This is xnu-4903.221.2. See this file in:
/*
 * Copyright (c) 2000-2017 Apple Computer, 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,
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 */

#ifndef _PTHREAD_PRIORITY_PRIVATE_H_
#define _PTHREAD_PRIORITY_PRIVATE_H_

/*!
 * @typedef pthread_priority_t
 *
 * @abstract
 * pthread_priority_t is an on opaque integer that is guaranteed to be ordered
 * such that combations of QoS classes and relative priorities are ordered
 * numerically, according to their combined priority.
 *
 * <b>xnu, pthread & libdispatch flags</b>
 *
 * @const _PTHREAD_PRIORITY_OVERCOMMIT_FLAG
 * The thread this priority is applied to is overcommit (affects the workqueue
 * creation policy for this priority).
 *
 * @const _PTHREAD_PRIORITY_FALLBACK_FLAG
 * Indicates that this priority is is used only when incoming events have no
 * priority at all. It is merely used as a fallback (hence the name) instead of
 * a floor.
 *
 * This is usually used with QOS_CLASS_DEFAULT and a 0 relative priority.
 *
 * @const _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG
 * The event manager flag indicates that this thread/request is for a event
 * manager thread.  There can only ever be one event manager thread at a time
 * and it is brought up at the highest of all event manager priorities pthread
 * knows about.
 *
 * <b>pthread & dispatch only flags</b>
 *
 * @const _PTHREAD_PRIORITY_SCHED_PRI_FLAG
 * @const _PTHREAD_PRIORITY_SCHED_PRI_MASK
 * This flag indicates that the bits extracted using
 * _PTHREAD_PRIORITY_SCHED_PRI_MASK represent a scheduler priority instead of
 * a {qos, relative priority} pair.
 *
 * This flag is only used by the pthread kext to indicate libdispatch that the
 * event manager queue priority is a scheduling priority and not a QoS. This
 * flag is never used as an input by anything else and is why it can perform
 * a double duty with _PTHREAD_PRIORITY_ROOTQUEUE_FLAG.
 *
 * @const _PTHREAD_PRIORITY_NEEDS_UNBIND_FLAG
 * This flag is used for the priority of event delivery threads to indicate
 * to libdispatch that this thread is bound to a kqueue.
 *
 * <b>dispatch only flags</b>
 *
 * @const _PTHREAD_PRIORITY_INHERIT_FLAG
 * This flag is meaningful to libdispatch only and has no meanting for the
 * kernel and/or pthread.
 *
 * @const _PTHREAD_PRIORITY_ROOTQUEUE_FLAG
 * This flag is meaningful to libdispatch only and has no meanting for the
 * kernel and/or pthread.
 *
 * @const _PTHREAD_PRIORITY_ENFORCE_FLAG
 * This flag is used to indicate that this priority should be prefered for work
 * submited asynchronously over the intrinsic priority of the queue/thread the
 * work is submitted to.
 *
 * @const _PTHREAD_PRIORITY_OVERRIDE_FLAG
 * No longer used
 */
typedef unsigned long pthread_priority_t;

#define _PTHREAD_PRIORITY_FLAGS_MASK			0xff000000
#define _PTHREAD_PRIORITY_FLAGS_SHIFT			(24ull)

#define _PTHREAD_PRIORITY_OVERCOMMIT_FLAG		0x80000000
#define _PTHREAD_PRIORITY_INHERIT_FLAG			0x40000000 /* dispatch only */
#define _PTHREAD_PRIORITY_ROOTQUEUE_FLAG		0x20000000 /* dispatch only */
#define _PTHREAD_PRIORITY_SCHED_PRI_FLAG		0x20000000
#define _PTHREAD_PRIORITY_SCHED_PRI_MASK		0x0000ffff
#define _PTHREAD_PRIORITY_ENFORCE_FLAG			0x10000000 /* dispatch only */
#define _PTHREAD_PRIORITY_OVERRIDE_FLAG			0x08000000 /* unused */
#define _PTHREAD_PRIORITY_FALLBACK_FLAG			0x04000000
#define _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG	0x02000000
#define _PTHREAD_PRIORITY_NEEDS_UNBIND_FLAG		0x01000000
#define _PTHREAD_PRIORITY_DEFAULTQUEUE_FLAG		_PTHREAD_PRIORITY_FALLBACK_FLAG // compat

#define _PTHREAD_PRIORITY_ENCODING_MASK			0x00a00000
#define _PTHREAD_PRIORITY_ENCODING_SHIFT		(22ull)
#define _PTHREAD_PRIORITY_ENCODING_V0			0x00000000
#define _PTHREAD_PRIORITY_ENCODING_V1			0x00400000 /* unused */
#define _PTHREAD_PRIORITY_ENCODING_V2			0x00800000 /* unused */
#define _PTHREAD_PRIORITY_ENCODING_V3			0x00a00000 /* unused */

#define _PTHREAD_PRIORITY_QOS_CLASS_MASK		0x003fff00
#define _PTHREAD_PRIORITY_VALID_QOS_CLASS_MASK	0x00003f00
#define _PTHREAD_PRIORITY_QOS_CLASS_SHIFT		(8ull)

#define _PTHREAD_PRIORITY_PRIORITY_MASK			0x000000ff
#define _PTHREAD_PRIORITY_PRIORITY_SHIFT		(0)

#if PRIVATE
#if XNU_KERNEL_PRIVATE && !defined(__PTHREAD_EXPOSE_INTERNALS__)
#define __PTHREAD_EXPOSE_INTERNALS__ 1
#endif // XNU_KERNEL_PRIVATE
#ifdef __PTHREAD_EXPOSE_INTERNALS__
/*
 * This exposes the encoding used for pthread_priority_t
 * and is meant to be used by pthread and XNU only
 */
#include <mach/thread_policy.h> // THREAD_QOS_*
#include <stdbool.h>

__attribute__((always_inline, const))
static inline bool
_pthread_priority_has_qos(pthread_priority_t pp)
{
	return (pp & (_PTHREAD_PRIORITY_SCHED_PRI_FLAG |
					_PTHREAD_PRIORITY_EVENT_MANAGER_FLAG)) == 0 &&
			(pp & (_PTHREAD_PRIORITY_QOS_CLASS_MASK &
					~_PTHREAD_PRIORITY_VALID_QOS_CLASS_MASK)) == 0 &&
			(pp & _PTHREAD_PRIORITY_VALID_QOS_CLASS_MASK) != 0;
}

__attribute__((always_inline, const))
static inline pthread_priority_t
_pthread_priority_make_from_thread_qos(thread_qos_t qos, int relpri,
		unsigned long flags)
{
	pthread_priority_t pp = (flags & _PTHREAD_PRIORITY_FLAGS_MASK);
	if (qos && qos < THREAD_QOS_LAST) {
		pp |= (1 << (_PTHREAD_PRIORITY_QOS_CLASS_SHIFT + qos - 1));
		pp |= ((uint8_t)relpri - 1) & _PTHREAD_PRIORITY_PRIORITY_MASK;
	}
	return pp;
}

__attribute__((always_inline, const))
static inline pthread_priority_t
_pthread_event_manager_priority(void)
{
	return _PTHREAD_PRIORITY_EVENT_MANAGER_FLAG;
}

__attribute__((always_inline, const))
static inline pthread_priority_t
_pthread_unspecified_priority(void)
{
	return _pthread_priority_make_from_thread_qos(THREAD_QOS_UNSPECIFIED, 0, 0);
}

__attribute__((always_inline, const))
static inline pthread_priority_t
_pthread_default_priority(unsigned long flags)
{
	return _pthread_priority_make_from_thread_qos(THREAD_QOS_LEGACY, 0, flags);
}

__attribute__((always_inline, const))
static inline thread_qos_t
_pthread_priority_thread_qos(pthread_priority_t pp)
{
	if (_pthread_priority_has_qos(pp)) {
		pp &= _PTHREAD_PRIORITY_QOS_CLASS_MASK;
		pp >>= _PTHREAD_PRIORITY_QOS_CLASS_SHIFT;
		return (thread_qos_t)__builtin_ffs((int)pp);
	}
	return THREAD_QOS_UNSPECIFIED;
}

__attribute__((always_inline, const))
static inline int
_pthread_priority_relpri(pthread_priority_t pp)
{
	if (_pthread_priority_has_qos(pp)) {
		pp &= _PTHREAD_PRIORITY_PRIORITY_MASK;
		pp >>= _PTHREAD_PRIORITY_PRIORITY_SHIFT;
		return (int8_t)pp + 1;
	}
	return 0;
}

#if KERNEL
// Interfaces only used by the kernel and not implemented in userspace.

/*
 * Keep managerness, overcomitness and fallback, discard other flags.
 * Normalize and validate QoS/relpri
 */
__attribute__((const))
pthread_priority_t
_pthread_priority_normalize(pthread_priority_t pp);

/*
 * Keep managerness, discard other flags.
 * Normalize and validate QoS/relpri
 */
__attribute__((const))
pthread_priority_t
_pthread_priority_normalize_for_ipc(pthread_priority_t pp);

/*
 * Keep the flags from base_pp and return the priority with the maximum priority
 * of base_pp and _pthread_priority_make_from_thread_qos(qos, 0, 0)
 */
__attribute__((const))
pthread_priority_t
_pthread_priority_combine(pthread_priority_t base_pp, thread_qos_t qos);

#endif // KERNEL
#endif // __PTHREAD_EXPOSE_INTERNALS__
#endif // PRIVATE
#endif // _PTHREAD_PRIORITY_PRIVATE_H_