/*
 * 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 2010 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */
/*
 * Copyright 2012 Garrett D'Amore <garrett@damore.org>.  All rights reserved.
 * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
 * Copyright 2017 RackTop Systems.
 * Copyright 2018, Joyent, Inc.
 */

#include <sys/taskq_impl.h>

#include <sys/class.h>
#include <sys/debug.h>
#include <sys/ksynch.h>
#include <sys/kmem.h>
#include <sys/time.h>
#include <sys/systm.h>
#include <sys/sysmacros.h>
#include <sys/unistd.h>

/* avoid <sys/disp.h> */
#define maxclsyspri     99

/* avoid <unistd.h> */
extern long sysconf(int);

/* avoiding <thread.h> */
typedef unsigned int thread_t;
typedef unsigned int thread_key_t;

extern int thr_create(void *, size_t, void *(*)(void *), void *, long,
                        thread_t *);
extern int thr_join(thread_t, thread_t *, void **);

/*
 * POSIX.1c Note:
 * THR_BOUND is defined same as PTHREAD_SCOPE_SYSTEM in <pthread.h>
 * THR_DETACHED is defined same as PTHREAD_CREATE_DETACHED in <pthread.h>
 * Any changes in these definitions should be reflected in <pthread.h>
 */
#define THR_BOUND               0x00000001      /* = PTHREAD_SCOPE_SYSTEM */
#define THR_NEW_LWP             0x00000002
#define THR_DETACHED            0x00000040      /* = PTHREAD_CREATE_DETACHED */
#define THR_SUSPENDED           0x00000080
#define THR_DAEMON              0x00000100


int taskq_now;
taskq_t *system_taskq;

#define TASKQ_ACTIVE    0x00010000

struct taskq {
        kmutex_t        tq_lock;
        krwlock_t       tq_threadlock;
        kcondvar_t      tq_dispatch_cv;
        kcondvar_t      tq_wait_cv;
        thread_t        *tq_threadlist;
        int             tq_flags;
        int             tq_active;
        int             tq_nthreads;
        int             tq_nalloc;
        int             tq_minalloc;
        int             tq_maxalloc;
        kcondvar_t      tq_maxalloc_cv;
        int             tq_maxalloc_wait;
        taskq_ent_t     *tq_freelist;
        taskq_ent_t     tq_task;
};

static taskq_ent_t *
task_alloc(taskq_t *tq, int tqflags)
{
        taskq_ent_t *t;
        int rv;

again:  if ((t = tq->tq_freelist) != NULL && tq->tq_nalloc >= tq->tq_minalloc) {
                tq->tq_freelist = t->tqent_next;
        } else {
                if (tq->tq_nalloc >= tq->tq_maxalloc) {
                        if (tqflags & KM_NOSLEEP)
                                return (NULL);

                        /*
                         * We don't want to exceed tq_maxalloc, but we can't
                         * wait for other tasks to complete (and thus free up
                         * task structures) without risking deadlock with
                         * the caller.  So, we just delay for one second
                         * to throttle the allocation rate. If we have tasks
                         * complete before one second timeout expires then
                         * taskq_ent_free will signal us and we will
                         * immediately retry the allocation.
                         */
                        tq->tq_maxalloc_wait++;
                        rv = cv_timedwait(&tq->tq_maxalloc_cv,
                            &tq->tq_lock, ddi_get_lbolt() + hz);
                        tq->tq_maxalloc_wait--;
                        if (rv > 0)
                                goto again;             /* signaled */
                }
                mutex_exit(&tq->tq_lock);

                t = kmem_alloc(sizeof (taskq_ent_t), tqflags);

                mutex_enter(&tq->tq_lock);
                if (t != NULL)
                        tq->tq_nalloc++;
        }
        return (t);
}

static void
task_free(taskq_t *tq, taskq_ent_t *t)
{
        if (tq->tq_nalloc <= tq->tq_minalloc) {
                t->tqent_next = tq->tq_freelist;
                tq->tq_freelist = t;
        } else {
                tq->tq_nalloc--;
                mutex_exit(&tq->tq_lock);
                kmem_free(t, sizeof (taskq_ent_t));
                mutex_enter(&tq->tq_lock);
        }

        if (tq->tq_maxalloc_wait)
                cv_signal(&tq->tq_maxalloc_cv);
}

taskqid_t
taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t tqflags)
{
        taskq_ent_t *t;

        if (taskq_now) {
                func(arg);
                return (1);
        }

        mutex_enter(&tq->tq_lock);
        ASSERT(tq->tq_flags & TASKQ_ACTIVE);
        if ((t = task_alloc(tq, tqflags)) == NULL) {
                mutex_exit(&tq->tq_lock);
                return (TASKQID_INVALID);
        }
        if (tqflags & TQ_FRONT) {
                t->tqent_next = tq->tq_task.tqent_next;
                t->tqent_prev = &tq->tq_task;
        } else {
                t->tqent_next = &tq->tq_task;
                t->tqent_prev = tq->tq_task.tqent_prev;
        }
        t->tqent_next->tqent_prev = t;
        t->tqent_prev->tqent_next = t;
        t->tqent_func = func;
        t->tqent_arg = arg;
        t->tqent_flags = 0;
        cv_signal(&tq->tq_dispatch_cv);
        mutex_exit(&tq->tq_lock);
        return (1);
}

void
taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
    taskq_ent_t *t)
{
        ASSERT(func != NULL);
        ASSERT(!(tq->tq_flags & TASKQ_DYNAMIC));

        /*
         * Mark it as a prealloc'd task.  This is important
         * to ensure that we don't free it later.
         */
        t->tqent_flags |= TQENT_FLAG_PREALLOC;
        /*
         * Enqueue the task to the underlying queue.
         */
        mutex_enter(&tq->tq_lock);

        if (flags & TQ_FRONT) {
                t->tqent_next = tq->tq_task.tqent_next;
                t->tqent_prev = &tq->tq_task;
        } else {
                t->tqent_next = &tq->tq_task;
                t->tqent_prev = tq->tq_task.tqent_prev;
        }
        t->tqent_next->tqent_prev = t;
        t->tqent_prev->tqent_next = t;
        t->tqent_func = func;
        t->tqent_arg = arg;
        cv_signal(&tq->tq_dispatch_cv);
        mutex_exit(&tq->tq_lock);
}

boolean_t
taskq_empty(taskq_t *tq)
{
        boolean_t rv;

        mutex_enter(&tq->tq_lock);
        rv = (tq->tq_task.tqent_next == &tq->tq_task) && (tq->tq_active == 0);
        mutex_exit(&tq->tq_lock);

        return (rv);
}

void
taskq_wait(taskq_t *tq)
{
        mutex_enter(&tq->tq_lock);
        while (tq->tq_task.tqent_next != &tq->tq_task || tq->tq_active != 0)
                cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
        mutex_exit(&tq->tq_lock);
}

void
taskq_wait_id(taskq_t *tq, taskqid_t id __unused)
{
        taskq_wait(tq);
}

static void *
taskq_thread(void *arg)
{
        taskq_t *tq = arg;
        taskq_ent_t *t;
        boolean_t prealloc;

        mutex_enter(&tq->tq_lock);
        while (tq->tq_flags & TASKQ_ACTIVE) {
                if ((t = tq->tq_task.tqent_next) == &tq->tq_task) {
                        if (--tq->tq_active == 0)
                                cv_broadcast(&tq->tq_wait_cv);
                        cv_wait(&tq->tq_dispatch_cv, &tq->tq_lock);
                        tq->tq_active++;
                        continue;
                }
                t->tqent_prev->tqent_next = t->tqent_next;
                t->tqent_next->tqent_prev = t->tqent_prev;
                t->tqent_next = NULL;
                t->tqent_prev = NULL;
                prealloc = t->tqent_flags & TQENT_FLAG_PREALLOC;
                mutex_exit(&tq->tq_lock);

                rw_enter(&tq->tq_threadlock, RW_READER);
                t->tqent_func(t->tqent_arg);
                rw_exit(&tq->tq_threadlock);

                mutex_enter(&tq->tq_lock);
                if (!prealloc)
                        task_free(tq, t);
        }
        tq->tq_nthreads--;
        cv_broadcast(&tq->tq_wait_cv);
        mutex_exit(&tq->tq_lock);
        return (NULL);
}

/*ARGSUSED*/
taskq_t *
taskq_create(const char *name, int nthr, pri_t pri, int minalloc,
    int maxalloc, uint_t flags)
{
        return (taskq_create_proc(name, nthr, pri,
            minalloc, maxalloc, NULL, flags));
}

/*ARGSUSED*/
taskq_t *
taskq_create_sysdc(const char *name, int nthr, int minalloc,
    int maxalloc, proc_t *proc, uint_t dc, uint_t flags)
{
        return (taskq_create_proc(name, nthr, maxclsyspri,
            minalloc, maxalloc, proc, flags));
}

/*ARGSUSED*/
taskq_t *
taskq_create_proc(const char *name, int nthreads, pri_t pri,
    int minalloc, int maxalloc, proc_t *proc, uint_t flags)
{
        taskq_t *tq = kmem_zalloc(sizeof (taskq_t), KM_SLEEP);
        int t;

        if (flags & TASKQ_THREADS_CPU_PCT) {
                int pct;
                ASSERT3S(nthreads, >=, 0);
                ASSERT3S(nthreads, <=, 100);
                pct = MIN(nthreads, 100);
                pct = MAX(pct, 0);

                nthreads = (sysconf(_SC_NPROCESSORS_ONLN) * pct) / 100;
                nthreads = MAX(nthreads, 1);    /* need at least 1 thread */
        } else {
                ASSERT3S(nthreads, >=, 1);
        }

        rw_init(&tq->tq_threadlock, NULL, RW_DEFAULT, NULL);
        mutex_init(&tq->tq_lock, NULL, MUTEX_DEFAULT, NULL);
        cv_init(&tq->tq_dispatch_cv, NULL, CV_DEFAULT, NULL);
        cv_init(&tq->tq_wait_cv, NULL, CV_DEFAULT, NULL);
        cv_init(&tq->tq_maxalloc_cv, NULL, CV_DEFAULT, NULL);
        tq->tq_flags = flags | TASKQ_ACTIVE;
        tq->tq_active = nthreads;
        tq->tq_nthreads = nthreads;
        tq->tq_minalloc = minalloc;
        tq->tq_maxalloc = maxalloc;
        tq->tq_task.tqent_next = &tq->tq_task;
        tq->tq_task.tqent_prev = &tq->tq_task;
        tq->tq_threadlist = kmem_alloc(nthreads * sizeof (thread_t), KM_SLEEP);

        if (flags & TASKQ_PREPOPULATE) {
                mutex_enter(&tq->tq_lock);
                while (minalloc-- > 0)
                        task_free(tq, task_alloc(tq, KM_SLEEP));
                mutex_exit(&tq->tq_lock);
        }

        for (t = 0; t < nthreads; t++)
                (void) thr_create(0, 0, taskq_thread,
                    tq, THR_BOUND, &tq->tq_threadlist[t]);

        return (tq);
}

void
taskq_destroy(taskq_t *tq)
{
        int t;
        int nthreads = tq->tq_nthreads;

        taskq_wait(tq);

        mutex_enter(&tq->tq_lock);

        tq->tq_flags &= ~TASKQ_ACTIVE;
        cv_broadcast(&tq->tq_dispatch_cv);

        while (tq->tq_nthreads != 0)
                cv_wait(&tq->tq_wait_cv, &tq->tq_lock);

        tq->tq_minalloc = 0;
        while (tq->tq_nalloc != 0) {
                ASSERT(tq->tq_freelist != NULL);
                task_free(tq, task_alloc(tq, KM_SLEEP));
        }

        mutex_exit(&tq->tq_lock);

        for (t = 0; t < nthreads; t++)
                (void) thr_join(tq->tq_threadlist[t], NULL, NULL);

        kmem_free(tq->tq_threadlist, nthreads * sizeof (thread_t));

        rw_destroy(&tq->tq_threadlock);
        mutex_destroy(&tq->tq_lock);
        cv_destroy(&tq->tq_dispatch_cv);
        cv_destroy(&tq->tq_wait_cv);
        cv_destroy(&tq->tq_maxalloc_cv);

        kmem_free(tq, sizeof (taskq_t));
}

int
taskq_member(taskq_t *tq, struct _kthread *t)
{
        int i;

        if (taskq_now)
                return (1);

        for (i = 0; i < tq->tq_nthreads; i++)
                if (tq->tq_threadlist[i] == (thread_t)(uintptr_t)t)
                        return (1);

        return (0);
}

void
system_taskq_init(void)
{
        system_taskq = taskq_create("system_taskq", 64, minclsyspri, 4, 512,
            TASKQ_DYNAMIC | TASKQ_PREPOPULATE);
}

void
system_taskq_fini(void)
{
        taskq_destroy(system_taskq);
        system_taskq = NULL; /* defensive */
}