xnu-4903.221.2.tar.gz

[apple/xnu.git] / osfmk / kern / thread_act.c

/*
 * Copyright (c) 2000-2016 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@
 */
/*
 * @OSF_FREE_COPYRIGHT@
 */
/*
 * Copyright (c) 1993 The University of Utah and
 * the Center for Software Science (CSS).  All rights reserved.
 *
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * THE UNIVERSITY OF UTAH AND CSS ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS
 * IS" CONDITION.  THE UNIVERSITY OF UTAH AND CSS DISCLAIM ANY LIABILITY OF
 * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * CSS requests users of this software to return to css-dist@cs.utah.edu any
 * improvements that they make and grant CSS redistribution rights.
 *
 *      Author: Bryan Ford, University of Utah CSS
 *
 *      Thread management routines
 */

#include <mach/mach_types.h>
#include <mach/kern_return.h>
#include <mach/thread_act_server.h>

#include <kern/kern_types.h>
#include <kern/ast.h>
#include <kern/mach_param.h>
#include <kern/zalloc.h>
#include <kern/extmod_statistics.h>
#include <kern/thread.h>
#include <kern/task.h>
#include <kern/sched_prim.h>
#include <kern/misc_protos.h>
#include <kern/assert.h>
#include <kern/exception.h>
#include <kern/ipc_mig.h>
#include <kern/ipc_tt.h>
#include <kern/machine.h>
#include <kern/spl.h>
#include <kern/syscall_subr.h>
#include <kern/sync_lock.h>
#include <kern/processor.h>
#include <kern/timer.h>
#include <kern/affinity.h>

#include <stdatomic.h>

#include <security/mac_mach_internal.h>

static void act_abort(thread_t thread);

static void thread_suspended(void *arg, wait_result_t result);
static void thread_set_apc_ast(thread_t thread);
static void thread_set_apc_ast_locked(thread_t thread);

/*
 * Internal routine to mark a thread as started.
 * Always called with the thread mutex locked.
 */
void
thread_start(
        thread_t                        thread)
{
        clear_wait(thread, THREAD_AWAKENED);
        thread->started = TRUE;
}

/*
 * Internal routine to mark a thread as waiting
 * right after it has been created.  The caller
 * is responsible to call wakeup()/thread_wakeup()
 * or thread_terminate() to get it going.
 *
 * Always called with the thread mutex locked.
 *
 * Task and task_threads mutexes also held 
 * (so nobody can set the thread running before
 * this point)
 *
 * Converts TH_UNINT wait to THREAD_INTERRUPTIBLE
 * to allow termination from this point forward.
 */
void
thread_start_in_assert_wait(
        thread_t                        thread,
        event_t             event,
        wait_interrupt_t    interruptible)
{
        struct waitq *waitq = assert_wait_queue(event);
        wait_result_t wait_result;
        spl_t spl;

        spl = splsched();
        waitq_lock(waitq);

        /* clear out startup condition (safe because thread not started yet) */
        thread_lock(thread);
        assert(!thread->started);
        assert((thread->state & (TH_WAIT | TH_UNINT)) == (TH_WAIT | TH_UNINT));
        thread->state &= ~(TH_WAIT | TH_UNINT);
        thread_unlock(thread);

        /* assert wait interruptibly forever */
        wait_result = waitq_assert_wait64_locked(waitq, CAST_EVENT64_T(event),
                                         interruptible,
                                         TIMEOUT_URGENCY_SYS_NORMAL,
                                         TIMEOUT_WAIT_FOREVER,
                                         TIMEOUT_NO_LEEWAY,
                                         thread);
        assert (wait_result == THREAD_WAITING);

        /* mark thread started while we still hold the waitq lock */
        thread_lock(thread);
        thread->started = TRUE;
        thread_unlock(thread);

        waitq_unlock(waitq);
        splx(spl);
}

/*
 * Internal routine to terminate a thread.
 * Sometimes called with task already locked.
 */
kern_return_t
thread_terminate_internal(
        thread_t                        thread)
{
        kern_return_t           result = KERN_SUCCESS;

        thread_mtx_lock(thread);

        if (thread->active) {
                thread->active = FALSE;

                act_abort(thread);

                if (thread->started)
                        clear_wait(thread, THREAD_INTERRUPTED);
                else {
                        thread_start(thread);
                }
        }
        else
                result = KERN_TERMINATED;

        if (thread->affinity_set != NULL)
                thread_affinity_terminate(thread);

        thread_mtx_unlock(thread);

        if (thread != current_thread() && result == KERN_SUCCESS)
                thread_wait(thread, FALSE);

        return (result);
}

/*
 * Terminate a thread.
 */
kern_return_t
thread_terminate(
        thread_t                thread)
{
        if (thread == THREAD_NULL)
                return (KERN_INVALID_ARGUMENT);

        /* Kernel threads can't be terminated without their own cooperation */
        if (thread->task == kernel_task && thread != current_thread())
                return (KERN_FAILURE);

        kern_return_t result = thread_terminate_internal(thread);

        /*
         * If a kernel thread is terminating itself, force handle the APC_AST here.
         * Kernel threads don't pass through the return-to-user AST checking code,
         * but all threads must finish their own termination in thread_apc_ast.
         */
        if (thread->task == kernel_task) {
                assert(thread->active == FALSE);
                thread_ast_clear(thread, AST_APC);
                thread_apc_ast(thread);

                panic("thread_terminate");
                /* NOTREACHED */
        }

        return (result);
}

/*
 * Suspend execution of the specified thread.
 * This is a recursive-style suspension of the thread, a count of
 * suspends is maintained.
 *
 * Called with thread mutex held.
 */
void
thread_hold(thread_t thread)
{
        if (thread->suspend_count++ == 0) {
                thread_set_apc_ast(thread);
                assert(thread->suspend_parked == FALSE);
        }
}

/*
 * Decrement internal suspension count, setting thread
 * runnable when count falls to zero.
 *
 * Because the wait is abortsafe, we can't be guaranteed that the thread
 * is currently actually waiting even if suspend_parked is set.
 *
 * Called with thread mutex held.
 */
void
thread_release(thread_t thread)
{
        assertf(thread->suspend_count > 0, "thread %p over-resumed", thread);

        /* fail-safe on non-assert builds */
        if (thread->suspend_count == 0)
                return;

        if (--thread->suspend_count == 0) {
                if (!thread->started) {
                        thread_start(thread);
                } else if (thread->suspend_parked) {
                        thread->suspend_parked = FALSE;
                        thread_wakeup_thread(&thread->suspend_count, thread);
                }
        }
}

kern_return_t
thread_suspend(thread_t thread)
{
        kern_return_t result = KERN_SUCCESS;

        if (thread == THREAD_NULL || thread->task == kernel_task)
                return (KERN_INVALID_ARGUMENT);

        thread_mtx_lock(thread);

        if (thread->active) {
                if (thread->user_stop_count++ == 0)
                        thread_hold(thread);
        } else {
                result = KERN_TERMINATED;
        }

        thread_mtx_unlock(thread);

        if (thread != current_thread() && result == KERN_SUCCESS)
                thread_wait(thread, FALSE);

        return (result);
}

kern_return_t
thread_resume(thread_t thread)
{
        kern_return_t result = KERN_SUCCESS;

        if (thread == THREAD_NULL || thread->task == kernel_task)
                return (KERN_INVALID_ARGUMENT);

        thread_mtx_lock(thread);

        if (thread->active) {
                if (thread->user_stop_count > 0) {
                        if (--thread->user_stop_count == 0)
                                thread_release(thread);
                } else {
                        result = KERN_FAILURE;
                }
        } else {
                result = KERN_TERMINATED;
        }

        thread_mtx_unlock(thread);

        return (result);
}

/*
 *      thread_depress_abort_from_user:
 *
 *      Prematurely abort priority depression if there is one.
 */
kern_return_t
thread_depress_abort_from_user(thread_t thread)
{
        kern_return_t result;

        if (thread == THREAD_NULL)
                return (KERN_INVALID_ARGUMENT);

        thread_mtx_lock(thread);

        if (thread->active)
                result = thread_depress_abort(thread);
        else
                result = KERN_TERMINATED;

        thread_mtx_unlock(thread);

        return (result);
}


/*
 * Indicate that the thread should run the AST_APC callback
 * to detect an abort condition.
 *
 * Called with thread mutex held.
 */
static void
act_abort(
        thread_t        thread)
{
        spl_t           s = splsched();

        thread_lock(thread);

        if (!(thread->sched_flags & TH_SFLAG_ABORT)) {
                thread->sched_flags |= TH_SFLAG_ABORT;
                thread_set_apc_ast_locked(thread);
                thread_depress_abort_locked(thread);
        } else {
                thread->sched_flags &= ~TH_SFLAG_ABORTSAFELY;
        }

        thread_unlock(thread);
        splx(s);
}

kern_return_t
thread_abort(
        thread_t        thread)
{
        kern_return_t   result = KERN_SUCCESS;

        if (thread == THREAD_NULL)
                return (KERN_INVALID_ARGUMENT);

        thread_mtx_lock(thread);

        if (thread->active) {
                act_abort(thread);
                clear_wait(thread, THREAD_INTERRUPTED);
        }
        else
                result = KERN_TERMINATED;

        thread_mtx_unlock(thread);

        return (result);
}

kern_return_t
thread_abort_safely(
        thread_t                thread)
{
        kern_return_t   result = KERN_SUCCESS;

        if (thread == THREAD_NULL)
                return (KERN_INVALID_ARGUMENT);

        thread_mtx_lock(thread);

        if (thread->active) {
                spl_t           s = splsched();

                thread_lock(thread);
                if (!thread->at_safe_point ||
                                clear_wait_internal(thread, THREAD_INTERRUPTED) != KERN_SUCCESS) {
                        if (!(thread->sched_flags & TH_SFLAG_ABORT)) {
                                thread->sched_flags |= TH_SFLAG_ABORTED_MASK;
                                thread_set_apc_ast_locked(thread);
                                thread_depress_abort_locked(thread);
                        }
                }
                thread_unlock(thread);
                splx(s);
        } else {
                result = KERN_TERMINATED;
        }

        thread_mtx_unlock(thread);

        return (result);
}

/*** backward compatibility hacks ***/
#include <mach/thread_info.h>
#include <mach/thread_special_ports.h>
#include <ipc/ipc_port.h>

kern_return_t
thread_info(
        thread_t                        thread,
        thread_flavor_t                 flavor,
        thread_info_t                   thread_info_out,
        mach_msg_type_number_t  *thread_info_count)
{
        kern_return_t                   result;

        if (thread == THREAD_NULL)
                return (KERN_INVALID_ARGUMENT);

        thread_mtx_lock(thread);

        if (thread->active || thread->inspection)
                result = thread_info_internal(
                                                thread, flavor, thread_info_out, thread_info_count);
        else
                result = KERN_TERMINATED;

        thread_mtx_unlock(thread);

        return (result);
}

static inline kern_return_t
thread_get_state_internal(
        thread_t                thread,
        int                                             flavor,
        thread_state_t                  state,                  /* pointer to OUT array */
        mach_msg_type_number_t  *state_count,   /*IN/OUT*/
        boolean_t                               to_user)
{
        kern_return_t           result = KERN_SUCCESS;

        if (thread == THREAD_NULL)
                return (KERN_INVALID_ARGUMENT);

        thread_mtx_lock(thread);

        if (thread->active) {
                if (thread != current_thread()) {
                        thread_hold(thread);

                        thread_mtx_unlock(thread);

                        if (thread_stop(thread, FALSE)) {
                                thread_mtx_lock(thread);
                                result = machine_thread_get_state(
                                                                                thread, flavor, state, state_count);
                                thread_unstop(thread);
                        }
                        else {
                                thread_mtx_lock(thread);
                                result = KERN_ABORTED;
                        }

                        thread_release(thread);
                }
                else
                        result = machine_thread_get_state(
                                                                        thread, flavor, state, state_count);
        }
        else if (thread->inspection)
        {
                result = machine_thread_get_state(
                                                                        thread, flavor, state, state_count);
        }
        else
                result = KERN_TERMINATED;

        if (to_user && result == KERN_SUCCESS) {
                result = machine_thread_state_convert_to_user(thread, flavor, state,
                                state_count);
        }

        thread_mtx_unlock(thread);

        return (result);
}

/* No prototype, since thread_act_server.h has the _to_user version if KERNEL_SERVER */

kern_return_t
thread_get_state(
        thread_t                thread,
        int                                             flavor,
        thread_state_t                  state,
        mach_msg_type_number_t  *state_count);

kern_return_t
thread_get_state(
        thread_t                thread,
        int                                             flavor,
        thread_state_t                  state,                  /* pointer to OUT array */
        mach_msg_type_number_t  *state_count)   /*IN/OUT*/
{
        return thread_get_state_internal(thread, flavor, state, state_count, FALSE);
}

kern_return_t
thread_get_state_to_user(
        thread_t                thread,
        int                                             flavor,
        thread_state_t                  state,                  /* pointer to OUT array */
        mach_msg_type_number_t  *state_count)   /*IN/OUT*/
{
        return thread_get_state_internal(thread, flavor, state, state_count, TRUE);
}

/*
 *      Change thread's machine-dependent state.  Called with nothing
 *      locked.  Returns same way.
 */
static inline kern_return_t
thread_set_state_internal(
        thread_t                thread,
        int                                             flavor,
        thread_state_t                  state,
        mach_msg_type_number_t  state_count,
        boolean_t                               from_user)
{
        kern_return_t           result = KERN_SUCCESS;

        if (thread == THREAD_NULL)
                return (KERN_INVALID_ARGUMENT);

        thread_mtx_lock(thread);

        if (thread->active) {
                if (from_user) {
                        result = machine_thread_state_convert_from_user(thread, flavor,
                                        state, state_count);
                        if (result != KERN_SUCCESS) {
                                goto out;
                        }
                }
                if (thread != current_thread()) {
                        thread_hold(thread);

                        thread_mtx_unlock(thread);

                        if (thread_stop(thread, TRUE)) {
                                thread_mtx_lock(thread);
                                result = machine_thread_set_state(
                                                                                thread, flavor, state, state_count);
                                thread_unstop(thread);
                        }
                        else {
                                thread_mtx_lock(thread);
                                result = KERN_ABORTED;
                        }

                        thread_release(thread);
                }
                else
                        result = machine_thread_set_state(
                                                                        thread, flavor, state, state_count);
        }
        else
                result = KERN_TERMINATED;

        if ((result == KERN_SUCCESS) && from_user)
                extmod_statistics_incr_thread_set_state(thread);

out:
        thread_mtx_unlock(thread);

        return (result);
}

/* No prototype, since thread_act_server.h has the _from_user version if KERNEL_SERVER */ 
kern_return_t
thread_set_state(
        thread_t                thread,
        int                                             flavor,
        thread_state_t                  state,
        mach_msg_type_number_t  state_count);

kern_return_t
thread_set_state(
        thread_t                thread,
        int                                             flavor,
        thread_state_t                  state,
        mach_msg_type_number_t  state_count)
{
        return thread_set_state_internal(thread, flavor, state, state_count, FALSE);
}
 
kern_return_t
thread_set_state_from_user(
        thread_t                thread,
        int                                             flavor,
        thread_state_t                  state,
        mach_msg_type_number_t  state_count)
{
        return thread_set_state_internal(thread, flavor, state, state_count, TRUE);
}
 
/*
 * Kernel-internal "thread" interfaces used outside this file:
 */

/* Initialize (or re-initialize) a thread state.  Called from execve
 * with nothing locked, returns same way.
 */
kern_return_t
thread_state_initialize(
        thread_t                thread)
{
        kern_return_t           result = KERN_SUCCESS;

        if (thread == THREAD_NULL)
                return (KERN_INVALID_ARGUMENT);

        thread_mtx_lock(thread);

        if (thread->active) {
                if (thread != current_thread()) {
                        thread_hold(thread);

                        thread_mtx_unlock(thread);

                        if (thread_stop(thread, TRUE)) {
                                thread_mtx_lock(thread);
                                result = machine_thread_state_initialize( thread );
                                thread_unstop(thread);
                        }
                        else {
                                thread_mtx_lock(thread);
                                result = KERN_ABORTED;
                        }

                        thread_release(thread);
                }
                else
                        result = machine_thread_state_initialize( thread );
        }
        else
                result = KERN_TERMINATED;

        thread_mtx_unlock(thread);

        return (result);
}


kern_return_t
thread_dup(
        thread_t        target)
{
        thread_t                        self = current_thread();
        kern_return_t           result = KERN_SUCCESS;

        if (target == THREAD_NULL || target == self)
                return (KERN_INVALID_ARGUMENT);

        thread_mtx_lock(target);

        if (target->active) {
                thread_hold(target);

                thread_mtx_unlock(target);

                if (thread_stop(target, TRUE)) {
                        thread_mtx_lock(target);
                        result = machine_thread_dup(self, target, FALSE);

                        if (self->affinity_set != AFFINITY_SET_NULL)
                                thread_affinity_dup(self, target);
                        thread_unstop(target);
                }
                else {
                        thread_mtx_lock(target);
                        result = KERN_ABORTED;
                }

                thread_release(target);
        }
        else
                result = KERN_TERMINATED;

        thread_mtx_unlock(target);

        return (result);
}


kern_return_t
thread_dup2(
        thread_t        source,
        thread_t        target)
{
        kern_return_t           result = KERN_SUCCESS;
        uint32_t                active = 0;

        if (source == THREAD_NULL || target == THREAD_NULL || target == source)
                return (KERN_INVALID_ARGUMENT);

        thread_mtx_lock(source);
        active = source->active;
        thread_mtx_unlock(source);

        if (!active) {
                return KERN_TERMINATED;
        }

        thread_mtx_lock(target);

        if (target->active || target->inspection) {
                thread_hold(target);

                thread_mtx_unlock(target);

                if (thread_stop(target, TRUE)) {
                        thread_mtx_lock(target);
                        result = machine_thread_dup(source, target, TRUE);
                        if (source->affinity_set != AFFINITY_SET_NULL)
                                thread_affinity_dup(source, target);
                        thread_unstop(target);
                }
                else {
                        thread_mtx_lock(target);
                        result = KERN_ABORTED;
                }

                thread_release(target);
        }
        else
                result = KERN_TERMINATED;

        thread_mtx_unlock(target);

        return (result);
}

/*
 *      thread_setstatus:
 *
 *      Set the status of the specified thread.
 *      Called with (and returns with) no locks held.
 */
kern_return_t
thread_setstatus(
        thread_t                thread,
        int                                             flavor,
        thread_state_t                  tstate,
        mach_msg_type_number_t  count)
{

        return (thread_set_state(thread, flavor, tstate, count));
}

kern_return_t
thread_setstatus_from_user(
        thread_t                thread,
        int                                             flavor,
        thread_state_t                  tstate,
        mach_msg_type_number_t  count)
{

        return (thread_set_state_from_user(thread, flavor, tstate, count));
}

/*
 *      thread_getstatus:
 *
 *      Get the status of the specified thread.
 */
kern_return_t
thread_getstatus(
        thread_t                thread,
        int                                             flavor,
        thread_state_t                  tstate,
        mach_msg_type_number_t  *count)
{
        return (thread_get_state(thread, flavor, tstate, count));
}

kern_return_t
thread_getstatus_to_user(
        thread_t                thread,
        int                                             flavor,
        thread_state_t                  tstate,
        mach_msg_type_number_t  *count)
{
        return (thread_get_state_to_user(thread, flavor, tstate, count));
}

/*
 *      Change thread's machine-dependent userspace TSD base.
 *  Called with nothing locked.  Returns same way.
 */
kern_return_t
thread_set_tsd_base(
        thread_t                        thread,
        mach_vm_offset_t        tsd_base)
{
        kern_return_t           result = KERN_SUCCESS;

        if (thread == THREAD_NULL)
                return (KERN_INVALID_ARGUMENT);

        thread_mtx_lock(thread);

        if (thread->active) {
                if (thread != current_thread()) {
                        thread_hold(thread);

                        thread_mtx_unlock(thread);

                        if (thread_stop(thread, TRUE)) {
                                thread_mtx_lock(thread);
                                result = machine_thread_set_tsd_base(thread, tsd_base);
                                thread_unstop(thread);
                        }
                        else {
                                thread_mtx_lock(thread);
                                result = KERN_ABORTED;
                        }

                        thread_release(thread);
                }
                else
                        result = machine_thread_set_tsd_base(thread, tsd_base);
        }
        else
                result = KERN_TERMINATED;

        thread_mtx_unlock(thread);

        return (result);
}

/*
 * thread_set_apc_ast:
 *
 * Register the AST_APC callback that handles suspension and
 * termination, if it hasn't been installed already.
 *
 * Called with the thread mutex held.
 */
static void
thread_set_apc_ast(thread_t thread)
{
        spl_t s = splsched();

        thread_lock(thread);
        thread_set_apc_ast_locked(thread);
        thread_unlock(thread);

        splx(s);
}

/*
 * thread_set_apc_ast_locked:
 *
 * Do the work of registering for the AST_APC callback.
 *
 * Called with the thread mutex and scheduling lock held.
 */
static void
thread_set_apc_ast_locked(thread_t thread)
{
        thread_ast_set(thread, AST_APC);

        if (thread == current_thread()) {
                ast_propagate(thread);
        } else {
                processor_t processor = thread->last_processor;

                if (processor != PROCESSOR_NULL &&
                    processor->state == PROCESSOR_RUNNING &&
                    processor->active_thread == thread) {
                        cause_ast_check(processor);
                }
        }
}

/*
 * Activation control support routines internal to this file:
 *
 */

/*
 * thread_suspended
 *
 * Continuation routine for thread suspension.  It checks
 * to see whether there has been any new suspensions.  If so, it
 * installs the AST_APC handler again.
 */
__attribute__((noreturn))
static void
thread_suspended(__unused void *parameter, wait_result_t result)
{
        thread_t thread = current_thread();

        thread_mtx_lock(thread);

        if (result == THREAD_INTERRUPTED)
                thread->suspend_parked = FALSE;
        else
                assert(thread->suspend_parked == FALSE);

        if (thread->suspend_count > 0)
                thread_set_apc_ast(thread);

        thread_mtx_unlock(thread);

        thread_exception_return();
        /*NOTREACHED*/
}

/*
 * thread_apc_ast - handles AST_APC and drives thread suspension and termination.
 * Called with nothing locked.  Returns (if it returns) the same way.
 */
void
thread_apc_ast(thread_t thread)
{
        thread_mtx_lock(thread);

        assert(thread->suspend_parked == FALSE);

        spl_t s = splsched();
        thread_lock(thread);

        /* TH_SFLAG_POLLDEPRESS is OK to have here */
        assert((thread->sched_flags & TH_SFLAG_DEPRESS) == 0);

        thread->sched_flags &= ~TH_SFLAG_ABORTED_MASK;
        thread_unlock(thread);
        splx(s);

        if (!thread->active) {
                /* Thread is ready to terminate, time to tear it down */
                thread_mtx_unlock(thread);

                thread_terminate_self();
                /*NOTREACHED*/
        }

        /* If we're suspended, go to sleep and wait for someone to wake us up. */
        if (thread->suspend_count > 0) {
                thread->suspend_parked = TRUE;
                assert_wait(&thread->suspend_count,
                                THREAD_ABORTSAFE | THREAD_WAIT_NOREPORT_USER);
                thread_mtx_unlock(thread);

                thread_block(thread_suspended);
                /*NOTREACHED*/
        }

        thread_mtx_unlock(thread);
}

/* Prototype, see justification above */
kern_return_t
act_set_state(
        thread_t                                thread,
        int                                             flavor,
        thread_state_t                  state,
        mach_msg_type_number_t  count);

kern_return_t
act_set_state(
        thread_t                                thread,
        int                                             flavor,
        thread_state_t                  state,
        mach_msg_type_number_t  count)
{
    if (thread == current_thread())
            return (KERN_INVALID_ARGUMENT);

    return (thread_set_state(thread, flavor, state, count));
    
}

kern_return_t
act_set_state_from_user(
        thread_t                                thread,
        int                                             flavor,
        thread_state_t                  state,
        mach_msg_type_number_t  count)
{
    if (thread == current_thread())
            return (KERN_INVALID_ARGUMENT);

    return (thread_set_state_from_user(thread, flavor, state, count));
    
}

/* Prototype, see justification above */
kern_return_t
act_get_state(
        thread_t                                thread,
        int                                             flavor,
        thread_state_t                  state,
        mach_msg_type_number_t  *count);

kern_return_t
act_get_state(
        thread_t                                thread,
        int                                             flavor,
        thread_state_t                  state,
        mach_msg_type_number_t  *count)
{
    if (thread == current_thread())
            return (KERN_INVALID_ARGUMENT);

    return (thread_get_state(thread, flavor, state, count));
}

kern_return_t
act_get_state_to_user(
        thread_t                                thread,
        int                                             flavor,
        thread_state_t                  state,
        mach_msg_type_number_t  *count)
{
    if (thread == current_thread())
            return (KERN_INVALID_ARGUMENT);

    return (thread_get_state_to_user(thread, flavor, state, count));
}

static void
act_set_ast(
            thread_t thread,
            ast_t ast)
{
        spl_t s = splsched();

        if (thread == current_thread()) {
                thread_ast_set(thread, ast);
                ast_propagate(thread);
        } else {
                processor_t processor;

                thread_lock(thread);
                thread_ast_set(thread, ast);
                processor = thread->last_processor;
                if ( processor != PROCESSOR_NULL            &&
                     processor->state == PROCESSOR_RUNNING  &&
                     processor->active_thread == thread     )
                        cause_ast_check(processor);
                thread_unlock(thread);
        }

        splx(s);
}

/*
 * set AST on thread without causing an AST check
 * and without taking the thread lock
 *
 * If thread is not the current thread, then it may take
 * up until the next context switch or quantum expiration
 * on that thread for it to notice the AST.
 */
static void
act_set_ast_async(thread_t  thread,
                  ast_t     ast)
{
        thread_ast_set(thread, ast);

        if (thread == current_thread()) {
                spl_t s = splsched();
                ast_propagate(thread);
                splx(s);
        }
}

void
act_set_astbsd(
        thread_t        thread)
{
        act_set_ast( thread, AST_BSD );
}

void
act_set_astkevent(thread_t thread, uint16_t bits)
{
        atomic_fetch_or(&thread->kevent_ast_bits, bits);

        /* kevent AST shouldn't send immediate IPIs */
        act_set_ast_async(thread, AST_KEVENT);
}

void
act_set_kperf(
        thread_t        thread)
{
        /* safety check */
        if (thread != current_thread())
                if( !ml_get_interrupts_enabled() )
                        panic("unsafe act_set_kperf operation");

        act_set_ast( thread, AST_KPERF );
}

#if CONFIG_MACF
void
act_set_astmacf(
        thread_t        thread)
{
        act_set_ast( thread, AST_MACF);
}
#endif

void
act_set_astledger(thread_t thread)
{
        act_set_ast(thread, AST_LEDGER);
}

/*
 * The ledger AST may need to be set while already holding
 * the thread lock.  This routine skips sending the IPI,
 * allowing us to avoid the lock hold.
 *
 * However, it means the targeted thread must context switch
 * to recognize the ledger AST.
 */
void
act_set_astledger_async(thread_t thread)
{
        act_set_ast_async(thread, AST_LEDGER);
}

void
act_set_io_telemetry_ast(thread_t thread)
{
        act_set_ast(thread, AST_TELEMETRY_IO);
}