        *thread = t;
        return 0;
}

int
pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                void *(*start_routine)(void *), void *arg)
{
        unsigned int flags = _PTHREAD_CREATE_NONE;
        return _pthread_create(thread, attr, start_routine, arg, flags);
}

int
pthread_create_from_mach_thread(pthread_t *thread, const pthread_attr_t *attr,
                void *(*start_routine)(void *), void *arg)
{
        unsigned int flags = _PTHREAD_CREATE_FROM_MACH_THREAD;
        return _pthread_create(thread, attr, start_routine, arg, flags);
}

#if !defined(__OPEN_SOURCE__) && TARGET_OS_OSX // 40703288
/* Functions defined in machine-dependent files. */
PTHREAD_NOEXPORT void _pthread_setup_suspended(pthread_t th, void (*f)(pthread_t), void *sp);

PTHREAD_NORETURN
static void
_pthread_suspended_body(pthread_t self)
{
        _pthread_set_self(self);
        __pthread_started_thread(self);
        _pthread_exit(self, (self->fun)(self->arg));
}

static int
_pthread_create_suspended_np(pthread_t *thread, const pthread_attr_t *attrs,
                void *(*start_routine)(void *), void *arg)
{
        pthread_t t;
        void *stack;
        mach_port_t kernel_thread = MACH_PORT_NULL;

        if (attrs == NULL) {
                attrs = &_pthread_attr_default;
        } else if (attrs->sig != _PTHREAD_ATTR_SIG) {
                return EINVAL;
        }

        t = _pthread_allocate(attrs, &stack);
        if (t == NULL) {
                return EAGAIN;
        }

        if (thread_create(mach_task_self(), &kernel_thread) != KERN_SUCCESS) {
                _pthread_deallocate(t, false);
                return EAGAIN;
        }

        _pthread_set_kernel_thread(t, kernel_thread);
        (void)pthread_setschedparam_internal(t, kernel_thread,
                        t->tl_policy, &t->tl_param);

        __is_threaded = 1;

        t->arg = arg;
        t->fun = start_routine;
        t->cancel_state |= _PTHREAD_CANCEL_INITIALIZED;
        __pthread_add_thread(t, false);

        // Set up a suspended thread.
        _pthread_setup_suspended(t, _pthread_suspended_body, stack);
        *thread = t;
        return 0;
}
#endif // !defined(__OPEN_SOURCE__) && TARGET_OS_OSX

int
pthread_create_suspended_np(pthread_t *thread, const pthread_attr_t *attr,
                void *(*start_routine)(void *), void *arg)
{
#if !defined(__OPEN_SOURCE__) && TARGET_OS_OSX // 40703288
        if (_os_xbs_chrooted) {
                return _pthread_create_suspended_np(thread, attr, start_routine, arg);
        }
#endif
        unsigned int flags = _PTHREAD_CREATE_SUSPENDED;
        return _pthread_create(thread, attr, start_routine, arg, flags);
}


PTHREAD_NOEXPORT_VARIANT
int
pthread_detach(pthread_t thread)
{
        int res = 0;
        bool join = false, wake = false;

        if (!_pthread_validate_thread_and_list_lock(thread)) {
                return ESRCH;
        }

        if (!thread->tl_joinable) {
                res = EINVAL;
        } else if (thread->tl_exit_gate == MACH_PORT_DEAD) {
                // Join the thread if it's already exited.
                join = true;
        } else {
                thread->tl_joinable = false; // _pthread_joiner_prepost_wake uses this
                if (thread->tl_join_ctx) {
                        (void)_pthread_joiner_prepost_wake(thread);
                        wake = true;
                }
        }
        _PTHREAD_UNLOCK(_pthread_list_lock);

        if (join) {
                pthread_join(thread, NULL);
        } else if (wake) {
                _pthread_joiner_wake(thread);
        }
        return res;
}

PTHREAD_NOEXPORT_VARIANT
int
pthread_kill(pthread_t th, int sig)
{
        if (sig < 0 || sig > NSIG) {
                return EINVAL;
        }

        mach_port_t kport = MACH_PORT_NULL;
        if (!_pthread_is_valid(th, &kport)) {
                return ESRCH; // Not a valid thread.
        }

        // Don't signal workqueue threads.
        if (th->wqthread != 0 && th->wqkillset == 0) {
                return ENOTSUP;
        }

        int ret = __pthread_kill(kport, sig);

        if (ret == -1) {
                ret = errno;
        }
        return ret;
}

PTHREAD_NOEXPORT_VARIANT
int
__pthread_workqueue_setkill(int enable)
{
        pthread_t self = pthread_self();

        _PTHREAD_LOCK(self->lock);
        self->wqkillset = enable ? 1 : 0;
        _PTHREAD_UNLOCK(self->lock);

        return 0;
}


/* For compatibility... */

pthread_t
_pthread_self(void)
{
        return pthread_self();
}

/*
 * Terminate a thread.
 */
extern int __disable_threadsignal(int);

PTHREAD_NORETURN
static void
_pthread_exit(pthread_t self, void *exit_value)
{
        struct __darwin_pthread_handler_rec *handler;

        // Disable signal delivery while we clean up
        __disable_threadsignal(1);

        // Set cancel state to disable and type to deferred
        _pthread_setcancelstate_exit(self, exit_value);

        while ((handler = self->__cleanup_stack) != 0) {
                (handler->__routine)(handler->__arg);
                self->__cleanup_stack = handler->__next;
        }
        _pthread_tsd_cleanup(self);

        // Clear per-thread semaphore cache
        os_put_cached_semaphore(SEMAPHORE_NULL);

        _pthread_terminate_invoke(self, exit_value);
}

void
pthread_exit(void *exit_value)
{
        pthread_t self = pthread_self();
        if (os_unlikely(self->wqthread)) {
                PTHREAD_CLIENT_CRASH(0, "pthread_exit() called from a thread "
                                "not created by pthread_create()");
        }
        _pthread_exit(self, exit_value);
}


PTHREAD_NOEXPORT_VARIANT
int
pthread_getschedparam(pthread_t thread, int *policy, struct sched_param *param)
{
        if (!_pthread_validate_thread_and_list_lock(thread)) {
                return ESRCH;
        }

        if (policy) *policy = thread->tl_policy;
        if (param) *param = thread->tl_param;
        _PTHREAD_UNLOCK(_pthread_list_lock);
        return 0;
}



PTHREAD_ALWAYS_INLINE
static inline int
pthread_setschedparam_internal(pthread_t thread, mach_port_t kport, int policy,
                const struct sched_param *param)
{
        policy_base_data_t bases;
        policy_base_t base;
        mach_msg_type_number_t count;
        kern_return_t ret;

        switch (policy) {
                case SCHED_OTHER:
                        bases.ts.base_priority = param->sched_priority;
                        base = (policy_base_t)&bases.ts;
                        count = POLICY_TIMESHARE_BASE_COUNT;
                        break;
                case SCHED_FIFO:
                        bases.fifo.base_priority = param->sched_priority;
                        base = (policy_base_t)&bases.fifo;
                        count = POLICY_FIFO_BASE_COUNT;
                        break;
                case SCHED_RR:
                        bases.rr.base_priority = param->sched_priority;
                        /* quantum isn't public yet */
                        bases.rr.quantum = param->quantum;
                        base = (policy_base_t)&bases.rr;
                        count = POLICY_RR_BASE_COUNT;
                        break;
                default:
                        return EINVAL;
        }
        ret = thread_policy(kport, policy, base, count, TRUE);
        return (ret != KERN_SUCCESS) ? EINVAL : 0;
}

PTHREAD_NOEXPORT_VARIANT
int
pthread_setschedparam(pthread_t t, int policy, const struct sched_param *param)
{
        mach_port_t kport = MACH_PORT_NULL;
        int bypass = 1;

        // since the main thread will not get de-allocated from underneath us
        if (t == pthread_self() || t == main_thread()) {
                kport = _pthread_kernel_thread(t);
        } else {
                bypass = 0;
                if (!_pthread_is_valid(t, &kport)) {
                        return ESRCH;
                }
        }

        int res = pthread_setschedparam_internal(t, kport, policy, param);
        if (res) return res;

        if (bypass) {
                _PTHREAD_LOCK(_pthread_list_lock);
        } else if (!_pthread_validate_thread_and_list_lock(t)) {
                // Ensure the thread is still valid.
                return ESRCH;
        }

        t->tl_policy = policy;
        t->tl_param = *param;
        _PTHREAD_UNLOCK(_pthread_list_lock);
        return 0;
}


int
sched_get_priority_min(int policy)
{
        return default_priority - 16;
}

int
sched_get_priority_max(int policy)
{
        return default_priority + 16;
}

int
pthread_equal(pthread_t t1, pthread_t t2)
{
        return (t1 == t2);
}

/*
 * Force LLVM not to optimise this to a call to __pthread_set_self, if it does
 * then _pthread_set_self won't be bound when secondary threads try and start up.
 */
PTHREAD_NOINLINE
void
_pthread_set_self(pthread_t p)
{
#if VARIANT_DYLD
        if (os_likely(!p)) {
                return _pthread_set_self_dyld();
        }
#endif // VARIANT_DYLD
        _pthread_set_self_internal(p, true);
}

#if VARIANT_DYLD
// _pthread_set_self_dyld is noinline+noexport to allow the option for
// static libsyscall to adopt this as the entry point from mach_init if
// desired
PTHREAD_NOINLINE PTHREAD_NOEXPORT
void
_pthread_set_self_dyld(void)
{
        pthread_t p = main_thread();
        p->thread_id = __thread_selfid();

        if (os_unlikely(p->thread_id == -1ull)) {
                PTHREAD_INTERNAL_CRASH(0, "failed to set thread_id");
        }

        // <rdar://problem/40930651> pthread self and the errno address are the
        // bare minimium TSD setup that dyld needs to actually function.  Without
        // this, TSD access will fail and crash if it uses bits of Libc prior to
        // library initialization. __pthread_init will finish the initialization
        // during library init.
        p->tsd[_PTHREAD_TSD_SLOT_PTHREAD_SELF] = p;
        p->tsd[_PTHREAD_TSD_SLOT_ERRNO] = &p->err_no;
        _thread_set_tsd_base(&p->tsd[0]);
}
#endif // VARIANT_DYLD

PTHREAD_ALWAYS_INLINE
static inline void
_pthread_set_self_internal(pthread_t p, bool needs_tsd_base_set)
{
        p->thread_id = __thread_selfid();

        if (os_unlikely(p->thread_id == -1ull)) {
                PTHREAD_INTERNAL_CRASH(0, "failed to set thread_id");
        }

        if (needs_tsd_base_set) {
                _thread_set_tsd_base(&p->tsd[0]);
        }
}


// <rdar://problem/28984807> pthread_once should have an acquire barrier
PTHREAD_ALWAYS_INLINE
static inline void
_os_once_acquire(os_once_t *predicate, void *context, os_function_t function)
{
        if (OS_EXPECT(os_atomic_load(predicate, acquire), ~0l) != ~0l) {
                _os_once(predicate, context, function);
                OS_COMPILER_CAN_ASSUME(*predicate == ~0l);
        }
}

struct _pthread_once_context {
        pthread_once_t *pthread_once;
        void (*routine)(void);
};

static void
__pthread_once_handler(void *context)
{
        struct _pthread_once_context *ctx = context;
        pthread_cleanup_push((void*)__os_once_reset, &ctx->pthread_once->once);
        ctx->routine();
        pthread_cleanup_pop(0);
        ctx->pthread_once->sig = _PTHREAD_ONCE_SIG;
}

PTHREAD_NOEXPORT_VARIANT
int
pthread_once(pthread_once_t *once_control, void (*init_routine)(void))
{
        struct _pthread_once_context ctx = { once_control, init_routine };
        do {
                _os_once_acquire(&once_control->once, &ctx, __pthread_once_handler);
        } while (once_control->sig == _PTHREAD_ONCE_SIG_init);
        return 0;
}


int
pthread_getconcurrency(void)
{
        return pthread_concurrency;
}

int
pthread_setconcurrency(int new_level)
{
        if (new_level < 0) {
                return EINVAL;
        }
        pthread_concurrency = new_level;
        return 0;
}

#if !defined(VARIANT_STATIC)
void *
malloc(size_t sz)
{
        if (_pthread_malloc) {
                return _pthread_malloc(sz);
        } else {
                return NULL;
        }
}

void
free(void *p)
{
        if (_pthread_free) {
                _pthread_free(p);
        }
}
#endif // VARIANT_STATIC

/*
 * Perform package initialization - called automatically when application starts
 */
struct ProgramVars; /* forward reference */

#if !VARIANT_DYLD
static unsigned long
_pthread_strtoul(const char *p, const char **endptr, int base)
{
        uintptr_t val = 0;

        // Expect hex string starting with "0x"
        if ((base == 16 || base == 0) && p && p[0] == '0' && p[1] == 'x') {
                p += 2;
                while (1) {
                        char c = *p;
                        if ('0' <= c && c <= '9') {
                                val = (val << 4) + (c - '0');
                        } else if ('a' <= c && c <= 'f') {
                                val = (val << 4) + (c - 'a' + 10);
                        } else if ('A' <= c && c <= 'F') {
                                val = (val << 4) + (c - 'A' + 10);
                        } else {
                                break;
                        }
                        ++p;
                }
        }

        *endptr = (char *)p;
        return val;
}

static int
parse_main_stack_params(const char *apple[],
                        void **stackaddr,
                        size_t *stacksize,
                        void **allocaddr,
                        size_t *allocsize)
{
        const char *p = _simple_getenv(apple, "main_stack");
        if (!p) return 0;

        int ret = 0;
        const char *s = p;

        *stackaddr = _pthread_strtoul(s, &s, 16);
        if (*s != ',') goto out;

        *stacksize = _pthread_strtoul(s + 1, &s, 16);
        if (*s != ',') goto out;

        *allocaddr = _pthread_strtoul(s + 1, &s, 16);
        if (*s != ',') goto out;

        *allocsize = _pthread_strtoul(s + 1, &s, 16);
        if (*s != ',' && *s != 0) goto out;

        ret = 1;
out:
        bzero((char *)p, strlen(p));
        return ret;
}

static void
parse_ptr_munge_params(const char *envp[], const char *apple[])
{
        const char *p, *s;
        p = _simple_getenv(apple, "ptr_munge");
        if (p) {
                _pthread_ptr_munge_token = _pthread_strtoul(p, &s, 16);
                bzero((char *)p, strlen(p));
        }
#if !DEBUG
        if (_pthread_ptr_munge_token) return;
#endif
        p = _simple_getenv(envp, "PTHREAD_PTR_MUNGE_TOKEN");
        if (p) {
                uintptr_t t = _pthread_strtoul(p, &s, 16);
                if (t) _pthread_ptr_munge_token = t;
        }
}

int
__pthread_init(const struct _libpthread_functions *pthread_funcs,
                const char *envp[], const char *apple[],
                const struct ProgramVars *vars __unused)
{
        // Save our provided pushed-down functions
        if (pthread_funcs) {
                exitf = pthread_funcs->exit;

                if (pthread_funcs->version >= 2) {
                        _pthread_malloc = pthread_funcs->malloc;
                        _pthread_free = pthread_funcs->free;
                }
        }

        //
        // Get host information
        //

        kern_return_t kr;
        host_flavor_t flavor = HOST_PRIORITY_INFO;
        mach_msg_type_number_t count = HOST_PRIORITY_INFO_COUNT;
        host_priority_info_data_t priority_info;
        host_t host = mach_host_self();
        kr = host_info(host, flavor, (host_info_t)&priority_info, &count);
        if (kr != KERN_SUCCESS) {
                PTHREAD_INTERNAL_CRASH(kr, "host_info() failed");
        } else {
                default_priority = (uint8_t)priority_info.user_priority;
                min_priority = (uint8_t)priority_info.minimum_priority;
                max_priority = (uint8_t)priority_info.maximum_priority;
        }
        mach_port_deallocate(mach_task_self(), host);

        //
        // Set up the main thread structure
        //

        // Get the address and size of the main thread's stack from the kernel.
        void *stackaddr = 0;
        size_t stacksize = 0;
        void *allocaddr = 0;
        size_t allocsize = 0;
        if (!parse_main_stack_params(apple, &stackaddr, &stacksize, &allocaddr, &allocsize) ||
                stackaddr == NULL || stacksize == 0) {
                // Fall back to previous bevhaior.
                size_t len = sizeof(stackaddr);
                int mib[] = { CTL_KERN, KERN_USRSTACK };
                if (__sysctl(mib, 2, &stackaddr, &len, NULL, 0) != 0) {
#if defined(__LP64__)
                        stackaddr = (void *)USRSTACK64;
#else
                        stackaddr = (void *)USRSTACK;
#endif
                }
                stacksize = DFLSSIZ;
                allocaddr = 0;
                allocsize = 0;
        }

        // Initialize random ptr_munge token from the kernel.
        parse_ptr_munge_params(envp, apple);

        // libpthread.a in dyld "owns" the main thread structure itself and sets
        // up the tsd to point to it. So take the pthread_self() from there
        // and make it our main thread point.
        pthread_t thread = (pthread_t)_pthread_getspecific_direct(
                        _PTHREAD_TSD_SLOT_PTHREAD_SELF);
        PTHREAD_ASSERT(thread);
        _main_thread_ptr = thread;

        PTHREAD_ASSERT(_pthread_attr_default.qosclass ==
                        _pthread_default_priority(0));
        _pthread_struct_init(thread, &_pthread_attr_default,
                        stackaddr, stacksize, allocaddr, allocsize);
        thread->tl_joinable = true;

        // Finish initialization with common code that is reinvoked on the
        // child side of a fork.

        // Finishes initialization of main thread attributes.
        // Initializes the thread list and add the main thread.
        // Calls _pthread_set_self() to prepare the main thread for execution.
        _pthread_main_thread_init(thread);

        struct _pthread_registration_data registration_data;
        // Set up kernel entry points with __bsdthread_register.
        _pthread_bsdthread_init(&registration_data);

        // Have pthread_key and pthread_mutex do their init envvar checks.
        _pthread_key_global_init(envp);
        _pthread_mutex_global_init(envp, &registration_data);

#if PTHREAD_DEBUG_LOG
        _SIMPLE_STRING path = _simple_salloc();
        _simple_sprintf(path, "/var/tmp/libpthread.%d.log", getpid());
        _pthread_debuglog = open(_simple_string(path),
                        O_WRONLY | O_APPEND | O_CREAT | O_NOFOLLOW | O_CLOEXEC, 0666);
        _simple_sfree(path);
        _pthread_debugstart = mach_absolute_time();
#endif

        return 0;
}
#endif // !VARIANT_DYLD

PTHREAD_NOEXPORT void
_pthread_main_thread_init(pthread_t p)
{
        TAILQ_INIT(&__pthread_head);
        _PTHREAD_LOCK_INIT(_pthread_list_lock);
        _PTHREAD_LOCK_INIT(p->lock);
        _pthread_set_kernel_thread(p, mach_thread_self());
        _pthread_set_reply_port(p, mach_reply_port());
        p->__cleanup_stack = NULL;
        p->tl_join_ctx = NULL;
        p->tl_exit_gate = MACH_PORT_NULL;
        p->tsd[__TSD_SEMAPHORE_CACHE] = (void*)SEMAPHORE_NULL;
        p->tsd[__TSD_MACH_SPECIAL_REPLY] = 0;
        p->cancel_state |= _PTHREAD_CANCEL_INITIALIZED;

        // Initialize the list of threads with the new main thread.
        TAILQ_INSERT_HEAD(&__pthread_head, p, tl_plist);
        _pthread_count = 1;

        _pthread_introspection_thread_start(p);
}

int
sched_yield(void)
{
        swtch_pri(0);
        return 0;
}

// XXX remove
void
cthread_yield(void)
{
        sched_yield();
}

void
pthread_yield_np(void)
{
        sched_yield();
}



// Libsystem knows about this symbol and exports it to libsyscall
PTHREAD_NOEXPORT_VARIANT
void
_pthread_clear_qos_tsd(mach_port_t thread_port)
{
        if (thread_port == MACH_PORT_NULL || (uintptr_t)_pthread_getspecific_direct(_PTHREAD_TSD_SLOT_MACH_THREAD_SELF) == thread_port) {
                /* Clear the current thread's TSD, that can be done inline. */
                _pthread_setspecific_direct(_PTHREAD_TSD_SLOT_PTHREAD_QOS_CLASS,
                                _pthread_unspecified_priority());
        } else {
                pthread_t p;

                _PTHREAD_LOCK(_pthread_list_lock);

                TAILQ_FOREACH(p, &__pthread_head, tl_plist) {
                        mach_port_t kp = _pthread_kernel_thread(p);
                        if (thread_port == kp) {
                                p->tsd[_PTHREAD_TSD_SLOT_PTHREAD_QOS_CLASS] =
                                                _pthread_unspecified_priority();
                                break;
                        }
                }

                _PTHREAD_UNLOCK(_pthread_list_lock);
        }
}


#pragma mark pthread/stack_np.h public interface


#if defined(__i386__) || defined(__x86_64__) || defined(__arm__) || defined(__arm64__)
typedef uintptr_t frame_data_addr_t;

struct frame_data {
        frame_data_addr_t frame_addr_next;
        frame_data_addr_t ret_addr;
};
#else
#error ********** Unimplemented architecture
#endif

uintptr_t
pthread_stack_frame_decode_np(uintptr_t frame_addr, uintptr_t *return_addr)
{
        struct frame_data *frame = (struct frame_data *)frame_addr;

        if (return_addr) {
                *return_addr = (uintptr_t)frame->ret_addr;
        }

        return (uintptr_t)frame->frame_addr_next;
}


#pragma mark pthread workqueue support routines


PTHREAD_NOEXPORT void
_pthread_bsdthread_init(struct _pthread_registration_data *data)
{
        bzero(data, sizeof(*data));
        data->version = sizeof(struct _pthread_registration_data);
        data->dispatch_queue_offset = __PTK_LIBDISPATCH_KEY0 * sizeof(void *);
        data->return_to_kernel_offset = __TSD_RETURN_TO_KERNEL * sizeof(void *);
        data->tsd_offset = offsetof(struct _pthread, tsd);
        data->mach_thread_self_offset = __TSD_MACH_THREAD_SELF * sizeof(void *);

        int rv = __bsdthread_register(thread_start, start_wqthread, (int)PTHREAD_SIZE,
                        (void*)data, (uintptr_t)sizeof(*data), data->dispatch_queue_offset);

        if (rv > 0) {
                int required_features =
                                PTHREAD_FEATURE_FINEPRIO |
                                PTHREAD_FEATURE_BSDTHREADCTL |
                                PTHREAD_FEATURE_SETSELF |
                                PTHREAD_FEATURE_QOS_MAINTENANCE |
                                PTHREAD_FEATURE_QOS_DEFAULT;
                if ((rv & required_features) != required_features) {
                        PTHREAD_INTERNAL_CRASH(rv, "Missing required kernel support");
                }
                __pthread_supported_features = rv;
        }

        /*
         * TODO: differentiate between (-1, EINVAL) after fork (which has the side
         * effect of resetting the child's stack_addr_hint before bailing out) and
         * (-1, EINVAL) because of invalid arguments.  We'd probably like to treat
         * the latter as fatal.
         *
         * <rdar://problem/36451838>
         */

        pthread_priority_t main_qos = (pthread_priority_t)data->main_qos;

        if (_pthread_priority_thread_qos(main_qos) != THREAD_QOS_UNSPECIFIED) {
                _pthread_set_main_qos(main_qos);
                main_thread()->tsd[_PTHREAD_TSD_SLOT_PTHREAD_QOS_CLASS] = main_qos;
        }

        if (data->stack_addr_hint) {
                __pthread_stack_hint = data->stack_addr_hint;
        }

        if (__libdispatch_workerfunction != NULL) {
                // prepare the kernel for workq action
                (void)__workq_open();
        }
}

PTHREAD_NOINLINE
static void
_pthread_wqthread_legacy_worker_wrap(pthread_priority_t pp)
{
        /* Old thread priorities are inverted from where we have them in
         * the new flexible priority scheme. The highest priority is zero,
         * up to 2, with background at 3.
         */
        pthread_workqueue_function_t func = (pthread_workqueue_function_t)__libdispatch_workerfunction;
        bool overcommit = (pp & _PTHREAD_PRIORITY_OVERCOMMIT_FLAG);
        int opts = overcommit ? WORKQ_ADDTHREADS_OPTION_OVERCOMMIT : 0;

        switch (_pthread_priority_thread_qos(pp)) {
        case THREAD_QOS_USER_INITIATED:
                return (*func)(WORKQ_HIGH_PRIOQUEUE, opts, NULL);
        case THREAD_QOS_LEGACY:
                /* B&I builders can't pass a QOS_CLASS_DEFAULT thread to dispatch, for fear of the QoS being
                 * picked up by NSThread (et al) and transported around the system. So change the TSD to
                 * make this thread look like QOS_CLASS_USER_INITIATED even though it will still run as legacy.
                 */
                _pthread_setspecific_direct(_PTHREAD_TSD_SLOT_PTHREAD_QOS_CLASS,
                                _pthread_priority_make_from_thread_qos(THREAD_QOS_USER_INITIATED, 0, 0));
                return (*func)(WORKQ_DEFAULT_PRIOQUEUE, opts, NULL);
        case THREAD_QOS_UTILITY:
                return (*func)(WORKQ_LOW_PRIOQUEUE, opts, NULL);
        case THREAD_QOS_BACKGROUND:
                return (*func)(WORKQ_BG_PRIOQUEUE, opts, NULL);
        }
        PTHREAD_INTERNAL_CRASH(pp, "Invalid pthread priority for the legacy interface");
}

PTHREAD_ALWAYS_INLINE
static inline pthread_priority_t
_pthread_wqthread_priority(int flags)
{
        pthread_priority_t pp = 0;
        thread_qos_t qos;

        if (flags & WQ_FLAG_THREAD_KEVENT) {
                pp |= _PTHREAD_PRIORITY_NEEDS_UNBIND_FLAG;
        }
        if (flags & WQ_FLAG_THREAD_EVENT_MANAGER) {
                return pp | _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG;
        }

        if (flags & WQ_FLAG_THREAD_OVERCOMMIT) {
                pp |= _PTHREAD_PRIORITY_OVERCOMMIT_FLAG;
        }
        if (flags & WQ_FLAG_THREAD_PRIO_QOS) {
                qos = (thread_qos_t)(flags & WQ_FLAG_THREAD_PRIO_MASK);
                pp = _pthread_priority_make_from_thread_qos(qos, 0, pp);
        } else if (flags & WQ_FLAG_THREAD_PRIO_SCHED) {
                pp |= _PTHREAD_PRIORITY_SCHED_PRI_MASK;
                pp |= (flags & WQ_FLAG_THREAD_PRIO_MASK);
        } else {
                PTHREAD_INTERNAL_CRASH(flags, "Missing priority");
        }
        return pp;
}

PTHREAD_NOINLINE
static void
_pthread_wqthread_setup(pthread_t self, mach_port_t kport, void *stacklowaddr,
                int flags)
{
        void *stackaddr = self;
        size_t stacksize = (uintptr_t)self - (uintptr_t)stacklowaddr;

        _pthread_struct_init(self, &_pthread_attr_default, stackaddr, stacksize,
                        PTHREAD_ALLOCADDR(stackaddr, stacksize),
                        PTHREAD_ALLOCSIZE(stackaddr, stacksize));

        _pthread_set_kernel_thread(self, kport);
        self->wqthread = 1;
        self->wqkillset = 0;
        self->tl_joinable = false;
        self->cancel_state |= _PTHREAD_CANCEL_INITIALIZED;

        // Update the running thread count and set childrun bit.
        bool thread_tsd_base_set = (bool)(flags & WQ_FLAG_THREAD_TSD_BASE_SET);
        _pthread_set_self_internal(self, !thread_tsd_base_set);
        __pthread_add_thread(self, false);
        __pthread_started_thread(self);
}

PTHREAD_NORETURN PTHREAD_NOINLINE
static void
_pthread_wqthread_exit(pthread_t self)
{
        pthread_priority_t pp;
        thread_qos_t qos;

        pp = (pthread_priority_t)self->tsd[_PTHREAD_TSD_SLOT_PTHREAD_QOS_CLASS];
        qos = _pthread_priority_thread_qos(pp);
        if (qos == THREAD_QOS_UNSPECIFIED || qos > WORKQ_THREAD_QOS_CLEANUP) {
                // Reset QoS to something low for the cleanup process
                pp = _pthread_priority_make_from_thread_qos(WORKQ_THREAD_QOS_CLEANUP, 0, 0);
                self->tsd[_PTHREAD_TSD_SLOT_PTHREAD_QOS_CLASS] = (void *)pp;
        }

        _pthread_exit(self, NULL);
}

// workqueue entry point from kernel
void
_pthread_wqthread(pthread_t self, mach_port_t kport, void *stacklowaddr,
                void *keventlist, int flags, int nkevents)
{
        if ((flags & WQ_FLAG_THREAD_REUSE) == 0) {
                _pthread_wqthread_setup(self, kport, stacklowaddr, flags);
        }

        pthread_priority_t pp;
        if (flags & WQ_FLAG_THREAD_OUTSIDEQOS) {
                self->wqoutsideqos = 1;
                pp = _pthread_priority_make_from_thread_qos(THREAD_QOS_LEGACY, 0,
                                _PTHREAD_PRIORITY_FALLBACK_FLAG);
        } else {
                self->wqoutsideqos = 0;
                pp = _pthread_wqthread_priority(flags);
        }

        self->tsd[_PTHREAD_TSD_SLOT_PTHREAD_QOS_CLASS] = (void *)pp;

        // avoid spills on the stack hard to keep used stack space minimal
        if (nkevents == WORKQ_EXIT_THREAD_NKEVENT) {
                goto exit;
        } else if (flags & WQ_FLAG_THREAD_WORKLOOP) {
                self->fun = (void *(*)(void*))__libdispatch_workloopfunction;
                self->wq_retop = WQOPS_THREAD_WORKLOOP_RETURN;
                self->wq_kqid_ptr = ((kqueue_id_t *)keventlist - 1);
                self->arg = keventlist;
                self->wq_nevents = nkevents;
        } else if (flags & WQ_FLAG_THREAD_KEVENT) {
                self->fun = (void *(*)(void*))__libdispatch_keventfunction;
                self->wq_retop = WQOPS_THREAD_KEVENT_RETURN;
                self->wq_kqid_ptr = NULL;
                self->arg = keventlist;
                self->wq_nevents = nkevents;
        } else {
                self->fun = (void *(*)(void*))__libdispatch_workerfunction;
                self->wq_retop = WQOPS_THREAD_RETURN;
                self->wq_kqid_ptr = NULL;
                self->arg = (void *)(uintptr_t)pp;
                self->wq_nevents = 0;
                if (os_likely(__workq_newapi)) {
                        (*__libdispatch_workerfunction)(pp);
                } else {
                        _pthread_wqthread_legacy_worker_wrap(pp);
                }
                goto just_return;
        }

        if (nkevents > 0) {
kevent_errors_retry:
                if (self->wq_retop == WQOPS_THREAD_WORKLOOP_RETURN) {
                        ((pthread_workqueue_function_workloop_t)self->fun)
                                        (self->wq_kqid_ptr, &self->arg, &self->wq_nevents);
                } else {
                        ((pthread_workqueue_function_kevent_t)self->fun)
                                        (&self->arg, &self->wq_nevents);
                }
                int rc = __workq_kernreturn(self->wq_retop, self->arg, self->wq_nevents, 0);
                if (os_unlikely(rc > 0)) {
                        self->wq_nevents = rc;
                        goto kevent_errors_retry;
                }
                if (os_unlikely(rc < 0)) {
                        PTHREAD_INTERNAL_CRASH(self->err_no, "kevent (workloop) failed");
                }
        } else {
just_return:
                __workq_kernreturn(self->wq_retop, NULL, 0, 0);
        }

exit:
        _pthread_wqthread_exit(self);
}


#pragma mark pthread workqueue API for libdispatch


_Static_assert(WORKQ_KEVENT_EVENT_BUFFER_LEN == WQ_KEVENT_LIST_LEN,
                "Kernel and userland should agree on the event list size");

void
pthread_workqueue_setdispatchoffset_np(int offset)
{
        __libdispatch_offset = offset;
}

static int
pthread_workqueue_setdispatch_with_workloop_np(pthread_workqueue_function2_t queue_func,
                pthread_workqueue_function_kevent_t kevent_func,
                pthread_workqueue_function_workloop_t workloop_func)
{
        int res = EBUSY;
        if (__libdispatch_workerfunction == NULL) {
                // Check whether the kernel supports new SPIs
                res = __workq_kernreturn(WQOPS_QUEUE_NEWSPISUPP, NULL, __libdispatch_offset, kevent_func != NULL ? 0x01 : 0x00);
                if (res == -1){
                        res = ENOTSUP;
                } else {
                        __libdispatch_workerfunction = queue_func;
                        __libdispatch_keventfunction = kevent_func;
                        __libdispatch_workloopfunction = workloop_func;

                        // Prepare the kernel for workq action
                        (void)__workq_open();
                        if (__is_threaded == 0) {
                                __is_threaded = 1;
                        }
                }
        }
        return res;
}

int
_pthread_workqueue_init_with_workloop(pthread_workqueue_function2_t queue_func,
                pthread_workqueue_function_kevent_t kevent_func,
                pthread_workqueue_function_workloop_t workloop_func,
                int offset, int flags)
{
        if (flags != 0) {
                return ENOTSUP;
        }

        __workq_newapi = true;
        __libdispatch_offset = offset;

        int rv = pthread_workqueue_setdispatch_with_workloop_np(queue_func, kevent_func, workloop_func);
        return rv;
}

int
_pthread_workqueue_init_with_kevent(pthread_workqueue_function2_t queue_func,
                pthread_workqueue_function_kevent_t kevent_func,
                int offset, int flags)
{
        return _pthread_workqueue_init_with_workloop(queue_func, kevent_func, NULL, offset, flags);
}

int
_pthread_workqueue_init(pthread_workqueue_function2_t func, int offset, int flags)
{
        return _pthread_workqueue_init_with_kevent(func, NULL, offset, flags);
}

int
pthread_workqueue_setdispatch_np(pthread_workqueue_function_t worker_func)
{
        return pthread_workqueue_setdispatch_with_workloop_np((pthread_workqueue_function2_t)worker_func, NULL, NULL);
}

int
_pthread_workqueue_supported(void)
{
        if (os_unlikely(!__pthread_supported_features)) {
                PTHREAD_INTERNAL_CRASH(0, "libpthread has not been initialized");
        }

        return __pthread_supported_features;
}

int
pthread_workqueue_addthreads_np(int queue_priority, int options, int numthreads)
{
        int res = 0;

        // Cannot add threads without a worker function registered.
        if (__libdispatch_workerfunction == NULL) {
                return EPERM;
        }

        pthread_priority_t kp = 0;
        int compat_priority = queue_priority & WQ_FLAG_THREAD_PRIO_MASK;
        int flags = 0;

        if (options & WORKQ_ADDTHREADS_OPTION_OVERCOMMIT) {
                flags = _PTHREAD_PRIORITY_OVERCOMMIT_FLAG;
        }

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
        kp = _pthread_qos_class_encode_workqueue(compat_priority, flags);
#pragma clang diagnostic pop

        res = __workq_kernreturn(WQOPS_QUEUE_REQTHREADS, NULL, numthreads, (int)kp);
        if (res == -1) {
                res = errno;
        }
        return res;
}

bool
_pthread_workqueue_should_narrow(pthread_priority_t pri)
{
        int res = __workq_kernreturn(WQOPS_SHOULD_NARROW, NULL, (int)pri, 0);
        if (res == -1) {
                return false;
        }
        return res;
}

int
_pthread_workqueue_addthreads(int numthreads, pthread_priority_t priority)
{
        int res = 0;

        if (__libdispatch_workerfunction == NULL) {
                return EPERM;
        }

#if TARGET_OS_OSX
        // <rdar://problem/37687655> Legacy simulators fail to boot
        //
        // Older sims set the deprecated _PTHREAD_PRIORITY_ROOTQUEUE_FLAG wrongly,
        // which is aliased to _PTHREAD_PRIORITY_SCHED_PRI_FLAG and that XNU
        // validates and rejects.
        //
        // As a workaround, forcefully unset this bit that cannot be set here
        // anyway.
        priority &= ~_PTHREAD_PRIORITY_SCHED_PRI_FLAG;
#endif

        res = __workq_kernreturn(WQOPS_QUEUE_REQTHREADS, NULL, numthreads, (int)priority);
        if (res == -1) {
                res = errno;
        }
        return res;
}

int
_pthread_workqueue_set_event_manager_priority(pthread_priority_t priority)
{
        int res = __workq_kernreturn(WQOPS_SET_EVENT_MANAGER_PRIORITY, NULL, (int)priority, 0);
        if (res == -1) {
                res = errno;
        }
        return res;
}

int
_pthread_workloop_create(uint64_t workloop_id, uint64_t options, pthread_attr_t *attr)
{
        struct kqueue_workloop_params params = {
                .kqwlp_version = sizeof(struct kqueue_workloop_params),
                .kqwlp_id = workloop_id,
                .kqwlp_flags = 0,
        };

        if (!attr) {
                return EINVAL;
        }

        if (attr->schedset) {
                params.kqwlp_flags |= KQ_WORKLOOP_CREATE_SCHED_PRI;
                params.kqwlp_sched_pri = attr->param.sched_priority;
        }

        if (attr->policyset) {
                params.kqwlp_flags |= KQ_WORKLOOP_CREATE_SCHED_POL;
                params.kqwlp_sched_pol = attr->policy;
        }

        if (attr->cpupercentset) {
                params.kqwlp_flags |= KQ_WORKLOOP_CREATE_CPU_PERCENT;
                params.kqwlp_cpu_percent = attr->cpupercent;
                params.kqwlp_cpu_refillms = attr->refillms;
        }

        int res = __kqueue_workloop_ctl(KQ_WORKLOOP_CREATE, 0, &params,
                        sizeof(params));
        if (res == -1) {
                res = errno;
        }
        return res;
}

int
_pthread_workloop_destroy(uint64_t workloop_id)
{
        struct kqueue_workloop_params params = {
                .kqwlp_version = sizeof(struct kqueue_workloop_params),
                .kqwlp_id = workloop_id,
        };

        int res = __kqueue_workloop_ctl(KQ_WORKLOOP_DESTROY, 0, &params,
                        sizeof(params));
        if (res == -1) {
                res = errno;
        }
        return res;
}


#pragma mark Introspection SPI for libpthread.


static pthread_introspection_hook_t _pthread_introspection_hook;

pthread_introspection_hook_t
pthread_introspection_hook_install(pthread_introspection_hook_t hook)
{
        pthread_introspection_hook_t prev;
        prev = _pthread_atomic_xchg_ptr((void**)&_pthread_introspection_hook, hook);
        return prev;
}

PTHREAD_NOINLINE
static void
_pthread_introspection_hook_callout_thread_create(pthread_t t)
{
        _pthread_introspection_hook(PTHREAD_INTROSPECTION_THREAD_CREATE, t, t,
                        PTHREAD_SIZE);
}

static inline void
_pthread_introspection_thread_create(pthread_t t)
{
        if (os_fastpath(!_pthread_introspection_hook)) return;
        _pthread_introspection_hook_callout_thread_create(t);
}

PTHREAD_NOINLINE
static void
_pthread_introspection_hook_callout_thread_start(pthread_t t)
{
        size_t freesize;
        void *freeaddr;
        if (t == main_thread()) {
                size_t stacksize = t->stackaddr - t->stackbottom;
                freesize = stacksize + t->guardsize;
                freeaddr = t->stackaddr - freesize;
        } else {
                freesize = t->freesize - PTHREAD_SIZE;
                freeaddr = t->freeaddr;
        }
        _pthread_introspection_hook(PTHREAD_INTROSPECTION_THREAD_START, t,
                        freeaddr, freesize);
}

static inline void
_pthread_introspection_thread_start(pthread_t t)
{
        if (os_fastpath(!_pthread_introspection_hook)) return;
        _pthread_introspection_hook_callout_thread_start(t);
}

PTHREAD_NOINLINE
static void
_pthread_introspection_hook_callout_thread_terminate(pthread_t t)
{
        size_t freesize;
        void *freeaddr;
        if (t == main_thread()) {
                size_t stacksize = t->stackaddr - t->stackbottom;
                freesize = stacksize + t->guardsize;
                freeaddr = t->stackaddr - freesize;
        } else {
                freesize = t->freesize - PTHREAD_SIZE;
                freeaddr = t->freeaddr;
        }
        _pthread_introspection_hook(PTHREAD_INTROSPECTION_THREAD_TERMINATE, t,
                        freeaddr, freesize);
}

static inline void
_pthread_introspection_thread_terminate(pthread_t t)
{
        if (os_fastpath(!_pthread_introspection_hook)) return;
        _pthread_introspection_hook_callout_thread_terminate(t);
}

PTHREAD_NOINLINE
static void
_pthread_introspection_hook_callout_thread_destroy(pthread_t t)
{
        _pthread_introspection_hook(PTHREAD_INTROSPECTION_THREAD_DESTROY, t, t,
                        PTHREAD_SIZE);
}

static inline void
_pthread_introspection_thread_destroy(pthread_t t)
{
        if (os_fastpath(!_pthread_introspection_hook)) return;
        _pthread_introspection_hook_callout_thread_destroy(t);
}

#pragma mark libplatform shims

#include <platform/string.h>

// pthread_setup initializes large structures to 0,
// which the compiler turns into a library call to memset.
//
// To avoid linking against Libc, provide a simple wrapper
// that calls through to the libplatform primitives

#undef memset
PTHREAD_NOEXPORT
void *
memset(void *b, int c, size_t len)
{
        return _platform_memset(b, c, len);
}

#undef bzero
PTHREAD_NOEXPORT
void
bzero(void *s, size_t n)
{
        _platform_bzero(s, n);
}

#undef memcpy
PTHREAD_NOEXPORT
void *
memcpy(void* a, const void* b, unsigned long s)
{
        return _platform_memmove(a, b, s);
}