common/disp/thread.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 1991, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2013, Joyent, Inc.  All rights reserved.
 */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/sysmacros.h>
#include <sys/signal.h>
#include <sys/stack.h>
#include <sys/pcb.h>
#include <sys/user.h>
#include <sys/systm.h>
#include <sys/sysinfo.h>
#include <sys/errno.h>
#include <sys/cmn_err.h>
#include <sys/cred.h>
#include <sys/resource.h>
#include <sys/task.h>
#include <sys/project.h>
#include <sys/proc.h>
#include <sys/debug.h>
#include <sys/disp.h>
#include <sys/class.h>
#include <vm/seg_kmem.h>
#include <vm/seg_kp.h>
#include <sys/machlock.h>
#include <sys/kmem.h>
#include <sys/varargs.h>
#include <sys/turnstile.h>
#include <sys/poll.h>
#include <sys/vtrace.h>
#include <sys/callb.h>
#include <c2/audit.h>
#include <sys/tnf.h>
#include <sys/sobject.h>
#include <sys/cpupart.h>
#include <sys/pset.h>
#include <sys/door.h>
#include <sys/spl.h>
#include <sys/copyops.h>
#include <sys/rctl.h>
#include <sys/brand.h>
#include <sys/pool.h>
#include <sys/zone.h>
#include <sys/tsol/label.h>
#include <sys/tsol/tndb.h>
#include <sys/cpc_impl.h>
#include <sys/sdt.h>
#include <sys/reboot.h>
#include <sys/kdi.h>
#include <sys/schedctl.h>
#include <sys/waitq.h>
#include <sys/cpucaps.h>
#include <sys/kiconv.h>

struct kmem_cache *thread_cache;    /* cache of free threads */
struct kmem_cache *lwp_cache;       /* cache of free lwps */
struct kmem_cache *turnstile_cache; /* cache of free turnstiles */

/*
 * allthreads is only for use by kmem_readers.  All kernel loops can use
 * the current thread as a start/end point.
 */
kthread_t *allthreads = &t0;    /* circular list of all threads */

static kcondvar_t reaper_cv;        /* synchronization var */
kthread_t   *thread_deathrow;   /* circular list of reapable threads */
kthread_t   *lwp_deathrow;      /* circular list of reapable threads */
kmutex_t    reaplock;       /* protects lwp and thread deathrows */
int thread_reapcnt = 0;     /* number of threads on deathrow */
int lwp_reapcnt = 0;        /* number of lwps on deathrow */
int reaplimit = 16;         /* delay reaping until reaplimit */

thread_free_lock_t  *thread_free_lock;
                    /* protects tick thread from reaper */

extern int nthread;

/* System Scheduling classes. */
id_t    syscid;             /* system scheduling class ID */
id_t    sysdccid = CLASS_UNUSED;    /* reset when SDC loads */

void    *segkp_thread;          /* cookie for segkp pool */

int lwp_cache_sz = 32;
int t_cache_sz = 8;
static kt_did_t next_t_id = 1;

/* Default mode for thread binding to CPUs and processor sets */
int default_binding_mode = TB_ALLHARD;

/*
 * Min/Max stack sizes for stack size parameters
 */
#define MAX_STKSIZE (32 * DEFAULTSTKSZ)
#define MIN_STKSIZE DEFAULTSTKSZ

/*
 * default_stksize overrides lwp_default_stksize if it is set.
 */
int default_stksize;
int lwp_default_stksize;

static zone_key_t zone_thread_key;

unsigned int kmem_stackinfo;        /* stackinfo feature on-off */
kmem_stkinfo_t *kmem_stkinfo_log;   /* stackinfo circular log */
static kmutex_t kmem_stkinfo_lock;  /* protects kmem_stkinfo_log */

/*
 * forward declarations for internal thread specific data (tsd)
 */
static void *tsd_realloc(void *, size_t, size_t);

void thread_reaper(void);

/* forward declarations for stackinfo feature */
static void stkinfo_begin(kthread_t *);
static void stkinfo_end(kthread_t *);
static size_t stkinfo_percent(caddr_t, caddr_t, caddr_t);

/*ARGSUSED*/
static int
turnstile_constructor(void *buf, void *cdrarg, int kmflags)
{
    bzero(buf, sizeof (turnstile_t));
    return (0);
}

/*ARGSUSED*/
static void
turnstile_destructor(void *buf, void *cdrarg)
{
    turnstile_t *ts = buf;

    ASSERT(ts->ts_free == NULL);
    ASSERT(ts->ts_waiters == 0);
    ASSERT(ts->ts_inheritor == NULL);
    ASSERT(ts->ts_sleepq[0].sq_first == NULL);
    ASSERT(ts->ts_sleepq[1].sq_first == NULL);
}

void
thread_init(void)
{
    kthread_t *tp;
    extern char sys_name[];
    extern void idle();
    struct cpu *cpu = CPU;
    int i;
    kmutex_t *lp;

    mutex_init(&reaplock, NULL, MUTEX_SPIN, (void *)ipltospl(DISP_LEVEL));
    thread_free_lock =
        kmem_alloc(sizeof (thread_free_lock_t) * THREAD_FREE_NUM, KM_SLEEP);
    for (i = 0; i < THREAD_FREE_NUM; i++) {
        lp = &thread_free_lock[i].tf_lock;
        mutex_init(lp, NULL, MUTEX_DEFAULT, NULL);
    }

#if defined(__i386) || defined(__amd64)
    thread_cache = kmem_cache_create("thread_cache", sizeof (kthread_t),
        PTR24_ALIGN, NULL, NULL, NULL, NULL, NULL, 0);

    /*
     * "struct _klwp" includes a "struct pcb", which includes a
     * "struct fpu", which needs to be 64-byte aligned on amd64
     * (and even on i386) for xsave/xrstor.
     */
    lwp_cache = kmem_cache_create("lwp_cache", sizeof (klwp_t),
        64, NULL, NULL, NULL, NULL, NULL, 0);
#else
    /*
     * Allocate thread structures from static_arena.  This prevents
     * issues where a thread tries to relocate its own thread
     * structure and touches it after the mapping has been suspended.
     */
    thread_cache = kmem_cache_create("thread_cache", sizeof (kthread_t),
        PTR24_ALIGN, NULL, NULL, NULL, NULL, static_arena, 0);

    lwp_stk_cache_init();

    lwp_cache = kmem_cache_create("lwp_cache", sizeof (klwp_t),
        0, NULL, NULL, NULL, NULL, NULL, 0);
#endif

    turnstile_cache = kmem_cache_create("turnstile_cache",
        sizeof (turnstile_t), 0,
        turnstile_constructor, turnstile_destructor, NULL, NULL, NULL, 0);

    label_init();
    cred_init();

    /*
     * Initialize various resource management facilities.
     */
    rctl_init();
    cpucaps_init();
    /*
     * Zone_init() should be called before project_init() so that project ID
     * for the first project is initialized correctly.
     */
    zone_init();
    project_init();
    brand_init();
    kiconv_init();
    task_init();
    tcache_init();
    pool_init();

    curthread->t_ts = kmem_cache_alloc(turnstile_cache, KM_SLEEP);

    /*
     * Originally, we had two parameters to set default stack
     * size: one for lwp's (lwp_default_stksize), and one for
     * kernel-only threads (DEFAULTSTKSZ, a.k.a. _defaultstksz).
     * Now we have a third parameter that overrides both if it is
     * set to a legal stack size, called default_stksize.
     */

    if (default_stksize == 0) {
        default_stksize = DEFAULTSTKSZ;
    } else if (default_stksize % PAGESIZE != 0 ||
        default_stksize > MAX_STKSIZE ||
        default_stksize < MIN_STKSIZE) {
        cmn_err(CE_WARN, "Illegal stack size. Using %d",
            (int)DEFAULTSTKSZ);
        default_stksize = DEFAULTSTKSZ;
    } else {
        lwp_default_stksize = default_stksize;
    }

    if (lwp_default_stksize == 0) {
        lwp_default_stksize = default_stksize;
    } else if (lwp_default_stksize % PAGESIZE != 0 ||
        lwp_default_stksize > MAX_STKSIZE ||
        lwp_default_stksize < MIN_STKSIZE) {
        cmn_err(CE_WARN, "Illegal stack size. Using %d",
            default_stksize);
        lwp_default_stksize = default_stksize;
    }

    segkp_lwp = segkp_cache_init(segkp, lwp_cache_sz,
        lwp_default_stksize,
        (KPD_NOWAIT | KPD_HASREDZONE | KPD_LOCKED));

    segkp_thread = segkp_cache_init(segkp, t_cache_sz,
        default_stksize, KPD_HASREDZONE | KPD_LOCKED | KPD_NO_ANON);

    (void) getcid(sys_name, &syscid);
    curthread->t_cid = syscid;  /* current thread is t0 */

    /*
     * Set up the first CPU's idle thread.
     * It runs whenever the CPU has nothing worthwhile to do.
     */
    tp = thread_create(NULL, 0, idle, NULL, 0, &p0, TS_STOPPED, -1);
    cpu->cpu_idle_thread = tp;
    tp->t_preempt = 1;
    tp->t_disp_queue = cpu->cpu_disp;
    ASSERT(tp->t_disp_queue != NULL);
    tp->t_bound_cpu = cpu;
    tp->t_affinitycnt = 1;

    /*
     * Registering a thread in the callback table is usually
     * done in the initialization code of the thread. In this
     * case, we do it right after thread creation to avoid
     * blocking idle thread while registering itself. It also
     * avoids the possibility of reregistration in case a CPU
     * restarts its idle thread.
     */
    CALLB_CPR_INIT_SAFE(tp, "idle");

    /*
     * Create the thread_reaper daemon. From this point on, exited
     * threads will get reaped.
     */
    (void) thread_create(NULL, 0, (void (*)())thread_reaper,
        NULL, 0, &p0, TS_RUN, minclsyspri);

    /*
     * Finish initializing the kernel memory allocator now that
     * thread_create() is available.
     */
    kmem_thread_init();

    if (boothowto & RB_DEBUG)
        kdi_dvec_thravail();
}

/*
 * Create a thread.
 *
 * thread_create() blocks for memory if necessary.  It never fails.
 *
 * If stk is NULL, the thread is created at the base of the stack
 * and cannot be swapped.
 */
kthread_t *
thread_create(
    caddr_t stk,
    size_t  stksize,
    void    (*proc)(),
    void    *arg,
    size_t  len,
    proc_t   *pp,
    int state,
    pri_t   pri)
{
    kthread_t *t;
    extern struct classfuncs sys_classfuncs;
    turnstile_t *ts;

    /*
     * Every thread keeps a turnstile around in case it needs to block.
     * The only reason the turnstile is not simply part of the thread
     * structure is that we may have to break the association whenever
     * more than one thread blocks on a given synchronization object.
     * From a memory-management standpoint, turnstiles are like the
     * "attached mblks" that hang off dblks in the streams allocator.
     */
    ts = kmem_cache_alloc(turnstile_cache, KM_SLEEP);

    if (stk == NULL) {
        /*
         * alloc both thread and stack in segkp chunk
         */

        if (stksize < default_stksize)
            stksize = default_stksize;

        if (stksize == default_stksize) {
            stk = (caddr_t)segkp_cache_get(segkp_thread);
        } else {
            stksize = roundup(stksize, PAGESIZE);
            stk = (caddr_t)segkp_get(segkp, stksize,
                (KPD_HASREDZONE | KPD_NO_ANON | KPD_LOCKED));
        }

        ASSERT(stk != NULL);

        /*
         * The machine-dependent mutex code may require that
         * thread pointers (since they may be used for mutex owner
         * fields) have certain alignment requirements.
         * PTR24_ALIGN is the size of the alignment quanta.
         * XXX - assumes stack grows toward low addresses.
         */
        if (stksize <= sizeof (kthread_t) + PTR24_ALIGN)
            cmn_err(CE_PANIC, "thread_create: proposed stack size"
                " too small to hold thread.");
#ifdef STACK_GROWTH_DOWN
        stksize -= SA(sizeof (kthread_t) + PTR24_ALIGN - 1);
        stksize &= -PTR24_ALIGN;    /* make thread aligned */
        t = (kthread_t *)(stk + stksize);
        bzero(t, sizeof (kthread_t));
        if (audit_active)
            audit_thread_create(t);
        t->t_stk = stk + stksize;
        t->t_stkbase = stk;
#else   /* stack grows to larger addresses */
        stksize -= SA(sizeof (kthread_t));
        t = (kthread_t *)(stk);
        bzero(t, sizeof (kthread_t));
        t->t_stk = stk + sizeof (kthread_t);
        t->t_stkbase = stk + stksize + sizeof (kthread_t);
#endif  /* STACK_GROWTH_DOWN */
        t->t_flag |= T_TALLOCSTK;
        t->t_swap = stk;
    } else {
        t = kmem_cache_alloc(thread_cache, KM_SLEEP);
        bzero(t, sizeof (kthread_t));
        ASSERT(((uintptr_t)t & (PTR24_ALIGN - 1)) == 0);
        if (audit_active)
            audit_thread_create(t);
        /*
         * Initialize t_stk to the kernel stack pointer to use
         * upon entry to the kernel
         */
#ifdef STACK_GROWTH_DOWN
        t->t_stk = stk + stksize;
        t->t_stkbase = stk;
#else
        t->t_stk = stk;         /* 3b2-like */
        t->t_stkbase = stk + stksize;
#endif /* STACK_GROWTH_DOWN */
    }

    if (kmem_stackinfo != 0) {
        stkinfo_begin(t);
    }

    t->t_ts = ts;

    /*
     * p_cred could be NULL if it thread_create is called before cred_init
     * is called in main.
     */
    mutex_enter(&pp->p_crlock);
    if (pp->p_cred)
        crhold(t->t_cred = pp->p_cred);
    mutex_exit(&pp->p_crlock);
    t->t_start = gethrestime_sec();
    t->t_startpc = proc;
    t->t_procp = pp;
    t->t_clfuncs = &sys_classfuncs.thread;
    t->t_cid = syscid;
    t->t_pri = pri;
    t->t_stime = ddi_get_lbolt();
    t->t_schedflag = TS_LOAD | TS_DONT_SWAP;
    t->t_bind_cpu = PBIND_NONE;
    t->t_bindflag = (uchar_t)default_binding_mode;
    t->t_bind_pset = PS_NONE;
    t->t_plockp = &pp->p_lock;
    t->t_copyops = NULL;
    t->t_taskq = NULL;
    t->t_anttime = 0;
    t->t_hatdepth = 0;

    t->t_dtrace_vtime = 1;  /* assure vtimestamp is always non-zero */

    CPU_STATS_ADDQ(CPU, sys, nthreads, 1);
#ifndef NPROBE
    /* Kernel probe */
    tnf_thread_create(t);
#endif /* NPROBE */
    LOCK_INIT_CLEAR(&t->t_lock);

    /*
     * Callers who give us a NULL proc must do their own
     * stack initialization.  e.g. lwp_create()
     */
    if (proc != NULL) {
        t->t_stk = thread_stk_init(t->t_stk);
        thread_load(t, proc, arg, len);
    }

    /*
     * Put a hold on project0. If this thread is actually in a
     * different project, then t_proj will be changed later in
     * lwp_create().  All kernel-only threads must be in project 0.
     */
    t->t_proj = project_hold(proj0p);

    lgrp_affinity_init(&t->t_lgrp_affinity);

    mutex_enter(&pidlock);
    nthread++;
    t->t_did = next_t_id++;
    t->t_prev = curthread->t_prev;
    t->t_next = curthread;

    /*
     * Add the thread to the list of all threads, and initialize
     * its t_cpu pointer.  We need to block preemption since
     * cpu_offline walks the thread list looking for threads
     * with t_cpu pointing to the CPU being offlined.  We want
     * to make sure that the list is consistent and that if t_cpu
     * is set, the thread is on the list.
     */
    kpreempt_disable();
    curthread->t_prev->t_next = t;
    curthread->t_prev = t;

    /*
     * Threads should never have a NULL t_cpu pointer so assign it
     * here.  If the thread is being created with state TS_RUN a
     * better CPU may be chosen when it is placed on the run queue.
     *
     * We need to keep kernel preemption disabled when setting all
     * three fields to keep them in sync.  Also, always create in
     * the default partition since that's where kernel threads go
     * (if this isn't a kernel thread, t_cpupart will be changed
     * in lwp_create before setting the thread runnable).
     */
    t->t_cpupart = &cp_default;

    /*
     * For now, affiliate this thread with the root lgroup.
     * Since the kernel does not (presently) allocate its memory
     * in a locality aware fashion, the root is an appropriate home.
     * If this thread is later associated with an lwp, it will have
     * it's lgroup re-assigned at that time.
     */
    lgrp_move_thread(t, &cp_default.cp_lgrploads[LGRP_ROOTID], 1);

    /*
     * Inherit the current cpu.  If this cpu isn't part of the chosen
     * lgroup, a new cpu will be chosen by cpu_choose when the thread
     * is ready to run.
     */
    if (CPU->cpu_part == &cp_default)
        t->t_cpu = CPU;
    else
        t->t_cpu = disp_lowpri_cpu(cp_default.cp_cpulist, t->t_lpl,
            t->t_pri, NULL);

    t->t_disp_queue = t->t_cpu->cpu_disp;
    kpreempt_enable();

    /*
     * Initialize thread state and the dispatcher lock pointer.
     * Need to hold onto pidlock to block allthreads walkers until
     * the state is set.
     */
    switch (state) {
    case TS_RUN:
        curthread->t_oldspl = splhigh();    /* get dispatcher spl */
        THREAD_SET_STATE(t, TS_STOPPED, &transition_lock);
        CL_SETRUN(t);
        thread_unlock(t);
        break;

    case TS_ONPROC:
        THREAD_ONPROC(t, t->t_cpu);
        break;

    case TS_FREE:
        /*
         * Free state will be used for intr threads.
         * The interrupt routine must set the thread dispatcher
         * lock pointer (t_lockp) if starting on a CPU
         * other than the current one.
         */
        THREAD_FREEINTR(t, CPU);
        break;

    case TS_STOPPED:
        THREAD_SET_STATE(t, TS_STOPPED, &stop_lock);
        break;

    default:            /* TS_SLEEP, TS_ZOMB or TS_TRANS */
        cmn_err(CE_PANIC, "thread_create: invalid state %d", state);
    }
    mutex_exit(&pidlock);
    return (t);
}

/*
 * Move thread to project0 and take care of project reference counters.
 */
void
thread_rele(kthread_t *t)
{
    kproject_t *kpj;

    thread_lock(t);

    ASSERT(t == curthread || t->t_state == TS_FREE || t->t_procp == &p0);
    kpj = ttoproj(t);
    t->t_proj = proj0p;

    thread_unlock(t);

    if (kpj != proj0p) {
        project_rele(kpj);
        (void) project_hold(proj0p);
    }
}

void
thread_exit(void)
{
    kthread_t *t = curthread;

    if ((t->t_proc_flag & TP_ZTHREAD) != 0)
        cmn_err(CE_PANIC, "thread_exit: zthread_exit() not called");

    tsd_exit();     /* Clean up this thread's TSD */

    kcpc_passivate();   /* clean up performance counter state */

    /*
     * No kernel thread should have called poll() without arranging
     * calling pollcleanup() here.
     */
    ASSERT(t->t_pollstate == NULL);
    ASSERT(t->t_schedctl == NULL);
    if (t->t_door)
        door_slam();    /* in case thread did an upcall */

#ifndef NPROBE
    /* Kernel probe */
    if (t->t_tnf_tpdp)
        tnf_thread_exit();
#endif /* NPROBE */

    thread_rele(t);
    t->t_preempt++;

    /*
     * remove thread from the all threads list so that
     * death-row can use the same pointers.
     */
    mutex_enter(&pidlock);
    t->t_next->t_prev = t->t_prev;
    t->t_prev->t_next = t->t_next;
    ASSERT(allthreads != t);    /* t0 never exits */
    cv_broadcast(&t->t_joincv); /* wake up anyone in thread_join */
    mutex_exit(&pidlock);

    if (t->t_ctx != NULL)
        exitctx(t);
    if (t->t_procp->p_pctx != NULL)
        exitpctx(t->t_procp);

    if (kmem_stackinfo != 0) {
        stkinfo_end(t);
    }

    t->t_state = TS_ZOMB;   /* set zombie thread */

    swtch_from_zombie();    /* give up the CPU */
    /* NOTREACHED */
}

/*
 * Check to see if the specified thread is active (defined as being on
 * the thread list).  This is certainly a slow way to do this; if there's
 * ever a reason to speed it up, we could maintain a hash table of active
 * threads indexed by their t_did.
 */
static kthread_t *
did_to_thread(kt_did_t tid)
{
    kthread_t *t;

    ASSERT(MUTEX_HELD(&pidlock));
    for (t = curthread->t_next; t != curthread; t = t->t_next) {
        if (t->t_did == tid)
            break;
    }
    if (t->t_did == tid)
        return (t);
    else
        return (NULL);
}

/*
 * Wait for specified thread to exit.  Returns immediately if the thread
 * could not be found, meaning that it has either already exited or never
 * existed.
 */
void
thread_join(kt_did_t tid)
{
    kthread_t *t;

    ASSERT(tid != curthread->t_did);
    ASSERT(tid != t0.t_did);

    mutex_enter(&pidlock);
    /*
     * Make sure we check that the thread is on the thread list
     * before blocking on it; otherwise we could end up blocking on
     * a cv that's already been freed.  In other words, don't cache
     * the thread pointer across calls to cv_wait.
     *
     * The choice of loop invariant means that whenever a thread
     * is taken off the allthreads list, a cv_broadcast must be
     * performed on that thread's t_joincv to wake up any waiters.
     * The broadcast doesn't have to happen right away, but it
     * shouldn't be postponed indefinitely (e.g., by doing it in
     * thread_free which may only be executed when the deathrow
     * queue is processed.
     */
    while (t = did_to_thread(tid))
        cv_wait(&t->t_joincv, &pidlock);
    mutex_exit(&pidlock);
}

void
thread_free_prevent(kthread_t *t)
{
    kmutex_t *lp;

    lp = &thread_free_lock[THREAD_FREE_HASH(t)].tf_lock;
    mutex_enter(lp);
}

void
thread_free_allow(kthread_t *t)
{
    kmutex_t *lp;

    lp = &thread_free_lock[THREAD_FREE_HASH(t)].tf_lock;
    mutex_exit(lp);
}

static void
thread_free_barrier(kthread_t *t)
{
    kmutex_t *lp;

    lp = &thread_free_lock[THREAD_FREE_HASH(t)].tf_lock;
    mutex_enter(lp);
    mutex_exit(lp);
}

void
thread_free(kthread_t *t)
{
    boolean_t allocstk = (t->t_flag & T_TALLOCSTK);
    klwp_t *lwp = t->t_lwp;
    caddr_t swap = t->t_swap;

    ASSERT(t != &t0 && t->t_state == TS_FREE);
    ASSERT(t->t_door == NULL);
    ASSERT(t->t_schedctl == NULL);
    ASSERT(t->t_pollstate == NULL);

    t->t_pri = 0;
    t->t_pc = 0;
    t->t_sp = 0;
    t->t_wchan0 = NULL;
    t->t_wchan = NULL;
    if (t->t_cred != NULL) {
        crfree(t->t_cred);
        t->t_cred = 0;
    }
    if (t->t_pdmsg) {
        kmem_free(t->t_pdmsg, strlen(t->t_pdmsg) + 1);
        t->t_pdmsg = NULL;
    }
    if (audit_active)
        audit_thread_free(t);
#ifndef NPROBE
    if (t->t_tnf_tpdp)
        tnf_thread_free(t);
#endif /* NPROBE */
    if (t->t_cldata) {
        CL_EXITCLASS(t->t_cid, (caddr_t *)t->t_cldata);
    }
    if (t->t_rprof != NULL) {
        kmem_free(t->t_rprof, sizeof (*t->t_rprof));
        t->t_rprof = NULL;
    }
    t->t_lockp = NULL;  /* nothing should try to lock this thread now */
    if (lwp)
        lwp_freeregs(lwp, 0);
    if (t->t_ctx)
        freectx(t, 0);
    t->t_stk = NULL;
    if (lwp)
        lwp_stk_fini(lwp);
    lock_clear(&t->t_lock);

    if (t->t_ts->ts_waiters > 0)
        panic("thread_free: turnstile still active");

    kmem_cache_free(turnstile_cache, t->t_ts);

    free_afd(&t->t_activefd);

    /*
     * Barrier for the tick accounting code.  The tick accounting code
     * holds this lock to keep the thread from going away while it's
     * looking at it.
     */
    thread_free_barrier(t);

    ASSERT(ttoproj(t) == proj0p);
    project_rele(ttoproj(t));

    lgrp_affinity_free(&t->t_lgrp_affinity);

    mutex_enter(&pidlock);
    nthread--;
    mutex_exit(&pidlock);

    /*
     * Free thread, lwp and stack.  This needs to be done carefully, since
     * if T_TALLOCSTK is set, the thread is part of the stack.
     */
    t->t_lwp = NULL;
    t->t_swap = NULL;

    if (swap) {
        segkp_release(segkp, swap);
    }
    if (lwp) {
        kmem_cache_free(lwp_cache, lwp);
    }
    if (!allocstk) {
        kmem_cache_free(thread_cache, t);
    }
}

/*
 * Removes threads associated with the given zone from a deathrow queue.
 * tp is a pointer to the head of the deathrow queue, and countp is a
 * pointer to the current deathrow count.  Returns a linked list of
 * threads removed from the list.
 */
static kthread_t *
thread_zone_cleanup(kthread_t **tp, int *countp, zoneid_t zoneid)
{
    kthread_t *tmp, *list = NULL;
    cred_t *cr;

    ASSERT(MUTEX_HELD(&reaplock));
    while (*tp != NULL) {
        if ((cr = (*tp)->t_cred) != NULL && crgetzoneid(cr) == zoneid) {
            tmp = *tp;
            *tp = tmp->t_forw;
            tmp->t_forw = list;
            list = tmp;
            (*countp)--;
        } else {
            tp = &(*tp)->t_forw;
        }
    }
    return (list);
}

static void
thread_reap_list(kthread_t *t)
{
    kthread_t *next;

    while (t != NULL) {
        next = t->t_forw;
        thread_free(t);
        t = next;
    }
}

/* ARGSUSED */
static void
thread_zone_destroy(zoneid_t zoneid, void *unused)
{
    kthread_t *t, *l;

    mutex_enter(&reaplock);
    /*
     * Pull threads and lwps associated with zone off deathrow lists.
     */
    t = thread_zone_cleanup(&thread_deathrow, &thread_reapcnt, zoneid);
    l = thread_zone_cleanup(&lwp_deathrow, &lwp_reapcnt, zoneid);
    mutex_exit(&reaplock);

    /*
     * Guard against race condition in mutex_owner_running:
     *  thread=owner(mutex)
     *  <interrupt>
     *              thread exits mutex
     *              thread exits
     *              thread reaped
     *              thread struct freed
     * cpu = thread->t_cpu <- BAD POINTER DEREFERENCE.
     * A cross call to all cpus will cause the interrupt handler
     * to reset the PC if it is in mutex_owner_running, refreshing
     * stale thread pointers.
     */
    mutex_sync();   /* sync with mutex code */

    /*
     * Reap threads
     */
    thread_reap_list(t);

    /*
     * Reap lwps
     */
    thread_reap_list(l);
}

/*
 * cleanup zombie threads that are on deathrow.
 */
void
thread_reaper()
{
    kthread_t *t, *l;
    callb_cpr_t cprinfo;

    /*
     * Register callback to clean up threads when zone is destroyed.
     */
    zone_key_create(&zone_thread_key, NULL, NULL, thread_zone_destroy);

    CALLB_CPR_INIT(&cprinfo, &reaplock, callb_generic_cpr, "t_reaper");
    for (;;) {
        mutex_enter(&reaplock);
        while (thread_deathrow == NULL && lwp_deathrow == NULL) {
            CALLB_CPR_SAFE_BEGIN(&cprinfo);
            cv_wait(&reaper_cv, &reaplock);
            CALLB_CPR_SAFE_END(&cprinfo, &reaplock);
        }
        /*
         * mutex_sync() needs to be called when reaping, but
         * not too often.  We limit reaping rate to once
         * per second.  Reaplimit is max rate at which threads can
         * be freed. Does not impact thread destruction/creation.
         */
        t = thread_deathrow;
        l = lwp_deathrow;
        thread_deathrow = NULL;
        lwp_deathrow = NULL;
        thread_reapcnt = 0;
        lwp_reapcnt = 0;
        mutex_exit(&reaplock);

        /*
         * Guard against race condition in mutex_owner_running:
         *  thread=owner(mutex)
         *  <interrupt>
         *              thread exits mutex
         *              thread exits
         *              thread reaped
         *              thread struct freed
         * cpu = thread->t_cpu <- BAD POINTER DEREFERENCE.
         * A cross call to all cpus will cause the interrupt handler
         * to reset the PC if it is in mutex_owner_running, refreshing
         * stale thread pointers.
         */
        mutex_sync();   /* sync with mutex code */
        /*
         * Reap threads
         */
        thread_reap_list(t);

        /*
         * Reap lwps
         */
        thread_reap_list(l);
        delay(hz);
    }
}

/*
 * This is called by lwpcreate, etc.() to put a lwp_deathrow thread onto
 * thread_deathrow. The thread's state is changed already TS_FREE to indicate
 * that is reapable. The thread already holds the reaplock, and was already
 * freed.
 */
void
reapq_move_lq_to_tq(kthread_t *t)
{
    ASSERT(t->t_state == TS_FREE);
    ASSERT(MUTEX_HELD(&reaplock));
    t->t_forw = thread_deathrow;
    thread_deathrow = t;
    thread_reapcnt++;
    if (lwp_reapcnt + thread_reapcnt > reaplimit)
        cv_signal(&reaper_cv);  /* wake the reaper */
}

/*
 * This is called by resume() to put a zombie thread onto deathrow.
 * The thread's state is changed to TS_FREE to indicate that is reapable.
 * This is called from the idle thread so it must not block - just spin.
 */
void
reapq_add(kthread_t *t)
{
    mutex_enter(&reaplock);

    /*
     * lwp_deathrow contains threads with lwp linkage and
     * swappable thread stacks which have the default stacksize.
     * These threads' lwps and stacks may be reused by lwp_create().
     *
     * Anything else goes on thread_deathrow(), where it will eventually
     * be thread_free()d.
     */
    if (t->t_flag & T_LWPREUSE) {
        ASSERT(ttolwp(t) != NULL);
        t->t_forw = lwp_deathrow;
        lwp_deathrow = t;
        lwp_reapcnt++;
    } else {
        t->t_forw = thread_deathrow;
        thread_deathrow = t;
        thread_reapcnt++;
    }
    if (lwp_reapcnt + thread_reapcnt > reaplimit)
        cv_signal(&reaper_cv);  /* wake the reaper */
    t->t_state = TS_FREE;
    lock_clear(&t->t_lock);

    /*
     * Before we return, we need to grab and drop the thread lock for
     * the dead thread.  At this point, the current thread is the idle
     * thread, and the dead thread's CPU lock points to the current
     * CPU -- and we must grab and drop the lock to synchronize with
     * a racing thread walking a blocking chain that the zombie thread
     * was recently in.  By this point, that blocking chain is (by
     * definition) stale:  the dead thread is not holding any locks, and
     * is therefore not in any blocking chains -- but if we do not regrab
     * our lock before freeing the dead thread's data structures, the
     * thread walking the (stale) blocking chain will die on memory
     * corruption when it attempts to drop the dead thread's lock.  We
     * only need do this once because there is no way for the dead thread
     * to ever again be on a blocking chain:  once we have grabbed and
     * dropped the thread lock, we are guaranteed that anyone that could
     * have seen this thread in a blocking chain can no longer see it.
     */
    thread_lock(t);
    thread_unlock(t);

    mutex_exit(&reaplock);
}

/*
 * Install thread context ops for the current thread.
 */
void
installctx(
    kthread_t *t,
    void    *arg,
    void    (*save)(void *),
    void    (*restore)(void *),
    void    (*fork)(void *, void *),
    void    (*lwp_create)(void *, void *),
    void    (*exit)(void *),
    void    (*free)(void *, int))
{
    struct ctxop *ctx;

    ctx = kmem_alloc(sizeof (struct ctxop), KM_SLEEP);
    ctx->save_op = save;
    ctx->restore_op = restore;
    ctx->fork_op = fork;
    ctx->lwp_create_op = lwp_create;
    ctx->exit_op = exit;
    ctx->free_op = free;
    ctx->arg = arg;
    ctx->next = t->t_ctx;
    t->t_ctx = ctx;
}

/*
 * Remove the thread context ops from a thread.
 */
int
removectx(
    kthread_t *t,
    void    *arg,
    void    (*save)(void *),
    void    (*restore)(void *),
    void    (*fork)(void *, void *),
    void    (*lwp_create)(void *, void *),
    void    (*exit)(void *),
    void    (*free)(void *, int))
{
    struct ctxop *ctx, *prev_ctx;

    /*
     * The incoming kthread_t (which is the thread for which the
     * context ops will be removed) should be one of the following:
     *
     * a) the current thread,
     *
     * b) a thread of a process that's being forked (SIDL),
     *
     * c) a thread that belongs to the same process as the current
     *    thread and for which the current thread is the agent thread,
     *
     * d) a thread that is TS_STOPPED which is indicative of it
     *    being (if curthread is not an agent) a thread being created
     *    as part of an lwp creation.
     */
    ASSERT(t == curthread || ttoproc(t)->p_stat == SIDL ||
        ttoproc(t)->p_agenttp == curthread || t->t_state == TS_STOPPED);

    /*
     * Serialize modifications to t->t_ctx to prevent the agent thread
     * and the target thread from racing with each other during lwp exit.
     */
    mutex_enter(&t->t_ctx_lock);
    prev_ctx = NULL;
    kpreempt_disable();
    for (ctx = t->t_ctx; ctx != NULL; ctx = ctx->next) {
        if (ctx->save_op == save && ctx->restore_op == restore &&
            ctx->fork_op == fork && ctx->lwp_create_op == lwp_create &&
            ctx->exit_op == exit && ctx->free_op == free &&
            ctx->arg == arg) {
            if (prev_ctx)
                prev_ctx->next = ctx->next;
            else
                t->t_ctx = ctx->next;
            mutex_exit(&t->t_ctx_lock);
            if (ctx->free_op != NULL)
                (ctx->free_op)(ctx->arg, 0);
            kmem_free(ctx, sizeof (struct ctxop));
            kpreempt_enable();
            return (1);
        }
        prev_ctx = ctx;
    }
    mutex_exit(&t->t_ctx_lock);
    kpreempt_enable();

    return (0);
}

void
savectx(kthread_t *t)
{
    struct ctxop *ctx;

    ASSERT(t == curthread);
    for (ctx = t->t_ctx; ctx != 0; ctx = ctx->next)
        if (ctx->save_op != NULL)
            (ctx->save_op)(ctx->arg);
}

void
restorectx(kthread_t *t)
{
    struct ctxop *ctx;

    ASSERT(t == curthread);
    for (ctx = t->t_ctx; ctx != 0; ctx = ctx->next)
        if (ctx->restore_op != NULL)
            (ctx->restore_op)(ctx->arg);
}

void
forkctx(kthread_t *t, kthread_t *ct)
{
    struct ctxop *ctx;

    for (ctx = t->t_ctx; ctx != NULL; ctx = ctx->next)
        if (ctx->fork_op != NULL)
            (ctx->fork_op)(t, ct);
}

/*
 * Note that this operator is only invoked via the _lwp_create
 * system call.  The system may have other reasons to create lwps
 * e.g. the agent lwp or the doors unreferenced lwp.
 */
void
lwp_createctx(kthread_t *t, kthread_t *ct)
{
    struct ctxop *ctx;

    for (ctx = t->t_ctx; ctx != NULL; ctx = ctx->next)
        if (ctx->lwp_create_op != NULL)
            (ctx->lwp_create_op)(t, ct);
}

/*
 * exitctx is called from thread_exit() and lwp_exit() to perform any actions
 * needed when the thread/LWP leaves the processor for the last time. This
 * routine is not intended to deal with freeing memory; freectx() is used for
 * that purpose during thread_free(). This routine is provided to allow for
 * clean-up that can't wait until thread_free().
 */
void
exitctx(kthread_t *t)
{
    struct ctxop *ctx;

    for (ctx = t->t_ctx; ctx != NULL; ctx = ctx->next)
        if (ctx->exit_op != NULL)
            (ctx->exit_op)(t);
}

/*
 * freectx is called from thread_free() and exec() to get
 * rid of old thread context ops.
 */
void
freectx(kthread_t *t, int isexec)
{
    struct ctxop *ctx;

    kpreempt_disable();
    while ((ctx = t->t_ctx) != NULL) {
        t->t_ctx = ctx->next;
        if (ctx->free_op != NULL)
            (ctx->free_op)(ctx->arg, isexec);
        kmem_free(ctx, sizeof (struct ctxop));
    }
    kpreempt_enable();
}

/*
 * freectx_ctx is called from lwp_create() when lwp is reused from
 * lwp_deathrow and its thread structure is added to thread_deathrow.
 * The thread structure to which this ctx was attached may be already
 * freed by the thread reaper so free_op implementations shouldn't rely
 * on thread structure to which this ctx was attached still being around.
 */
void
freectx_ctx(struct ctxop *ctx)
{
    struct ctxop *nctx;

    ASSERT(ctx != NULL);

    kpreempt_disable();
    do {
        nctx = ctx->next;
        if (ctx->free_op != NULL)
            (ctx->free_op)(ctx->arg, 0);
        kmem_free(ctx, sizeof (struct ctxop));
    } while ((ctx = nctx) != NULL);
    kpreempt_enable();
}

/*
 * Set the thread running; arrange for it to be swapped in if necessary.
 */
void
setrun_locked(kthread_t *t)
{
    ASSERT(THREAD_LOCK_HELD(t));
    if (t->t_state == TS_SLEEP) {
        /*
         * Take off sleep queue.
         */
        SOBJ_UNSLEEP(t->t_sobj_ops, t);
    } else if (t->t_state & (TS_RUN | TS_ONPROC)) {
        /*
         * Already on dispatcher queue.
         */
        return;
    } else if (t->t_state == TS_WAIT) {
        waitq_setrun(t);
    } else if (t->t_state == TS_STOPPED) {
        /*
         * All of the sending of SIGCONT (TC_XSTART) and /proc
         * (TC_PSTART) and lwp_continue() (TC_CSTART) must have
         * requested that the thread be run.
         * Just calling setrun() is not sufficient to set a stopped
         * thread running.  TP_TXSTART is always set if the thread
         * is not stopped by a jobcontrol stop signal.
         * TP_TPSTART is always set if /proc is not controlling it.
         * TP_TCSTART is always set if lwp_suspend() didn't stop it.
         * The thread won't be stopped unless one of these
         * three mechanisms did it.
         *
         * These flags must be set before calling setrun_locked(t).
         * They can't be passed as arguments because the streams
         * code calls setrun() indirectly and the mechanism for
         * doing so admits only one argument.  Note that the
         * thread must be locked in order to change t_schedflags.
         */
        if ((t->t_schedflag & TS_ALLSTART) != TS_ALLSTART)
            return;
        /*
         * Process is no longer stopped (a thread is running).
         */
        t->t_whystop = 0;
        t->t_whatstop = 0;
        /*
         * Strictly speaking, we do not have to clear these
         * flags here; they are cleared on entry to stop().
         * However, they are confusing when doing kernel
         * debugging or when they are revealed by ps(1).
         */
        t->t_schedflag &= ~TS_ALLSTART;
        THREAD_TRANSITION(t);   /* drop stopped-thread lock */
        ASSERT(t->t_lockp == &transition_lock);
        ASSERT(t->t_wchan0 == NULL && t->t_wchan == NULL);
        /*
         * Let the class put the process on the dispatcher queue.
         */
        CL_SETRUN(t);
    }
}

void
setrun(kthread_t *t)
{
    thread_lock(t);
    setrun_locked(t);
    thread_unlock(t);
}

/*
 * Unpin an interrupted thread.
 *  When an interrupt occurs, the interrupt is handled on the stack
 *  of an interrupt thread, taken from a pool linked to the CPU structure.
 *
 *  When swtch() is switching away from an interrupt thread because it
 *  blocked or was preempted, this routine is called to complete the
 *  saving of the interrupted thread state, and returns the interrupted
 *  thread pointer so it may be resumed.
 *
 *  Called by swtch() only at high spl.
 */
kthread_t *
thread_unpin()
{
    kthread_t   *t = curthread; /* current thread */
    kthread_t   *itp;       /* interrupted thread */
    int     i;      /* interrupt level */
    extern int  intr_passivate();

    ASSERT(t->t_intr != NULL);

    itp = t->t_intr;        /* interrupted thread */
    t->t_intr = NULL;       /* clear interrupt ptr */

    /*
     * Get state from interrupt thread for the one
     * it interrupted.
     */

    i = intr_passivate(t, itp);

    TRACE_5(TR_FAC_INTR, TR_INTR_PASSIVATE,
        "intr_passivate:level %d curthread %p (%T) ithread %p (%T)",
        i, t, t, itp, itp);

    /*
     * Dissociate the current thread from the interrupted thread's LWP.
     */
    t->t_lwp = NULL;

    /*
     * Interrupt handlers above the level that spinlocks block must
     * not block.
     */
#if DEBUG
    if (i < 0 || i > LOCK_LEVEL)
        cmn_err(CE_PANIC, "thread_unpin: ipl out of range %x", i);
#endif

    /*
     * Compute the CPU's base interrupt level based on the active
     * interrupts.
     */
    ASSERT(CPU->cpu_intr_actv & (1 << i));
    set_base_spl();

    return (itp);
}

/*
 * Create and initialize an interrupt thread.
 *  Returns non-zero on error.
 *  Called at spl7() or better.
 */
void
thread_create_intr(struct cpu *cp)
{
    kthread_t *tp;

    tp = thread_create(NULL, 0,
        (void (*)())thread_create_intr, NULL, 0, &p0, TS_ONPROC, 0);

    /*
     * Set the thread in the TS_FREE state.  The state will change
     * to TS_ONPROC only while the interrupt is active.  Think of these
     * as being on a private free list for the CPU.  Being TS_FREE keeps
     * inactive interrupt threads out of debugger thread lists.
     *
     * We cannot call thread_create with TS_FREE because of the current
     * checks there for ONPROC.  Fix this when thread_create takes flags.
     */
    THREAD_FREEINTR(tp, cp);

    /*
     * Nobody should ever reference the credentials of an interrupt
     * thread so make it NULL to catch any such references.
     */
    tp->t_cred = NULL;
    tp->t_flag |= T_INTR_THREAD;
    tp->t_cpu = cp;
    tp->t_bound_cpu = cp;
    tp->t_disp_queue = cp->cpu_disp;
    tp->t_affinitycnt = 1;
    tp->t_preempt = 1;

    /*
     * Don't make a user-requested binding on this thread so that
     * the processor can be offlined.
     */
    tp->t_bind_cpu = PBIND_NONE;    /* no USER-requested binding */
    tp->t_bind_pset = PS_NONE;

#if defined(__i386) || defined(__amd64)
    tp->t_stk -= STACK_ALIGN;
    *(tp->t_stk) = 0;       /* terminate intr thread stack */
#endif

    /*
     * Link onto CPU's interrupt pool.
     */
    tp->t_link = cp->cpu_intr_thread;
    cp->cpu_intr_thread = tp;
}

/*
 * TSD -- THREAD SPECIFIC DATA
 */
static kmutex_t     tsd_mutex;   /* linked list spin lock */
static uint_t       tsd_nkeys;   /* size of destructor array */
/* per-key destructor funcs */
static void         (**tsd_destructor)(void *);
/* list of tsd_thread's */
static struct tsd_thread    *tsd_list;

/*
 * Default destructor
 *  Needed because NULL destructor means that the key is unused
 */
/* ARGSUSED */
void
tsd_defaultdestructor(void *value)
{}

/*
 * Create a key (index into per thread array)
 *  Locks out tsd_create, tsd_destroy, and tsd_exit
 *  May allocate memory with lock held
 */
void
tsd_create(uint_t *keyp, void (*destructor)(void *))
{
    int i;
    uint_t  nkeys;

    /*
     * if key is allocated, do nothing
     */
    mutex_enter(&tsd_mutex);
    if (*keyp) {
        mutex_exit(&tsd_mutex);
        return;
    }
    /*
     * find an unused key
     */
    if (destructor == NULL)
        destructor = tsd_defaultdestructor;

    for (i = 0; i < tsd_nkeys; ++i)
        if (tsd_destructor[i] == NULL)
            break;

    /*
     * if no unused keys, increase the size of the destructor array
     */
    if (i == tsd_nkeys) {
        if ((nkeys = (tsd_nkeys << 1)) == 0)
            nkeys = 1;
        tsd_destructor =
            (void (**)(void *))tsd_realloc((void *)tsd_destructor,
            (size_t)(tsd_nkeys * sizeof (void (*)(void *))),
            (size_t)(nkeys * sizeof (void (*)(void *))));
        tsd_nkeys = nkeys;
    }

    /*
     * allocate the next available unused key
     */
    tsd_destructor[i] = destructor;
    *keyp = i + 1;
    mutex_exit(&tsd_mutex);
}

/*
 * Destroy a key -- this is for unloadable modules
 *
 * Assumes that the caller is preventing tsd_set and tsd_get
 * Locks out tsd_create, tsd_destroy, and tsd_exit
 * May free memory with lock held
 */
void
tsd_destroy(uint_t *keyp)
{
    uint_t key;
    struct tsd_thread *tsd;

    /*
     * protect the key namespace and our destructor lists
     */
    mutex_enter(&tsd_mutex);
    key = *keyp;
    *keyp = 0;

    ASSERT(key <= tsd_nkeys);

    /*
     * if the key is valid
     */
    if (key != 0) {
        uint_t k = key - 1;
        /*
         * for every thread with TSD, call key's destructor
         */
        for (tsd = tsd_list; tsd; tsd = tsd->ts_next) {
            /*
             * no TSD for key in this thread
             */
            if (key > tsd->ts_nkeys)
                continue;
            /*
             * call destructor for key
             */
            if (tsd->ts_value[k] && tsd_destructor[k])
                (*tsd_destructor[k])(tsd->ts_value[k]);
            /*
             * reset value for key
             */
            tsd->ts_value[k] = NULL;
        }
        /*
         * actually free the key (NULL destructor == unused)
         */
        tsd_destructor[k] = NULL;
    }

    mutex_exit(&tsd_mutex);
}

/*
 * Quickly return the per thread value that was stored with the specified key
 * Assumes the caller is protecting key from tsd_create and tsd_destroy
 */
void *
tsd_get(uint_t key)
{
    return (tsd_agent_get(curthread, key));
}

/*
 * Set a per thread value indexed with the specified key
 */
int
tsd_set(uint_t key, void *value)
{
    return (tsd_agent_set(curthread, key, value));
}

/*
 * Like tsd_get(), except that the agent lwp can get the tsd of
 * another thread in the same process (the agent thread only runs when the
 * process is completely stopped by /proc), or syslwp is creating a new lwp.
 */
void *
tsd_agent_get(kthread_t *t, uint_t key)
{
    struct tsd_thread *tsd = t->t_tsd;

    ASSERT(t == curthread ||
        ttoproc(t)->p_agenttp == curthread || t->t_state == TS_STOPPED);

    if (key && tsd != NULL && key <= tsd->ts_nkeys)
        return (tsd->ts_value[key - 1]);
    return (NULL);
}

/*
 * Like tsd_set(), except that the agent lwp can set the tsd of
 * another thread in the same process, or syslwp can set the tsd
 * of a thread it's in the middle of creating.
 *
 * Assumes the caller is protecting key from tsd_create and tsd_destroy
 * May lock out tsd_destroy (and tsd_create), may allocate memory with
 * lock held
 */
int
tsd_agent_set(kthread_t *t, uint_t key, void *value)
{
    struct tsd_thread *tsd = t->t_tsd;

    ASSERT(t == curthread ||
        ttoproc(t)->p_agenttp == curthread || t->t_state == TS_STOPPED);

    if (key == 0)
        return (EINVAL);
    if (tsd == NULL)
        tsd = t->t_tsd = kmem_zalloc(sizeof (*tsd), KM_SLEEP);
    if (key <= tsd->ts_nkeys) {
        tsd->ts_value[key - 1] = value;
        return (0);
    }

    ASSERT(key <= tsd_nkeys);

    /*
     * lock out tsd_destroy()
     */
    mutex_enter(&tsd_mutex);
    if (tsd->ts_nkeys == 0) {
        /*
         * Link onto list of threads with TSD
         */
        if ((tsd->ts_next = tsd_list) != NULL)
            tsd_list->ts_prev = tsd;
        tsd_list = tsd;
    }

    /*
     * Allocate thread local storage and set the value for key
     */
    tsd->ts_value = tsd_realloc(tsd->ts_value,
        tsd->ts_nkeys * sizeof (void *),
        key * sizeof (void *));
    tsd->ts_nkeys = key;
    tsd->ts_value[key - 1] = value;
    mutex_exit(&tsd_mutex);

    return (0);
}


/*
 * Return the per thread value that was stored with the specified key
 *  If necessary, create the key and the value
 *  Assumes the caller is protecting *keyp from tsd_destroy
 */
void *
tsd_getcreate(uint_t *keyp, void (*destroy)(void *), void *(*allocate)(void))
{
    void *value;
    uint_t key = *keyp;
    struct tsd_thread *tsd = curthread->t_tsd;

    if (tsd == NULL)
        tsd = curthread->t_tsd = kmem_zalloc(sizeof (*tsd), KM_SLEEP);
    if (key && key <= tsd->ts_nkeys && (value = tsd->ts_value[key - 1]))
        return (value);
    if (key == 0)
        tsd_create(keyp, destroy);
    (void) tsd_set(*keyp, value = (*allocate)());

    return (value);
}

/*
 * Called from thread_exit() to run the destructor function for each tsd
 *  Locks out tsd_create and tsd_destroy
 *  Assumes that the destructor *DOES NOT* use tsd
 */
void
tsd_exit(void)
{
    int i;
    struct tsd_thread *tsd = curthread->t_tsd;

    if (tsd == NULL)
        return;

    if (tsd->ts_nkeys == 0) {
        kmem_free(tsd, sizeof (*tsd));
        curthread->t_tsd = NULL;
        return;
    }

    /*
     * lock out tsd_create and tsd_destroy, call
     * the destructor, and mark the value as destroyed.
     */
    mutex_enter(&tsd_mutex);

    for (i = 0; i < tsd->ts_nkeys; i++) {
        if (tsd->ts_value[i] && tsd_destructor[i])
            (*tsd_destructor[i])(tsd->ts_value[i]);
        tsd->ts_value[i] = NULL;
    }

    /*
     * remove from linked list of threads with TSD
     */
    if (tsd->ts_next)
        tsd->ts_next->ts_prev = tsd->ts_prev;
    if (tsd->ts_prev)
        tsd->ts_prev->ts_next = tsd->ts_next;
    if (tsd_list == tsd)
        tsd_list = tsd->ts_next;

    mutex_exit(&tsd_mutex);

    /*
     * free up the TSD
     */
    kmem_free(tsd->ts_value, tsd->ts_nkeys * sizeof (void *));
    kmem_free(tsd, sizeof (struct tsd_thread));
    curthread->t_tsd = NULL;
}

/*
 * realloc
 */
static void *
tsd_realloc(void *old, size_t osize, size_t nsize)
{
    void *new;

    new = kmem_zalloc(nsize, KM_SLEEP);
    if (old) {
        bcopy(old, new, osize);
        kmem_free(old, osize);
    }
    return (new);
}

/*
 * Return non-zero if an interrupt is being serviced.
 */
int
servicing_interrupt()
{
    int onintr = 0;

    /* Are we an interrupt thread */
    if (curthread->t_flag & T_INTR_THREAD)
        return (1);
    /* Are we servicing a high level interrupt? */
    if (CPU_ON_INTR(CPU)) {
        kpreempt_disable();
        onintr = CPU_ON_INTR(CPU);
        kpreempt_enable();
    }
    return (onintr);
}


/*
 * Change the dispatch priority of a thread in the system.
 * Used when raising or lowering a thread's priority.
 * (E.g., priority inheritance)
 *
 * Since threads are queued according to their priority, we
 * we must check the thread's state to determine whether it
 * is on a queue somewhere. If it is, we've got to:
 *
 *  o Dequeue the thread.
 *  o Change its effective priority.
 *  o Enqueue the thread.
 *
 * Assumptions: The thread whose priority we wish to change
 * must be locked before we call thread_change_(e)pri().
 * The thread_change(e)pri() function doesn't drop the thread
 * lock--that must be done by its caller.
 */
void
thread_change_epri(kthread_t *t, pri_t disp_pri)
{
    uint_t  state;

    ASSERT(THREAD_LOCK_HELD(t));

    /*
     * If the inherited priority hasn't actually changed,
     * just return.
     */
    if (t->t_epri == disp_pri)
        return;

    state = t->t_state;

    /*
     * If it's not on a queue, change the priority with impunity.
     */
    if ((state & (TS_SLEEP | TS_RUN | TS_WAIT)) == 0) {
        t->t_epri = disp_pri;
        if (state == TS_ONPROC) {
            cpu_t *cp = t->t_disp_queue->disp_cpu;

            if (t == cp->cpu_dispthread)
                cp->cpu_dispatch_pri = DISP_PRIO(t);
        }
    } else if (state == TS_SLEEP) {
        /*
         * Take the thread out of its sleep queue.
         * Change the inherited priority.
         * Re-enqueue the thread.
         * Each synchronization object exports a function
         * to do this in an appropriate manner.
         */
        SOBJ_CHANGE_EPRI(t->t_sobj_ops, t, disp_pri);
    } else if (state == TS_WAIT) {
        /*
         * Re-enqueue a thread on the wait queue if its
         * effective priority needs to change.
         */
        if (disp_pri != t->t_epri)
            waitq_change_pri(t, disp_pri);
    } else {
        /*
         * The thread is on a run queue.
         * Note: setbackdq() may not put the thread
         * back on the same run queue where it originally
         * resided.
         */
        (void) dispdeq(t);
        t->t_epri = disp_pri;
        setbackdq(t);
    }
    schedctl_set_cidpri(t);
}

/*
 * Function: Change the t_pri field of a thread.
 * Side Effects: Adjust the thread ordering on a run queue
 *       or sleep queue, if necessary.
 * Returns: 1 if the thread was on a run queue, else 0.
 */
int
thread_change_pri(kthread_t *t, pri_t disp_pri, int front)
{
    uint_t  state;
    int on_rq = 0;

    ASSERT(THREAD_LOCK_HELD(t));

    state = t->t_state;
    THREAD_WILLCHANGE_PRI(t, disp_pri);

    /*
     * If it's not on a queue, change the priority with impunity.
     */
    if ((state & (TS_SLEEP | TS_RUN | TS_WAIT)) == 0) {
        t->t_pri = disp_pri;

        if (state == TS_ONPROC) {
            cpu_t *cp = t->t_disp_queue->disp_cpu;

            if (t == cp->cpu_dispthread)
                cp->cpu_dispatch_pri = DISP_PRIO(t);
        }
    } else if (state == TS_SLEEP) {
        /*
         * If the priority has changed, take the thread out of
         * its sleep queue and change the priority.
         * Re-enqueue the thread.
         * Each synchronization object exports a function
         * to do this in an appropriate manner.
         */
        if (disp_pri != t->t_pri)
            SOBJ_CHANGE_PRI(t->t_sobj_ops, t, disp_pri);
    } else if (state == TS_WAIT) {
        /*
         * Re-enqueue a thread on the wait queue if its
         * priority needs to change.
         */
        if (disp_pri != t->t_pri)
            waitq_change_pri(t, disp_pri);
    } else {
        /*
         * The thread is on a run queue.
         * Note: setbackdq() may not put the thread
         * back on the same run queue where it originally
         * resided.
         *
         * We still requeue the thread even if the priority
         * is unchanged to preserve round-robin (and other)
         * effects between threads of the same priority.
         */
        on_rq = dispdeq(t);
        ASSERT(on_rq);
        t->t_pri = disp_pri;
        if (front) {
            setfrontdq(t);
        } else {
            setbackdq(t);
        }
    }
    schedctl_set_cidpri(t);
    return (on_rq);
}

/*
 * Tunable kmem_stackinfo is set, fill the kernel thread stack with a
 * specific pattern.
 */
static void
stkinfo_begin(kthread_t *t)
{
    caddr_t start;  /* stack start */
    caddr_t end;    /* stack end  */
    uint64_t *ptr;  /* pattern pointer */

    /*
     * Stack grows up or down, see thread_create(),
     * compute stack memory area start and end (start < end).
     */
    if (t->t_stk > t->t_stkbase) {
        /* stack grows down */
        start = t->t_stkbase;
        end = t->t_stk;
    } else {
        /* stack grows up */
        start = t->t_stk;
        end = t->t_stkbase;
    }

    /*
     * Stackinfo pattern size is 8 bytes. Ensure proper 8 bytes
     * alignement for start and end in stack area boundaries
     * (protection against corrupt t_stkbase/t_stk data).
     */
    if ((((uintptr_t)start) & 0x7) != 0) {
        start = (caddr_t)((((uintptr_t)start) & (~0x7)) + 8);
    }
    end = (caddr_t)(((uintptr_t)end) & (~0x7));

    if ((end <= start) || (end - start) > (1024 * 1024)) {
        /* negative or stack size > 1 meg, assume bogus */
        return;
    }

    /* fill stack area with a pattern (instead of zeros) */
    ptr = (uint64_t *)((void *)start);
    while (ptr < (uint64_t *)((void *)end)) {
        *ptr++ = KMEM_STKINFO_PATTERN;
    }
}


/*
 * Tunable kmem_stackinfo is set, create stackinfo log if doesn't already exist,
 * compute the percentage of kernel stack really used, and set in the log
 * if it's the latest highest percentage.
 */
static void
stkinfo_end(kthread_t *t)
{
    caddr_t start;  /* stack start */
    caddr_t end;    /* stack end  */
    uint64_t *ptr;  /* pattern pointer */
    size_t stksz;   /* stack size */
    size_t smallest = 0;
    size_t percent = 0;
    uint_t index = 0;
    uint_t i;
    static size_t smallest_percent = (size_t)-1;
    static uint_t full = 0;

    /* create the stackinfo log, if doesn't already exist */
    mutex_enter(&kmem_stkinfo_lock);
    if (kmem_stkinfo_log == NULL) {
        kmem_stkinfo_log = (kmem_stkinfo_t *)
            kmem_zalloc(KMEM_STKINFO_LOG_SIZE *
            (sizeof (kmem_stkinfo_t)), KM_NOSLEEP);
        if (kmem_stkinfo_log == NULL) {
            mutex_exit(&kmem_stkinfo_lock);
            return;
        }
    }
    mutex_exit(&kmem_stkinfo_lock);

    /*
     * Stack grows up or down, see thread_create(),
     * compute stack memory area start and end (start < end).
     */
    if (t->t_stk > t->t_stkbase) {
        /* stack grows down */
        start = t->t_stkbase;
        end = t->t_stk;
    } else {
        /* stack grows up */
        start = t->t_stk;
        end = t->t_stkbase;
    }

    /* stack size as found in kthread_t */
    stksz = end - start;

    /*
     * Stackinfo pattern size is 8 bytes. Ensure proper 8 bytes
     * alignement for start and end in stack area boundaries
     * (protection against corrupt t_stkbase/t_stk data).
     */
    if ((((uintptr_t)start) & 0x7) != 0) {
        start = (caddr_t)((((uintptr_t)start) & (~0x7)) + 8);
    }
    end = (caddr_t)(((uintptr_t)end) & (~0x7));

    if ((end <= start) || (end - start) > (1024 * 1024)) {
        /* negative or stack size > 1 meg, assume bogus */
        return;
    }

    /* search until no pattern in the stack */
    if (t->t_stk > t->t_stkbase) {
        /* stack grows down */
#if defined(__i386) || defined(__amd64)
        /*
         * 6 longs are pushed on stack, see thread_load(). Skip
         * them, so if kthread has never run, percent is zero.
         * 8 bytes alignement is preserved for a 32 bit kernel,
         * 6 x 4 = 24, 24 is a multiple of 8.
         *
         */
        end -= (6 * sizeof (long));
#endif
        ptr = (uint64_t *)((void *)start);
        while (ptr < (uint64_t *)((void *)end)) {
            if (*ptr != KMEM_STKINFO_PATTERN) {
                percent = stkinfo_percent(end,
                    start, (caddr_t)ptr);
                break;
            }
            ptr++;
        }
    } else {
        /* stack grows up */
        ptr = (uint64_t *)((void *)end);
        ptr--;
        while (ptr >= (uint64_t *)((void *)start)) {
            if (*ptr != KMEM_STKINFO_PATTERN) {
                percent = stkinfo_percent(start,
                    end, (caddr_t)ptr);
                break;
            }
            ptr--;
        }
    }

    DTRACE_PROBE3(stack__usage, kthread_t *, t,
        size_t, stksz, size_t, percent);

    if (percent == 0) {
        return;
    }

    mutex_enter(&kmem_stkinfo_lock);
    if (full == KMEM_STKINFO_LOG_SIZE && percent < smallest_percent) {
        /*
         * The log is full and already contains the highest values
         */
        mutex_exit(&kmem_stkinfo_lock);
        return;
    }

    /* keep a log of the highest used stack */
    for (i = 0; i < KMEM_STKINFO_LOG_SIZE; i++) {
        if (kmem_stkinfo_log[i].percent == 0) {
            index = i;
            full++;
            break;
        }
        if (smallest == 0) {
            smallest = kmem_stkinfo_log[i].percent;
            index = i;
            continue;
        }
        if (kmem_stkinfo_log[i].percent < smallest) {
            smallest = kmem_stkinfo_log[i].percent;
            index = i;
        }
    }

    if (percent >= kmem_stkinfo_log[index].percent) {
        kmem_stkinfo_log[index].kthread = (caddr_t)t;
        kmem_stkinfo_log[index].t_startpc = (caddr_t)t->t_startpc;
        kmem_stkinfo_log[index].start = start;
        kmem_stkinfo_log[index].stksz = stksz;
        kmem_stkinfo_log[index].percent = percent;
        kmem_stkinfo_log[index].t_tid = t->t_tid;
        kmem_stkinfo_log[index].cmd[0] = '\0';
        if (t->t_tid != 0) {
            stksz = strlen((t->t_procp)->p_user.u_comm);
            if (stksz >= KMEM_STKINFO_STR_SIZE) {
                stksz = KMEM_STKINFO_STR_SIZE - 1;
                kmem_stkinfo_log[index].cmd[stksz] = '\0';
            } else {
                stksz += 1;
            }
            (void) memcpy(kmem_stkinfo_log[index].cmd,
                (t->t_procp)->p_user.u_comm, stksz);
        }
        if (percent < smallest_percent) {
            smallest_percent = percent;
        }
    }
    mutex_exit(&kmem_stkinfo_lock);
}

/*
 * Tunable kmem_stackinfo is set, compute stack utilization percentage.
 */
static size_t
stkinfo_percent(caddr_t t_stk, caddr_t t_stkbase, caddr_t sp)
{
    size_t percent;
    size_t s;

    if (t_stk > t_stkbase) {
        /* stack grows down */
        if (sp > t_stk) {
            return (0);
        }
        if (sp < t_stkbase) {
            return (100);
        }
        percent = t_stk - sp + 1;
        s = t_stk - t_stkbase + 1;
    } else {
        /* stack grows up */
        if (sp < t_stk) {
            return (0);
        }
        if (sp > t_stkbase) {
            return (100);
        }
        percent = sp - t_stk + 1;
        s = t_stkbase - t_stk + 1;
    }
    percent = ((100 * percent) / s) + 1;
    if (percent > 100) {
        percent = 100;
    }
    return (percent);
}