loader: remove devdesc comments and assertions

[unleashed.git] / kernel / 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/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);

        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();
        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_schedflag = 0;
        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);
                ddi_sleep(1);
        }
}

/*
 * 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);
}