source: trunk/server/source3/lib/pthreadpool/pthreadpool.c@ 898

/*
 * Unix SMB/CIFS implementation.
 * thread pool implementation
 * Copyright (C) Volker Lendecke 2009
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <errno.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <signal.h>
#include <assert.h>
#include <fcntl.h>
#include <sys/time.h>

#include "pthreadpool.h"
#include "lib/util/dlinklist.h"
#ifdef __OS2__
#define pipe(A) os2_pipe(A)
#endif

struct pthreadpool_job {
        struct pthreadpool_job *next;
        int id;
        void (*fn)(void *private_data);
        void *private_data;
};

struct pthreadpool {
        /*
         * List pthreadpools for fork safety
         */
        struct pthreadpool *prev, *next;

        /*
         * Control access to this struct
         */
        pthread_mutex_t mutex;

        /*
         * Threads waiting for work do so here
         */
        pthread_cond_t condvar;

        /*
         * List of work jobs
         */
        struct pthreadpool_job *jobs, *last_job;

        /*
         * pipe for signalling
         */
        int sig_pipe[2];

        /*
         * indicator to worker threads that they should shut down
         */
        int shutdown;

        /*
         * maximum number of threads
         */
        int max_threads;

        /*
         * Number of threads
         */
        int num_threads;

        /*
         * Number of idle threads
         */
        int num_idle;

        /*
         * An array of threads that require joining.
         */
        int                     num_exited;
        pthread_t               *exited; /* We alloc more */
};

static pthread_mutex_t pthreadpools_mutex = PTHREAD_MUTEX_INITIALIZER;
static struct pthreadpool *pthreadpools = NULL;
static pthread_once_t pthreadpool_atfork_initialized = PTHREAD_ONCE_INIT;

static void pthreadpool_prep_atfork(void);

/*
 * Initialize a thread pool
 */

int pthreadpool_init(unsigned max_threads, struct pthreadpool **presult)
{
        struct pthreadpool *pool;
        int ret;

        pool = (struct pthreadpool *)malloc(sizeof(struct pthreadpool));
        if (pool == NULL) {
                return ENOMEM;
        }

        ret = pipe(pool->sig_pipe);
        if (ret == -1) {
                int err = errno;
                free(pool);
                return err;
        }

        ret = pthread_mutex_init(&pool->mutex, NULL);
        if (ret != 0) {
                close(pool->sig_pipe[0]);
                close(pool->sig_pipe[1]);
                free(pool);
                return ret;
        }

        ret = pthread_cond_init(&pool->condvar, NULL);
        if (ret != 0) {
                pthread_mutex_destroy(&pool->mutex);
                close(pool->sig_pipe[0]);
                close(pool->sig_pipe[1]);
                free(pool);
                return ret;
        }

        pool->shutdown = 0;
        pool->jobs = pool->last_job = NULL;
        pool->num_threads = 0;
        pool->num_exited = 0;
        pool->exited = NULL;
        pool->max_threads = max_threads;
        pool->num_idle = 0;

        ret = pthread_mutex_lock(&pthreadpools_mutex);
        if (ret != 0) {
                pthread_cond_destroy(&pool->condvar);
                pthread_mutex_destroy(&pool->mutex);
                close(pool->sig_pipe[0]);
                close(pool->sig_pipe[1]);
                free(pool);
                return ret;
        }
        DLIST_ADD(pthreadpools, pool);

        ret = pthread_mutex_unlock(&pthreadpools_mutex);
        assert(ret == 0);

        pthread_once(&pthreadpool_atfork_initialized, pthreadpool_prep_atfork);

        *presult = pool;

        return 0;
}

static void pthreadpool_prepare(void)
{
        int ret;
        struct pthreadpool *pool;

        ret = pthread_mutex_lock(&pthreadpools_mutex);
        assert(ret == 0);

        pool = pthreadpools;

        while (pool != NULL) {
                ret = pthread_mutex_lock(&pool->mutex);
                assert(ret == 0);
                pool = pool->next;
        }
}

static void pthreadpool_parent(void)
{
        int ret;
        struct pthreadpool *pool;

        pool = DLIST_TAIL(pthreadpools);

        while (1) {
                ret = pthread_mutex_unlock(&pool->mutex);
                assert(ret == 0);

                if (pool == pthreadpools) {
                        break;
                }
                pool = pool->prev;
        }

        ret = pthread_mutex_unlock(&pthreadpools_mutex);
        assert(ret == 0);
}

static void pthreadpool_child(void)
{
        int ret;
        struct pthreadpool *pool;

        pool = DLIST_TAIL(pthreadpools);

        while (1) {
                close(pool->sig_pipe[0]);
                close(pool->sig_pipe[1]);

                ret = pipe(pool->sig_pipe);
                assert(ret == 0);

                pool->num_threads = 0;

                pool->num_exited = 0;
                free(pool->exited);
                pool->exited = NULL;

                pool->num_idle = 0;

                while (pool->jobs != NULL) {
                        struct pthreadpool_job *job;
                        job = pool->jobs;
                        pool->jobs = job->next;
                        free(job);
                }
                pool->last_job = NULL;

                ret = pthread_mutex_unlock(&pool->mutex);
                assert(ret == 0);

                if (pool == pthreadpools) {
                        break;
                }
                pool = pool->prev;
        }

        ret = pthread_mutex_unlock(&pthreadpools_mutex);
        assert(ret == 0);
}

static void pthreadpool_prep_atfork(void)
{
        pthread_atfork(pthreadpool_prepare, pthreadpool_parent,
                       pthreadpool_child);
}

/*
 * Return the file descriptor which becomes readable when a job has
 * finished
 */

int pthreadpool_signal_fd(struct pthreadpool *pool)
{
        return pool->sig_pipe[0];
}

/*
 * Do a pthread_join() on all children that have exited, pool->mutex must be
 * locked
 */
static void pthreadpool_join_children(struct pthreadpool *pool)
{
        int i;

        for (i=0; i<pool->num_exited; i++) {
                pthread_join(pool->exited[i], NULL);
        }
        pool->num_exited = 0;

        /*
         * Deliberately not free and NULL pool->exited. That will be
         * re-used by realloc later.
         */
}

/*
 * Fetch a finished job number from the signal pipe
 */

int pthreadpool_finished_job(struct pthreadpool *pool, int *jobid)
{
        int ret_jobid;
        ssize_t nread;

        nread = -1;
        errno = EINTR;

        while ((nread == -1) && (errno == EINTR)) {
                nread = read(pool->sig_pipe[0], &ret_jobid, sizeof(int));
        }
        if (nread == -1) {
                return errno;
        }
        if (nread != sizeof(int)) {
                return EINVAL;
        }
        *jobid = ret_jobid;
        return 0;
}

/*
 * Destroy a thread pool, finishing all threads working for it
 */

int pthreadpool_destroy(struct pthreadpool *pool)
{
        int ret, ret1;

        ret = pthread_mutex_lock(&pool->mutex);
        if (ret != 0) {
                return ret;
        }

        if ((pool->jobs != NULL) || pool->shutdown) {
                ret = pthread_mutex_unlock(&pool->mutex);
                assert(ret == 0);
                return EBUSY;
        }

        if (pool->num_threads > 0) {
                /*
                 * We have active threads, tell them to finish, wait for that.
                 */

                pool->shutdown = 1;

                if (pool->num_idle > 0) {
                        /*
                         * Wake the idle threads. They will find pool->quit to
                         * be set and exit themselves
                         */
                        ret = pthread_cond_broadcast(&pool->condvar);
                        if (ret != 0) {
                                pthread_mutex_unlock(&pool->mutex);
                                return ret;
                        }
                }

                while ((pool->num_threads > 0) || (pool->num_exited > 0)) {

                        if (pool->num_exited > 0) {
                                pthreadpool_join_children(pool);
                                continue;
                        }