/*
 * 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) 1992, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2016 by Delphix. All rights reserved.
 */

#include <sys/callo.h>
#include <sys/param.h>
#include <sys/types.h>
#include <sys/cpuvar.h>
#include <sys/thread.h>
#include <sys/kmem.h>
#include <sys/kmem_impl.h>
#include <sys/cmn_err.h>
#include <sys/callb.h>
#include <sys/debug.h>
#include <sys/vtrace.h>
#include <sys/sysmacros.h>
#include <sys/sdt.h>

int callout_init_done;                          /* useful during boot */

/*
 * Callout tables.  See timeout(9F) for details.
 */
static int callout_threads;                     /* callout normal threads */
static hrtime_t callout_debug_hrtime;           /* debugger entry time */
static int callout_chunk;                       /* callout heap chunk size */
static int callout_min_reap;                    /* callout minimum reap count */
static int callout_tolerance;                   /* callout hires tolerance */
static callout_table_t *callout_boot_ct;        /* Boot CPU's callout tables */
static clock_t callout_max_ticks;               /* max interval */
static hrtime_t callout_longterm;               /* longterm nanoseconds */
static ulong_t callout_counter_low;             /* callout ID increment */
static ulong_t callout_table_bits;              /* number of table bits in ID */
static ulong_t callout_table_mask;              /* mask for the table bits */
static callout_cache_t *callout_caches;         /* linked list of caches */
#pragma align 64(callout_table)
static callout_table_t *callout_table;          /* global callout table array */

/*
 * We run 'realtime' callouts at PIL 1 (CY_LOW_LEVEL). For 'normal'
 * callouts, from PIL 10 (CY_LOCK_LEVEL) we dispatch the callout,
 * via taskq, to a thread that executes at PIL 0 - so we end up running
 * 'normal' callouts at PIL 0.
 */
static volatile int callout_realtime_level = CY_LOW_LEVEL;
static volatile int callout_normal_level = CY_LOCK_LEVEL;

static char *callout_kstat_names[] = {
        "callout_timeouts",
        "callout_timeouts_pending",
        "callout_untimeouts_unexpired",
        "callout_untimeouts_executing",
        "callout_untimeouts_expired",
        "callout_expirations",
        "callout_allocations",
        "callout_cleanups",
};

static hrtime_t callout_heap_process(callout_table_t *, hrtime_t, int);

#define CALLOUT_HASH_INSERT(hash, cp, cnext, cprev)     \
{                                                       \
        callout_hash_t *hashp = &(hash);                \
                                                        \
        cp->cprev = NULL;                               \
        cp->cnext = hashp->ch_head;                     \
        if (hashp->ch_head == NULL)                     \
                hashp->ch_tail = cp;                    \
        else                                            \
                cp->cnext->cprev = cp;                  \
        hashp->ch_head = cp;                            \
}

#define CALLOUT_HASH_APPEND(hash, cp, cnext, cprev)     \
{                                                       \
        callout_hash_t *hashp = &(hash);                \
                                                        \
        cp->cnext = NULL;                               \
        cp->cprev = hashp->ch_tail;                     \
        if (hashp->ch_tail == NULL)                     \
                hashp->ch_head = cp;                    \
        else                                            \
                cp->cprev->cnext = cp;                  \
        hashp->ch_tail = cp;                            \
}

#define CALLOUT_HASH_DELETE(hash, cp, cnext, cprev)     \
{                                                       \
        callout_hash_t *hashp = &(hash);                \
                                                        \
        if (cp->cnext == NULL)                          \
                hashp->ch_tail = cp->cprev;             \
        else                                            \
                cp->cnext->cprev = cp->cprev;           \
        if (cp->cprev == NULL)                          \
                hashp->ch_head = cp->cnext;             \
        else                                            \
                cp->cprev->cnext = cp->cnext;           \
}

/*
 * These definitions help us queue callouts and callout lists. Here is
 * the queueing rationale:
 *
 *      - callouts are queued in a FIFO manner in the ID hash table.
 *        TCP timers are typically cancelled in the same order that they
 *        were issued. The FIFO queueing shortens the search for a callout
 *        during untimeout().
 *
 *      - callouts are queued in a FIFO manner in their callout lists.
 *        This ensures that the callouts are executed in the same order that
 *        they were queued. This is fair. Plus, it helps to make each
 *        callout expiration timely. It also favors cancellations.
 *
 *      - callout lists are queued in the following manner in the callout
 *        hash table buckets:
 *
 *              - appended, if the callout list is a 1-nanosecond resolution
 *                callout list. When a callout is created, we first look for
 *                a callout list that has the same expiration so we can avoid
 *                allocating a callout list and inserting the expiration into
 *                the heap. However, we do not want to look at 1-nanosecond
 *                resolution callout lists as we will seldom find a match in
 *                them. Keeping these callout lists in the rear of the hash
 *                buckets allows us to skip these during the lookup.
 *
 *              - inserted at the beginning, if the callout list is not a
 *                1-nanosecond resolution callout list. This also has the
 *                side-effect of keeping the long term timers away from the
 *                front of the buckets.
 *
 *      - callout lists are queued in a FIFO manner in the expired callouts
 *        list. This ensures that callout lists are executed in the order
 *        of expiration.
 */
#define CALLOUT_APPEND(ct, cp)                                          \
        CALLOUT_HASH_APPEND(ct->ct_idhash[CALLOUT_IDHASH(cp->c_xid)],   \
                cp, c_idnext, c_idprev);                                \
        CALLOUT_HASH_APPEND(cp->c_list->cl_callouts, cp, c_clnext, c_clprev)

#define CALLOUT_DELETE(ct, cp)                                          \
        CALLOUT_HASH_DELETE(ct->ct_idhash[CALLOUT_IDHASH(cp->c_xid)],   \
                cp, c_idnext, c_idprev);                                \
        CALLOUT_HASH_DELETE(cp->c_list->cl_callouts, cp, c_clnext, c_clprev)

#define CALLOUT_LIST_INSERT(hash, cl)                           \
        CALLOUT_HASH_INSERT(hash, cl, cl_next, cl_prev)

#define CALLOUT_LIST_APPEND(hash, cl)                           \
        CALLOUT_HASH_APPEND(hash, cl, cl_next, cl_prev)

#define CALLOUT_LIST_DELETE(hash, cl)                           \
        CALLOUT_HASH_DELETE(hash, cl, cl_next, cl_prev)

#define CALLOUT_LIST_BEFORE(cl, nextcl)                 \
{                                                       \
        (cl)->cl_prev = (nextcl)->cl_prev;              \
        (cl)->cl_next = (nextcl);                       \
        (nextcl)->cl_prev = (cl);                       \
        if (cl->cl_prev != NULL)                        \
                cl->cl_prev->cl_next = cl;              \
}

/*
 * For normal callouts, there is a deadlock scenario if two callouts that
 * have an inter-dependency end up on the same callout list. To break the
 * deadlock, you need two taskq threads running in parallel. We compute
 * the number of taskq threads here using a bunch of conditions to make
 * it optimal for the common case. This is an ugly hack, but one that is
 * necessary (sigh).
 */
#define CALLOUT_THRESHOLD       100000000
#define CALLOUT_EXEC_COMPUTE(ct, nextexp, exec)                         \
{                                                                       \
        callout_list_t *cl;                                             \
                                                                        \
        cl = ct->ct_expired.ch_head;                                    \
        if (cl == NULL) {                                               \
                /*                                                      \
                 * If the expired list is NULL, there is nothing to     \
                 * process.                                             \
                 */                                                     \
                exec = 0;                                               \
        } else if ((cl->cl_next == NULL) &&                             \
            (cl->cl_callouts.ch_head == cl->cl_callouts.ch_tail)) {     \
                /*                                                      \
                 * If there is only one callout list and it contains    \
                 * only one callout, there is no need for two threads.  \
                 */                                                     \
                exec = 1;                                               \
        } else if ((nextexp) > (gethrtime() + CALLOUT_THRESHOLD)) {     \
                /*                                                      \
                 * If the next expiration of the cyclic is way out into \
                 * the future, we need two threads.                     \
                 */                                                     \
                exec = 2;                                               \
        } else {                                                        \
                /*                                                      \
                 * We have multiple callouts to process. But the cyclic \
                 * will fire in the near future. So, we only need one   \
                 * thread for now.                                      \
                 */                                                     \
                exec = 1;                                               \
        }                                                               \
}

/*
 * Macro to swap two heap items.
 */
#define CALLOUT_SWAP(h1, h2)            \
{                                       \
        callout_heap_t tmp;             \
                                        \
        tmp = *h1;                      \
        *h1 = *h2;                      \
        *h2 = tmp;                      \
}

/*
 * Macro to free a callout list.
 */
#define CALLOUT_LIST_FREE(ct, cl)                       \
{                                                       \
        cl->cl_next = ct->ct_lfree;                     \
        ct->ct_lfree = cl;                              \
        cl->cl_flags |= CALLOUT_LIST_FLAG_FREE;         \
}

/*
 * Macro to free a callout.
 */
#define CALLOUT_FREE(ct, cl)                    \
{                                               \
        cp->c_idnext = ct->ct_free;             \
        ct->ct_free = cp;                       \
        cp->c_xid |= CALLOUT_ID_FREE;           \
}

/*
 * Allocate a callout structure.  We try quite hard because we
 * can't sleep, and if we can't do the allocation, we're toast.
 * Failing all, we try a KM_PANIC allocation. Note that we never
 * deallocate a callout. See untimeout() for the reasoning.
 */
static callout_t *
callout_alloc(callout_table_t *ct)
{
        size_t size;
        callout_t *cp;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));
        mutex_exit(&ct->ct_mutex);

        cp = kmem_cache_alloc(ct->ct_cache, KM_NOSLEEP);
        if (cp == NULL) {
                size = sizeof (callout_t);
                cp = kmem_alloc_tryhard(size, &size, KM_NOSLEEP | KM_PANIC);
        }
        cp->c_xid = 0;
        cp->c_executor = NULL;
        cv_init(&cp->c_done, NULL, CV_DEFAULT, NULL);
        cp->c_waiting = 0;

        mutex_enter(&ct->ct_mutex);
        ct->ct_allocations++;
        return (cp);
}

/*
 * Allocate a callout list structure.  We try quite hard because we
 * can't sleep, and if we can't do the allocation, we're toast.
 * Failing all, we try a KM_PANIC allocation. Note that we never
 * deallocate a callout list.
 */
static void
callout_list_alloc(callout_table_t *ct)
{
        size_t size;
        callout_list_t *cl;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));
        mutex_exit(&ct->ct_mutex);

        cl = kmem_cache_alloc(ct->ct_lcache, KM_NOSLEEP);
        if (cl == NULL) {
                size = sizeof (callout_list_t);
                cl = kmem_alloc_tryhard(size, &size, KM_NOSLEEP | KM_PANIC);
        }
        bzero(cl, sizeof (callout_list_t));

        mutex_enter(&ct->ct_mutex);
        CALLOUT_LIST_FREE(ct, cl);
}

/*
 * Find a callout list that corresponds to an expiration and matching flags.
 */
static callout_list_t *
callout_list_get(callout_table_t *ct, hrtime_t expiration, int flags, int hash)
{
        callout_list_t *cl;
        int clflags;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));

        if (flags & CALLOUT_LIST_FLAG_NANO) {
                /*
                 * This is a 1-nanosecond resolution callout. We will rarely
                 * find a match for this. So, bail out.
                 */
                return (NULL);
        }

        clflags = (CALLOUT_LIST_FLAG_ABSOLUTE | CALLOUT_LIST_FLAG_HRESTIME);
        for (cl = ct->ct_clhash[hash].ch_head; (cl != NULL); cl = cl->cl_next) {
                /*
                 * If we have reached a 1-nanosecond resolution callout list,
                 * we don't have much hope of finding a match in this hash
                 * bucket. So, just bail out.
                 */
                if (cl->cl_flags & CALLOUT_LIST_FLAG_NANO)
                        return (NULL);

                if ((cl->cl_expiration == expiration) &&
                    ((cl->cl_flags & clflags) == (flags & clflags)))
                        return (cl);
        }

        return (NULL);
}

/*
 * Add a new callout list into a callout table's queue in sorted order by
 * expiration.
 */
static int
callout_queue_add(callout_table_t *ct, callout_list_t *cl)
{
        callout_list_t *nextcl;
        hrtime_t expiration;

        expiration = cl->cl_expiration;
        nextcl = ct->ct_queue.ch_head;
        if ((nextcl == NULL) || (expiration < nextcl->cl_expiration)) {
                CALLOUT_LIST_INSERT(ct->ct_queue, cl);
                return (1);
        }

        while (nextcl != NULL) {
                if (expiration < nextcl->cl_expiration) {
                        CALLOUT_LIST_BEFORE(cl, nextcl);
                        return (0);
                }
                nextcl = nextcl->cl_next;
        }
        CALLOUT_LIST_APPEND(ct->ct_queue, cl);

        return (0);
}

/*
 * Insert a callout list into a callout table's queue and reprogram the queue
 * cyclic if needed.
 */
static void
callout_queue_insert(callout_table_t *ct, callout_list_t *cl)
{
        cl->cl_flags |= CALLOUT_LIST_FLAG_QUEUED;

        /*
         * Add the callout to the callout queue. If it ends up at the head,
         * the cyclic needs to be reprogrammed as we have an earlier
         * expiration.
         *
         * Also, during the CPR suspend phase, do not reprogram the cyclic.
         * We don't want any callout activity. When the CPR resume phase is
         * entered, the cyclic will be programmed for the earliest expiration
         * in the queue.
         */
        if (callout_queue_add(ct, cl) && (ct->ct_suspend == 0))
                (void) cyclic_reprogram(ct->ct_qcyclic, cl->cl_expiration);
}

/*
 * Delete and handle all past expirations in a callout table's queue.
 */
static hrtime_t
callout_queue_delete(callout_table_t *ct)
{
        callout_list_t *cl;
        hrtime_t now;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));

        now = gethrtime();
        while ((cl = ct->ct_queue.ch_head) != NULL) {
                if (cl->cl_expiration > now)
                        break;
                cl->cl_flags &= ~CALLOUT_LIST_FLAG_QUEUED;
                CALLOUT_LIST_DELETE(ct->ct_queue, cl);
                CALLOUT_LIST_APPEND(ct->ct_expired, cl);
        }

        /*
         * If this callout queue is empty or callouts have been suspended,
         * just return.
         */
        if ((cl == NULL) || (ct->ct_suspend > 0))
                return (CY_INFINITY);

        (void) cyclic_reprogram(ct->ct_qcyclic, cl->cl_expiration);

        return (cl->cl_expiration);
}

static hrtime_t
callout_queue_process(callout_table_t *ct, hrtime_t delta, int timechange)
{
        callout_list_t *firstcl, *cl;
        hrtime_t expiration, now;
        int clflags;
        callout_hash_t temp;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));

        firstcl = ct->ct_queue.ch_head;
        if (firstcl == NULL)
                return (CY_INFINITY);

        /*
         * We walk the callout queue. If we encounter a hrestime entry that
         * must be removed, we clean it out. Otherwise, we apply any
         * adjustments needed to it. Because of the latter, we need to
         * recreate the list as we go along.
         */
        temp = ct->ct_queue;
        ct->ct_queue.ch_head = NULL;
        ct->ct_queue.ch_tail = NULL;

        clflags = (CALLOUT_LIST_FLAG_HRESTIME | CALLOUT_LIST_FLAG_ABSOLUTE);
        now = gethrtime();
        while ((cl = temp.ch_head) != NULL) {
                CALLOUT_LIST_DELETE(temp, cl);

                /*
                 * Delete the callout and expire it, if one of the following
                 * is true:
                 *      - the callout has expired
                 *      - the callout is an absolute hrestime one and
                 *        there has been a system time change
                 */
                if ((cl->cl_expiration <= now) ||
                    (timechange && ((cl->cl_flags & clflags) == clflags))) {
                        cl->cl_flags &= ~CALLOUT_LIST_FLAG_QUEUED;
                        CALLOUT_LIST_APPEND(ct->ct_expired, cl);
                        continue;
                }

                /*
                 * Apply adjustments, if any. Adjustments are applied after
                 * the system returns from KMDB or OBP. They are only applied
                 * to relative callout lists.
                 */
                if (delta && !(cl->cl_flags & CALLOUT_LIST_FLAG_ABSOLUTE)) {
                        expiration = cl->cl_expiration + delta;
                        if (expiration <= 0)
                                expiration = CY_INFINITY;
                        cl->cl_expiration = expiration;
                }

                (void) callout_queue_add(ct, cl);
        }

        /*
         * We need to return the expiration to help program the cyclic.
         * If there are expired callouts, the cyclic needs to go off
         * immediately. If the queue has become empty, then we return infinity.
         * Else, we return the expiration of the earliest callout in the queue.
         */
        if (ct->ct_expired.ch_head != NULL)
                return (gethrtime());

        cl = ct->ct_queue.ch_head;
        if (cl == NULL)
                return (CY_INFINITY);

        return (cl->cl_expiration);
}

/*
 * Initialize a callout table's heap, if necessary. Preallocate some free
 * entries so we don't have to check for NULL elsewhere.
 */
static void
callout_heap_init(callout_table_t *ct)
{
        size_t size;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));
        ASSERT(ct->ct_heap == NULL);

        ct->ct_heap_num = 0;
        ct->ct_heap_max = callout_chunk;
        size = sizeof (callout_heap_t) * callout_chunk;
        ct->ct_heap = kmem_alloc(size, KM_SLEEP);
}

/*
 * Reallocate the heap. Return 0 if the heap is still full at the end of it.
 * Return 1 otherwise. Note that the heap only expands, it never contracts.
 */
static int
callout_heap_expand(callout_table_t *ct)
{
        size_t max, size, osize;
        callout_heap_t *heap;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));
        ASSERT(ct->ct_heap_num <= ct->ct_heap_max);

        while (ct->ct_heap_num == ct->ct_heap_max) {
                max = ct->ct_heap_max;
                mutex_exit(&ct->ct_mutex);

                osize = sizeof (callout_heap_t) * max;
                size = sizeof (callout_heap_t) * (max + callout_chunk);
                heap = kmem_alloc(size, KM_NOSLEEP);

                mutex_enter(&ct->ct_mutex);
                if (heap == NULL) {
                        /*
                         * We could not allocate memory. If we can free up
                         * some entries, that would be great.
                         */
                        if (ct->ct_nreap > 0)
                                (void) callout_heap_process(ct, 0, 0);
                        /*
                         * If we still have no space in the heap, inform the
                         * caller.
                         */
                        if (ct->ct_heap_num == ct->ct_heap_max)
                                return (0);
                        return (1);
                }
                if (max < ct->ct_heap_max) {
                        /*
                         * Someone beat us to the allocation. Free what we
                         * just allocated and proceed.
                         */
                        kmem_free(heap, size);
                        continue;
                }

                bcopy(ct->ct_heap, heap, osize);
                kmem_free(ct->ct_heap, osize);
                ct->ct_heap = heap;
                ct->ct_heap_max = size / sizeof (callout_heap_t);
        }

        return (1);
}

/*
 * Move an expiration from the bottom of the heap to its correct place
 * in the heap. If we reached the root doing this, return 1. Else,
 * return 0.
 */
static int
callout_upheap(callout_table_t *ct)
{
        int current, parent;
        callout_heap_t *heap, *hcurrent, *hparent;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));
        ASSERT(ct->ct_heap_num >= 1);

        if (ct->ct_heap_num == 1) {
                return (1);
        }

        heap = ct->ct_heap;
        current = ct->ct_heap_num - 1;

        for (;;) {
                parent = CALLOUT_HEAP_PARENT(current);
                hparent = &heap[parent];
                hcurrent = &heap[current];

                /*
                 * We have an expiration later than our parent; we're done.
                 */
                if (hcurrent->ch_expiration >= hparent->ch_expiration) {
                        return (0);
                }

                /*
                 * We need to swap with our parent, and continue up the heap.
                 */
                CALLOUT_SWAP(hparent, hcurrent);

                /*
                 * If we just reached the root, we're done.
                 */
                if (parent == 0) {
                        return (1);
                }

                current = parent;
        }
        /*NOTREACHED*/
}

/*
 * Insert a new heap item into a callout table's heap.
 */
static void
callout_heap_insert(callout_table_t *ct, callout_list_t *cl)
{
        ASSERT(MUTEX_HELD(&ct->ct_mutex));
        ASSERT(ct->ct_heap_num < ct->ct_heap_max);

        cl->cl_flags |= CALLOUT_LIST_FLAG_HEAPED;
        /*
         * First, copy the expiration and callout list pointer to the bottom
         * of the heap.
         */
        ct->ct_heap[ct->ct_heap_num].ch_expiration = cl->cl_expiration;
        ct->ct_heap[ct->ct_heap_num].ch_list = cl;
        ct->ct_heap_num++;

        /*
         * Now, perform an upheap operation. If we reached the root, then
         * the cyclic needs to be reprogrammed as we have an earlier
         * expiration.
         *
         * Also, during the CPR suspend phase, do not reprogram the cyclic.
         * We don't want any callout activity. When the CPR resume phase is
         * entered, the cyclic will be programmed for the earliest expiration
         * in the heap.
         */
        if (callout_upheap(ct) && (ct->ct_suspend == 0))
                (void) cyclic_reprogram(ct->ct_cyclic, cl->cl_expiration);
}

/*
 * Move an expiration from the top of the heap to its correct place
 * in the heap.
 */
static void
callout_downheap(callout_table_t *ct)
{
        int current, left, right, nelems;
        callout_heap_t *heap, *hleft, *hright, *hcurrent;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));
        ASSERT(ct->ct_heap_num >= 1);

        heap = ct->ct_heap;
        current = 0;
        nelems = ct->ct_heap_num;

        for (;;) {
                /*
                 * If we don't have a left child (i.e., we're a leaf), we're
                 * done.
                 */
                if ((left = CALLOUT_HEAP_LEFT(current)) >= nelems)
                        return;

                hleft = &heap[left];
                hcurrent = &heap[current];

                right = CALLOUT_HEAP_RIGHT(current);

                /*
                 * Even if we don't have a right child, we still need to compare
                 * our expiration against that of our left child.
                 */
                if (right >= nelems)
                        goto comp_left;

                hright = &heap[right];

                /*
                 * We have both a left and a right child.  We need to compare
                 * the expiration of the children to determine which
                 * expires earlier.
                 */
                if (hright->ch_expiration < hleft->ch_expiration) {
                        /*
                         * Our right child is the earlier of our children.
                         * We'll now compare our expiration to its expiration.
                         * If ours is the earlier one, we're done.
                         */
                        if (hcurrent->ch_expiration <= hright->ch_expiration)
                                return;

                        /*
                         * Our right child expires earlier than we do; swap
                         * with our right child, and descend right.
                         */
                        CALLOUT_SWAP(hright, hcurrent);
                        current = right;
                        continue;
                }

comp_left:
                /*
                 * Our left child is the earlier of our children (or we have
                 * no right child).  We'll now compare our expiration
                 * to its expiration. If ours is the earlier one, we're done.
                 */
                if (hcurrent->ch_expiration <= hleft->ch_expiration)
                        return;

                /*
                 * Our left child expires earlier than we do; swap with our
                 * left child, and descend left.
                 */
                CALLOUT_SWAP(hleft, hcurrent);
                current = left;
        }
}

/*
 * Delete and handle all past expirations in a callout table's heap.
 */
static hrtime_t
callout_heap_delete(callout_table_t *ct)
{
        hrtime_t now, expiration, next;
        callout_list_t *cl;
        callout_heap_t *heap;
        int hash;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));

        if (CALLOUT_CLEANUP(ct)) {
                /*
                 * There are too many heap elements pointing to empty callout
                 * lists. Clean them out.
                 */
                (void) callout_heap_process(ct, 0, 0);
        }

        now = gethrtime();
        heap = ct->ct_heap;

        while (ct->ct_heap_num > 0) {
                expiration = heap->ch_expiration;
                hash = CALLOUT_CLHASH(expiration);
                cl = heap->ch_list;
                ASSERT(expiration == cl->cl_expiration);

                if (cl->cl_callouts.ch_head == NULL) {
                        /*
                         * If the callout list is empty, reap it.
                         * Decrement the reap count.
                         */
                        CALLOUT_LIST_DELETE(ct->ct_clhash[hash], cl);
                        CALLOUT_LIST_FREE(ct, cl);
                        ct->ct_nreap--;
                } else {
                        /*
                         * If the root of the heap expires in the future,
                         * bail out.
                         */
                        if (expiration > now)
                                break;

                        /*
                         * Move the callout list for this expiration to the
                         * list of expired callout lists. It will be processed
                         * by the callout executor.
                         */
                        cl->cl_flags &= ~CALLOUT_LIST_FLAG_HEAPED;
                        CALLOUT_LIST_DELETE(ct->ct_clhash[hash], cl);
                        CALLOUT_LIST_APPEND(ct->ct_expired, cl);
                }

                /*
                 * Now delete the root. This is done by swapping the root with
                 * the last item in the heap and downheaping the item.
                 */
                ct->ct_heap_num--;
                if (ct->ct_heap_num > 0) {
                        heap[0] = heap[ct->ct_heap_num];
                        callout_downheap(ct);
                }
        }

        /*
         * If this callout table is empty or callouts have been suspended,
         * just return. The cyclic has already been programmed to
         * infinity by the cyclic subsystem.
         */
        if ((ct->ct_heap_num == 0) || (ct->ct_suspend > 0))
                return (CY_INFINITY);

        /*
         * If the top expirations are within callout_tolerance of each other,
         * delay the cyclic expire so that they can be processed together.
         * This is to prevent high resolution timers from swamping the system
         * with cyclic activity.
         */
        if (ct->ct_heap_num > 2) {
                next = expiration + callout_tolerance;
                if ((heap[1].ch_expiration < next) ||
                    (heap[2].ch_expiration < next))
                        expiration = next;
        }

        (void) cyclic_reprogram(ct->ct_cyclic, expiration);

        return (expiration);
}

/*
 * There are some situations when the entire heap is walked and processed.
 * This function is called to do the processing. These are the situations:
 *
 * 1. When the reap count reaches its threshold, the heap has to be cleared
 *    of all empty callout lists.
 *
 * 2. When the system enters and exits KMDB/OBP, all entries in the heap
 *    need to be adjusted by the interval spent in KMDB/OBP.
 *
 * 3. When system time is changed, the heap has to be scanned for
 *    absolute hrestime timers. These need to be removed from the heap
 *    and expired immediately.
 *
 * In cases 2 and 3, it is a good idea to do 1 as well since we are
 * scanning the heap anyway.
 *
 * If the root gets changed and/or callout lists are expired, return the
 * new expiration to the caller so it can reprogram the cyclic accordingly.
 */
static hrtime_t
callout_heap_process(callout_table_t *ct, hrtime_t delta, int timechange)
{
        callout_heap_t *heap;
        callout_list_t *cl;
        hrtime_t expiration, now;
        int i, hash, clflags;
        ulong_t num;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));

        if (ct->ct_heap_num == 0)
                return (CY_INFINITY);

        if (ct->ct_nreap > 0)
                ct->ct_cleanups++;

        heap = ct->ct_heap;

        /*
         * We walk the heap from the top to the bottom. If we encounter
         * a heap item that points to an empty callout list, we clean
         * it out. If we encounter a hrestime entry that must be removed,
         * again we clean it out. Otherwise, we apply any adjustments needed
         * to an element.
         *
         * During the walk, we also compact the heap from the bottom and
         * reconstruct the heap using upheap operations. This is very
         * efficient if the number of elements to be cleaned is greater than
         * or equal to half the heap. This is the common case.
         *
         * Even in the non-common case, the upheap operations should be short
         * as the entries below generally tend to be bigger than the entries
         * above.
         */
        num = ct->ct_heap_num;
        ct->ct_heap_num = 0;
        clflags = (CALLOUT_LIST_FLAG_HRESTIME | CALLOUT_LIST_FLAG_ABSOLUTE);
        now = gethrtime();
        for (i = 0; i < num; i++) {
                cl = heap[i].ch_list;
                /*
                 * If the callout list is empty, delete the heap element and
                 * free the callout list.
                 */
                if (cl->cl_callouts.ch_head == NULL) {
                        hash = CALLOUT_CLHASH(cl->cl_expiration);
                        CALLOUT_LIST_DELETE(ct->ct_clhash[hash], cl);
                        CALLOUT_LIST_FREE(ct, cl);
                        continue;
                }

                /*
                 * Delete the heap element and expire the callout list, if
                 * one of the following is true:
                 *      - the callout list has expired
                 *      - the callout list is an absolute hrestime one and
                 *        there has been a system time change
                 */
                if ((cl->cl_expiration <= now) ||
                    (timechange && ((cl->cl_flags & clflags) == clflags))) {
                        hash = CALLOUT_CLHASH(cl->cl_expiration);
                        cl->cl_flags &= ~CALLOUT_LIST_FLAG_HEAPED;
                        CALLOUT_LIST_DELETE(ct->ct_clhash[hash], cl);
                        CALLOUT_LIST_APPEND(ct->ct_expired, cl);
                        continue;
                }

                /*
                 * Apply adjustments, if any. Adjustments are applied after
                 * the system returns from KMDB or OBP. They are only applied
                 * to relative callout lists.
                 */
                if (delta && !(cl->cl_flags & CALLOUT_LIST_FLAG_ABSOLUTE)) {
                        hash = CALLOUT_CLHASH(cl->cl_expiration);
                        CALLOUT_LIST_DELETE(ct->ct_clhash[hash], cl);
                        expiration = cl->cl_expiration + delta;
                        if (expiration <= 0)
                                expiration = CY_INFINITY;
                        heap[i].ch_expiration = expiration;
                        cl->cl_expiration = expiration;
                        hash = CALLOUT_CLHASH(cl->cl_expiration);
                        if (cl->cl_flags & CALLOUT_LIST_FLAG_NANO) {
                                CALLOUT_LIST_APPEND(ct->ct_clhash[hash], cl);
                        } else {
                                CALLOUT_LIST_INSERT(ct->ct_clhash[hash], cl);
                        }
                }

                heap[ct->ct_heap_num] = heap[i];
                ct->ct_heap_num++;
                (void) callout_upheap(ct);
        }

        ct->ct_nreap = 0;

        /*
         * We need to return the expiration to help program the cyclic.
         * If there are expired callouts, the cyclic needs to go off
         * immediately. If the heap has become empty, then we return infinity.
         * Else, return the expiration of the earliest callout in the heap.
         */
        if (ct->ct_expired.ch_head != NULL)
                return (gethrtime());

        if (ct->ct_heap_num == 0)
                return (CY_INFINITY);

        return (heap->ch_expiration);
}

/*
 * Common function used to create normal and realtime callouts.
 *
 * Realtime callouts are handled at CY_LOW_PIL by a cyclic handler. So,
 * there is one restriction on a realtime callout handler - it should not
 * directly or indirectly acquire cpu_lock. CPU offline waits for pending
 * cyclic handlers to complete while holding cpu_lock. So, if a realtime
 * callout handler were to try to get cpu_lock, there would be a deadlock
 * during CPU offline.
 */
callout_id_t
timeout_generic(int type, void (*func)(void *), void *arg,
        hrtime_t expiration, hrtime_t resolution, int flags)
{
        callout_table_t *ct;
        callout_t *cp;
        callout_id_t id;
        callout_list_t *cl;
        hrtime_t now, interval;
        int hash, clflags;

        ASSERT(resolution > 0);
        ASSERT(func != NULL);

        /*
         * We get the current hrtime right upfront so that latencies in
         * this function do not affect the accuracy of the callout.
         */
        now = gethrtime();

        /*
         * We disable kernel preemption so that we remain on the same CPU
         * throughout. If we needed to reprogram the callout table's cyclic,
         * we can avoid X-calls if we are on the same CPU.
         *
         * Note that callout_alloc() releases and reacquires the callout
         * table mutex. While reacquiring the mutex, it is possible for us
         * to go to sleep and later migrate to another CPU. This should be
         * pretty rare, though.
         */
        kpreempt_disable();

        ct = &callout_table[CALLOUT_TABLE(type, CPU->cpu_seqid)];
        mutex_enter(&ct->ct_mutex);

        if (ct->ct_cyclic == CYCLIC_NONE) {
                mutex_exit(&ct->ct_mutex);
                /*
                 * The callout table has not yet been initialized fully.
                 * So, put this one on the boot callout table which is
                 * always initialized.
                 */
                ct = &callout_boot_ct[type];
                mutex_enter(&ct->ct_mutex);
        }

        if (CALLOUT_CLEANUP(ct)) {
                /*
                 * There are too many heap elements pointing to empty callout
                 * lists. Clean them out. Since cleanup is only done once
                 * in a while, no need to reprogram the cyclic if the root
                 * of the heap gets cleaned out.
                 */
                (void) callout_heap_process(ct, 0, 0);
        }

        if ((cp = ct->ct_free) == NULL)
                cp = callout_alloc(ct);
        else
                ct->ct_free = cp->c_idnext;

        cp->c_func = func;
        cp->c_arg = arg;

        /*
         * Compute the expiration hrtime.
         */
        if (flags & CALLOUT_FLAG_ABSOLUTE) {
                interval = expiration - now;
        } else {
                interval = expiration;
                expiration += now;
        }

        if (resolution > 1) {
                /*
                 * Align expiration to the specified resolution.
                 */
                if (flags & CALLOUT_FLAG_ROUNDUP)
                        expiration += resolution - 1;
                expiration = (expiration / resolution) * resolution;
        }

        if (expiration <= 0) {
                /*
                 * expiration hrtime overflow has occurred. Just set the
                 * expiration to infinity.
                 */
                expiration = CY_INFINITY;
        }

        /*
         * Assign an ID to this callout
         */
        if (flags & CALLOUT_FLAG_32BIT) {
                if (interval > callout_longterm) {
                        id = (ct->ct_long_id - callout_counter_low);
                        id |= CALLOUT_COUNTER_HIGH;
                        ct->ct_long_id = id;
                } else {
                        id = (ct->ct_short_id - callout_counter_low);
                        id |= CALLOUT_COUNTER_HIGH;
                        ct->ct_short_id = id;
                }
        } else {
                id = (ct->ct_gen_id - callout_counter_low);
                if ((id & CALLOUT_COUNTER_HIGH) == 0) {
                        id |= CALLOUT_COUNTER_HIGH;
                        id += CALLOUT_GENERATION_LOW;
                }
                ct->ct_gen_id = id;
        }

        cp->c_xid = id;

        clflags = 0;
        if (flags & CALLOUT_FLAG_ABSOLUTE)
                clflags |= CALLOUT_LIST_FLAG_ABSOLUTE;
        if (flags & CALLOUT_FLAG_HRESTIME)
                clflags |= CALLOUT_LIST_FLAG_HRESTIME;
        if (resolution == 1)
                clflags |= CALLOUT_LIST_FLAG_NANO;
        hash = CALLOUT_CLHASH(expiration);

again:
        /*
         * Try to see if a callout list already exists for this expiration.
         */
        cl = callout_list_get(ct, expiration, clflags, hash);
        if (cl == NULL) {
                /*
                 * Check the free list. If we don't find one, we have to
                 * take the slow path and allocate from kmem.
                 */
                if ((cl = ct->ct_lfree) == NULL) {
                        callout_list_alloc(ct);
                        /*
                         * In the above call, we drop the lock, allocate and
                         * reacquire the lock. So, we could have been away
                         * for a while. In the meantime, someone could have
                         * inserted a callout list with the same expiration.
                         * Plus, the heap could have become full. So, the best
                         * course is to repeat the steps. This should be an
                         * infrequent event.
                         */
                        goto again;
                }
                ct->ct_lfree = cl->cl_next;
                cl->cl_expiration = expiration;
                cl->cl_flags = clflags;

                /*
                 * Check if we have enough space in the heap to insert one
                 * expiration. If not, expand the heap.
                 */
                if (ct->ct_heap_num == ct->ct_heap_max) {
                        if (callout_heap_expand(ct) == 0) {
                                /*
                                 * Could not expand the heap. Just queue it.
                                 */
                                callout_queue_insert(ct, cl);
                                goto out;
                        }

                        /*
                         * In the above call, we drop the lock, allocate and
                         * reacquire the lock. So, we could have been away
                         * for a while. In the meantime, someone could have
                         * inserted a callout list with the same expiration.
                         * But we will not go back and check for it as this
                         * should be a really infrequent event. There is no
                         * point.
                         */
                }

                if (clflags & CALLOUT_LIST_FLAG_NANO) {
                        CALLOUT_LIST_APPEND(ct->ct_clhash[hash], cl);
                } else {
                        CALLOUT_LIST_INSERT(ct->ct_clhash[hash], cl);
                }

                /*
                 * This is a new expiration. So, insert it into the heap.
                 * This will also reprogram the cyclic, if the expiration
                 * propagated to the root of the heap.
                 */
                callout_heap_insert(ct, cl);
        } else {
                /*
                 * If the callout list was empty, untimeout_generic() would
                 * have incremented a reap count. Decrement the reap count
                 * as we are going to insert a callout into this list.
                 */
                if (cl->cl_callouts.ch_head == NULL)
                        ct->ct_nreap--;
        }
out:
        cp->c_list = cl;
        CALLOUT_APPEND(ct, cp);

        ct->ct_timeouts++;
        ct->ct_timeouts_pending++;

        mutex_exit(&ct->ct_mutex);

        kpreempt_enable();

        TRACE_4(TR_FAC_CALLOUT, TR_TIMEOUT,
            "timeout:%K(%p) in %llx expiration, cp %p", func, arg, expiration,
            cp);

        return (id);
}

timeout_id_t
timeout(void (*func)(void *), void *arg, clock_t delta)
{
        ulong_t id;

        /*
         * Make sure the callout runs at least 1 tick in the future.
         */
        if (delta <= 0)
                delta = 1;
        else if (delta > callout_max_ticks)
                delta = callout_max_ticks;

        id =  (ulong_t)timeout_generic(CALLOUT_NORMAL, func, arg,
            TICK_TO_NSEC(delta), nsec_per_tick, CALLOUT_LEGACY);

        return ((timeout_id_t)id);
}

/*
 * Convenience function that creates a normal callout with default parameters
 * and returns a full ID.
 */
callout_id_t
timeout_default(void (*func)(void *), void *arg, clock_t delta)
{
        callout_id_t id;

        /*
         * Make sure the callout runs at least 1 tick in the future.
         */
        if (delta <= 0)
                delta = 1;
        else if (delta > callout_max_ticks)
                delta = callout_max_ticks;

        id = timeout_generic(CALLOUT_NORMAL, func, arg, TICK_TO_NSEC(delta),
            nsec_per_tick, 0);

        return (id);
}

timeout_id_t
realtime_timeout(void (*func)(void *), void *arg, clock_t delta)
{
        ulong_t id;

        /*
         * Make sure the callout runs at least 1 tick in the future.
         */
        if (delta <= 0)
                delta = 1;
        else if (delta > callout_max_ticks)
                delta = callout_max_ticks;

        id =  (ulong_t)timeout_generic(CALLOUT_REALTIME, func, arg,
            TICK_TO_NSEC(delta), nsec_per_tick, CALLOUT_LEGACY);

        return ((timeout_id_t)id);
}

/*
 * Convenience function that creates a realtime callout with default parameters
 * and returns a full ID.
 */
callout_id_t
realtime_timeout_default(void (*func)(void *), void *arg, clock_t delta)
{
        callout_id_t id;

        /*
         * Make sure the callout runs at least 1 tick in the future.
         */
        if (delta <= 0)
                delta = 1;
        else if (delta > callout_max_ticks)
                delta = callout_max_ticks;

        id = timeout_generic(CALLOUT_REALTIME, func, arg, TICK_TO_NSEC(delta),
            nsec_per_tick, 0);

        return (id);
}

hrtime_t
untimeout_generic(callout_id_t id, int nowait)
{
        callout_table_t *ct;
        callout_t *cp;
        callout_id_t xid;
        callout_list_t *cl;
        int hash, flags;
        callout_id_t bogus;

        ct = &callout_table[CALLOUT_ID_TO_TABLE(id)];
        hash = CALLOUT_IDHASH(id);

        mutex_enter(&ct->ct_mutex);

        /*
         * Search the ID hash table for the callout.
         */
        for (cp = ct->ct_idhash[hash].ch_head; cp; cp = cp->c_idnext) {

                xid = cp->c_xid;

                /*
                 * Match the ID and generation number.
                 */
                if ((xid & CALLOUT_ID_MASK) != id)
                        continue;

                if ((xid & CALLOUT_EXECUTING) == 0) {
                        hrtime_t expiration;

                        /*
                         * Delete the callout. If the callout list becomes
                         * NULL, we don't remove it from the table. This is
                         * so it can be reused. If the empty callout list
                         * corresponds to the top of the the callout heap, we
                         * don't reprogram the table cyclic here. This is in
                         * order to avoid lots of X-calls to the CPU associated
                         * with the callout table.
                         */
                        cl = cp->c_list;
                        expiration = cl->cl_expiration;
                        CALLOUT_DELETE(ct, cp);
                        CALLOUT_FREE(ct, cp);
                        ct->ct_untimeouts_unexpired++;
                        ct->ct_timeouts_pending--;

                        /*
                         * If the callout list has become empty, there are 3
                         * possibilities. If it is present:
                         *      - in the heap, it needs to be cleaned along
                         *        with its heap entry. Increment a reap count.
                         *      - in the callout queue, free it.
                         *      - in the expired list, free it.
                         */
                        if (cl->cl_callouts.ch_head == NULL) {
                                flags = cl->cl_flags;
                                if (flags & CALLOUT_LIST_FLAG_HEAPED) {
                                        ct->ct_nreap++;
                                } else if (flags & CALLOUT_LIST_FLAG_QUEUED) {
                                        CALLOUT_LIST_DELETE(ct->ct_queue, cl);
                                        CALLOUT_LIST_FREE(ct, cl);
                                } else {
                                        CALLOUT_LIST_DELETE(ct->ct_expired, cl);
                                        CALLOUT_LIST_FREE(ct, cl);
                                }
                        }
                        mutex_exit(&ct->ct_mutex);

                        expiration -= gethrtime();
                        TRACE_2(TR_FAC_CALLOUT, TR_UNTIMEOUT,
                            "untimeout:ID %lx hrtime left %llx", id,
                            expiration);
                        return (expiration < 0 ? 0 : expiration);
                }

                ct->ct_untimeouts_executing++;
                /*
                 * The callout we want to delete is currently executing.
                 * The DDI states that we must wait until the callout
                 * completes before returning, so we block on c_done until the
                 * callout ID changes (to the old ID if it's on the freelist,
                 * or to a new callout ID if it's in use).  This implicitly
                 * assumes that callout structures are persistent (they are).
                 */
                if (cp->c_executor == curthread) {
                        /*
                         * The timeout handler called untimeout() on itself.
                         * Stupid, but legal.  We can't wait for the timeout
                         * to complete without deadlocking, so we just return.
                         */
                        mutex_exit(&ct->ct_mutex);
                        TRACE_1(TR_FAC_CALLOUT, TR_UNTIMEOUT_SELF,
                            "untimeout_self:ID %x", id);
                        return (-1);
                }
                if (nowait == 0) {
                        /*
                         * We need to wait. Indicate that we are waiting by
                         * incrementing c_waiting. This prevents the executor
                         * from doing a wakeup on c_done if there are no
                         * waiters.
                         */
                        while (cp->c_xid == xid) {
                                cp->c_waiting = 1;
                                cv_wait(&cp->c_done, &ct->ct_mutex);
                        }
                }
                mutex_exit(&ct->ct_mutex);
                TRACE_1(TR_FAC_CALLOUT, TR_UNTIMEOUT_EXECUTING,
                    "untimeout_executing:ID %lx", id);
                return (-1);
        }
        ct->ct_untimeouts_expired++;

        mutex_exit(&ct->ct_mutex);
        TRACE_1(TR_FAC_CALLOUT, TR_UNTIMEOUT_BOGUS_ID,
            "untimeout_bogus_id:ID %lx", id);

        /*
         * We didn't find the specified callout ID.  This means either
         * (1) the callout already fired, or (2) the caller passed us
         * a bogus value.  Perform a sanity check to detect case (2).
         */
        bogus = (CALLOUT_ID_FLAGS | CALLOUT_COUNTER_HIGH);
        if (((id & bogus) != CALLOUT_COUNTER_HIGH) && (id != 0))
                panic("untimeout: impossible timeout id %llx",
                    (unsigned long long)id);

        return (-1);
}

clock_t
untimeout(timeout_id_t id_arg)
{
        hrtime_t hleft;
        clock_t tleft;
        callout_id_t id;

        id = (ulong_t)id_arg;
        hleft = untimeout_generic(id, 0);
        if (hleft < 0)
                tleft = -1;
        else if (hleft == 0)
                tleft = 0;
        else
                tleft = NSEC_TO_TICK(hleft);

        return (tleft);
}

/*
 * Convenience function to untimeout a timeout with a full ID with default
 * parameters.
 */
clock_t
untimeout_default(callout_id_t id, int nowait)
{
        hrtime_t hleft;
        clock_t tleft;

        hleft = untimeout_generic(id, nowait);
        if (hleft < 0)
                tleft = -1;
        else if (hleft == 0)
                tleft = 0;
        else
                tleft = NSEC_TO_TICK(hleft);

        return (tleft);
}

/*
 * Expire all the callouts queued in the specified callout list.
 */
static void
callout_list_expire(callout_table_t *ct, callout_list_t *cl)
{
        callout_t *cp, *cnext;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));
        ASSERT(cl != NULL);

        for (cp = cl->cl_callouts.ch_head; cp != NULL; cp = cnext) {
                /*
                 * Multiple executor threads could be running at the same
                 * time. If this callout is already being executed,
                 * go on to the next one.
                 */
                if (cp->c_xid & CALLOUT_EXECUTING) {
                        cnext = cp->c_clnext;
                        continue;
                }

                /*
                 * Indicate to untimeout() that a callout is
                 * being expired by the executor.
                 */
                cp->c_xid |= CALLOUT_EXECUTING;
                cp->c_executor = curthread;
                mutex_exit(&ct->ct_mutex);

                DTRACE_PROBE1(callout__start, callout_t *, cp);
                (*cp->c_func)(cp->c_arg);
                DTRACE_PROBE1(callout__end, callout_t *, cp);

                mutex_enter(&ct->ct_mutex);

                ct->ct_expirations++;
                ct->ct_timeouts_pending--;
                /*
                 * Indicate completion for c_done.
                 */
                cp->c_xid &= ~CALLOUT_EXECUTING;
                cp->c_executor = NULL;
                cnext = cp->c_clnext;

                /*
                 * Delete callout from ID hash table and the callout
                 * list, return to freelist, and tell any untimeout() that
                 * cares that we're done.
                 */
                CALLOUT_DELETE(ct, cp);
                CALLOUT_FREE(ct, cp);

                if (cp->c_waiting) {
                        cp->c_waiting = 0;
                        cv_broadcast(&cp->c_done);
                }
        }
}

/*
 * Execute all expired callout lists for a callout table.
 */
static void
callout_expire(callout_table_t *ct)
{
        callout_list_t *cl, *clnext;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));

        for (cl = ct->ct_expired.ch_head; (cl != NULL); cl = clnext) {
                /*
                 * Expire all the callouts in this callout list.
                 */
                callout_list_expire(ct, cl);

                clnext = cl->cl_next;
                if (cl->cl_callouts.ch_head == NULL) {
                        /*
                         * Free the callout list.
                         */
                        CALLOUT_LIST_DELETE(ct->ct_expired, cl);
                        CALLOUT_LIST_FREE(ct, cl);
                }
        }
}

/*
 * The cyclic handlers below process callouts in two steps:
 *
 *      1. Find all expired callout lists and queue them in a separate
 *         list of expired callouts.
 *      2. Execute the expired callout lists.
 *
 * This is done for two reasons:
 *
 *      1. We want to quickly find the next earliest expiration to program
 *         the cyclic to and reprogram it. We can do this right at the end
 *         of step 1.
 *      2. The realtime cyclic handler expires callouts in place. However,
 *         for normal callouts, callouts are expired by a taskq thread.
 *         So, it is simpler and more robust to have the taskq thread just
 *         do step 2.
 */

/*
 * Realtime callout cyclic handlers.
 */
void
callout_realtime(callout_table_t *ct)
{
        mutex_enter(&ct->ct_mutex);
        (void) callout_heap_delete(ct);
        callout_expire(ct);
        mutex_exit(&ct->ct_mutex);
}

void
callout_queue_realtime(callout_table_t *ct)
{
        mutex_enter(&ct->ct_mutex);
        (void) callout_queue_delete(ct);
        callout_expire(ct);
        mutex_exit(&ct->ct_mutex);
}

void
callout_execute(callout_table_t *ct)
{
        mutex_enter(&ct->ct_mutex);
        callout_expire(ct);
        mutex_exit(&ct->ct_mutex);
}

/*
 * Normal callout cyclic handlers.
 */
void
callout_normal(callout_table_t *ct)
{
        int i, exec;
        hrtime_t exp;

        mutex_enter(&ct->ct_mutex);
        exp = callout_heap_delete(ct);
        CALLOUT_EXEC_COMPUTE(ct, exp, exec);
        mutex_exit(&ct->ct_mutex);

        for (i = 0; i < exec; i++) {
                ASSERT(ct->ct_taskq != NULL);
                (void) taskq_dispatch(ct->ct_taskq,
                    (task_func_t *)callout_execute, ct, TQ_NOSLEEP);
        }
}

void
callout_queue_normal(callout_table_t *ct)
{
        int i, exec;
        hrtime_t exp;

        mutex_enter(&ct->ct_mutex);
        exp = callout_queue_delete(ct);
        CALLOUT_EXEC_COMPUTE(ct, exp, exec);
        mutex_exit(&ct->ct_mutex);

        for (i = 0; i < exec; i++) {
                ASSERT(ct->ct_taskq != NULL);
                (void) taskq_dispatch(ct->ct_taskq,
                    (task_func_t *)callout_execute, ct, TQ_NOSLEEP);
        }
}

/*
 * Suspend callout processing.
 */
static void
callout_suspend(void)
{
        int t, f;
        callout_table_t *ct;

        /*
         * Traverse every callout table in the system and suspend callout
         * processing.
         *
         * We need to suspend all the tables (including the inactive ones)
         * so that if a table is made active while the suspend is still on,
         * the table remains suspended.
         */
        for (f = 0; f < max_ncpus; f++) {
                for (t = 0; t < CALLOUT_NTYPES; t++) {
                        ct = &callout_table[CALLOUT_TABLE(t, f)];

                        mutex_enter(&ct->ct_mutex);
                        ct->ct_suspend++;
                        if (ct->ct_cyclic == CYCLIC_NONE) {
                                mutex_exit(&ct->ct_mutex);
                                continue;
                        }
                        if (ct->ct_suspend == 1) {
                                (void) cyclic_reprogram(ct->ct_cyclic,
                                    CY_INFINITY);
                                (void) cyclic_reprogram(ct->ct_qcyclic,
                                    CY_INFINITY);
                        }
                        mutex_exit(&ct->ct_mutex);
                }
        }
}

/*
 * Resume callout processing.
 */
static void
callout_resume(hrtime_t delta, int timechange)
{
        hrtime_t hexp, qexp;
        int t, f;
        callout_table_t *ct;

        /*
         * Traverse every callout table in the system and resume callout
         * processing. For active tables, perform any hrtime adjustments
         * necessary.
         */
        for (f = 0; f < max_ncpus; f++) {
                for (t = 0; t < CALLOUT_NTYPES; t++) {
                        ct = &callout_table[CALLOUT_TABLE(t, f)];

                        mutex_enter(&ct->ct_mutex);
                        if (ct->ct_cyclic == CYCLIC_NONE) {
                                ct->ct_suspend--;
                                mutex_exit(&ct->ct_mutex);
                                continue;
                        }

                        /*
                         * If a delta is specified, adjust the expirations in
                         * the heap by delta. Also, if the caller indicates
                         * a timechange, process that. This step also cleans
                         * out any empty callout lists that might happen to
                         * be there.
                         */
                        hexp = callout_heap_process(ct, delta, timechange);
                        qexp = callout_queue_process(ct, delta, timechange);

                        ct->ct_suspend--;
                        if (ct->ct_suspend == 0) {
                                (void) cyclic_reprogram(ct->ct_cyclic, hexp);
                                (void) cyclic_reprogram(ct->ct_qcyclic, qexp);
                        }

                        mutex_exit(&ct->ct_mutex);
                }
        }
}

/*
 * Callback handler used by CPR to stop and resume callouts.
 * The cyclic subsystem saves and restores hrtime during CPR.
 * That is why callout_resume() is called with a 0 delta.
 * Although hrtime is the same, hrestime (system time) has
 * progressed during CPR. So, we have to indicate a time change
 * to expire the absolute hrestime timers.
 */
/*ARGSUSED*/
static boolean_t
callout_cpr_callb(void *arg, int code)
{
        if (code == CB_CODE_CPR_CHKPT)
                callout_suspend();
        else
                callout_resume(0, 1);

        return (B_TRUE);
}

/*
 * Callback handler invoked when the debugger is entered or exited.
 */
/*ARGSUSED*/
static boolean_t
callout_debug_callb(void *arg, int code)
{
        hrtime_t delta;

        /*
         * When the system enters the debugger. make a note of the hrtime.
         * When it is resumed, compute how long the system was in the
         * debugger. This interval should not be counted for callouts.
         */
        if (code == 0) {
                callout_suspend();
                callout_debug_hrtime = gethrtime();
        } else {
                delta = gethrtime() - callout_debug_hrtime;
                callout_resume(delta, 0);
        }

        return (B_TRUE);
}

/*
 * Move the absolute hrestime callouts to the expired list. Then program the
 * table's cyclic to expire immediately so that the callouts can be executed
 * immediately.
 */
static void
callout_hrestime_one(callout_table_t *ct)
{
        hrtime_t hexp, qexp;

        mutex_enter(&ct->ct_mutex);
        if (ct->ct_cyclic == CYCLIC_NONE) {
                mutex_exit(&ct->ct_mutex);
                return;
        }

        /*
         * Walk the heap and process all the absolute hrestime entries.
         */
        hexp = callout_heap_process(ct, 0, 1);
        qexp = callout_queue_process(ct, 0, 1);

        if (ct->ct_suspend == 0) {
                (void) cyclic_reprogram(ct->ct_cyclic, hexp);
                (void) cyclic_reprogram(ct->ct_qcyclic, qexp);
        }

        mutex_exit(&ct->ct_mutex);
}

/*
 * This function is called whenever system time (hrestime) is changed
 * explicitly. All the HRESTIME callouts must be expired at once.
 */
/*ARGSUSED*/
void
callout_hrestime(void)
{
        int t, f;
        callout_table_t *ct;

        /*
         * Traverse every callout table in the system and process the hrestime
         * callouts therein.
         *
         * We look at all the tables because we don't know which ones were
         * onlined and offlined in the past. The offlined tables may still
         * have active cyclics processing timers somewhere.
         */
        for (f = 0; f < max_ncpus; f++) {
                for (t = 0; t < CALLOUT_NTYPES; t++) {
                        ct = &callout_table[CALLOUT_TABLE(t, f)];
                        callout_hrestime_one(ct);
                }
        }
}

/*
 * Create the hash tables for this callout table.
 */
static void
callout_hash_init(callout_table_t *ct)
{
        size_t size;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));
        ASSERT((ct->ct_idhash == NULL) && (ct->ct_clhash == NULL));

        size = sizeof (callout_hash_t) * CALLOUT_BUCKETS;
        ct->ct_idhash = kmem_zalloc(size, KM_SLEEP);
        ct->ct_clhash = kmem_zalloc(size, KM_SLEEP);
}

/*
 * Create per-callout table kstats.
 */
static void
callout_kstat_init(callout_table_t *ct)
{
        callout_stat_type_t stat;
        kstat_t *ct_kstats;
        int ndx;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));
        ASSERT(ct->ct_kstats == NULL);

        ndx = ct - callout_table;
        ct_kstats = kstat_create("unix", ndx, "callout",
            "misc", KSTAT_TYPE_NAMED, CALLOUT_NUM_STATS, KSTAT_FLAG_VIRTUAL);

        if (ct_kstats == NULL) {
                cmn_err(CE_WARN, "kstat_create for callout table %p failed",
                    (void *)ct);
        } else {
                ct_kstats->ks_data = ct->ct_kstat_data;
                for (stat = 0; stat < CALLOUT_NUM_STATS; stat++)
                        kstat_named_init(&ct->ct_kstat_data[stat],
                            callout_kstat_names[stat], KSTAT_DATA_INT64);
                ct->ct_kstats = ct_kstats;
                kstat_install(ct_kstats);
        }
}

static void
callout_cyclic_init(callout_table_t *ct)
{
        cyc_handler_t hdlr;
        cyc_time_t when;
        processorid_t seqid;
        int t;
        cyclic_id_t cyclic, qcyclic;

        ASSERT(MUTEX_HELD(&ct->ct_mutex));

        t = ct->ct_type;
        seqid = CALLOUT_TABLE_SEQID(ct);

        /*
         * Create the taskq thread if the table type is normal.
         * Realtime tables are handled at PIL1 by a softint
         * handler.
         */
        if (t == CALLOUT_NORMAL) {
                ASSERT(ct->ct_taskq == NULL);
                /*
                 * Each callout thread consumes exactly one
                 * task structure while active.  Therefore,
                 * prepopulating with 2 * callout_threads tasks
                 * ensures that there's at least one task per
                 * thread that's either scheduled or on the
                 * freelist.  In turn, this guarantees that
                 * taskq_dispatch() will always either succeed
                 * (because there's a free task structure) or
                 * be unnecessary (because "callout_excute(ct)"
                 * has already scheduled).
                 */
                ct->ct_taskq =
                    taskq_create_instance("callout_taskq", seqid,
                    callout_threads, maxclsyspri,
                    2 * callout_threads, 2 * callout_threads,
                    TASKQ_PREPOPULATE | TASKQ_CPR_SAFE);
        }

        /*
         * callouts can only be created in a table whose
         * cyclic has been initialized.
         */
        ASSERT(ct->ct_heap_num == 0);

        /*
         * Drop the mutex before creating the callout cyclics. cyclic_add()
         * could potentially expand the cyclic heap. We don't want to be
         * holding the callout table mutex in that case. Note that this
         * function is called during CPU online. cpu_lock is held at this
         * point. So, only one thread can be executing the cyclic add logic
         * below at any time.
         */
        mutex_exit(&ct->ct_mutex);

        /*
         * Create the callout table cyclics.
         *
         * The realtime cyclic handler executes at low PIL. The normal cyclic
         * handler executes at lock PIL. This is because there are cases
         * where code can block at PIL > 1 waiting for a normal callout handler
         * to unblock it directly or indirectly. If the normal cyclic were to
         * be executed at low PIL, it could get blocked out by the waiter
         * and cause a deadlock.
         */
        ASSERT(ct->ct_cyclic == CYCLIC_NONE);

        if (t == CALLOUT_REALTIME) {
                hdlr.cyh_level = callout_realtime_level;
                hdlr.cyh_func = (cyc_func_t)callout_realtime;
        } else {
                hdlr.cyh_level = callout_normal_level;
                hdlr.cyh_func = (cyc_func_t)callout_normal;
        }
        hdlr.cyh_arg = ct;
        when.cyt_when = CY_INFINITY;
        when.cyt_interval = CY_INFINITY;

        cyclic = cyclic_add(&hdlr, &when);

        if (t == CALLOUT_REALTIME)
                hdlr.cyh_func = (cyc_func_t)callout_queue_realtime;
        else
                hdlr.cyh_func = (cyc_func_t)callout_queue_normal;

        qcyclic = cyclic_add(&hdlr, &when);

        mutex_enter(&ct->ct_mutex);
        ct->ct_cyclic = cyclic;
        ct->ct_qcyclic = qcyclic;
}

void
callout_cpu_online(cpu_t *cp)
{
        lgrp_handle_t hand;
        callout_cache_t *cache;
        char s[KMEM_CACHE_NAMELEN];
        callout_table_t *ct;
        processorid_t seqid;
        int t;

        ASSERT(MUTEX_HELD(&cpu_lock));

        /*
         * Locate the cache corresponding to the onlined CPU's lgroup.
         * Note that access to callout_caches is protected by cpu_lock.
         */
        hand = lgrp_plat_cpu_to_hand(cp->cpu_id);
        for (cache = callout_caches; cache != NULL; cache = cache->cc_next) {
                if (cache->cc_hand == hand)
                        break;
        }

        /*
         * If not found, create one. The caches are never destroyed.
         */
        if (cache == NULL) {
                cache = kmem_alloc(sizeof (callout_cache_t), KM_SLEEP);
                cache->cc_hand = hand;
                (void) snprintf(s, KMEM_CACHE_NAMELEN, "callout_cache%lx",
                    (long)hand);
                cache->cc_cache = kmem_cache_create(s, sizeof (callout_t),
                    CALLOUT_ALIGN, NULL, NULL, NULL, NULL, NULL, 0);
                (void) snprintf(s, KMEM_CACHE_NAMELEN, "callout_lcache%lx",
                    (long)hand);
                cache->cc_lcache = kmem_cache_create(s, sizeof (callout_list_t),
                    CALLOUT_ALIGN, NULL, NULL, NULL, NULL, NULL, 0);
                cache->cc_next = callout_caches;
                callout_caches = cache;
        }

        seqid = cp->cpu_seqid;

        for (t = 0; t < CALLOUT_NTYPES; t++) {
                ct = &callout_table[CALLOUT_TABLE(t, seqid)];

                mutex_enter(&ct->ct_mutex);
                /*
                 * Store convinience pointers to the kmem caches
                 * in the callout table. These assignments should always be
                 * done as callout tables can map to different physical
                 * CPUs each time.
                 */
                ct->ct_cache = cache->cc_cache;
                ct->ct_lcache = cache->cc_lcache;

                /*
                 * We use the heap pointer to check if stuff has been
                 * initialized for this callout table.
                 */
                if (ct->ct_heap == NULL) {
                        callout_heap_init(ct);
                        callout_hash_init(ct);
                        callout_kstat_init(ct);
                        callout_cyclic_init(ct);
                }

                mutex_exit(&ct->ct_mutex);

                /*
                 * Move the cyclics to this CPU by doing a bind.
                 */
                cyclic_bind(ct->ct_cyclic, cp, NULL);
                cyclic_bind(ct->ct_qcyclic, cp, NULL);
        }
}

void
callout_cpu_offline(cpu_t *cp)
{
        callout_table_t *ct;
        processorid_t seqid;
        int t;

        ASSERT(MUTEX_HELD(&cpu_lock));

        seqid = cp->cpu_seqid;

        for (t = 0; t < CALLOUT_NTYPES; t++) {
                ct = &callout_table[CALLOUT_TABLE(t, seqid)];

                /*
                 * Unbind the cyclics. This will allow the cyclic subsystem
                 * to juggle the cyclics during CPU offline.
                 */
                cyclic_bind(ct->ct_cyclic, NULL, NULL);
                cyclic_bind(ct->ct_qcyclic, NULL, NULL);
        }
}

/*
 * This is called to perform per-CPU initialization for slave CPUs at
 * boot time.
 */
void
callout_mp_init(void)
{
        cpu_t *cp;
        size_t min, max;

        if (callout_chunk == CALLOUT_CHUNK) {
                /*
                 * No one has specified a chunk in /etc/system. We need to
                 * compute it here based on the number of online CPUs and
                 * available physical memory.
                 */
                min = CALLOUT_MIN_HEAP_SIZE;
                max = ptob(physmem / CALLOUT_MEM_FRACTION);
                if (min > max)
                        min = max;
                callout_chunk = min / sizeof (callout_heap_t);
                callout_chunk /= ncpus_online;
                callout_chunk = P2ROUNDUP(callout_chunk, CALLOUT_CHUNK);
        }

        mutex_enter(&cpu_lock);

        cp = cpu_active;
        do {
                callout_cpu_online(cp);
        } while ((cp = cp->cpu_next_onln) != cpu_active);

        mutex_exit(&cpu_lock);
}

/*
 * Initialize all callout tables.  Called at boot time just before clkstart().
 */
void
callout_init(void)
{
        int f, t;
        size_t size;
        int table_id;
        callout_table_t *ct;
        long bits, fanout;
        uintptr_t buf;

        /*
         * Initialize callout globals.
         */
        bits = 0;
        for (fanout = 1; (fanout < max_ncpus); fanout <<= 1)
                bits++;
        callout_table_bits = CALLOUT_TYPE_BITS + bits;
        callout_table_mask = (1 << callout_table_bits) - 1;
        callout_counter_low = 1 << CALLOUT_COUNTER_SHIFT;
        callout_longterm = TICK_TO_NSEC(CALLOUT_LONGTERM_TICKS);
        callout_max_ticks = CALLOUT_MAX_TICKS;
        if (callout_min_reap == 0)
                callout_min_reap = CALLOUT_MIN_REAP;

        if (callout_tolerance <= 0)
                callout_tolerance = CALLOUT_TOLERANCE;
        if (callout_threads <= 0)
                callout_threads = CALLOUT_THREADS;
        if (callout_chunk <= 0)
                callout_chunk = CALLOUT_CHUNK;
        else
                callout_chunk = P2ROUNDUP(callout_chunk, CALLOUT_CHUNK);

        /*
         * Allocate all the callout tables based on max_ncpus. We have chosen
         * to do boot-time allocation instead of dynamic allocation because:
         *
         *      - the size of the callout tables is not too large.
         *      - there are race conditions involved in making this dynamic.
         *      - the hash tables that go with the callout tables consume
         *        most of the memory and they are only allocated in
         *        callout_cpu_online().
         *
         * Each CPU has two tables that are consecutive in the array. The first
         * one is for realtime callouts and the second one is for normal ones.
         *
         * We do this alignment dance to make sure that callout table
         * structures will always be on a cache line boundary.
         */
        size = sizeof (callout_table_t) * CALLOUT_NTYPES * max_ncpus;
        size += CALLOUT_ALIGN;
        buf = (uintptr_t)kmem_zalloc(size, KM_SLEEP);
        callout_table = (callout_table_t *)P2ROUNDUP(buf, CALLOUT_ALIGN);

        size = sizeof (kstat_named_t) * CALLOUT_NUM_STATS;
        /*
         * Now, initialize the tables for all the CPUs.
         */
        for (f = 0; f < max_ncpus; f++) {
                for (t = 0; t < CALLOUT_NTYPES; t++) {
                        table_id = CALLOUT_TABLE(t, f);
                        ct = &callout_table[table_id];
                        ct->ct_type = t;
                        mutex_init(&ct->ct_mutex, NULL, MUTEX_DEFAULT, NULL);
                        /*
                         * Precompute the base IDs for long and short-term
                         * legacy IDs. This makes ID generation during
                         * timeout() fast.
                         */
                        ct->ct_short_id = CALLOUT_SHORT_ID(table_id);
                        ct->ct_long_id = CALLOUT_LONG_ID(table_id);
                        /*
                         * Precompute the base ID for generation-based IDs.
                         * Note that when the first ID gets allocated, the
                         * ID will wrap. This will cause the generation
                         * number to be incremented to 1.
                         */
                        ct->ct_gen_id = CALLOUT_SHORT_ID(table_id);
                        /*
                         * Initialize the cyclics as NONE. This will get set
                         * during CPU online. This is so that partially
                         * populated systems will only have the required
                         * number of cyclics, not more.
                         */
                        ct->ct_cyclic = CYCLIC_NONE;
                        ct->ct_qcyclic = CYCLIC_NONE;
                        ct->ct_kstat_data = kmem_zalloc(size, KM_SLEEP);
                }
        }

        /*
         * Add the callback for CPR. This is called during checkpoint
         * resume to suspend and resume callouts.
         */
        (void) callb_add(callout_cpr_callb, 0, CB_CL_CPR_CALLOUT,
            "callout_cpr");
        (void) callb_add(callout_debug_callb, 0, CB_CL_ENTER_DEBUGGER,
            "callout_debug");

        /*
         * Call the per-CPU initialization function for the boot CPU. This
         * is done here because the function is not called automatically for
         * the boot CPU from the CPU online/offline hooks. Note that the
         * CPU lock is taken here because of convention.
         */
        mutex_enter(&cpu_lock);
        callout_boot_ct = &callout_table[CALLOUT_TABLE(0, CPU->cpu_seqid)];
        callout_cpu_online(CPU);
        mutex_exit(&cpu_lock);

        /* heads-up to boot-time clients that timeouts now available */
        callout_init_done = 1;
}