libpthread-138.10.4.tar.gz

[apple/libpthread.git] / kern / kern_support.c

/*
 * Copyright (c) 2000-2012 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_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. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * 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_OSREFERENCE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995-2005 Apple Computer, Inc. All Rights Reserved */
/*
 *	pthread_synch.c
 */

#pragma mark - Front Matter

#define  _PTHREAD_CONDATTR_T
#define  _PTHREAD_COND_T
#define _PTHREAD_MUTEXATTR_T
#define _PTHREAD_MUTEX_T
#define _PTHREAD_RWLOCKATTR_T
#define _PTHREAD_RWLOCK_T

#undef pthread_mutexattr_t
#undef pthread_mutex_t
#undef pthread_condattr_t
#undef pthread_cond_t
#undef pthread_rwlockattr_t
#undef pthread_rwlock_t

#include <sys/param.h>
#include <sys/queue.h>
#include <sys/resourcevar.h>
//#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/systm.h>
#include <sys/timeb.h>
#include <sys/times.h>
#include <sys/acct.h>
#include <sys/kernel.h>
#include <sys/wait.h>
#include <sys/signalvar.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/stat.h>
#include <sys/lock.h>
#include <sys/kdebug.h>
//#include <sys/sysproto.h>
#include <sys/vm.h>
#include <sys/user.h>		/* for coredump */
#include <sys/proc_info.h>	/* for fill_procworkqueue */

#include <mach/mach_port.h>
#include <mach/mach_types.h>
#include <mach/semaphore.h>
#include <mach/sync_policy.h>
#include <mach/task.h>
#include <mach/vm_prot.h>
#include <kern/kern_types.h>
#include <kern/task.h>
#include <kern/clock.h>
#include <mach/kern_return.h>
#include <kern/thread.h>
#include <kern/sched_prim.h>
#include <kern/kalloc.h>
#include <kern/sched_prim.h>	/* for thread_exception_return */
#include <kern/processor.h>
#include <kern/assert.h>
#include <mach/mach_vm.h>
#include <mach/mach_param.h>
#include <mach/thread_status.h>
#include <mach/thread_policy.h>
#include <mach/message.h>
#include <mach/port.h>
//#include <vm/vm_protos.h>
#include <vm/vm_fault.h>
#include <vm/vm_map.h>
#include <mach/thread_act.h> /* for thread_resume */
#include <machine/machine_routines.h>
#include <mach/shared_region.h>

#include <libkern/OSAtomic.h>

#include <sys/pthread_shims.h>
#include "kern_internal.h"

#if DEBUG
#define kevent_qos_internal kevent_qos_internal_stub
static int kevent_qos_internal_stub(__unused struct proc *p, __unused int fd, 
						__unused user_addr_t changelist, __unused int nchanges, 
						__unused user_addr_t eventlist, __unused int nevents,
						__unused user_addr_t data_out, user_size_t *data_available,
						__unused unsigned int flags, int32_t *retval){
	if (data_available){	
		static int i = 0;
		switch (i++ % 4) {
			case 0:
			case 2:
				*data_available = *data_available / 2;
				*retval = 4;
				break;
			case 1:
				*data_available = 0;
				*retval = 4;
				break;
			case 3:
				*retval = 0;
				break;
		}
	} else {
		*retval = 0;
	}
	return 0;
}
#endif /* DEBUG */

uint32_t pthread_debug_tracing = 1;

SYSCTL_INT(_kern, OID_AUTO, pthread_debug_tracing, CTLFLAG_RW | CTLFLAG_LOCKED,
		   &pthread_debug_tracing, 0, "")

// XXX: Dirty import for sys/signarvar.h that's wrapped in BSD_KERNEL_PRIVATE
#define sigcantmask (sigmask(SIGKILL) | sigmask(SIGSTOP))

lck_grp_attr_t   *pthread_lck_grp_attr;
lck_grp_t    *pthread_lck_grp;
lck_attr_t   *pthread_lck_attr;

extern void thread_set_cthreadself(thread_t thread, uint64_t pself, int isLP64);
extern void workqueue_thread_yielded(void);

enum run_nextreq_mode {RUN_NEXTREQ_DEFAULT, RUN_NEXTREQ_OVERCOMMIT, RUN_NEXTREQ_DEFERRED_OVERCOMMIT, RUN_NEXTREQ_UNCONSTRAINED, RUN_NEXTREQ_EVENT_MANAGER};
static boolean_t workqueue_run_nextreq(proc_t p, struct workqueue *wq, thread_t th, enum run_nextreq_mode mode, pthread_priority_t oc_prio);

static boolean_t workqueue_run_one(proc_t p, struct workqueue *wq, boolean_t overcommit, pthread_priority_t priority);

static void wq_runreq(proc_t p, pthread_priority_t priority, thread_t th, struct threadlist *tl,
		       int reuse_thread, int wake_thread, int return_directly);

static int _setup_wqthread(proc_t p, thread_t th, pthread_priority_t priority, int reuse_thread, struct threadlist *tl);

static void wq_unpark_continue(void);
static void wq_unsuspend_continue(void);

static boolean_t workqueue_addnewthread(struct workqueue *wq, boolean_t ignore_constrained_thread_limit);
static void workqueue_removethread(struct threadlist *tl, int fromexit);
static void workqueue_lock_spin(proc_t);
static void workqueue_unlock(proc_t);

static boolean_t may_start_constrained_thread(struct workqueue *wq, uint32_t at_priclass, uint32_t my_priclass, boolean_t *start_timer);

static mach_vm_offset_t stackaddr_hint(proc_t p);

int proc_settargetconc(pid_t pid, int queuenum, int32_t targetconc);
int proc_setalltargetconc(pid_t pid, int32_t * targetconcp);

#define WQ_MAXPRI_MIN	0	/* low prio queue num */
#define WQ_MAXPRI_MAX	2	/* max  prio queuenum */
#define WQ_PRI_NUM	3	/* number of prio work queues */

#define C_32_STK_ALIGN          16
#define C_64_STK_ALIGN          16
#define C_64_REDZONE_LEN        128

#define PTHREAD_T_OFFSET 0

/*
 * Flags filed passed to bsdthread_create and back in pthread_start 
31  <---------------------------------> 0
_________________________________________
| flags(8) | policy(8) | importance(16) |
-----------------------------------------
*/

#define PTHREAD_START_CUSTOM	0x01000000
#define PTHREAD_START_SETSCHED	0x02000000
#define PTHREAD_START_DETACHED	0x04000000
#define PTHREAD_START_QOSCLASS	0x08000000
#define PTHREAD_START_QOSCLASS_MASK 0xffffff
#define PTHREAD_START_POLICY_BITSHIFT 16
#define PTHREAD_START_POLICY_MASK 0xff
#define PTHREAD_START_IMPORTANCE_MASK 0xffff

#define SCHED_OTHER      POLICY_TIMESHARE
#define SCHED_FIFO       POLICY_FIFO
#define SCHED_RR         POLICY_RR

#define BASEPRI_DEFAULT 31

#pragma mark - Process/Thread Setup/Teardown syscalls

static mach_vm_offset_t stackaddr_hint(proc_t p __unused){
	mach_vm_offset_t stackaddr;
#if defined(__i386__) || defined(__x86_64__)
	if (proc_is64bit(p)){
		// Above nanomalloc range (see NANOZONE_SIGNATURE)
		stackaddr = 0x700000000000;
	} else {
		stackaddr = SHARED_REGION_BASE_I386 + SHARED_REGION_SIZE_I386;
	}
#elif defined(__arm__) || defined(__arm64__)
	if (proc_is64bit(p)){
		// 64 stacks below nanomalloc (see NANOZONE_SIGNATURE)
		stackaddr = 0x170000000 - 64 * PTH_DEFAULT_STACKSIZE;
#if defined(__arm__)
	} else if (pthread_kern->map_is_1gb(get_task_map(pthread_kern->proc_get_task(p)))){
		stackaddr = SHARED_REGION_BASE_ARM - 32 * PTH_DEFAULT_STACKSIZE;
#endif
	} else {
		stackaddr = SHARED_REGION_BASE_ARM + SHARED_REGION_SIZE_ARM;
	}
#else
#error Need to define a stack address hint for this architecture
#endif
	return stackaddr;
}

/**
 * bsdthread_create system call.  Used by pthread_create.
 */
int
_bsdthread_create(struct proc *p, user_addr_t user_func, user_addr_t user_funcarg, user_addr_t user_stack, user_addr_t user_pthread, uint32_t flags, user_addr_t *retval)
{
	kern_return_t kret;
	void * sright;
	int error = 0;
	int allocated = 0;
	mach_vm_offset_t stackaddr;
	mach_vm_size_t th_allocsize = 0;
	mach_vm_size_t th_guardsize;
	mach_vm_offset_t th_stack;
	mach_vm_offset_t th_pthread;
	mach_port_name_t th_thport;
	thread_t th;
	vm_map_t vmap = pthread_kern->current_map();
	task_t ctask = current_task();
	unsigned int policy, importance;
	
	int isLP64 = 0;

	if (pthread_kern->proc_get_register(p) == 0) {
		return EINVAL;
	}

	PTHREAD_TRACE(TRACE_pthread_thread_create | DBG_FUNC_START, flags, 0, 0, 0, 0);

	isLP64 = proc_is64bit(p);
	th_guardsize = vm_map_page_size(vmap);

	stackaddr = stackaddr_hint(p);
	kret = pthread_kern->thread_create(ctask, &th);
	if (kret != KERN_SUCCESS)
		return(ENOMEM);
	thread_reference(th);

	sright = (void *)pthread_kern->convert_thread_to_port(th);
	th_thport = pthread_kern->ipc_port_copyout_send(sright, pthread_kern->task_get_ipcspace(ctask));

	if ((flags & PTHREAD_START_CUSTOM) == 0) {
		mach_vm_size_t pthread_size =
			vm_map_round_page_mask(pthread_kern->proc_get_pthsize(p) + PTHREAD_T_OFFSET, vm_map_page_mask(vmap));
		th_allocsize = th_guardsize + user_stack + pthread_size;
		user_stack += PTHREAD_T_OFFSET;

		kret = mach_vm_map(vmap, &stackaddr, 
				th_allocsize, 
				page_size-1,
				VM_MAKE_TAG(VM_MEMORY_STACK)| VM_FLAGS_ANYWHERE , NULL,
				0, FALSE, VM_PROT_DEFAULT, VM_PROT_ALL,
				VM_INHERIT_DEFAULT);
		if (kret != KERN_SUCCESS){
			kret = mach_vm_allocate(vmap, 
					&stackaddr, th_allocsize,
					VM_MAKE_TAG(VM_MEMORY_STACK)| VM_FLAGS_ANYWHERE);
		}
		if (kret != KERN_SUCCESS) {
			error = ENOMEM;
			goto out;
		}

		PTHREAD_TRACE(TRACE_pthread_thread_create|DBG_FUNC_NONE, th_allocsize, stackaddr, 0, 2, 0);

		allocated = 1;
		/*
		 * The guard page is at the lowest address
		 * The stack base is the highest address
		 */
		kret = mach_vm_protect(vmap,  stackaddr, th_guardsize, FALSE, VM_PROT_NONE);

		if (kret != KERN_SUCCESS) { 
			error = ENOMEM;
			goto out1;
		}

		th_pthread = stackaddr + th_guardsize + user_stack;
		th_stack = th_pthread;
		
		/*
		* Pre-fault the first page of the new thread's stack and the page that will
		* contain the pthread_t structure.
		*/	
		if (vm_map_trunc_page_mask((vm_map_offset_t)(th_stack - C_64_REDZONE_LEN), vm_map_page_mask(vmap)) != 
				vm_map_trunc_page_mask((vm_map_offset_t)th_pthread, vm_map_page_mask(vmap))){
			vm_fault( vmap,
					vm_map_trunc_page_mask((vm_map_offset_t)(th_stack - C_64_REDZONE_LEN), vm_map_page_mask(vmap)),
					VM_PROT_READ | VM_PROT_WRITE,
					FALSE, 
					THREAD_UNINT, NULL, 0);
		}
		
		vm_fault( vmap,
				vm_map_trunc_page_mask((vm_map_offset_t)th_pthread, vm_map_page_mask(vmap)),
				VM_PROT_READ | VM_PROT_WRITE,
				FALSE, 
				THREAD_UNINT, NULL, 0);

	} else {
		th_stack = user_stack;
		th_pthread = user_pthread;

		PTHREAD_TRACE(TRACE_pthread_thread_create|DBG_FUNC_NONE, 0, 0, 0, 3, 0);
	}
	
#if defined(__i386__) || defined(__x86_64__)
	/*
	 * Set up i386 registers & function call.
	 */
	if (isLP64 == 0) {
		x86_thread_state32_t state = {
			.eip = (unsigned int)pthread_kern->proc_get_threadstart(p),
			.eax = (unsigned int)th_pthread,
			.ebx = (unsigned int)th_thport,
			.ecx = (unsigned int)user_func,
			.edx = (unsigned int)user_funcarg,
			.edi = (unsigned int)user_stack,
			.esi = (unsigned int)flags,
			/*
			 * set stack pointer
			 */
			.esp = (int)((vm_offset_t)(th_stack-C_32_STK_ALIGN))
		};

		error = pthread_kern->thread_set_wq_state32(th, (thread_state_t)&state);
		if (error != KERN_SUCCESS) {
			error = EINVAL;
			goto out;
		}
	} else {
		x86_thread_state64_t state64 = {
			.rip = (uint64_t)pthread_kern->proc_get_threadstart(p),
			.rdi = (uint64_t)th_pthread,
			.rsi = (uint64_t)(th_thport),
			.rdx = (uint64_t)user_func,
			.rcx = (uint64_t)user_funcarg,
			.r8 = (uint64_t)user_stack,
			.r9 = (uint64_t)flags,
			/*
			 * set stack pointer aligned to 16 byte boundary
			 */
			.rsp = (uint64_t)(th_stack - C_64_REDZONE_LEN)
		};

		error = pthread_kern->thread_set_wq_state64(th, (thread_state_t)&state64);
		if (error != KERN_SUCCESS) {
			error = EINVAL;
			goto out;
		}
		
	}
#elif defined(__arm__)
	arm_thread_state_t state = {
		.pc = (int)pthread_kern->proc_get_threadstart(p),
		.r[0] = (unsigned int)th_pthread,
		.r[1] = (unsigned int)th_thport,
		.r[2] = (unsigned int)user_func,
		.r[3] = (unsigned int)user_funcarg,
		.r[4] = (unsigned int)user_stack,
		.r[5] = (unsigned int)flags,

		/* Set r7 & lr to 0 for better back tracing */
		.r[7] = 0,
		.lr = 0,

		/*	
		 * set stack pointer
		 */
		.sp = (int)((vm_offset_t)(th_stack-C_32_STK_ALIGN))
	};

	(void) pthread_kern->thread_set_wq_state32(th, (thread_state_t)&state);

#else
#error bsdthread_create  not defined for this architecture
#endif

	if ((flags & PTHREAD_START_SETSCHED) != 0) {
		/* Set scheduling parameters if needed */
		thread_extended_policy_data_t    extinfo;
		thread_precedence_policy_data_t   precedinfo;

		importance = (flags & PTHREAD_START_IMPORTANCE_MASK);
		policy = (flags >> PTHREAD_START_POLICY_BITSHIFT) & PTHREAD_START_POLICY_MASK;

		if (policy == SCHED_OTHER) {
			extinfo.timeshare = 1;
		} else {
			extinfo.timeshare = 0;
		}

		thread_policy_set(th, THREAD_EXTENDED_POLICY, (thread_policy_t)&extinfo, THREAD_EXTENDED_POLICY_COUNT);

		precedinfo.importance = (importance - BASEPRI_DEFAULT);
		thread_policy_set(th, THREAD_PRECEDENCE_POLICY, (thread_policy_t)&precedinfo, THREAD_PRECEDENCE_POLICY_COUNT);
	} else if ((flags & PTHREAD_START_QOSCLASS) != 0) {
		/* Set thread QoS class if requested. */
		pthread_priority_t priority = (pthread_priority_t)(flags & PTHREAD_START_QOSCLASS_MASK);

		thread_qos_policy_data_t qos;
		qos.qos_tier = pthread_priority_get_qos_class(priority);
		qos.tier_importance = (qos.qos_tier == QOS_CLASS_UNSPECIFIED) ? 0 :
				_pthread_priority_get_relpri(priority);

		pthread_kern->thread_policy_set_internal(th, THREAD_QOS_POLICY, (thread_policy_t)&qos, THREAD_QOS_POLICY_COUNT);
	}

	kret = pthread_kern->thread_resume(th);
	if (kret != KERN_SUCCESS) {
		error = EINVAL;
		goto out1;
	}
	thread_deallocate(th);	/* drop the creator reference */

	PTHREAD_TRACE(TRACE_pthread_thread_create|DBG_FUNC_END, error, th_pthread, 0, 0, 0);

	// cast required as mach_vm_offset_t is always 64 bits even on 32-bit platforms
	*retval = (user_addr_t)th_pthread;

	return(0);

out1:
	if (allocated != 0) {
		(void)mach_vm_deallocate(vmap, stackaddr, th_allocsize);
	}
out:
	(void)pthread_kern->mach_port_deallocate(pthread_kern->task_get_ipcspace(ctask), th_thport);
	(void)thread_terminate(th);
	(void)thread_deallocate(th);
	return(error);
}

/**
 * bsdthread_terminate system call.  Used by pthread_terminate
 */
int
_bsdthread_terminate(__unused struct proc *p,
		     user_addr_t stackaddr,
		     size_t size,
		     uint32_t kthport,
		     uint32_t sem,
		     __unused int32_t *retval)
{
	mach_vm_offset_t freeaddr;
	mach_vm_size_t freesize;
	kern_return_t kret;

	freeaddr = (mach_vm_offset_t)stackaddr;
	freesize = size;

	PTHREAD_TRACE(TRACE_pthread_thread_terminate|DBG_FUNC_START, freeaddr, freesize, kthport, 0xff, 0);

	if ((freesize != (mach_vm_size_t)0) && (freeaddr != (mach_vm_offset_t)0)) {
		kret = mach_vm_deallocate(pthread_kern->current_map(), freeaddr, freesize);
		if (kret != KERN_SUCCESS) {
			PTHREAD_TRACE(TRACE_pthread_thread_terminate|DBG_FUNC_END, kret, 0, 0, 0, 0);
			return(EINVAL);
		}
	}
	
	(void) thread_terminate(current_thread());
	if (sem != MACH_PORT_NULL) {
		 kret = pthread_kern->semaphore_signal_internal_trap(sem);
		if (kret != KERN_SUCCESS) {
			PTHREAD_TRACE(TRACE_pthread_thread_terminate|DBG_FUNC_END, kret, 0, 0, 0, 0);
			return(EINVAL);
		}
	}
	
	if (kthport != MACH_PORT_NULL) {
		pthread_kern->mach_port_deallocate(pthread_kern->task_get_ipcspace(current_task()), kthport);
	}

	PTHREAD_TRACE(TRACE_pthread_thread_terminate|DBG_FUNC_END, 0, 0, 0, 0, 0);

	pthread_kern->thread_exception_return();
	panic("bsdthread_terminate: still running\n");

	PTHREAD_TRACE(TRACE_pthread_thread_terminate|DBG_FUNC_END, 0, 0xff, 0, 0, 0);

	return(0);
}

/**
 * bsdthread_register system call.  Performs per-process setup.  Responsible for
 * returning capabilitiy bits to userspace and receiving userspace function addresses.
 */
int
_bsdthread_register(struct proc *p,
		    user_addr_t threadstart,
		    user_addr_t wqthread,
		    int pthsize,
		    user_addr_t pthread_init_data,
		    user_addr_t targetconc_ptr,
		    uint64_t dispatchqueue_offset,
		    int32_t *retval)
{
	/* prevent multiple registrations */
	if (pthread_kern->proc_get_register(p) != 0) {
		return(EINVAL);
	}
	/* syscall randomizer test can pass bogus values */
	if (pthsize < 0 || pthsize > MAX_PTHREAD_SIZE) {
		return(EINVAL);
	}
	pthread_kern->proc_set_threadstart(p, threadstart);
	pthread_kern->proc_set_wqthread(p, wqthread);
	pthread_kern->proc_set_pthsize(p, pthsize);
	pthread_kern->proc_set_register(p);

	/* if we have pthread_init_data, then we use that and target_concptr (which is an offset) get data. */
	if (pthread_init_data != 0) {
		thread_qos_policy_data_t qos;

		struct _pthread_registration_data data;
		size_t pthread_init_sz = MIN(sizeof(struct _pthread_registration_data), (size_t)targetconc_ptr);

		kern_return_t kr = copyin(pthread_init_data, &data, pthread_init_sz);
		if (kr != KERN_SUCCESS) {
			return EINVAL;
		}

		/* Incoming data from the data structure */
		pthread_kern->proc_set_dispatchqueue_offset(p, data.dispatch_queue_offset);

		/* Outgoing data that userspace expects as a reply */
		if (pthread_kern->qos_main_thread_active()) {
			mach_msg_type_number_t nqos = THREAD_QOS_POLICY_COUNT;
			boolean_t gd = FALSE;

			kr = pthread_kern->thread_policy_get(current_thread(), THREAD_QOS_POLICY, (thread_policy_t)&qos, &nqos, &gd);
			if (kr != KERN_SUCCESS || qos.qos_tier == THREAD_QOS_UNSPECIFIED) {
				/* Unspecified threads means the kernel wants us to impose legacy upon the thread. */
				qos.qos_tier = THREAD_QOS_LEGACY;
				qos.tier_importance = 0;

				kr = pthread_kern->thread_policy_set_internal(current_thread(), THREAD_QOS_POLICY, (thread_policy_t)&qos, THREAD_QOS_POLICY_COUNT);
			}

			if (kr == KERN_SUCCESS) {
				data.main_qos = pthread_qos_class_get_priority(qos.qos_tier);
			} else {
				data.main_qos = _pthread_priority_make_newest(QOS_CLASS_UNSPECIFIED, 0, 0);
			}
		} else {
			data.main_qos = _pthread_priority_make_newest(QOS_CLASS_UNSPECIFIED, 0, 0);
		}

		kr = copyout(&data, pthread_init_data, pthread_init_sz);
		if (kr != KERN_SUCCESS) {
			return EINVAL;
		}
	} else {
		pthread_kern->proc_set_dispatchqueue_offset(p, dispatchqueue_offset);
		pthread_kern->proc_set_targconc(p, targetconc_ptr);
	}

	/* return the supported feature set as the return value. */
	*retval = PTHREAD_FEATURE_SUPPORTED;

	return(0);
}

#pragma mark - QoS Manipulation

int
_bsdthread_ctl_set_qos(struct proc *p, user_addr_t __unused cmd, mach_port_name_t kport, user_addr_t tsd_priority_addr, user_addr_t arg3, int *retval)
{
 	kern_return_t kr;
	thread_t th;

	pthread_priority_t priority;

	/* Unused parameters must be zero. */
	if (arg3 != 0) {
		return EINVAL;
	}

	/* QoS is stored in a given slot in the pthread TSD. We need to copy that in and set our QoS based on it. */
	if (proc_is64bit(p)) {
		uint64_t v;
		kr = copyin(tsd_priority_addr, &v, sizeof(v));
		if (kr != KERN_SUCCESS) {
			return kr;
		}
		priority = (int)(v & 0xffffffff);
	} else {
		uint32_t v;
		kr = copyin(tsd_priority_addr, &v, sizeof(v));
		if (kr != KERN_SUCCESS) {
			return kr;
		}
		priority = v;
	}

	if ((th = port_name_to_thread(kport)) == THREAD_NULL) {
		return ESRCH;
	}

	/* <rdar://problem/16211829> Disable pthread_set_qos_class_np() on threads other than pthread_self */
	if (th != current_thread()) {
		thread_deallocate(th);
		return EPERM;
	}

	int rv = _bsdthread_ctl_set_self(p, 0, priority, 0, _PTHREAD_SET_SELF_QOS_FLAG, retval);

	/* Static param the thread, we just set QoS on it, so its stuck in QoS land now. */
	/* pthread_kern->thread_static_param(th, TRUE); */ // see <rdar://problem/16433744>, for details

	thread_deallocate(th);

	return rv;
}

static inline struct threadlist *
util_get_thread_threadlist_entry(thread_t th)
{
	struct uthread *uth = pthread_kern->get_bsdthread_info(th);
	if (uth) {
		struct threadlist *tl = pthread_kern->uthread_get_threadlist(uth);
		return tl;
	}
	return NULL;
}

static inline void
wq_thread_override_reset(thread_t th, user_addr_t resource)
{
	struct uthread *uth = pthread_kern->get_bsdthread_info(th);
	struct threadlist *tl = pthread_kern->uthread_get_threadlist(uth);

	if (tl) {
		/*
		 * Drop all outstanding overrides on this thread, done outside the wq lock
		 * because proc_usynch_thread_qos_remove_override_for_resource takes a spinlock that
		 * could cause us to panic.
		 */
		PTHREAD_TRACE(TRACE_wq_override_reset | DBG_FUNC_NONE, tl->th_workq, 0, 0, 0, 0);

		pthread_kern->proc_usynch_thread_qos_reset_override_for_resource(current_task(), uth, 0, resource, THREAD_QOS_OVERRIDE_TYPE_DISPATCH_ASYNCHRONOUS_OVERRIDE);
	}
}

int
_bsdthread_ctl_set_self(struct proc *p, user_addr_t __unused cmd, pthread_priority_t priority, mach_port_name_t voucher, _pthread_set_flags_t flags, int __unused *retval)
{
	thread_qos_policy_data_t qos;
	mach_msg_type_number_t nqos = THREAD_QOS_POLICY_COUNT;
	boolean_t gd = FALSE;

	kern_return_t kr;
	int qos_rv = 0, voucher_rv = 0, fixedpri_rv = 0;

	if ((flags & _PTHREAD_SET_SELF_QOS_FLAG) != 0) {
		kr = pthread_kern->thread_policy_get(current_thread(), THREAD_QOS_POLICY, (thread_policy_t)&qos, &nqos, &gd);
		if (kr != KERN_SUCCESS) {
			qos_rv = EINVAL;
			goto voucher;
		}

		/* If we have main-thread QoS then we don't allow a thread to come out of QOS_CLASS_UNSPECIFIED. */
		if (pthread_kern->qos_main_thread_active() && qos.qos_tier == THREAD_QOS_UNSPECIFIED) {
			qos_rv = EPERM;
			goto voucher;
		}

		/* Get the work queue for tracing, also the threadlist for bucket manipluation. */
		struct workqueue *wq = NULL;
		struct threadlist *tl = util_get_thread_threadlist_entry(current_thread());
		if (tl) {
			wq = tl->th_workq;
		}

		PTHREAD_TRACE(TRACE_pthread_set_qos_self | DBG_FUNC_START, wq, qos.qos_tier, qos.tier_importance, 0, 0);

		qos.qos_tier = pthread_priority_get_qos_class(priority);
		qos.tier_importance = (qos.qos_tier == QOS_CLASS_UNSPECIFIED) ? 0 : _pthread_priority_get_relpri(priority);

		kr = pthread_kern->thread_policy_set_internal(current_thread(), THREAD_QOS_POLICY, (thread_policy_t)&qos, THREAD_QOS_POLICY_COUNT);
		if (kr != KERN_SUCCESS) {
			qos_rv = EINVAL;
			goto voucher;
		}

		/* If we're a workqueue, the threadlist item priority needs adjusting, along with the bucket we were running in. */
		if (tl) {
			workqueue_lock_spin(p);

			/* Fix up counters. */
			uint8_t old_bucket = tl->th_priority;
			uint8_t new_bucket = pthread_priority_get_class_index(priority);

			uint32_t old_active = OSAddAtomic(-1, &wq->wq_thactive_count[old_bucket]);
			OSAddAtomic(1, &wq->wq_thactive_count[new_bucket]);

			wq->wq_thscheduled_count[old_bucket]--;
			wq->wq_thscheduled_count[new_bucket]++;

			tl->th_priority = new_bucket;

			/* If we were at the ceiling of non-overcommitted threads for a given bucket, we have to
			 * reevaluate whether we should start more work.
			 */
			if (old_active == wq->wq_reqconc[old_bucket]) {
				/* workqueue_run_nextreq will drop the workqueue lock in all exit paths. */
				(void)workqueue_run_nextreq(p, wq, THREAD_NULL, RUN_NEXTREQ_DEFAULT, 0);
			} else {
				workqueue_unlock(p);
			}
		}

		PTHREAD_TRACE(TRACE_pthread_set_qos_self | DBG_FUNC_END, wq, qos.qos_tier, qos.tier_importance, 0, 0);
	}

voucher:
	if ((flags & _PTHREAD_SET_SELF_VOUCHER_FLAG) != 0) {
		kr = pthread_kern->thread_set_voucher_name(voucher);
		if (kr != KERN_SUCCESS) {
			voucher_rv = ENOENT;
			goto fixedpri;
		}
	}

fixedpri:
	if ((flags & _PTHREAD_SET_SELF_FIXEDPRIORITY_FLAG) != 0) {
		thread_extended_policy_data_t extpol = {.timeshare = 0};
		thread_t thread = current_thread();
		
		struct threadlist *tl = util_get_thread_threadlist_entry(thread);
		if (tl) {
			/* Not allowed on workqueue threads */
			fixedpri_rv = ENOTSUP;
			goto done;
		}

		kr = pthread_kern->thread_policy_set_internal(thread, THREAD_EXTENDED_POLICY, (thread_policy_t)&extpol, THREAD_EXTENDED_POLICY_COUNT);
		if (kr != KERN_SUCCESS) {
			fixedpri_rv = EINVAL;
			goto done;
		}
	} else if ((flags & _PTHREAD_SET_SELF_TIMESHARE_FLAG) != 0) {
		thread_extended_policy_data_t extpol = {.timeshare = 1};
		thread_t thread = current_thread();
		
		struct threadlist *tl = util_get_thread_threadlist_entry(thread);
		if (tl) {
			/* Not allowed on workqueue threads */
			fixedpri_rv = ENOTSUP;
			goto done;
		}

		kr = pthread_kern->thread_policy_set_internal(thread, THREAD_EXTENDED_POLICY, (thread_policy_t)&extpol, THREAD_EXTENDED_POLICY_COUNT);
		if (kr != KERN_SUCCESS) {
			fixedpri_rv = EINVAL;
			goto done;
		}
	}
	
done:
	if (qos_rv && voucher_rv) {
		/* Both failed, give that a unique error. */
		return EBADMSG;
	}

	if (qos_rv) {
		return qos_rv;
	}

	if (voucher_rv) {
		return voucher_rv;
	}

	if (fixedpri_rv) {
		return fixedpri_rv;
	}
	
	return 0;
}

int
_bsdthread_ctl_qos_override_start(struct proc __unused *p, user_addr_t __unused cmd, mach_port_name_t kport, pthread_priority_t priority, user_addr_t resource, int __unused *retval)
{
	thread_t th;
	int rv = 0;

	if ((th = port_name_to_thread(kport)) == THREAD_NULL) {
		return ESRCH;
	}

	struct uthread *uth = pthread_kern->get_bsdthread_info(th);
	int override_qos = pthread_priority_get_qos_class(priority);

	struct threadlist *tl = util_get_thread_threadlist_entry(th);
	if (tl) {
		PTHREAD_TRACE(TRACE_wq_override_start | DBG_FUNC_NONE, tl->th_workq, thread_tid(th), 1, priority, 0);
	}

	/* The only failure case here is if we pass a tid and have it lookup the thread, we pass the uthread, so this all always succeeds. */
	pthread_kern->proc_usynch_thread_qos_add_override_for_resource(current_task(), uth, 0, override_qos, TRUE, resource, THREAD_QOS_OVERRIDE_TYPE_PTHREAD_EXPLICIT_OVERRIDE);

	thread_deallocate(th);
	return rv;
}

int
_bsdthread_ctl_qos_override_end(struct proc __unused *p, user_addr_t __unused cmd, mach_port_name_t kport, user_addr_t resource, user_addr_t arg3, int __unused *retval)
{
	thread_t th;
	int rv = 0;

	if (arg3 != 0) {
		return EINVAL;
	}

	if ((th = port_name_to_thread(kport)) == THREAD_NULL) {
		return ESRCH;
	}

	struct uthread *uth = pthread_kern->get_bsdthread_info(th);

	struct threadlist *tl = util_get_thread_threadlist_entry(th);
	if (tl) {
		PTHREAD_TRACE(TRACE_wq_override_end | DBG_FUNC_NONE, tl->th_workq, thread_tid(th), 0, 0, 0);
	}

	pthread_kern->proc_usynch_thread_qos_remove_override_for_resource(current_task(), uth, 0, resource, THREAD_QOS_OVERRIDE_TYPE_PTHREAD_EXPLICIT_OVERRIDE);

	thread_deallocate(th);
	return rv;
}

int
_bsdthread_ctl_qos_override_dispatch(struct proc *p, user_addr_t cmd, mach_port_name_t kport, pthread_priority_t priority, user_addr_t arg3, int *retval)
{
	if (arg3 != 0) {
		return EINVAL;
	}

	return _bsdthread_ctl_qos_dispatch_asynchronous_override_add(p, cmd, kport, priority, USER_ADDR_NULL, retval);
}

int
_bsdthread_ctl_qos_dispatch_asynchronous_override_add(struct proc __unused *p, user_addr_t __unused cmd, mach_port_name_t kport, pthread_priority_t priority, user_addr_t resource, int __unused *retval)
{
	thread_t th;
	int rv = 0;

	if ((th = port_name_to_thread(kport)) == THREAD_NULL) {
		return ESRCH;
	}

	struct uthread *uth = pthread_kern->get_bsdthread_info(th);
	int override_qos = pthread_priority_get_qos_class(priority);

	struct threadlist *tl = util_get_thread_threadlist_entry(th);
	if (!tl) {
		thread_deallocate(th);
		return EPERM;
	}

	PTHREAD_TRACE(TRACE_wq_override_dispatch | DBG_FUNC_NONE, tl->th_workq, thread_tid(th), 1, priority, 0);

	/* The only failure case here is if we pass a tid and have it lookup the thread, we pass the uthread, so this all always succeeds. */
	pthread_kern->proc_usynch_thread_qos_add_override_for_resource(current_task(), uth, 0, override_qos, TRUE, resource, THREAD_QOS_OVERRIDE_TYPE_DISPATCH_ASYNCHRONOUS_OVERRIDE);

	thread_deallocate(th);
	return rv;
}

int
_bsdthread_ctl_qos_override_reset(struct proc *p, user_addr_t cmd, user_addr_t arg1, user_addr_t arg2, user_addr_t arg3, int *retval)
{
	if (arg1 != 0 || arg2 != 0 || arg3 != 0) {
		return EINVAL;
	}

	return _bsdthread_ctl_qos_dispatch_asynchronous_override_reset(p, cmd, 1 /* reset_all */, 0, 0, retval);
}

int
_bsdthread_ctl_qos_dispatch_asynchronous_override_reset(struct proc __unused *p, user_addr_t __unused cmd, int reset_all, user_addr_t resource, user_addr_t arg3, int __unused *retval)
{
	thread_t th;
	struct threadlist *tl;
	int rv = 0;

	if ((reset_all && (resource != 0)) || arg3 != 0) {
		return EINVAL;
	}

	th = current_thread();
	tl = util_get_thread_threadlist_entry(th);

	if (tl) {
		wq_thread_override_reset(th, reset_all ? THREAD_QOS_OVERRIDE_RESOURCE_WILDCARD : resource);
	} else {
		rv = EPERM;
	}

	return rv;
}

int
_bsdthread_ctl(struct proc *p, user_addr_t cmd, user_addr_t arg1, user_addr_t arg2, user_addr_t arg3, int *retval)
{
	switch (cmd) {
		case BSDTHREAD_CTL_SET_QOS:
			return _bsdthread_ctl_set_qos(p, cmd, (mach_port_name_t)arg1, arg2, arg3, retval);
		case BSDTHREAD_CTL_QOS_OVERRIDE_START:
			return _bsdthread_ctl_qos_override_start(p, cmd, (mach_port_name_t)arg1, (pthread_priority_t)arg2, arg3, retval);
		case BSDTHREAD_CTL_QOS_OVERRIDE_END:
			return _bsdthread_ctl_qos_override_end(p, cmd, (mach_port_name_t)arg1, arg2, arg3, retval);
		case BSDTHREAD_CTL_QOS_OVERRIDE_RESET:
			return _bsdthread_ctl_qos_override_reset(p, cmd, arg1, arg2, arg3, retval);
		case BSDTHREAD_CTL_QOS_OVERRIDE_DISPATCH:
			return _bsdthread_ctl_qos_override_dispatch(p, cmd, (mach_port_name_t)arg1, (pthread_priority_t)arg2, arg3, retval);
		case BSDTHREAD_CTL_QOS_DISPATCH_ASYNCHRONOUS_OVERRIDE_ADD:
			return _bsdthread_ctl_qos_dispatch_asynchronous_override_add(p, cmd, (mach_port_name_t)arg1, (pthread_priority_t)arg2, arg3, retval);
		case BSDTHREAD_CTL_QOS_DISPATCH_ASYNCHRONOUS_OVERRIDE_RESET:
			return _bsdthread_ctl_qos_dispatch_asynchronous_override_reset(p, cmd, (int)arg1, arg2, arg3, retval);
		case BSDTHREAD_CTL_SET_SELF:
			return _bsdthread_ctl_set_self(p, cmd, (pthread_priority_t)arg1, (mach_port_name_t)arg2, (_pthread_set_flags_t)arg3, retval);
		default:
			return EINVAL;
	}
}

#pragma mark - Workqueue Implementation
#pragma mark sysctls

uint32_t wq_yielded_threshold		= WQ_YIELDED_THRESHOLD;
uint32_t wq_yielded_window_usecs	= WQ_YIELDED_WINDOW_USECS;
uint32_t wq_stalled_window_usecs	= WQ_STALLED_WINDOW_USECS;
uint32_t wq_reduce_pool_window_usecs	= WQ_REDUCE_POOL_WINDOW_USECS;
uint32_t wq_max_timer_interval_usecs	= WQ_MAX_TIMER_INTERVAL_USECS;
uint32_t wq_max_threads			= WORKQUEUE_MAXTHREADS;
uint32_t wq_max_constrained_threads	= WORKQUEUE_MAXTHREADS / 8;
uint32_t wq_max_concurrency = 1; // set to ncpus on load

SYSCTL_INT(_kern, OID_AUTO, wq_yielded_threshold, CTLFLAG_RW | CTLFLAG_LOCKED,
	   &wq_yielded_threshold, 0, "");

SYSCTL_INT(_kern, OID_AUTO, wq_yielded_window_usecs, CTLFLAG_RW | CTLFLAG_LOCKED,
	   &wq_yielded_window_usecs, 0, "");

SYSCTL_INT(_kern, OID_AUTO, wq_stalled_window_usecs, CTLFLAG_RW | CTLFLAG_LOCKED,
	   &wq_stalled_window_usecs, 0, "");

SYSCTL_INT(_kern, OID_AUTO, wq_reduce_pool_window_usecs, CTLFLAG_RW | CTLFLAG_LOCKED,
	   &wq_reduce_pool_window_usecs, 0, "");

SYSCTL_INT(_kern, OID_AUTO, wq_max_timer_interval_usecs, CTLFLAG_RW | CTLFLAG_LOCKED,
	   &wq_max_timer_interval_usecs, 0, "");

SYSCTL_INT(_kern, OID_AUTO, wq_max_threads, CTLFLAG_RW | CTLFLAG_LOCKED,
	   &wq_max_threads, 0, "");

SYSCTL_INT(_kern, OID_AUTO, wq_max_constrained_threads, CTLFLAG_RW | CTLFLAG_LOCKED,
	   &wq_max_constrained_threads, 0, "");

#ifdef DEBUG
SYSCTL_INT(_kern, OID_AUTO, wq_max_concurrency, CTLFLAG_RW | CTLFLAG_LOCKED,
		   &wq_max_concurrency, 0, "");

static int wq_kevent_test SYSCTL_HANDLER_ARGS;
SYSCTL_PROC(_debug, OID_AUTO, wq_kevent_test, CTLFLAG_MASKED | CTLFLAG_RW | CTLFLAG_LOCKED | CTLFLAG_ANYBODY | CTLTYPE_OPAQUE, NULL, 0, wq_kevent_test, 0, "-");
#endif

static uint32_t wq_init_constrained_limit = 1;

#pragma mark workqueue lock

void
_workqueue_init_lock(proc_t p)
{
	lck_spin_init(pthread_kern->proc_get_wqlockptr(p), pthread_lck_grp, pthread_lck_attr);
	*(pthread_kern->proc_get_wqinitingptr(p)) = FALSE;
}

void
_workqueue_destroy_lock(proc_t p)
{
	lck_spin_destroy(pthread_kern->proc_get_wqlockptr(p), pthread_lck_grp);
}


static void
workqueue_lock_spin(proc_t p)
{
	lck_spin_lock(pthread_kern->proc_get_wqlockptr(p));
}

static void
workqueue_unlock(proc_t p)
{
	lck_spin_unlock(pthread_kern->proc_get_wqlockptr(p));
}

#pragma mark workqueue add timer

/**
 * Sets up the timer which will call out to workqueue_add_timer
 */
static void
workqueue_interval_timer_start(struct workqueue *wq)
{
	uint64_t deadline;

	/* n.b. wq_timer_interval is reset to 0 in workqueue_add_timer if the
	 ATIMER_RUNNING flag is not present.  The net effect here is that if a
	 sequence of threads is required, we'll double the time before we give out
	 the next one. */
	if (wq->wq_timer_interval == 0) {
		wq->wq_timer_interval = wq_stalled_window_usecs;

	} else {
		wq->wq_timer_interval = wq->wq_timer_interval * 2;

		if (wq->wq_timer_interval > wq_max_timer_interval_usecs) {
			wq->wq_timer_interval = wq_max_timer_interval_usecs;
		}
	}
	clock_interval_to_deadline(wq->wq_timer_interval, 1000, &deadline);

	thread_call_enter_delayed(wq->wq_atimer_call, deadline);

	PTHREAD_TRACE(TRACE_wq_start_add_timer, wq, wq->wq_reqcount, wq->wq_flags, wq->wq_timer_interval, 0);
}

/**
 * returns whether lastblocked_tsp is within wq_stalled_window_usecs of cur_ts
 */
static boolean_t
wq_thread_is_busy(uint64_t cur_ts, uint64_t *lastblocked_tsp)
{
	clock_sec_t	secs;
	clock_usec_t	usecs;
	uint64_t lastblocked_ts;
	uint64_t elapsed;

	/*
	 * the timestamp is updated atomically w/o holding the workqueue lock
	 * so we need to do an atomic read of the 64 bits so that we don't see
	 * a mismatched pair of 32 bit reads... we accomplish this in an architecturally
	 * independent fashion by using OSCompareAndSwap64 to write back the
	 * value we grabbed... if it succeeds, then we have a good timestamp to
	 * evaluate... if it fails, we straddled grabbing the timestamp while it
	 * was being updated... treat a failed update as a busy thread since
	 * it implies we are about to see a really fresh timestamp anyway
	 */
	lastblocked_ts = *lastblocked_tsp;

	if ( !OSCompareAndSwap64((UInt64)lastblocked_ts, (UInt64)lastblocked_ts, lastblocked_tsp))
		return (TRUE);

	if (lastblocked_ts >= cur_ts) {
		/*
		 * because the update of the timestamp when a thread blocks isn't
		 * serialized against us looking at it (i.e. we don't hold the workq lock)
		 * it's possible to have a timestamp that matches the current time or
		 * that even looks to be in the future relative to when we grabbed the current
		 * time... just treat this as a busy thread since it must have just blocked.
		 */
		return (TRUE);
	}
	elapsed = cur_ts - lastblocked_ts;

	pthread_kern->absolutetime_to_microtime(elapsed, &secs, &usecs);

	if (secs == 0 && usecs < wq_stalled_window_usecs)
		return (TRUE);
	return (FALSE);
}

#define WQ_TIMER_NEEDED(wq, start_timer) do {		\
	int oldflags = wq->wq_flags;			\
							\
	if ( !(oldflags & (WQ_EXITING | WQ_ATIMER_RUNNING))) {	\
		if (OSCompareAndSwap(oldflags, oldflags | WQ_ATIMER_RUNNING, (UInt32 *)&wq->wq_flags)) \
			start_timer = TRUE;			\
	}							\
} while (0)

/**
 * handler function for the timer
 */
static void
workqueue_add_timer(struct workqueue *wq, __unused int param1)
{
	proc_t		p;
	boolean_t	start_timer = FALSE;
	boolean_t	retval;

	PTHREAD_TRACE(TRACE_wq_add_timer | DBG_FUNC_START, wq, wq->wq_flags, wq->wq_nthreads, wq->wq_thidlecount, 0);

	p = wq->wq_proc;

	workqueue_lock_spin(p);

	/*
	 * because workqueue_callback now runs w/o taking the workqueue lock
	 * we are unsynchronized w/r to a change in state of the running threads...
	 * to make sure we always evaluate that change, we allow it to start up 
	 * a new timer if the current one is actively evalutating the state
	 * however, we do not need more than 2 timers fired up (1 active and 1 pending)
	 * and we certainly do not want 2 active timers evaluating the state
	 * simultaneously... so use WQL_ATIMER_BUSY to serialize the timers...
	 * note that WQL_ATIMER_BUSY is in a different flag word from WQ_ATIMER_RUNNING since
	 * it is always protected by the workq lock... WQ_ATIMER_RUNNING is evaluated
	 * and set atomimcally since the callback function needs to manipulate it
	 * w/o holding the workq lock...
	 *
	 * !WQ_ATIMER_RUNNING && !WQL_ATIMER_BUSY   ==   no pending timer, no active timer
	 * !WQ_ATIMER_RUNNING && WQL_ATIMER_BUSY    ==   no pending timer, 1 active timer
	 * WQ_ATIMER_RUNNING && !WQL_ATIMER_BUSY    ==   1 pending timer, no active timer
	 * WQ_ATIMER_RUNNING && WQL_ATIMER_BUSY     ==   1 pending timer, 1 active timer
	 */
	while (wq->wq_lflags & WQL_ATIMER_BUSY) {
		wq->wq_lflags |= WQL_ATIMER_WAITING;

		assert_wait((caddr_t)wq, (THREAD_UNINT));
		workqueue_unlock(p);

		thread_block(THREAD_CONTINUE_NULL);

		workqueue_lock_spin(p);
	}
	wq->wq_lflags |= WQL_ATIMER_BUSY;

	/*
	 * the workq lock will protect us from seeing WQ_EXITING change state, but we
	 * still need to update this atomically in case someone else tries to start
	 * the timer just as we're releasing it
	 */
	while ( !(OSCompareAndSwap(wq->wq_flags, (wq->wq_flags & ~WQ_ATIMER_RUNNING), (UInt32 *)&wq->wq_flags)));

again:
	retval = TRUE;
	if ( !(wq->wq_flags & WQ_EXITING)) {
		boolean_t add_thread = FALSE;
		/*
		 * check to see if the stall frequency was beyond our tolerance
		 * or we have work on the queue, but haven't scheduled any 
		 * new work within our acceptable time interval because
		 * there were no idle threads left to schedule
		 */
		if (wq->wq_reqcount) {
			uint32_t	priclass = 0;
			uint32_t	thactive_count = 0;
			uint64_t	curtime = mach_absolute_time();
			uint64_t	busycount = 0;

			if (wq->wq_requests[WORKQUEUE_EVENT_MANAGER_BUCKET] &&
				wq->wq_thscheduled_count[WORKQUEUE_EVENT_MANAGER_BUCKET] == 0){
				priclass = WORKQUEUE_EVENT_MANAGER_BUCKET;
			} else {
				for (priclass = 0; priclass < WORKQUEUE_NUM_BUCKETS; priclass++) {
					if (wq->wq_requests[priclass])
						break;
				}
			}

			if (priclass < WORKQUEUE_EVENT_MANAGER_BUCKET){
				/*
				 * Compute a metric for many how many threads are active.  We
				 * find the highest priority request outstanding and then add up
				 * the number of active threads in that and all higher-priority
				 * buckets.  We'll also add any "busy" threads which are not
				 * active but blocked recently enough that we can't be sure
				 * they've gone idle yet.  We'll then compare this metric to our
				 * max concurrency to decide whether to add a new thread.
				 */
				for (uint32_t i = 0; i <= priclass; i++) {
					thactive_count += wq->wq_thactive_count[i];

					// XXX why isn't this checking thscheduled_count < thactive_count ?
					if (wq->wq_thscheduled_count[i]) {
						if (wq_thread_is_busy(curtime, &wq->wq_lastblocked_ts[i]))
							busycount++;
					}
				}
			}

			if (thactive_count + busycount < wq->wq_max_concurrency ||
				priclass == WORKQUEUE_EVENT_MANAGER_BUCKET) {

				if (wq->wq_thidlecount == 0) {
					/*
					 * if we have no idle threads, try to add one
					 */
					retval = workqueue_addnewthread(wq, priclass == WORKQUEUE_EVENT_MANAGER_BUCKET);
				}
				add_thread = TRUE;
			}

			if (wq->wq_reqcount) {
				/*
				 * as long as we have threads to schedule, and we successfully
				 * scheduled new work, keep trying
				 */
				while (wq->wq_thidlecount && !(wq->wq_flags & WQ_EXITING)) {
					/*
					 * workqueue_run_nextreq is responsible for
					 * dropping the workqueue lock in all cases
					 */
					retval = workqueue_run_nextreq(p, wq, THREAD_NULL, RUN_NEXTREQ_DEFAULT, 0);
					workqueue_lock_spin(p);

					if (retval == FALSE)
						break;
				}
				if ( !(wq->wq_flags & WQ_EXITING) && wq->wq_reqcount) {

					if (wq->wq_thidlecount == 0 && retval == TRUE && add_thread == TRUE)
						goto again;

					if (wq->wq_thidlecount == 0 || busycount)
						WQ_TIMER_NEEDED(wq, start_timer);

					PTHREAD_TRACE(TRACE_wq_add_timer | DBG_FUNC_NONE, wq, wq->wq_reqcount, wq->wq_thidlecount, busycount, 0);
				}
			}
		}
	}

	/* 
	 * If we called WQ_TIMER_NEEDED above, then this flag will be set if that
	 * call marked the timer running.  If so, we let the timer interval grow.
	 * Otherwise, we reset it back to 0.
	 */
	if ( !(wq->wq_flags & WQ_ATIMER_RUNNING))
		wq->wq_timer_interval = 0;

	wq->wq_lflags &= ~WQL_ATIMER_BUSY;

	if ((wq->wq_flags & WQ_EXITING) || (wq->wq_lflags & WQL_ATIMER_WAITING)) {
		/*
		 * wakeup the thread hung up in workqueue_exit or workqueue_add_timer waiting for this timer
		 * to finish getting out of the way
		 */
		wq->wq_lflags &= ~WQL_ATIMER_WAITING;
		wakeup(wq);
	}

	PTHREAD_TRACE(TRACE_wq_add_timer | DBG_FUNC_END, wq, start_timer, wq->wq_nthreads, wq->wq_thidlecount, 0);

	workqueue_unlock(p);

	if (start_timer == TRUE)
		workqueue_interval_timer_start(wq);
}

#pragma mark thread state tracking

// called by spinlock code when trying to yield to lock owner
void
_workqueue_thread_yielded(void)
{
	struct workqueue *wq;
	proc_t p;

	p = current_proc();

	if ((wq = pthread_kern->proc_get_wqptr(p)) == NULL || wq->wq_reqcount == 0)
		return;
	
	workqueue_lock_spin(p);

	if (wq->wq_reqcount) {
		uint64_t	curtime;
		uint64_t	elapsed;
		clock_sec_t	secs;
		clock_usec_t	usecs;

		if (wq->wq_thread_yielded_count++ == 0)
			wq->wq_thread_yielded_timestamp = mach_absolute_time();

		if (wq->wq_thread_yielded_count < wq_yielded_threshold) {
			workqueue_unlock(p);
			return;
		}

		PTHREAD_TRACE(TRACE_wq_thread_yielded | DBG_FUNC_START, wq, wq->wq_thread_yielded_count, wq->wq_reqcount, 0, 0);

		wq->wq_thread_yielded_count = 0;

		curtime = mach_absolute_time();
		elapsed = curtime - wq->wq_thread_yielded_timestamp;
		pthread_kern->absolutetime_to_microtime(elapsed, &secs, &usecs);

		if (secs == 0 && usecs < wq_yielded_window_usecs) {

			if (wq->wq_thidlecount == 0) {
				workqueue_addnewthread(wq, TRUE);
				/*
				 * 'workqueue_addnewthread' drops the workqueue lock
				 * when creating the new thread and then retakes it before
				 * returning... this window allows other threads to process
				 * requests, so we need to recheck for available work
				 * if none found, we just return...  the newly created thread
				 * will eventually get used (if it hasn't already)...
				 */
				if (wq->wq_reqcount == 0) {
					workqueue_unlock(p);
					return;
				}
			}
			if (wq->wq_thidlecount) {
				(void)workqueue_run_nextreq(p, wq, THREAD_NULL, RUN_NEXTREQ_UNCONSTRAINED, 0);
				/*
				 * workqueue_run_nextreq is responsible for
				 * dropping the workqueue lock in all cases
				 */
				PTHREAD_TRACE(TRACE_wq_thread_yielded | DBG_FUNC_END, wq, wq->wq_thread_yielded_count, wq->wq_reqcount, 1, 0);

				return;
			}
		}
		PTHREAD_TRACE(TRACE_wq_thread_yielded | DBG_FUNC_END, wq, wq->wq_thread_yielded_count, wq->wq_reqcount, 2, 0);
	}
	workqueue_unlock(p);
}



static void
workqueue_callback(int type, thread_t thread)
{
	struct uthread    *uth;
	struct threadlist *tl;
	struct workqueue  *wq;

	uth = pthread_kern->get_bsdthread_info(thread);
	tl = pthread_kern->uthread_get_threadlist(uth);
	wq = tl->th_workq;

	switch (type) {
	case SCHED_CALL_BLOCK: {
		uint32_t	old_activecount;
		boolean_t	start_timer = FALSE;

		old_activecount = OSAddAtomic(-1, &wq->wq_thactive_count[tl->th_priority]);

		/*
		 * If we blocked and were at the requested concurrency previously, we may
		 * need to spin up a new thread.  Of course, if it's the event manager
		 * then that's moot, so ignore that case.
		 */
		if (old_activecount == wq->wq_reqconc[tl->th_priority] &&
			tl->th_priority != WORKQUEUE_EVENT_MANAGER_BUCKET) {
			uint64_t	curtime;
			UInt64		*lastblocked_ptr;

			/*
			 * the number of active threads at this priority
			 * has fallen below the maximum number of concurrent
			 * threads that we're allowed to run
			 */
			lastblocked_ptr = (UInt64 *)&wq->wq_lastblocked_ts[tl->th_priority];
			curtime = mach_absolute_time();

			/*
			 * if we collide with another thread trying to update the last_blocked (really unlikely
			 * since another thread would have to get scheduled and then block after we start down
			 * this path), it's not a problem.  Either timestamp is adequate, so no need to retry
			 */

			OSCompareAndSwap64(*lastblocked_ptr, (UInt64)curtime, lastblocked_ptr);

			if (wq->wq_reqcount) {
				/*
				 * we have work to do so start up the timer
				 * if it's not running... we'll let it sort
				 * out whether we really need to start up
				 * another thread
				 */
				WQ_TIMER_NEEDED(wq, start_timer);
			}

			if (start_timer == TRUE) {
				workqueue_interval_timer_start(wq);
			}
		}
		PTHREAD_TRACE1(TRACE_wq_thread_block | DBG_FUNC_START, wq, old_activecount, tl->th_priority, start_timer, thread_tid(thread));
		break;
	}
	case SCHED_CALL_UNBLOCK:
		/*
		 * we cannot take the workqueue_lock here...
		 * an UNBLOCK can occur from a timer event which
		 * is run from an interrupt context... if the workqueue_lock
		 * is already held by this processor, we'll deadlock...
		 * the thread lock for the thread being UNBLOCKED
		 * is also held
		 */
		OSAddAtomic(1, &wq->wq_thactive_count[tl->th_priority]);
		
		PTHREAD_TRACE1(TRACE_wq_thread_block | DBG_FUNC_END, wq, wq->wq_threads_scheduled, tl->th_priority, 0, thread_tid(thread));
		
		break;
	}
}

sched_call_t
_workqueue_get_sched_callback(void)
{
	return workqueue_callback;
}

#pragma mark thread addition/removal

/**
 * pop goes the thread
 */
static void
workqueue_removethread(struct threadlist *tl, int fromexit)
{
	struct workqueue *wq;
	struct uthread * uth;

	/* 
	 * If fromexit is set, the call is from workqueue_exit(,
	 * so some cleanups are to be avoided.
	 */
	wq = tl->th_workq;

	TAILQ_REMOVE(&wq->wq_thidlelist, tl, th_entry);

	if (fromexit == 0) {
		wq->wq_nthreads--;
		wq->wq_thidlecount--;
	}

	/*
	 * Clear the threadlist pointer in uthread so 
	 * blocked thread on wakeup for termination will
	 * not access the thread list as it is going to be
	 * freed.
	 */
	pthread_kern->thread_sched_call(tl->th_thread, NULL);

	uth = pthread_kern->get_bsdthread_info(tl->th_thread);
	if (uth != (struct uthread *)0) {
		pthread_kern->uthread_set_threadlist(uth, NULL);
	}
	if (fromexit == 0) {
		/* during exit the lock is not held */
		workqueue_unlock(wq->wq_proc);
	}

	if ( (tl->th_flags & TH_LIST_SUSPENDED) ) {
		/*
		 * thread was created, but never used... 
		 * need to clean up the stack and port ourselves
		 * since we're not going to spin up through the
		 * normal exit path triggered from Libc
		 */
		if (fromexit == 0) {
			/* vm map is already deallocated when this is called from exit */
			(void)mach_vm_deallocate(wq->wq_map, tl->th_stackaddr, tl->th_allocsize);
		}
		(void)pthread_kern->mach_port_deallocate(pthread_kern->task_get_ipcspace(wq->wq_task), tl->th_thport);

		PTHREAD_TRACE1(TRACE_wq_thread_suspend | DBG_FUNC_END, wq, (uintptr_t)thread_tid(current_thread()), wq->wq_nthreads, 0xdead, thread_tid(tl->th_thread));
	} else {

		PTHREAD_TRACE1(TRACE_wq_thread_park | DBG_FUNC_END, wq, (uintptr_t)thread_tid(current_thread()), wq->wq_nthreads, 0xdead, thread_tid(tl->th_thread));
	}
	/*
	 * drop our ref on the thread
	 */
	thread_deallocate(tl->th_thread);

	kfree(tl, sizeof(struct threadlist));
}


/**
 * Try to add a new workqueue thread.
 *
 * - called with workq lock held
 * - dropped and retaken around thread creation
 * - return with workq lock held
 */
static boolean_t
workqueue_addnewthread(struct workqueue *wq, boolean_t ignore_constrained_thread_limit)
{
	struct threadlist *tl;
	struct uthread	*uth;
	kern_return_t	kret;
	thread_t	th;
	proc_t		p;
	void 	 	*sright;
	mach_vm_offset_t stackaddr;

	if ((wq->wq_flags & WQ_EXITING) == WQ_EXITING) {
		PTHREAD_TRACE(TRACE_wq_thread_add_during_exit | DBG_FUNC_NONE, wq, 0, 0, 0, 0);
		return (FALSE);
	}

	if (wq->wq_nthreads >= wq_max_threads || wq->wq_nthreads >= (pthread_kern->config_thread_max - 20)) {
		wq->wq_lflags |= WQL_EXCEEDED_TOTAL_THREAD_LIMIT;

		PTHREAD_TRACE(TRACE_wq_thread_limit_exceeded | DBG_FUNC_NONE, wq, wq->wq_nthreads, wq_max_threads,
				pthread_kern->config_thread_max - 20, 0);
		return (FALSE);
	}
	wq->wq_lflags &= ~WQL_EXCEEDED_TOTAL_THREAD_LIMIT;

	if (ignore_constrained_thread_limit == FALSE &&
		wq->wq_constrained_threads_scheduled >= wq_max_constrained_threads) {
		/* 
		 * If we're not creating this thread to service an overcommit or
		 * event manager request, then we check to see if we are over our
		 * constrained thread limit, in which case we error out.
		 */
		wq->wq_lflags |= WQL_EXCEEDED_CONSTRAINED_THREAD_LIMIT;

		PTHREAD_TRACE(TRACE_wq_thread_constrained_maxed | DBG_FUNC_NONE, wq, wq->wq_constrained_threads_scheduled,
				wq_max_constrained_threads, 0, 0);
		return (FALSE);
	}
	if (wq->wq_constrained_threads_scheduled < wq_max_constrained_threads)
		wq->wq_lflags &= ~WQL_EXCEEDED_CONSTRAINED_THREAD_LIMIT;

	wq->wq_nthreads++;

	p = wq->wq_proc;
	workqueue_unlock(p);

	kret = pthread_kern->thread_create_workq(wq->wq_task, (thread_continue_t)wq_unsuspend_continue, &th);
 	if (kret != KERN_SUCCESS) {
		PTHREAD_TRACE(TRACE_wq_thread_create_failed | DBG_FUNC_NONE, wq, kret, 0, 0, 0);
		goto failed;
	}

	tl = kalloc(sizeof(struct threadlist));
	bzero(tl, sizeof(struct threadlist));

	stackaddr = stackaddr_hint(p);

	mach_vm_size_t guardsize = vm_map_page_size(wq->wq_map);
	mach_vm_size_t pthread_size = 
		vm_map_round_page_mask(pthread_kern->proc_get_pthsize(p) + PTHREAD_T_OFFSET, vm_map_page_mask(wq->wq_map));
	tl->th_allocsize = guardsize + PTH_DEFAULT_STACKSIZE + pthread_size;

	kret = mach_vm_map(wq->wq_map, &stackaddr,
    			tl->th_allocsize,
    			page_size-1,
    			VM_MAKE_TAG(VM_MEMORY_STACK)| VM_FLAGS_ANYWHERE , NULL,
    			0, FALSE, VM_PROT_DEFAULT, VM_PROT_ALL,
    			VM_INHERIT_DEFAULT);

	if (kret != KERN_SUCCESS) {
		PTHREAD_TRACE(TRACE_wq_thread_create_failed | DBG_FUNC_NONE, wq, kret, 1, 0, 0);

		kret = mach_vm_allocate(wq->wq_map,
				&stackaddr, tl->th_allocsize,
				VM_MAKE_TAG(VM_MEMORY_STACK) | VM_FLAGS_ANYWHERE);
	}
	if (kret == KERN_SUCCESS) {
		/*
		 * The guard page is at the lowest address
		 * The stack base is the highest address
		 */
		kret = mach_vm_protect(wq->wq_map, stackaddr, guardsize, FALSE, VM_PROT_NONE);

		if (kret != KERN_SUCCESS) {
			(void) mach_vm_deallocate(wq->wq_map, stackaddr, tl->th_allocsize);
			PTHREAD_TRACE(TRACE_wq_thread_create_failed | DBG_FUNC_NONE, wq, kret, 2, 0, 0);
		}
	}
	if (kret != KERN_SUCCESS) {
		(void) thread_terminate(th);
		thread_deallocate(th);

		kfree(tl, sizeof(struct threadlist));
		goto failed;
	}
	thread_reference(th);

	sright = (void *)pthread_kern->convert_thread_to_port(th);
	tl->th_thport = pthread_kern->ipc_port_copyout_send(sright, pthread_kern->task_get_ipcspace(wq->wq_task));

	pthread_kern->thread_static_param(th, TRUE);

	tl->th_flags = TH_LIST_INITED | TH_LIST_SUSPENDED;

	tl->th_thread = th;
	tl->th_workq = wq;
	tl->th_stackaddr = stackaddr;
	tl->th_priority = WORKQUEUE_NUM_BUCKETS;
	tl->th_policy = -1;

	uth = pthread_kern->get_bsdthread_info(tl->th_thread);

	workqueue_lock_spin(p);

	pthread_kern->uthread_set_threadlist(uth, tl);
	TAILQ_INSERT_TAIL(&wq->wq_thidlelist, tl, th_entry);

	wq->wq_thidlecount++;

	PTHREAD_TRACE1(TRACE_wq_thread_suspend | DBG_FUNC_START, wq, wq->wq_nthreads, 0, thread_tid(current_thread()), thread_tid(tl->th_thread));

	return (TRUE);

failed:
	workqueue_lock_spin(p);
	wq->wq_nthreads--;

	return (FALSE);
}

/**
 * Setup per-process state for the workqueue.
 */
int
_workq_open(struct proc *p, __unused int32_t *retval)
{
	struct workqueue * wq;
	int wq_size;
	char * ptr;
	uint32_t i;
	uint32_t num_cpus;
	int error = 0;
	boolean_t need_wakeup = FALSE;

	if (pthread_kern->proc_get_register(p) == 0) {
		return EINVAL;
	}

	num_cpus = pthread_kern->ml_get_max_cpus();

	if (wq_init_constrained_limit) {
		uint32_t limit;
		/*
		 * set up the limit for the constrained pool
		 * this is a virtual pool in that we don't
		 * maintain it on a separate idle and run list
		 */
		limit = num_cpus * WORKQUEUE_CONSTRAINED_FACTOR;

		if (limit > wq_max_constrained_threads)
			wq_max_constrained_threads = limit;

		wq_init_constrained_limit = 0;
	}
	workqueue_lock_spin(p);

	if (pthread_kern->proc_get_wqptr(p) == NULL) {

		while (*pthread_kern->proc_get_wqinitingptr(p) == TRUE) {

			assert_wait((caddr_t)pthread_kern->proc_get_wqinitingptr(p), THREAD_UNINT);
			workqueue_unlock(p);

			thread_block(THREAD_CONTINUE_NULL);

			workqueue_lock_spin(p);
		}
		if (pthread_kern->proc_get_wqptr(p) != NULL) {
			goto out;
		}

		*(pthread_kern->proc_get_wqinitingptr(p)) = TRUE;

		workqueue_unlock(p);

		wq_size = sizeof(struct workqueue);

		ptr = (char *)kalloc(wq_size);
		bzero(ptr, wq_size);

		wq = (struct workqueue *)ptr;
		wq->wq_flags = WQ_LIST_INITED;
		wq->wq_proc = p;
		wq->wq_max_concurrency = wq_max_concurrency;
		wq->wq_task = current_task();
		wq->wq_map  = pthread_kern->current_map();

		for (i = 0; i < WORKQUEUE_NUM_BUCKETS; i++)
			wq->wq_reqconc[i] = (uint16_t)wq->wq_max_concurrency;

		// The event manager bucket is special, so its gets a concurrency of 1
		// though we shouldn't ever read this value for that bucket
		wq->wq_reqconc[WORKQUEUE_EVENT_MANAGER_BUCKET] = 1;

		// Always start the event manager at BACKGROUND
		wq->wq_event_manager_priority = (uint32_t)pthread_qos_class_get_priority(THREAD_QOS_BACKGROUND) | _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG;

		TAILQ_INIT(&wq->wq_thrunlist);
		TAILQ_INIT(&wq->wq_thidlelist);

		wq->wq_atimer_call = thread_call_allocate((thread_call_func_t)workqueue_add_timer, (thread_call_param_t)wq);

		workqueue_lock_spin(p);

		pthread_kern->proc_set_wqptr(p, wq);
		pthread_kern->proc_set_wqsize(p, wq_size);

		*(pthread_kern->proc_get_wqinitingptr(p)) = FALSE;
		need_wakeup = TRUE;
	}
out:
	workqueue_unlock(p);

	if (need_wakeup == TRUE) {
		wakeup(pthread_kern->proc_get_wqinitingptr(p));
	}
	return(error);
}

/*
 * Routine:	workqueue_mark_exiting
 *
 * Function:	Mark the work queue such that new threads will not be added to the
 *		work queue after we return.
 *
 * Conditions:	Called against the current process.
 */
void
_workqueue_mark_exiting(struct proc *p)
{
	struct workqueue *wq = pthread_kern->proc_get_wqptr(p);

	if (wq != NULL) {

		PTHREAD_TRACE(TRACE_wq_pthread_exit|DBG_FUNC_START, wq, 0, 0, 0, 0);

		workqueue_lock_spin(p);

		/*
		 * we now arm the timer in the callback function w/o holding the workq lock...
		 * we do this by setting  WQ_ATIMER_RUNNING via OSCompareAndSwap in order to
		 * insure only a single timer if running and to notice that WQ_EXITING has
		 * been set (we don't want to start a timer once WQ_EXITING is posted)
		 *
		 * so once we have successfully set WQ_EXITING, we cannot fire up a new timer...
		 * therefor no need to clear the timer state atomically from the flags
		 *
		 * since we always hold the workq lock when dropping WQ_ATIMER_RUNNING
		 * the check for and sleep until clear is protected
		 */
		while (!(OSCompareAndSwap(wq->wq_flags, (wq->wq_flags | WQ_EXITING), (UInt32 *)&wq->wq_flags)));

		if (wq->wq_flags & WQ_ATIMER_RUNNING) {
			if (thread_call_cancel(wq->wq_atimer_call) == TRUE) {
				wq->wq_flags &= ~WQ_ATIMER_RUNNING;
			}
		}
		while ((wq->wq_flags & WQ_ATIMER_RUNNING) || (wq->wq_lflags & WQL_ATIMER_BUSY)) {
			assert_wait((caddr_t)wq, (THREAD_UNINT));
			workqueue_unlock(p);

			thread_block(THREAD_CONTINUE_NULL);

			workqueue_lock_spin(p);
		}
		workqueue_unlock(p);

		PTHREAD_TRACE(TRACE_wq_pthread_exit|DBG_FUNC_END, 0, 0, 0, 0, 0);
	}
}

/*
 * Routine:	workqueue_exit
 *
 * Function:	clean up the work queue structure(s) now that there are no threads
 *		left running inside the work queue (except possibly current_thread).
 *
 * Conditions:	Called by the last thread in the process.
 *		Called against current process.
 */
void
_workqueue_exit(struct proc *p)
{
	struct workqueue  * wq;
	struct threadlist  * tl, *tlist;
	struct uthread	*uth;
	int wq_size = 0;

	wq = pthread_kern->proc_get_wqptr(p);
	if (wq != NULL) {

		PTHREAD_TRACE(TRACE_wq_workqueue_exit|DBG_FUNC_START, wq, 0, 0, 0, 0);

		wq_size = pthread_kern->proc_get_wqsize(p);
		pthread_kern->proc_set_wqptr(p, NULL);
		pthread_kern->proc_set_wqsize(p, 0);

		/*
		 * Clean up workqueue data structures for threads that exited and
		 * didn't get a chance to clean up after themselves.
		 */
		TAILQ_FOREACH_SAFE(tl, &wq->wq_thrunlist, th_entry, tlist) {
			pthread_kern->thread_sched_call(tl->th_thread, NULL);

			uth = pthread_kern->get_bsdthread_info(tl->th_thread);
			if (uth != (struct uthread *)0) {
				pthread_kern->uthread_set_threadlist(uth, NULL);
			}
			TAILQ_REMOVE(&wq->wq_thrunlist, tl, th_entry);

			/*
			 * drop our last ref on the thread
			 */
			thread_deallocate(tl->th_thread);

			kfree(tl, sizeof(struct threadlist));
		}
		TAILQ_FOREACH_SAFE(tl, &wq->wq_thidlelist, th_entry, tlist) {
			workqueue_removethread(tl, 1);
		}
		thread_call_free(wq->wq_atimer_call);

		kfree(wq, wq_size);

		PTHREAD_TRACE(TRACE_wq_workqueue_exit|DBG_FUNC_END, 0, 0, 0, 0, 0);
	}
}


#pragma mark workqueue thread manipulation

/**
 * Entry point for libdispatch to ask for threads
 */
static int wqops_queue_reqthreads(struct proc *p, int reqcount, pthread_priority_t priority){
	struct workqueue *wq;

	boolean_t overcommit = (_pthread_priority_get_flags(priority) & _PTHREAD_PRIORITY_OVERCOMMIT_FLAG) != 0;
	int class = pthread_priority_get_class_index(priority);

	boolean_t event_manager = (_pthread_priority_get_flags(priority) & _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG) != 0;
	if (event_manager){
		class = WORKQUEUE_EVENT_MANAGER_BUCKET;
	}

	if ((reqcount <= 0) || (class < 0) || (class >= WORKQUEUE_NUM_BUCKETS) || (overcommit && event_manager)) {
		return EINVAL;
	}
	
	workqueue_lock_spin(p);
	
	if ((wq = (struct workqueue *)pthread_kern->proc_get_wqptr(p)) == NULL) {
		workqueue_unlock(p);
		
		return EINVAL;
	}
	
	if (overcommit == 0 && event_manager == 0) {
		wq->wq_reqcount += reqcount;
		wq->wq_requests[class] += reqcount;
		
		PTHREAD_TRACE(TRACE_wq_req_threads | DBG_FUNC_NONE, wq, priority, wq->wq_requests[class], reqcount, 0);
		
		while (wq->wq_reqcount) {
			if (!workqueue_run_one(p, wq, overcommit, 0))
				break;
		}
	} else if (overcommit){
		PTHREAD_TRACE(TRACE_wq_req_octhreads | DBG_FUNC_NONE, wq, priority, wq->wq_ocrequests[class], reqcount, 0);
		
		while (reqcount) {
			if (!workqueue_run_one(p, wq, overcommit, priority))
				break;
			reqcount--;
		}
		if (reqcount) {
			/*
			 * we need to delay starting some of the overcommit requests...
			 * we should only fail to create the overcommit threads if
			 * we're at the max thread limit... as existing threads
			 * return to the kernel, we'll notice the ocrequests
			 * and spin them back to user space as the overcommit variety
			 */
			wq->wq_reqcount += reqcount;
			wq->wq_requests[class] += reqcount;
			wq->wq_ocrequests[class] += reqcount;
			
			PTHREAD_TRACE(TRACE_wq_delay_octhreads | DBG_FUNC_NONE, wq, priority, wq->wq_ocrequests[class], reqcount, 0);

			/* if we delayed this thread coming up but we're not constrained
			 * or at max threads then we need to start the timer so we don't
			 * risk dropping this request on the floor.
			 */
			if ((wq->wq_lflags & (WQL_EXCEEDED_TOTAL_THREAD_LIMIT | WQL_EXCEEDED_CONSTRAINED_THREAD_LIMIT)) == 0) {
				boolean_t start_timer = FALSE;
				WQ_TIMER_NEEDED(wq, start_timer);

				if (start_timer) {
					workqueue_interval_timer_start(wq);
				}
			}
		}
	} else if (event_manager) {
		PTHREAD_TRACE(TRACE_wq_req_event_manager | DBG_FUNC_NONE, wq, wq->wq_event_manager_priority, wq->wq_requests[WORKQUEUE_EVENT_MANAGER_BUCKET], wq->wq_thscheduled_count[WORKQUEUE_EVENT_MANAGER_BUCKET], 0);

		if (wq->wq_requests[WORKQUEUE_EVENT_MANAGER_BUCKET] == 0){
			wq->wq_reqcount += 1;
			wq->wq_requests[WORKQUEUE_EVENT_MANAGER_BUCKET] = 1;
		}

		// We've recorded the request for an event manager thread above.  We'll
		// let the timer pick it up as we would for a kernel callout.  We can
		// do a direct add/wakeup when that support is added for the kevent path.
		boolean_t start_timer = FALSE;
		if (wq->wq_thscheduled_count[WORKQUEUE_EVENT_MANAGER_BUCKET] == 0)
			WQ_TIMER_NEEDED(wq, start_timer);
		if (start_timer == TRUE)
			workqueue_interval_timer_start(wq);
	}
	workqueue_unlock(p);

	return 0;
}

/* Used by the kevent system to request threads.  Currently count is ignored
 * and we always return one thread per invocation.
 */
thread_t _workq_reqthreads(struct proc *p, int requests_count, workq_reqthreads_req_t requests){
	boolean_t start_timer = FALSE;
	assert(requests_count > 0);

#if DEBUG
	// Make sure that the requests array is sorted, highest priority first
	if (requests_count > 1){
		__assert_only qos_class_t priority = _pthread_priority_get_qos_newest(requests[0].priority);
		__assert_only unsigned long flags = ((_pthread_priority_get_flags(requests[0].priority) & (_PTHREAD_PRIORITY_OVERCOMMIT_FLAG|_PTHREAD_PRIORITY_EVENT_MANAGER_FLAG)) != 0);
		for (int i = 1; i < requests_count; i++){
			if (requests[i].count == 0) continue;
			__assert_only qos_class_t next_priority = _pthread_priority_get_qos_newest(requests[i].priority);
			__assert_only unsigned long next_flags = ((_pthread_priority_get_flags(requests[i].priority) & (_PTHREAD_PRIORITY_OVERCOMMIT_FLAG|_PTHREAD_PRIORITY_EVENT_MANAGER_FLAG)) != 0);
			if (next_flags != flags){
				flags = next_flags;
				priority = next_priority;
			} else {
				assert(next_priority <= priority);
			}
		}
	}
#endif // DEBUG

	int error = 0;
	struct workqueue *wq;

	workqueue_lock_spin(p);

	if ((wq = (struct workqueue *)pthread_kern->proc_get_wqptr(p)) == NULL) {
		error = EINVAL;
		goto done;
	}

	PTHREAD_TRACE(TRACE_wq_kevent_req_threads | DBG_FUNC_START, wq, requests_count, 0, 0, 0);

	// Look for overcommit or event-manager-only requests.
	boolean_t have_overcommit = FALSE;
	pthread_priority_t priority = 0;
	for (int i = 0; i < requests_count; i++){
		if (requests[i].count == 0)
			continue;
		priority = requests[i].priority;
		if (_pthread_priority_get_qos_newest(priority) == QOS_CLASS_UNSPECIFIED){
			priority |= _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG;
		}
		if ((_pthread_priority_get_flags(priority) & _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG) != 0){
			goto event_manager;
		}
		if ((_pthread_priority_get_flags(priority) & _PTHREAD_PRIORITY_OVERCOMMIT_FLAG) != 0){
			have_overcommit = TRUE;
			break;
		}
	}

	if (have_overcommit){
		// I can't make this call, since it's not safe from some contexts yet,
		// so just setup a delayed overcommit and let the timer do the work
		//boolean_t success = workqueue_run_one(p, wq, TRUE, priority);
		if (/* !success */ TRUE){
			int class = pthread_priority_get_class_index(priority);
			wq->wq_reqcount += 1;
			wq->wq_requests[class] += 1;
			wq->wq_kevent_ocrequests[class] += 1;
			
			PTHREAD_TRACE(TRACE_wq_req_kevent_octhreads | DBG_FUNC_NONE, wq, priority, wq->wq_kevent_ocrequests[class], 1, 0);

			WQ_TIMER_NEEDED(wq, start_timer);
		}
		goto done;
	}

	// Having no overcommit requests, try to find any request that can start
	// There's no TOCTTOU since we hold the workqueue lock
	for (int i = 0; i < requests_count; i++){
		workq_reqthreads_req_t req = requests + i;
		priority = req->priority;

		if (req->count == 0)
			continue;

		int class = pthread_priority_get_class_index(priority);

		// Ask if we can start a new thread at the given class.  Pass NUM_BUCKETS as
		// my class to indicate we won't reuse this thread
		if (may_start_constrained_thread(wq, class, WORKQUEUE_NUM_BUCKETS, NULL)){
			wq->wq_reqcount += 1;
			wq->wq_requests[class] += 1;
			wq->wq_kevent_requests[class] += 1;
		
			PTHREAD_TRACE(TRACE_wq_req_kevent_threads | DBG_FUNC_NONE, wq, priority, wq->wq_kevent_requests[class], 1, 0);

			// I can't make this call because it's not yet safe to make from
			// scheduler callout context, so instead we'll just start up the timer
			// which will spin up the thread when it files.
			// workqueue_run_one(p, wq, FALSE, priority);

			WQ_TIMER_NEEDED(wq, start_timer);

			goto done;
		}
	}

	// Okay, here's the fun case: we can't spin up any of the non-overcommit threads
	// that we've seen a request for, so we kick this over to the event manager thread

event_manager:
	PTHREAD_TRACE(TRACE_wq_req_event_manager | DBG_FUNC_NONE, wq, wq->wq_event_manager_priority, wq->wq_requests[WORKQUEUE_EVENT_MANAGER_BUCKET], wq->wq_thscheduled_count[WORKQUEUE_EVENT_MANAGER_BUCKET], 0);

	if (wq->wq_requests[WORKQUEUE_EVENT_MANAGER_BUCKET] == 0){
		wq->wq_reqcount += 1;
		wq->wq_requests[WORKQUEUE_EVENT_MANAGER_BUCKET] = 1;
	}
	wq->wq_kevent_requests[WORKQUEUE_EVENT_MANAGER_BUCKET] = 1;

	if (wq->wq_thscheduled_count[WORKQUEUE_EVENT_MANAGER_BUCKET] == 0)
		WQ_TIMER_NEEDED(wq, start_timer);

done:
	workqueue_unlock(p);

	if (start_timer == TRUE)
		workqueue_interval_timer_start(wq);

	PTHREAD_TRACE(TRACE_wq_kevent_req_threads | DBG_FUNC_END, wq, start_timer, 0, 0, 0);

	return THREAD_NULL;
}


static int wqops_thread_return(struct proc *p){
	thread_t th = current_thread();
	struct uthread *uth = pthread_kern->get_bsdthread_info(th);
	struct threadlist *tl = util_get_thread_threadlist_entry(th);
	
	/* reset signal mask on the workqueue thread to default state */
	if (pthread_kern->uthread_get_sigmask(uth) != (sigset_t)(~workq_threadmask)) {
		pthread_kern->proc_lock(p);
		pthread_kern->uthread_set_sigmask(uth, ~workq_threadmask);
		pthread_kern->proc_unlock(p);
	}
	
	/* dropping WQ override counts has to be done outside the wq lock. */
	wq_thread_override_reset(th, THREAD_QOS_OVERRIDE_RESOURCE_WILDCARD);
	
	workqueue_lock_spin(p);

	struct workqueue *wq = (struct workqueue *)pthread_kern->proc_get_wqptr(p);
	if (wq == NULL || !tl) {
		workqueue_unlock(p);
		
		return EINVAL;
	}
	PTHREAD_TRACE(TRACE_wq_runitem | DBG_FUNC_END, wq, 0, 0, 0, 0);

	(void)workqueue_run_nextreq(p, wq, th, RUN_NEXTREQ_DEFAULT, 0);
	/*
	 * workqueue_run_nextreq is responsible for
	 * dropping the workqueue lock in all cases
	 */
	return 0;
}

/**
 * Multiplexed call to interact with the workqueue mechanism
 */
int
_workq_kernreturn(struct proc *p,
		  int options,
		  __unused user_addr_t item,
		  int arg2,
		  int arg3,
		  int32_t *retval)
{
	int error = 0;

	if (pthread_kern->proc_get_register(p) == 0) {
		return EINVAL;
	}

	switch (options) {
	case WQOPS_QUEUE_NEWSPISUPP: {
		/*
		 * arg2 = offset of serialno into dispatch queue
		 * arg3 = kevent support
		 */
		int offset = arg2;
		if (arg3 & 0x01){
			// If we get here, then userspace has indicated support for kevent delivery.
		}

		pthread_kern->proc_set_dispatchqueue_serialno_offset(p, (uint64_t)offset);
		break;
	}
	case WQOPS_QUEUE_REQTHREADS: {
		/*
		 * arg2 = number of threads to start
		 * arg3 = priority
		 */
		error = wqops_queue_reqthreads(p, arg2, arg3);
		break;
	}
	case WQOPS_SET_EVENT_MANAGER_PRIORITY: {
		/*
		 * arg2 = priority for the manager thread
		 *
		 * if _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG is set, the
		 * ~_PTHREAD_PRIORITY_FLAGS_MASK contains a scheduling priority instead
		 * of a QOS value
		 */
		pthread_priority_t pri = arg2;

		workqueue_lock_spin(p);
		struct workqueue *wq = (struct workqueue *)pthread_kern->proc_get_wqptr(p);
		if (wq == NULL ) {
			workqueue_unlock(p);
			error = EINVAL;
			break;
		}
		if (pri & _PTHREAD_PRIORITY_SCHED_PRI_FLAG){
			// If userspace passes a scheduling priority, that takes precidence
			// over any QoS.  (So, userspace should take care not to accidenatally
			// lower the priority this way.)
			uint32_t sched_pri = pri & (~_PTHREAD_PRIORITY_FLAGS_MASK);
			if (wq->wq_event_manager_priority & _PTHREAD_PRIORITY_SCHED_PRI_FLAG){
				wq->wq_event_manager_priority = MAX(sched_pri, wq->wq_event_manager_priority & (~_PTHREAD_PRIORITY_FLAGS_MASK))
						| _PTHREAD_PRIORITY_SCHED_PRI_FLAG | _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG;
			} else {
				wq->wq_event_manager_priority = sched_pri
						| _PTHREAD_PRIORITY_SCHED_PRI_FLAG | _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG;
			}
		} else if ((wq->wq_event_manager_priority & _PTHREAD_PRIORITY_SCHED_PRI_FLAG) == 0){
			int cur_qos = pthread_priority_get_qos_class(wq->wq_event_manager_priority);
			int new_qos = pthread_priority_get_qos_class(pri);
			wq->wq_event_manager_priority = (uint32_t)pthread_qos_class_get_priority(MAX(cur_qos, new_qos)) | _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG;
		}
		workqueue_unlock(p);
		break;
	}
	case WQOPS_THREAD_KEVENT_RETURN: {
		int32_t kevent_retval;
		int ret = kevent_qos_internal(p, -1, item, arg2, item, arg2, NULL, NULL, KEVENT_FLAG_WORKQ | KEVENT_FLAG_IMMEDIATE | KEVENT_FLAG_ERROR_EVENTS, &kevent_retval);
		// We shouldn't be getting more errors out than events we put in, so
		// reusing the input buffer should always provide enough space
		assert(ret == KERN_SUCCESS && kevent_retval >= 0);
		if (ret != KERN_SUCCESS){
			error = ret;
			break;
		} else if (kevent_retval > 0){
			assert(kevent_retval <= arg2);
			*retval = kevent_retval;
			error = 0;
			break;
		}
	} /* FALLTHROUGH */
	case WQOPS_THREAD_RETURN: {
		error = wqops_thread_return(p);
		// NOT REACHED except in case of error
		assert(error);
		break;
	}
	default:
		error = EINVAL;
		break;
	}
	return (error);
}


static boolean_t
workqueue_run_one(proc_t p, struct workqueue *wq, boolean_t overcommit, pthread_priority_t priority)
{
	boolean_t	ran_one;

	if (wq->wq_thidlecount == 0) {
		if (overcommit == FALSE) {
			if (wq->wq_constrained_threads_scheduled < wq->wq_max_concurrency)
				workqueue_addnewthread(wq, overcommit);
		} else {
			workqueue_addnewthread(wq, overcommit);

			if (wq->wq_thidlecount == 0)
				return (FALSE);
		}
	}
	ran_one = workqueue_run_nextreq(p, wq, THREAD_NULL, overcommit ? RUN_NEXTREQ_OVERCOMMIT : RUN_NEXTREQ_DEFAULT, priority);
	/*
	 * workqueue_run_nextreq is responsible for
	 * dropping the workqueue lock in all cases
	 */
	workqueue_lock_spin(p);

	return (ran_one);
}

/*
 * this is a workqueue thread with no more
 * work to do... park it for now
 */
static void 
parkit(struct workqueue *wq, struct threadlist *tl, thread_t thread)
{
	uint32_t us_to_wait;
	
	TAILQ_REMOVE(&wq->wq_thrunlist, tl, th_entry);
	tl->th_flags &= ~TH_LIST_RUNNING;

	tl->th_flags |= TH_LIST_BLOCKED;
	TAILQ_INSERT_HEAD(&wq->wq_thidlelist, tl, th_entry);

	pthread_kern->thread_sched_call(thread, NULL);

	OSAddAtomic(-1, &wq->wq_thactive_count[tl->th_priority]);
	wq->wq_thscheduled_count[tl->th_priority]--;
	wq->wq_threads_scheduled--;

	if (tl->th_flags & TH_LIST_CONSTRAINED) {
		wq->wq_constrained_threads_scheduled--;
		wq->wq_lflags &= ~WQL_EXCEEDED_CONSTRAINED_THREAD_LIMIT;
		tl->th_flags &= ~TH_LIST_CONSTRAINED;
	}

	if (wq->wq_thidlecount < 100)
		us_to_wait = wq_reduce_pool_window_usecs - (wq->wq_thidlecount * (wq_reduce_pool_window_usecs / 100));
	else
		us_to_wait = wq_reduce_pool_window_usecs / 100;

	wq->wq_thidlecount++;
	wq->wq_lflags &= ~WQL_EXCEEDED_TOTAL_THREAD_LIMIT;

	assert_wait_timeout_with_leeway((caddr_t)tl, (THREAD_INTERRUPTIBLE),
			TIMEOUT_URGENCY_SYS_BACKGROUND|TIMEOUT_URGENCY_LEEWAY, us_to_wait,
			wq_reduce_pool_window_usecs, NSEC_PER_USEC);
	
	PTHREAD_TRACE1(TRACE_wq_thread_park | DBG_FUNC_START, wq, wq->wq_threads_scheduled, wq->wq_thidlecount, us_to_wait, thread_tid(thread));
}

static boolean_t may_start_constrained_thread(struct workqueue *wq, uint32_t at_priclass, uint32_t my_priclass, boolean_t *start_timer){
	if (wq->wq_constrained_threads_scheduled >= wq_max_constrained_threads) {
		/*
		 * we need 1 or more constrained threads to return to the kernel before
		 * we can dispatch additional work
		 */
		return FALSE;
	}

	uint32_t busycount = 0;
	uint32_t thactive_count = wq->wq_thactive_count[at_priclass];

	// Has our most recently blocked thread blocked recently enough that we
	// should still consider it busy?
	// XXX should this be wq->wq_thscheduled_count[at_priclass] > thactive_count ?
	if (wq->wq_thscheduled_count[at_priclass]) {
		if (wq_thread_is_busy(mach_absolute_time(), &wq->wq_lastblocked_ts[at_priclass])) {
			busycount++;
		}
	}

	if (my_priclass < WORKQUEUE_NUM_BUCKETS && my_priclass == at_priclass){
		/*
		 * dont't count this thread as currently active
		 */
		thactive_count--;
	}

	if (thactive_count + busycount >= wq->wq_max_concurrency) {
		if (busycount && start_timer) {
				/*
				 * we found at least 1 thread in the
				 * 'busy' state... make sure we start
				 * the timer because if they are the only
				 * threads keeping us from scheduling
				 * this work request, we won't get a callback
				 * to kick off the timer... we need to
				 * start it now...
				 */
				WQ_TIMER_NEEDED(wq, *start_timer);
		}

		PTHREAD_TRACE(TRACE_wq_overcommitted|DBG_FUNC_NONE, wq, (start_timer ? 1<<7 : 0) | pthread_priority_from_class_index(at_priclass), thactive_count, busycount, 0);

		return FALSE;
	}
	return TRUE;
}

static struct threadlist *pop_from_thidlelist(struct workqueue *wq, uint32_t priclass, int *upcall_flags, int *wake_thread){
	struct threadlist *tl = TAILQ_FIRST(&wq->wq_thidlelist);
	TAILQ_REMOVE(&wq->wq_thidlelist, tl, th_entry);
	wq->wq_thidlecount--;	

	TAILQ_INSERT_TAIL(&wq->wq_thrunlist, tl, th_entry);

	if ((tl->th_flags & TH_LIST_SUSPENDED) == TH_LIST_SUSPENDED) {
		tl->th_flags &= ~TH_LIST_SUSPENDED;
		*upcall_flags &= ~WQ_FLAG_THREAD_REUSE;

	} else if ((tl->th_flags & TH_LIST_BLOCKED) == TH_LIST_BLOCKED) {
		tl->th_flags &= ~TH_LIST_BLOCKED;
		*wake_thread = 1;
	}
	tl->th_flags |= TH_LIST_RUNNING | TH_LIST_BUSY;

	wq->wq_threads_scheduled++;
	wq->wq_thscheduled_count[priclass]++;
	OSAddAtomic(1, &wq->wq_thactive_count[priclass]);

	return tl;
}

static void
reset_to_priority(struct threadlist *tl, pthread_priority_t pri){
	kern_return_t ret;
	thread_t th = tl->th_thread;

	if (tl->th_flags & TH_LIST_EVENT_MGR_SCHED_PRI){
		thread_precedence_policy_data_t  precedinfo = {
			.importance = 0
		};
		ret = pthread_kern->thread_policy_set_internal(th, THREAD_PRECEDENCE_POLICY, (thread_policy_t)&precedinfo, THREAD_PRECEDENCE_POLICY_COUNT);
		assert(ret == KERN_SUCCESS || ret == KERN_TERMINATED);
		tl->th_flags &= ~TH_LIST_EVENT_MGR_SCHED_PRI;
	}

	thread_qos_policy_data_t qosinfo = {
		.qos_tier = pthread_priority_get_qos_class(pri),
		.tier_importance = 0
	};
	ret = pthread_kern->thread_policy_set_internal(th, THREAD_QOS_POLICY, (thread_policy_t)&qosinfo, THREAD_QOS_POLICY_COUNT);
	assert(ret == KERN_SUCCESS || ret == KERN_TERMINATED);
}

static void
reset_to_schedpri(struct threadlist *tl, pthread_priority_t pri){
	kern_return_t ret;
	thread_t th = tl->th_thread;

	thread_qos_policy_data_t qosinfo = {
		.qos_tier = THREAD_QOS_UNSPECIFIED,
		.tier_importance = 0
	};
	ret = pthread_kern->thread_policy_set_internal(th, THREAD_QOS_POLICY, (thread_policy_t)&qosinfo, THREAD_QOS_POLICY_COUNT);
	assert(ret == KERN_SUCCESS || ret == KERN_TERMINATED);

	thread_precedence_policy_data_t  precedinfo = {
		.importance = ((pri & (~_PTHREAD_PRIORITY_FLAGS_MASK)) - BASEPRI_DEFAULT)
	};
	ret = pthread_kern->thread_policy_set_internal(th, THREAD_PRECEDENCE_POLICY, (thread_policy_t)&precedinfo, THREAD_PRECEDENCE_POLICY_COUNT);
	assert(ret == KERN_SUCCESS || ret == KERN_TERMINATED);

	tl->th_flags |= TH_LIST_EVENT_MGR_SCHED_PRI;
}

/**
 * grabs a thread for a request
 *
 *  - called with the workqueue lock held...
 *  - responsible for dropping it in all cases
 *  - if provided mode is for overcommit, doesn't consume a reqcount
 *
 */
static boolean_t
workqueue_run_nextreq(proc_t p, struct workqueue *wq, thread_t thread,
		      enum run_nextreq_mode mode, pthread_priority_t oc_prio)
{
	thread_t th_to_run = THREAD_NULL;
	int wake_thread = 0;
	int upcall_flags = WQ_FLAG_THREAD_REUSE;
	uint32_t priclass;
	struct threadlist *tl = NULL;
	struct uthread *uth = NULL;
	boolean_t start_timer = FALSE;

	// valid modes to call this function with
	assert(mode == RUN_NEXTREQ_DEFAULT || mode == RUN_NEXTREQ_OVERCOMMIT || mode == RUN_NEXTREQ_UNCONSTRAINED);
	// may only have a priority if in OVERCOMMIT mode
	assert(mode == RUN_NEXTREQ_OVERCOMMIT || oc_prio == 0);
	// thread == thread_null means "please spin up a new workqueue thread, we can't reuse this"
	// thread != thread_null is thread reuse, and must be the current thread
	assert(thread == THREAD_NULL || thread == current_thread());

	PTHREAD_TRACE(TRACE_wq_run_nextitem|DBG_FUNC_START, wq, thread, wq->wq_thidlecount, wq->wq_reqcount, 0);

	if (thread != THREAD_NULL) {
		uth = pthread_kern->get_bsdthread_info(thread);

		if ((tl = pthread_kern->uthread_get_threadlist(uth)) == NULL) {
			panic("wq thread with no threadlist");
		}
	}

	/*
	 * from here until we drop the workq lock
	 * we can't be pre-empted since we hold 
	 * the lock in spin mode... this is important
	 * since we have to independently update the priority that 
	 * the thread is associated with and the priorty based
	 * counters that "workqueue_callback" also changes and bases
	 * decisons on.
	 */

	if (mode == RUN_NEXTREQ_OVERCOMMIT) {
		priclass = pthread_priority_get_class_index(oc_prio);
		upcall_flags |= WQ_FLAG_THREAD_OVERCOMMIT;
	} else if (wq->wq_reqcount == 0){
		// no work to do.  we'll check again when new work arrives.
		goto done;
	} else if (wq->wq_requests[WORKQUEUE_EVENT_MANAGER_BUCKET] &&
			   ((wq->wq_thscheduled_count[WORKQUEUE_EVENT_MANAGER_BUCKET] == 0) ||
				(thread != THREAD_NULL && tl->th_priority == WORKQUEUE_EVENT_MANAGER_BUCKET))){
		// There's an event manager request and either:
		//   - no event manager currently running
		//   - we are re-using the event manager
		mode = RUN_NEXTREQ_EVENT_MANAGER;
		priclass = WORKQUEUE_EVENT_MANAGER_BUCKET;
		upcall_flags |= WQ_FLAG_THREAD_EVENT_MANAGER;
		if (wq->wq_kevent_requests[WORKQUEUE_EVENT_MANAGER_BUCKET])
			upcall_flags |= WQ_FLAG_THREAD_KEVENT;
	} else {
		// Find highest priority and check for special request types
		for (priclass = 0; priclass < WORKQUEUE_EVENT_MANAGER_BUCKET; priclass++) {
			if (wq->wq_requests[priclass])
				break;
		}
		if (priclass == WORKQUEUE_EVENT_MANAGER_BUCKET){
			// only request should have been event manager since it's not in a bucket,
			// but we weren't able to handle it since there's already an event manager running,
			// so we fell into this case
			assert(wq->wq_requests[WORKQUEUE_EVENT_MANAGER_BUCKET] == 1 &&
				   wq->wq_thscheduled_count[WORKQUEUE_EVENT_MANAGER_BUCKET] == 1 &&
				   wq->wq_reqcount == 1);
			goto done;
		}

		if (wq->wq_kevent_ocrequests[priclass]){
			mode = RUN_NEXTREQ_DEFERRED_OVERCOMMIT;
			upcall_flags |= WQ_FLAG_THREAD_KEVENT;
			upcall_flags |= WQ_FLAG_THREAD_OVERCOMMIT;
		} else if (wq->wq_ocrequests[priclass]){
			mode = RUN_NEXTREQ_DEFERRED_OVERCOMMIT;
			upcall_flags |= WQ_FLAG_THREAD_OVERCOMMIT;
		} else if (wq->wq_kevent_requests[priclass]){
			upcall_flags |= WQ_FLAG_THREAD_KEVENT;
		}
	}

	if (mode == RUN_NEXTREQ_DEFAULT /* non-overcommit */){
		uint32_t my_priclass = (thread != THREAD_NULL) ? tl->th_priority : WORKQUEUE_NUM_BUCKETS;
		if (may_start_constrained_thread(wq, priclass, my_priclass, &start_timer) == FALSE){
			// per policy, we won't start another constrained thread
			goto done;
		}
	}

	if (thread != THREAD_NULL) {
		/*
		 * thread is non-NULL here when we return from userspace
		 * in workq_kernreturn, rather than trying to find a thread
		 * we pick up new work for this specific thread.
		 */
		th_to_run = thread;
	} else if (wq->wq_thidlecount == 0) {
		/*
		 * we have no additional threads waiting to pick up
		 * work, however, there is additional work to do.
		 */
		WQ_TIMER_NEEDED(wq, start_timer);

		PTHREAD_TRACE(TRACE_wq_stalled, wq, wq->wq_nthreads, start_timer, 0, 0);

		goto done;
	} else {
    	// there is both work available and an idle thread, so activate a thread
    	tl = pop_from_thidlelist(wq, priclass, &upcall_flags, &wake_thread);
    	th_to_run = tl->th_thread;
	}

	// Adjust counters and thread flags AKA consume the request
	// TODO: It would be lovely if OVERCOMMIT consumed reqcount
	switch (mode) {
		case RUN_NEXTREQ_DEFAULT:
		case RUN_NEXTREQ_UNCONSTRAINED:
			wq->wq_reqcount--;
			wq->wq_requests[priclass]--;

			if (mode == RUN_NEXTREQ_DEFAULT){
				if (!(tl->th_flags & TH_LIST_CONSTRAINED)) {
					wq->wq_constrained_threads_scheduled++;
					tl->th_flags |= TH_LIST_CONSTRAINED;
				}
			} else if (mode == RUN_NEXTREQ_UNCONSTRAINED){
				if (tl->th_flags & TH_LIST_CONSTRAINED) {
					// XXX: Why aren't we unsetting CONSTRAINED_THREAD_LIMIT here
					wq->wq_constrained_threads_scheduled--;
					tl->th_flags &= ~TH_LIST_CONSTRAINED;
				}
			}
			if (upcall_flags & WQ_FLAG_THREAD_KEVENT){
				wq->wq_kevent_requests[priclass]--;
			}
			break;

		case RUN_NEXTREQ_EVENT_MANAGER:
			wq->wq_reqcount--;
			wq->wq_requests[priclass]--;

			if (tl->th_flags & TH_LIST_CONSTRAINED) {
				wq->wq_constrained_threads_scheduled--;
				tl->th_flags &= ~TH_LIST_CONSTRAINED;
			}
			if (upcall_flags & WQ_FLAG_THREAD_KEVENT){
				wq->wq_kevent_requests[priclass]--;
			}
			break;

		case RUN_NEXTREQ_DEFERRED_OVERCOMMIT:
			wq->wq_reqcount--;
			wq->wq_requests[priclass]--;
			if (upcall_flags & WQ_FLAG_THREAD_KEVENT){
				wq->wq_kevent_ocrequests[priclass]--;
			} else {
    			wq->wq_ocrequests[priclass]--;
			}
			/* FALLTHROUGH */
		case RUN_NEXTREQ_OVERCOMMIT:
			if (tl->th_flags & TH_LIST_CONSTRAINED) {
				wq->wq_constrained_threads_scheduled--;
				tl->th_flags &= ~TH_LIST_CONSTRAINED;
			}
			break;
	}

	// Confirm we've maintained our counter invariants
	assert(wq->wq_requests[priclass] < UINT16_MAX);
	assert(wq->wq_ocrequests[priclass] < UINT16_MAX);
	assert(wq->wq_kevent_requests[priclass] < UINT16_MAX);
	assert(wq->wq_kevent_ocrequests[priclass] < UINT16_MAX);
	assert(wq->wq_ocrequests[priclass] + wq->wq_kevent_requests[priclass] +
			wq->wq_kevent_ocrequests[priclass] <=
			wq->wq_requests[priclass]);

	uint32_t orig_class = tl->th_priority;
	tl->th_priority = (uint8_t)priclass;

	if ((thread != THREAD_NULL) && (orig_class != priclass)) {
		/*
		 * we need to adjust these counters based on this
		 * thread's new disposition w/r to priority
		 */
		OSAddAtomic(-1, &wq->wq_thactive_count[orig_class]);
		OSAddAtomic(1, &wq->wq_thactive_count[priclass]);

		wq->wq_thscheduled_count[orig_class]--;
		wq->wq_thscheduled_count[priclass]++;
	}
	wq->wq_thread_yielded_count = 0;

	workqueue_unlock(p);

	pthread_priority_t outgoing_priority;
	if (mode == RUN_NEXTREQ_EVENT_MANAGER){
		outgoing_priority = wq->wq_event_manager_priority;
	} else {
		outgoing_priority = pthread_priority_from_class_index(priclass);
	}

	PTHREAD_TRACE(TRACE_wq_reset_priority | DBG_FUNC_START, wq, thread_tid(tl->th_thread), outgoing_priority, 0, 0);
	if (outgoing_priority & _PTHREAD_PRIORITY_SCHED_PRI_FLAG){
		reset_to_schedpri(tl, outgoing_priority & (~_PTHREAD_PRIORITY_FLAGS_MASK));
	} else if (orig_class != priclass) {
		reset_to_priority(tl, outgoing_priority);
	}
	PTHREAD_TRACE(TRACE_wq_reset_priority | DBG_FUNC_END, wq, thread_tid(tl->th_thread), outgoing_priority, 0, 0);

	/*
	 * if current thread is reused for work request, does not return via unix_syscall
	 */
	wq_runreq(p, outgoing_priority, th_to_run, tl, upcall_flags, wake_thread, (thread == th_to_run));
	
	PTHREAD_TRACE(TRACE_wq_run_nextitem|DBG_FUNC_END, wq, thread_tid(th_to_run), mode == RUN_NEXTREQ_OVERCOMMIT, 1, 0);

	return (TRUE);

done:
	if (thread != THREAD_NULL){
		parkit(wq,tl,thread);
	}

	workqueue_unlock(p);

	if (start_timer)
		workqueue_interval_timer_start(wq);

	PTHREAD_TRACE(TRACE_wq_run_nextitem | DBG_FUNC_END, wq, thread_tid(thread), start_timer, 3, 0);

	if (thread != THREAD_NULL){
    	thread_block((thread_continue_t)wq_unpark_continue);
		/* NOT REACHED */
	}

	return (FALSE);
}

/**
 * Called when a new thread is created
 */
static void
wq_unsuspend_continue(void)
{
	struct uthread *uth = NULL;
	thread_t th_to_unsuspend;
	struct threadlist *tl;
	proc_t	p;

	th_to_unsuspend = current_thread();
	uth = pthread_kern->get_bsdthread_info(th_to_unsuspend);

	if (uth != NULL && (tl = pthread_kern->uthread_get_threadlist(uth)) != NULL) {
		
		if ((tl->th_flags & (TH_LIST_RUNNING | TH_LIST_BUSY)) == TH_LIST_RUNNING) {
			/*
			 * most likely a normal resume of this thread occurred...
			 * it's also possible that the thread was aborted after we
			 * finished setting it up so that it could be dispatched... if
			 * so, thread_bootstrap_return will notice the abort and put
			 * the thread on the path to self-destruction
			 */
normal_resume_to_user:
			pthread_kern->thread_sched_call(th_to_unsuspend, workqueue_callback);
			pthread_kern->thread_bootstrap_return();
		}
		/*
		 * if we get here, it's because we've been resumed due to
		 * an abort of this thread (process is crashing)
		 */
		p = current_proc();

		workqueue_lock_spin(p);

		if (tl->th_flags & TH_LIST_SUSPENDED) {
			/*
			 * thread has been aborted while still on our idle
			 * queue... remove it from our domain...
			 * workqueue_removethread consumes the lock
			 */
			workqueue_removethread(tl, 0);
			pthread_kern->thread_bootstrap_return();
		}
		while ((tl->th_flags & TH_LIST_BUSY)) {
			/*
			 * this thread was aborted after we started making
			 * it runnable, but before we finished dispatching it...
			 * we need to wait for that process to finish,
			 * and we need to ask for a wakeup instead of a
			 * thread_resume since the abort has already resumed us
			 */
			tl->th_flags |= TH_LIST_NEED_WAKEUP;

			assert_wait((caddr_t)tl, (THREAD_UNINT));

			workqueue_unlock(p);
			thread_block(THREAD_CONTINUE_NULL);
			workqueue_lock_spin(p);
		}
		workqueue_unlock(p);
		/*
		 * we have finished setting up the thread's context...
		 * thread_bootstrap_return will take us through the abort path
		 * where the thread will self destruct
		 */
		goto normal_resume_to_user;
	}
	pthread_kern->thread_bootstrap_return();
}

/**
 * parked thread wakes up
 */
static void
wq_unpark_continue(void)
{
	struct uthread *uth;
	struct threadlist *tl;

	thread_t th_to_unpark = current_thread();

	if ((uth = pthread_kern->get_bsdthread_info(th_to_unpark)) == NULL)
		goto done;
	if ((tl = pthread_kern->uthread_get_threadlist(uth)) == NULL)
    	goto done;

	/*
	 * check if a normal wakeup of this thread occurred... if so, there's no need
	 * for any synchronization with the timer and wq_runreq so we just skip all this.
	 */
	if ((tl->th_flags & (TH_LIST_RUNNING | TH_LIST_BUSY)) != TH_LIST_RUNNING) {
		proc_t p = current_proc();

		workqueue_lock_spin(p);

		if ( !(tl->th_flags & TH_LIST_RUNNING)) {
			/*
			 * the timer popped us out and we've not
			 * been moved off of the idle list
			 * so we should now self-destruct
			 *
			 * workqueue_removethread consumes the lock
			 */
			workqueue_removethread(tl, 0);
			pthread_kern->unix_syscall_return(0);
		}

		/*
		 * the timer woke us up, but we have already
		 * started to make this a runnable thread,
		 * but have not yet finished that process...
		 * so wait for the normal wakeup
		 */
		while ((tl->th_flags & TH_LIST_BUSY)) {

			assert_wait((caddr_t)tl, (THREAD_UNINT));

			workqueue_unlock(p);

			thread_block(THREAD_CONTINUE_NULL);

			workqueue_lock_spin(p);
		}

		/*
		 * we have finished setting up the thread's context
		 * now we can return as if we got a normal wakeup
		 */
		workqueue_unlock(p);
	}

	pthread_kern->thread_sched_call(th_to_unpark, workqueue_callback);

	// FIXME: What's this?
	PTHREAD_TRACE(0xefffd018 | DBG_FUNC_END, tl->th_workq, 0, 0, 0, 0);

done:

	// XXX should be using unix_syscall_return(EJUSTRETURN)
	pthread_kern->thread_exception_return();
}



static void 
wq_runreq(proc_t p, pthread_priority_t priority, thread_t th, struct threadlist *tl,
	   int flags, int wake_thread, int return_directly)
{
	int ret = 0;
	boolean_t need_resume = FALSE;

	PTHREAD_TRACE1(TRACE_wq_runitem | DBG_FUNC_START, tl->th_workq, flags, priority, thread_tid(current_thread()), thread_tid(th));

	ret = _setup_wqthread(p, th, priority, flags, tl);

	if (ret != 0)
		panic("setup_wqthread failed  %x\n", ret);

	if (return_directly) {
		PTHREAD_TRACE(TRACE_wq_run_nextitem|DBG_FUNC_END, tl->th_workq, 0, 0, 4, 0);

		// XXX should be using unix_syscall_return(EJUSTRETURN)
		pthread_kern->thread_exception_return();
		panic("wq_runreq: thread_exception_return returned ...\n");
	}
	if (wake_thread) {
		workqueue_lock_spin(p);
		
		tl->th_flags &= ~TH_LIST_BUSY;
		wakeup(tl);

		workqueue_unlock(p);
	} else {
		PTHREAD_TRACE1(TRACE_wq_thread_suspend | DBG_FUNC_END, tl->th_workq, 0, 0, thread_tid(current_thread()), thread_tid(th));

		workqueue_lock_spin(p);

		if (tl->th_flags & TH_LIST_NEED_WAKEUP) {
			wakeup(tl);
		} else {
			need_resume = TRUE;
		}

		tl->th_flags &= ~(TH_LIST_BUSY | TH_LIST_NEED_WAKEUP);
		
		workqueue_unlock(p);

		if (need_resume) {
			/*
			 * need to do this outside of the workqueue spin lock
			 * since thread_resume locks the thread via a full mutex
			 */
			pthread_kern->thread_resume(th);
		}
	}
}

#define KEVENT_LIST_LEN 16
#define KEVENT_DATA_SIZE (32 * 1024)

/**
 * configures initial thread stack/registers to jump into:
 * _pthread_wqthread(pthread_t self, mach_port_t kport, void *stackaddr, void *keventlist, int flags, int nkevents);
 * to get there we jump through assembily stubs in pthread_asm.s.  Those
 * routines setup a stack frame, using the current stack pointer, and marshall
 * arguments from registers to the stack as required by the ABI.
 *
 * One odd thing we do here is to start the pthread_t 4k below what would be the
 * top of the stack otherwise.  This is because usually only the first 4k of the
 * pthread_t will be used and so we want to put it on the same 16k page as the
 * top of the stack to save memory.
 *
 * When we are done the stack will look like:
 * |-----------| th_stackaddr + th_allocsize
 * |pthread_t  | th_stackaddr + DEFAULT_STACKSIZE + guardsize + PTHREAD_STACK_OFFSET
 * |kevent list| optionally - at most KEVENT_LIST_LEN events
 * |kevent data| optionally - at most KEVENT_DATA_SIZE bytes
 * |stack gap  | bottom aligned to 16 bytes, and at least as big as stack_gap_min
 * |   STACK   |
 * |     ⇓     |
 * |           |
 * |guard page | guardsize
 * |-----------| th_stackaddr
 */
int
_setup_wqthread(proc_t p, thread_t th, pthread_priority_t priority, int flags, struct threadlist *tl)
{
	int error = 0;

	const vm_size_t guardsize = vm_map_page_size(tl->th_workq->wq_map);
	const vm_size_t stack_gap_min = (proc_is64bit(p) == 0) ? C_32_STK_ALIGN : C_64_REDZONE_LEN;
	const vm_size_t stack_align_min = (proc_is64bit(p) == 0) ? C_32_STK_ALIGN : C_64_STK_ALIGN;

	user_addr_t pthread_self_addr = (user_addr_t)(tl->th_stackaddr + PTH_DEFAULT_STACKSIZE + guardsize + PTHREAD_T_OFFSET);
	user_addr_t stack_top_addr = (user_addr_t)((pthread_self_addr - stack_gap_min) & -stack_align_min);
	user_addr_t stack_bottom_addr = (user_addr_t)(tl->th_stackaddr + guardsize);

	/* Put the QoS class value into the lower bits of the reuse_thread register, this is where
	 * the thread priority used to be stored anyway.
	 */
	flags |= (_pthread_priority_get_qos_newest(priority) & WQ_FLAG_THREAD_PRIOMASK);

	flags |= WQ_FLAG_THREAD_NEWSPI;

	user_addr_t kevent_list = NULL;
	int kevent_count = 0;
	if (flags & WQ_FLAG_THREAD_KEVENT){
		kevent_list = pthread_self_addr - KEVENT_LIST_LEN * sizeof(struct kevent_qos_s);
		kevent_count = KEVENT_LIST_LEN;

		user_addr_t kevent_data_buf = kevent_list - KEVENT_DATA_SIZE;
		user_size_t kevent_data_available = KEVENT_DATA_SIZE;

		int32_t events_out = 0;

		int ret = kevent_qos_internal(p, -1, NULL, 0, kevent_list, kevent_count,
									  kevent_data_buf, &kevent_data_available,
									  KEVENT_FLAG_WORKQ | KEVENT_FLAG_STACK_DATA | KEVENT_FLAG_STACK_EVENTS | KEVENT_FLAG_IMMEDIATE,
									  &events_out);

		// squash any errors into just empty output on non-debug builds
		assert(ret == KERN_SUCCESS && events_out != -1);
		if (ret != KERN_SUCCESS || events_out == -1){
			events_out = 0;
			kevent_data_available = KEVENT_DATA_SIZE;
		}

		// We shouldn't get data out if there aren't events available
		assert(events_out != 0 || kevent_data_available == KEVENT_DATA_SIZE);

		if (events_out >= 0){
			kevent_count = events_out;
			kevent_list = pthread_self_addr - kevent_count * sizeof(struct kevent_qos_s);

			if (kevent_data_available == KEVENT_DATA_SIZE){
				stack_top_addr = (kevent_list - stack_gap_min) & -stack_align_min;
			} else {
				stack_top_addr = (kevent_data_buf + kevent_data_available - stack_gap_min) & -stack_align_min;
			}
		} else {
			kevent_list = NULL;
			kevent_count = 0;
		}
	}

#if defined(__i386__) || defined(__x86_64__)
	int isLP64 = proc_is64bit(p);

	if (isLP64 == 0) {
		x86_thread_state32_t state = {
			.eip = (unsigned int)pthread_kern->proc_get_wqthread(p),
			.eax = /* arg0 */ (unsigned int)pthread_self_addr,
			.ebx = /* arg1 */ (unsigned int)tl->th_thport,
			.ecx = /* arg2 */ (unsigned int)stack_bottom_addr,
			.edx = /* arg3 */ (unsigned int)kevent_list,
			.edi = /* arg4 */ (unsigned int)flags,
			.esi = /* arg5 */ (unsigned int)kevent_count,

			.esp = (int)((vm_offset_t)stack_top_addr),
		};

		(void)pthread_kern->thread_set_wq_state32(th, (thread_state_t)&state);
	} else {
		x86_thread_state64_t state64 = {
			// x86-64 already passes all the arguments in registers, so we just put them in their final place here
			.rip = (uint64_t)pthread_kern->proc_get_wqthread(p),
			.rdi = (uint64_t)pthread_self_addr,
			.rsi = (uint64_t)tl->th_thport,
			.rdx = (uint64_t)stack_bottom_addr,
			.rcx = (uint64_t)kevent_list,
			.r8  = (uint64_t)flags,
			.r9  = (uint64_t)kevent_count,

			.rsp = (uint64_t)(stack_top_addr)
		};

		error = pthread_kern->thread_set_wq_state64(th, (thread_state_t)&state64);
		if (error != KERN_SUCCESS) {
			error = EINVAL;
		}
	}
#else
#error setup_wqthread  not defined for this architecture
#endif

	return error;
}

#if DEBUG
static int wq_kevent_test SYSCTL_HANDLER_ARGS {
	//(struct sysctl_oid *oidp, void *arg1, int arg2, struct sysctl_req *req)
#pragma unused(oidp, arg1, arg2)
	int error;
	struct workq_reqthreads_req_s requests[64] = {};

	if (req->newlen > sizeof(requests) || req->newlen < sizeof(struct workq_reqthreads_req_s))
		return EINVAL;

	error = copyin(req->newptr, requests, req->newlen);
	if (error) return error;

	_workq_reqthreads(req->p, (int)(req->newlen / sizeof(struct workq_reqthreads_req_s)), requests);
	
	return 0;
}
#endif // DEBUG
	
#pragma mark - Misc

int 
_fill_procworkqueue(proc_t p, struct proc_workqueueinfo * pwqinfo)
{
	struct workqueue * wq;
	int error = 0;
	int	activecount;
	uint32_t pri;

	workqueue_lock_spin(p);
	if ((wq = pthread_kern->proc_get_wqptr(p)) == NULL) {
		error = EINVAL;
		goto out;
	}
	activecount = 0;

	for (pri = 0; pri < WORKQUEUE_NUM_BUCKETS; pri++) {
		activecount += wq->wq_thactive_count[pri];
	}
	pwqinfo->pwq_nthreads = wq->wq_nthreads;
	pwqinfo->pwq_runthreads = activecount;
	pwqinfo->pwq_blockedthreads = wq->wq_threads_scheduled - activecount;
	pwqinfo->pwq_state = 0;

	if (wq->wq_lflags & WQL_EXCEEDED_CONSTRAINED_THREAD_LIMIT) {
		pwqinfo->pwq_state |= WQ_EXCEEDED_CONSTRAINED_THREAD_LIMIT;
	}

	if (wq->wq_lflags & WQL_EXCEEDED_TOTAL_THREAD_LIMIT) {
		pwqinfo->pwq_state |= WQ_EXCEEDED_TOTAL_THREAD_LIMIT;
	}

out:
	workqueue_unlock(p);
	return(error);
}

int 
_thread_selfid(__unused struct proc *p, uint64_t *retval)
{
	thread_t thread = current_thread();
	*retval = thread_tid(thread);
	return KERN_SUCCESS;
}

void
_pthread_init(void)
{
	pthread_lck_grp_attr = lck_grp_attr_alloc_init();
	pthread_lck_grp = lck_grp_alloc_init("pthread", pthread_lck_grp_attr);
	
	/*
	 * allocate the lock attribute for pthread synchronizers
	 */
	pthread_lck_attr = lck_attr_alloc_init();

	_workqueue_init_lock((proc_t)get_bsdtask_info(kernel_task));
	pthread_list_mlock = lck_mtx_alloc_init(pthread_lck_grp, pthread_lck_attr);
	
	pth_global_hashinit();
	psynch_thcall = thread_call_allocate(psynch_wq_cleanup, NULL);
	psynch_zoneinit();

	/*
	 * register sysctls
	 */
	sysctl_register_oid(&sysctl__kern_wq_yielded_threshold);
	sysctl_register_oid(&sysctl__kern_wq_yielded_window_usecs);
	sysctl_register_oid(&sysctl__kern_wq_stalled_window_usecs);
	sysctl_register_oid(&sysctl__kern_wq_reduce_pool_window_usecs);
	sysctl_register_oid(&sysctl__kern_wq_max_timer_interval_usecs);
	sysctl_register_oid(&sysctl__kern_wq_max_threads);
	sysctl_register_oid(&sysctl__kern_wq_max_constrained_threads);
	sysctl_register_oid(&sysctl__kern_pthread_debug_tracing);

#if DEBUG
	sysctl_register_oid(&sysctl__kern_wq_max_concurrency);
	sysctl_register_oid(&sysctl__debug_wq_kevent_test);
#endif

	wq_max_concurrency = pthread_kern->ml_get_max_cpus();

}