/*
 * 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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include "lint.h"
#include "thr_uberdata.h"
#include <stdlib.h>
#include <signal.h>
#include <errno.h>
#include "thread_pool_impl.h"

static mutex_t thread_pool_lock = DEFAULTMUTEX;
static tpool_t *thread_pools = NULL;

static void
delete_pool(tpool_t *tpool)
{
        tpool_job_t *job;

        ASSERT(tpool->tp_current == 0 && tpool->tp_active == NULL);

        /*
         * Unlink the pool from the global list of all pools.
         */
        lmutex_lock(&thread_pool_lock);
        if (thread_pools == tpool)
                thread_pools = tpool->tp_forw;
        if (thread_pools == tpool)
                thread_pools = NULL;
        else {
                tpool->tp_back->tp_forw = tpool->tp_forw;
                tpool->tp_forw->tp_back = tpool->tp_back;
        }
        lmutex_unlock(&thread_pool_lock);

        /*
         * There should be no pending jobs, but just in case...
         */
        for (job = tpool->tp_head; job != NULL; job = tpool->tp_head) {
                tpool->tp_head = job->tpj_next;
                lfree(job, sizeof (*job));
        }
        (void) pthread_attr_destroy(&tpool->tp_attr);
        lfree(tpool, sizeof (*tpool));
}

/*
 * Worker thread is terminating.
 */
static void
worker_cleanup(tpool_t *tpool)
{
        ASSERT(MUTEX_HELD(&tpool->tp_mutex));

        if (--tpool->tp_current == 0 &&
            (tpool->tp_flags & (TP_DESTROY | TP_ABANDON))) {
                if (tpool->tp_flags & TP_ABANDON) {
                        sig_mutex_unlock(&tpool->tp_mutex);
                        delete_pool(tpool);
                        return;
                }
                if (tpool->tp_flags & TP_DESTROY)
                        (void) cond_broadcast(&tpool->tp_busycv);
        }
        sig_mutex_unlock(&tpool->tp_mutex);
}

static void
notify_waiters(tpool_t *tpool)
{
        if (tpool->tp_head == NULL && tpool->tp_active == NULL) {
                tpool->tp_flags &= ~TP_WAIT;
                (void) cond_broadcast(&tpool->tp_waitcv);
        }
}

/*
 * Called by a worker thread on return from a tpool_dispatch()d job.
 */
static void
job_cleanup(tpool_t *tpool)
{
        pthread_t my_tid = pthread_self();
        tpool_active_t *activep;
        tpool_active_t **activepp;

        sig_mutex_lock(&tpool->tp_mutex);
        /* CSTYLED */
        for (activepp = &tpool->tp_active;; activepp = &activep->tpa_next) {
                activep = *activepp;
                if (activep->tpa_tid == my_tid) {
                        *activepp = activep->tpa_next;
                        break;
                }
        }
        if (tpool->tp_flags & TP_WAIT)
                notify_waiters(tpool);
}

static void *
tpool_worker(void *arg)
{
        tpool_t *tpool = (tpool_t *)arg;
        int elapsed;
        tpool_job_t *job;
        void (*func)(void *);
        tpool_active_t active;

        sig_mutex_lock(&tpool->tp_mutex);
        pthread_cleanup_push(worker_cleanup, tpool);

        /*
         * This is the worker's main loop.
         * It will only be left if a timeout or an error has occured.
         */
        active.tpa_tid = pthread_self();
        for (;;) {
                elapsed = 0;
                tpool->tp_idle++;
                if (tpool->tp_flags & TP_WAIT)
                        notify_waiters(tpool);
                while ((tpool->tp_head == NULL ||
                    (tpool->tp_flags & TP_SUSPEND)) &&
                    !(tpool->tp_flags & (TP_DESTROY | TP_ABANDON))) {
                        if (tpool->tp_current <= tpool->tp_minimum ||
                            tpool->tp_linger == 0) {
                                (void) sig_cond_wait(&tpool->tp_workcv,
                                    &tpool->tp_mutex);
                        } else {
                                timestruc_t timeout;

                                timeout.tv_sec = tpool->tp_linger;
                                timeout.tv_nsec = 0;
                                if (sig_cond_reltimedwait(&tpool->tp_workcv,
                                    &tpool->tp_mutex, &timeout) != 0) {
                                        elapsed = 1;
                                        break;
                                }
                        }
                }
                tpool->tp_idle--;
                if (tpool->tp_flags & TP_DESTROY)
                        break;
                if (tpool->tp_flags & TP_ABANDON) {
                        /* can't abandon a suspended pool */
                        if (tpool->tp_flags & TP_SUSPEND) {
                                tpool->tp_flags &= ~TP_SUSPEND;
                                (void) cond_broadcast(&tpool->tp_workcv);
                        }
                        if (tpool->tp_head == NULL)
                                break;
                }
                if ((job = tpool->tp_head) != NULL &&
                    !(tpool->tp_flags & TP_SUSPEND)) {
                        elapsed = 0;
                        func = job->tpj_func;
                        arg = job->tpj_arg;
                        tpool->tp_head = job->tpj_next;
                        if (job == tpool->tp_tail)
                                tpool->tp_tail = NULL;
                        tpool->tp_njobs--;
                        active.tpa_next = tpool->tp_active;
                        tpool->tp_active = &active;
                        sig_mutex_unlock(&tpool->tp_mutex);
                        pthread_cleanup_push(job_cleanup, tpool);
                        lfree(job, sizeof (*job));
                        /*
                         * Call the specified function.
                         */
                        func(arg);
                        /*
                         * We don't know what this thread has been doing,
                         * so we reset its signal mask and cancellation
                         * state back to the initial values.
                         */
                        (void) pthread_sigmask(SIG_SETMASK, &maskset, NULL);
                        (void) pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED,
                            NULL);
                        (void) pthread_setcancelstate(PTHREAD_CANCEL_ENABLE,
                            NULL);
                        pthread_cleanup_pop(1);
                }
                if (elapsed && tpool->tp_current > tpool->tp_minimum) {
                        /*
                         * We timed out and there is no work to be done
                         * and the number of workers exceeds the minimum.
                         * Exit now to reduce the size of the pool.
                         */
                        break;
                }
        }
        pthread_cleanup_pop(1);
        return (arg);
}

/*
 * Create a worker thread, with all signals blocked.
 */
static int
create_worker(tpool_t *tpool)
{
        sigset_t oset;
        int error;

        (void) pthread_sigmask(SIG_SETMASK, &maskset, &oset);
        error = pthread_create(NULL, &tpool->tp_attr, tpool_worker, tpool);
        (void) pthread_sigmask(SIG_SETMASK, &oset, NULL);
        return (error);
}

tpool_t *
tpool_create(uint_t min_threads, uint_t max_threads, uint_t linger,
        pthread_attr_t *attr)
{
        tpool_t *tpool;
        void *stackaddr;
        size_t stacksize;
        size_t minstack;
        int error;

        if (min_threads > max_threads || max_threads < 1) {
                errno = EINVAL;
                return (NULL);
        }
        if (attr != NULL) {
                if (pthread_attr_getstack(attr, &stackaddr, &stacksize) != 0) {
                        errno = EINVAL;
                        return (NULL);
                }
                /*
                 * Allow only one thread in the pool with a specified stack.
                 * Require threads to have at least the minimum stack size.
                 */
                minstack = thr_min_stack();
                if (stackaddr != NULL) {
                        if (stacksize < minstack || max_threads != 1) {
                                errno = EINVAL;
                                return (NULL);
                        }
                } else if (stacksize != 0 && stacksize < minstack) {
                        errno = EINVAL;
                        return (NULL);
                }
        }

        tpool = lmalloc(sizeof (*tpool));
        if (tpool == NULL) {
                errno = ENOMEM;
                return (NULL);
        }
        (void) mutex_init(&tpool->tp_mutex, USYNC_THREAD, NULL);
        (void) cond_init(&tpool->tp_busycv, USYNC_THREAD, NULL);
        (void) cond_init(&tpool->tp_workcv, USYNC_THREAD, NULL);
        (void) cond_init(&tpool->tp_waitcv, USYNC_THREAD, NULL);
        tpool->tp_minimum = min_threads;
        tpool->tp_maximum = max_threads;
        tpool->tp_linger = linger;

        /*
         * We cannot just copy the attribute pointer.
         * We need to initialize a new pthread_attr_t structure
         * with the values from the user-supplied pthread_attr_t.
         * If the attribute pointer is NULL, we need to initialize
         * the new pthread_attr_t structure with default values.
         */
        error = pthread_attr_clone(&tpool->tp_attr, attr);
        if (error) {
                lfree(tpool, sizeof (*tpool));
                errno = error;
                return (NULL);
        }

        /* make all pool threads be detached daemon threads */
        (void) pthread_attr_setdetachstate(&tpool->tp_attr,
            PTHREAD_CREATE_DETACHED);
        (void) pthread_attr_setdaemonstate_np(&tpool->tp_attr,
            PTHREAD_CREATE_DAEMON_NP);

        /* insert into the global list of all thread pools */
        lmutex_lock(&thread_pool_lock);
        if (thread_pools == NULL) {
                tpool->tp_forw = tpool;
                tpool->tp_back = tpool;
                thread_pools = tpool;
        } else {
                thread_pools->tp_back->tp_forw = tpool;
                tpool->tp_forw = thread_pools;
                tpool->tp_back = thread_pools->tp_back;
                thread_pools->tp_back = tpool;
        }
        lmutex_unlock(&thread_pool_lock);

        return (tpool);
}

/*
 * Dispatch a work request to the thread pool.
 * If there are idle workers, awaken one.
 * Else, if the maximum number of workers has
 * not been reached, spawn a new worker thread.
 * Else just return with the job added to the queue.
 */
int
tpool_dispatch(tpool_t *tpool, void (*func)(void *), void *arg)
{
        tpool_job_t *job;

        ASSERT(!(tpool->tp_flags & (TP_DESTROY | TP_ABANDON)));

        if ((job = lmalloc(sizeof (*job))) == NULL)
                return (-1);
        job->tpj_next = NULL;
        job->tpj_func = func;
        job->tpj_arg = arg;

        sig_mutex_lock(&tpool->tp_mutex);

        if (tpool->tp_head == NULL)
                tpool->tp_head = job;
        else
                tpool->tp_tail->tpj_next = job;
        tpool->tp_tail = job;
        tpool->tp_njobs++;

        if (!(tpool->tp_flags & TP_SUSPEND)) {
                if (tpool->tp_idle > 0)
                        (void) cond_signal(&tpool->tp_workcv);
                else if (tpool->tp_current < tpool->tp_maximum &&
                    create_worker(tpool) == 0)
                        tpool->tp_current++;
        }

        sig_mutex_unlock(&tpool->tp_mutex);
        return (0);
}

/*
 * Assumes: by the time tpool_destroy() is called no one will use this
 * thread pool in any way and no one will try to dispatch entries to it.
 * Calling tpool_destroy() from a job in the pool will cause deadlock.
 */
void
tpool_destroy(tpool_t *tpool)
{
        tpool_active_t *activep;

        ASSERT(!tpool_member(tpool));
        ASSERT(!(tpool->tp_flags & (TP_DESTROY | TP_ABANDON)));

        sig_mutex_lock(&tpool->tp_mutex);
        pthread_cleanup_push(sig_mutex_unlock, &tpool->tp_mutex);

        /* mark the pool as being destroyed; wakeup idle workers */
        tpool->tp_flags |= TP_DESTROY;
        tpool->tp_flags &= ~TP_SUSPEND;
        (void) cond_broadcast(&tpool->tp_workcv);

        /* cancel all active workers */
        for (activep = tpool->tp_active; activep; activep = activep->tpa_next)
                (void) pthread_cancel(activep->tpa_tid);

        /* wait for all active workers to finish */
        while (tpool->tp_active != NULL) {
                tpool->tp_flags |= TP_WAIT;
                (void) sig_cond_wait(&tpool->tp_waitcv, &tpool->tp_mutex);
        }

        /* the last worker to terminate will wake us up */
        while (tpool->tp_current != 0)
                (void) sig_cond_wait(&tpool->tp_busycv, &tpool->tp_mutex);

        pthread_cleanup_pop(1); /* sig_mutex_unlock(&tpool->tp_mutex); */
        delete_pool(tpool);
}

/*
 * Like tpool_destroy(), but don't cancel workers or wait for them to finish.
 * The last worker to terminate will delete the pool.
 */
void
tpool_abandon(tpool_t *tpool)
{
        ASSERT(!(tpool->tp_flags & (TP_DESTROY | TP_ABANDON)));

        sig_mutex_lock(&tpool->tp_mutex);
        if (tpool->tp_current == 0) {
                /* no workers, just delete the pool */
                sig_mutex_unlock(&tpool->tp_mutex);
                delete_pool(tpool);
        } else {
                /* wake up all workers, last one will delete the pool */
                tpool->tp_flags |= TP_ABANDON;
                tpool->tp_flags &= ~TP_SUSPEND;
                (void) cond_broadcast(&tpool->tp_workcv);
                sig_mutex_unlock(&tpool->tp_mutex);
        }
}

/*
 * Wait for all jobs to complete.
 * Calling tpool_wait() from a job in the pool will cause deadlock.
 */
void
tpool_wait(tpool_t *tpool)
{
        ASSERT(!tpool_member(tpool));
        ASSERT(!(tpool->tp_flags & (TP_DESTROY | TP_ABANDON)));

        sig_mutex_lock(&tpool->tp_mutex);
        pthread_cleanup_push(sig_mutex_unlock, &tpool->tp_mutex);
        while (tpool->tp_head != NULL || tpool->tp_active != NULL) {
                tpool->tp_flags |= TP_WAIT;
                (void) sig_cond_wait(&tpool->tp_waitcv, &tpool->tp_mutex);
                ASSERT(!(tpool->tp_flags & (TP_DESTROY | TP_ABANDON)));
        }
        pthread_cleanup_pop(1); /* sig_mutex_unlock(&tpool->tp_mutex); */
}

void
tpool_suspend(tpool_t *tpool)
{
        ASSERT(!(tpool->tp_flags & (TP_DESTROY | TP_ABANDON)));

        sig_mutex_lock(&tpool->tp_mutex);
        tpool->tp_flags |= TP_SUSPEND;
        sig_mutex_unlock(&tpool->tp_mutex);
}

int
tpool_suspended(tpool_t *tpool)
{
        int suspended;

        ASSERT(!(tpool->tp_flags & (TP_DESTROY | TP_ABANDON)));

        sig_mutex_lock(&tpool->tp_mutex);
        suspended = (tpool->tp_flags & TP_SUSPEND) != 0;
        sig_mutex_unlock(&tpool->tp_mutex);

        return (suspended);
}

void
tpool_resume(tpool_t *tpool)
{
        int excess;

        ASSERT(!(tpool->tp_flags & (TP_DESTROY | TP_ABANDON)));

        sig_mutex_lock(&tpool->tp_mutex);
        if (!(tpool->tp_flags & TP_SUSPEND)) {
                sig_mutex_unlock(&tpool->tp_mutex);
                return;
        }
        tpool->tp_flags &= ~TP_SUSPEND;
        (void) cond_broadcast(&tpool->tp_workcv);
        excess = tpool->tp_njobs - tpool->tp_idle;
        while (excess-- > 0 && tpool->tp_current < tpool->tp_maximum) {
                if (create_worker(tpool) != 0)
                        break;          /* pthread_create() failed */
                tpool->tp_current++;
        }
        sig_mutex_unlock(&tpool->tp_mutex);
}

int
tpool_member(tpool_t *tpool)
{
        pthread_t my_tid = pthread_self();
        tpool_active_t *activep;

        ASSERT(!(tpool->tp_flags & (TP_DESTROY | TP_ABANDON)));

        sig_mutex_lock(&tpool->tp_mutex);
        for (activep = tpool->tp_active; activep; activep = activep->tpa_next) {
                if (activep->tpa_tid == my_tid) {
                        sig_mutex_unlock(&tpool->tp_mutex);
                        return (1);
                }
        }
        sig_mutex_unlock(&tpool->tp_mutex);
        return (0);
}

void
postfork1_child_tpool(void)
{
        pthread_t my_tid = pthread_self();
        tpool_t *tpool;
        tpool_job_t *job;

        /*
         * All of the thread pool workers are gone, except possibly
         * for the current thread, if it is a thread pool worker thread.
         * Retain the thread pools, but make them all empty.  Whatever
         * jobs were queued or running belong to the parent process.
         */
top:
        if ((tpool = thread_pools) == NULL)
                return;

        do {
                tpool_active_t *activep;

                (void) mutex_init(&tpool->tp_mutex, USYNC_THREAD, NULL);
                (void) cond_init(&tpool->tp_busycv, USYNC_THREAD, NULL);
                (void) cond_init(&tpool->tp_workcv, USYNC_THREAD, NULL);
                (void) cond_init(&tpool->tp_waitcv, USYNC_THREAD, NULL);
                for (job = tpool->tp_head; job; job = tpool->tp_head) {
                        tpool->tp_head = job->tpj_next;
                        lfree(job, sizeof (*job));
                }
                tpool->tp_tail = NULL;
                tpool->tp_njobs = 0;
                for (activep = tpool->tp_active; activep;
                    activep = activep->tpa_next) {
                        if (activep->tpa_tid == my_tid) {
                                activep->tpa_next = NULL;
                                break;
                        }
                }
                tpool->tp_idle = 0;
                tpool->tp_current = 0;
                if ((tpool->tp_active = activep) != NULL)
                        tpool->tp_current = 1;
                tpool->tp_flags &= ~TP_WAIT;
                if (tpool->tp_flags & (TP_DESTROY | TP_ABANDON)) {
                        tpool->tp_flags &= ~TP_DESTROY;
                        tpool->tp_flags |= TP_ABANDON;
                        if (tpool->tp_current == 0) {
                                delete_pool(tpool);
                                goto top;       /* start over */
                        }
                }
        } while ((tpool = tpool->tp_forw) != thread_pools);
}