mpm/worker/fdqueue.c

	fdqueue.c revision ffaf5de7264cede655067f4425ab64c88578b7ff
/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2000-2002 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 * Portions of this software are based upon public domain software
 * originally written at the National Center for Supercomputing Applications,
 * University of Illinois, Urbana-Champaign.
 */

#include "fdqueue.h"

struct fd_queue_info_t {
    int idlers;
    apr_thread_mutex_t *idlers_mutex;
    apr_thread_cond_t *wait_for_idler;
    int terminated;
};

static apr_status_t queue_info_cleanup(void *data_)
{
    fd_queue_info_t *qi = data_;
    apr_thread_cond_destroy(qi->wait_for_idler);
    apr_thread_mutex_destroy(qi->idlers_mutex);
    return APR_SUCCESS;
}

apr_status_t ap_queue_info_create(fd_queue_info_t **queue_info,
                                  apr_pool_t *pool)
{
    apr_status_t rv;
    fd_queue_info_t *qi;

    qi = apr_palloc(pool, sizeof(*qi));
    memset(qi, 0, sizeof(*qi));

    rv = apr_thread_mutex_create(&qi->idlers_mutex, APR_THREAD_MUTEX_DEFAULT,
                                 pool);
    if (rv != APR_SUCCESS) {
        return rv;
    }
    rv = apr_thread_cond_create(&qi->wait_for_idler, pool);
    if (rv != APR_SUCCESS) {
        return rv;
    }
    apr_pool_cleanup_register(pool, qi, queue_info_cleanup,
                              apr_pool_cleanup_null);

    *queue_info = qi;

    return APR_SUCCESS;
}

apr_status_t ap_queue_info_set_idle(fd_queue_info_t *queue_info)
{
    apr_status_t rv;
    rv = apr_thread_mutex_lock(queue_info->idlers_mutex);
    if (rv != APR_SUCCESS) {
        return rv;
    }
    AP_DEBUG_ASSERT(queue_info->idlers >= 0);
    if (queue_info->idlers++ == 0) {
        /* Only signal if we had no idlers before. */
        apr_thread_cond_signal(queue_info->wait_for_idler);
    }
    rv = apr_thread_mutex_unlock(queue_info->idlers_mutex);
    if (rv != APR_SUCCESS) {
        return rv;
    }
    return APR_SUCCESS;
}

apr_status_t ap_queue_info_wait_for_idler(fd_queue_info_t *queue_info)
{
    apr_status_t rv;
    rv = apr_thread_mutex_lock(queue_info->idlers_mutex);
    if (rv != APR_SUCCESS) {
        return rv;
    }
    AP_DEBUG_ASSERT(queue_info->idlers >= 0);
    while ((queue_info->idlers == 0) && (!queue_info->terminated)) {
        rv = apr_thread_cond_wait(queue_info->wait_for_idler,
                                  queue_info->idlers_mutex);
        if (rv != APR_SUCCESS) {
            apr_status_t rv2;
            rv2 = apr_thread_mutex_unlock(queue_info->idlers_mutex);
            if (rv2 != APR_SUCCESS) {
                return rv2;
            }
            return rv;
        }
    }
    queue_info->idlers--; /* Oh, and idler? Let's take 'em! */
    rv = apr_thread_mutex_unlock(queue_info->idlers_mutex);
    if (rv != APR_SUCCESS) {
        return rv;
    }
    else if (queue_info->terminated) {
        return APR_EOF;
    }
    else {
        return APR_SUCCESS;
    }
}

apr_status_t ap_queue_info_term(fd_queue_info_t *queue_info)
{
    apr_status_t rv;
    rv = apr_thread_mutex_lock(queue_info->idlers_mutex);
    if (rv != APR_SUCCESS) {
        return rv;
    }
    queue_info->terminated = 1;
    apr_thread_cond_broadcast(queue_info->wait_for_idler);
    rv = apr_thread_mutex_unlock(queue_info->idlers_mutex);
    if (rv != APR_SUCCESS) {
        return rv;
    }
    return APR_SUCCESS;
}

/**
 * Detects when the fd_queue_t is full. This utility function is expected
 * to be called from within critical sections, and is not threadsafe.
 */
#define ap_queue_full(queue) ((queue)->nelts == (queue)->bounds)

/**
 * Detects when the fd_queue_t is empty. This utility function is expected
 * to be called from within critical sections, and is not threadsafe.
 */
#define ap_queue_empty(queue) ((queue)->nelts == 0)

/**
 * Callback routine that is called to destroy this
 * fd_queue_t when its pool is destroyed.
 */
static apr_status_t ap_queue_destroy(void *data)
{
    fd_queue_t *queue = data;

    /* Ignore errors here, we can't do anything about them anyway.
     * XXX: We should at least try to signal an error here, it is
     * indicative of a programmer error. -aaron */
    apr_thread_cond_destroy(queue->not_empty);
    apr_thread_cond_destroy(queue->not_full);
    apr_thread_mutex_destroy(queue->one_big_mutex);

    return APR_SUCCESS;
}

/**
 * Initialize the fd_queue_t.
 */
apr_status_t ap_queue_init(fd_queue_t *queue, int queue_capacity, apr_pool_t *a)
{
    int i;
    apr_status_t rv;

    if ((rv = apr_thread_mutex_create(&queue->one_big_mutex,
                                      APR_THREAD_MUTEX_DEFAULT, a)) != APR_SUCCESS) {
        return rv;
    }
    if ((rv = apr_thread_cond_create(&queue->not_empty, a)) != APR_SUCCESS) {
        return rv;
    }
    if ((rv = apr_thread_cond_create(&queue->not_full, a)) != APR_SUCCESS) {
        return rv;
    }

    queue->head = queue->tail = 0;
    queue->data = apr_palloc(a, queue_capacity * sizeof(fd_queue_elem_t));
    queue->bounds = queue_capacity;
    queue->nelts = 0;

    /* Set all the sockets in the queue to NULL */
    for (i = 0; i < queue_capacity; ++i)
        queue->data[i].sd = NULL;

    queue->recycled_pools = apr_palloc(a,
                                       queue_capacity * sizeof(apr_pool_t *));
    queue->num_recycled = 0;

    apr_pool_cleanup_register(a, queue, ap_queue_destroy, apr_pool_cleanup_null);

    return APR_SUCCESS;
}

/**
 * Push a new socket onto the queue. Blocks if the queue is full. Once
 * the push operation has completed, it signals other threads waiting
 * in apr_queue_pop() that they may continue consuming sockets.
 */
apr_status_t ap_queue_push(fd_queue_t *queue, apr_socket_t *sd, apr_pool_t *p,
                           apr_pool_t **recycled_pool)
{
    fd_queue_elem_t *elem;
    apr_status_t rv;

    *recycled_pool = NULL;
    if ((rv = apr_thread_mutex_lock(queue->one_big_mutex)) != APR_SUCCESS) {
        return rv;
    }

    AP_DEBUG_ASSERT(!queue->terminated);

    while (ap_queue_full(queue)) {
        apr_thread_cond_wait(queue->not_full, queue->one_big_mutex);
    }

    elem = &queue->data[queue->tail];
    queue->tail = (queue->tail + 1) % queue->bounds;
    elem->sd = sd;
    elem->p = p;
    queue->nelts++;

    if (queue->num_recycled != 0) {
        *recycled_pool = queue->recycled_pools[--queue->num_recycled];
    }

    apr_thread_cond_signal(queue->not_empty);

    if ((rv = apr_thread_mutex_unlock(queue->one_big_mutex)) != APR_SUCCESS) {
        return rv;
    }

    return APR_SUCCESS;
}

/**
 * Retrieves the next available socket from the queue. If there are no
 * sockets available, it will block until one becomes available.
 * Once retrieved, the socket is placed into the address specified by
 * 'sd'.
 */
apr_status_t ap_queue_pop(fd_queue_t *queue, apr_socket_t **sd, apr_pool_t **p,
                          apr_pool_t *recycled_pool)
{
    fd_queue_elem_t *elem;
    apr_status_t rv;

    if ((rv = apr_thread_mutex_lock(queue->one_big_mutex)) != APR_SUCCESS) {
        if (recycled_pool) {
            apr_pool_destroy(recycled_pool);
        }
        return rv;
    }

    if (recycled_pool) {
        if (queue->num_recycled < queue->bounds) {
            queue->recycled_pools[queue->num_recycled++] = recycled_pool;
        }
        else {
            apr_pool_destroy(recycled_pool);
        }
    }

    /* Keep waiting until we wake up and find that the queue is not empty. */
    if (ap_queue_empty(queue)) {
        if (!queue->terminated) {
            apr_thread_cond_wait(queue->not_empty, queue->one_big_mutex);
        }
        /* If we wake up and it's still empty, then we were interrupted */
        if (ap_queue_empty(queue)) {
            if ((rv = apr_thread_mutex_unlock(queue->one_big_mutex)) != APR_SUCCESS) {
                return rv;
            }
            if (queue->terminated) {
                return APR_EOF; /* no more elements ever again */
            }
            else {
                return APR_EINTR;
            }
        }
    }

    elem = &queue->data[queue->head];
    queue->head = (queue->head + 1) % queue->bounds;
    *sd = elem->sd;
    *p = elem->p;
    elem->sd = NULL;
    elem->p = NULL;
    queue->nelts--;

    /* signal not_full if we were full before this pop */
    if (queue->nelts == queue->bounds - 1) {
        apr_thread_cond_signal(queue->not_full);
    }

    if ((rv = apr_thread_mutex_unlock(queue->one_big_mutex)) != APR_SUCCESS) {
        return rv;
    }

    return APR_SUCCESS;
}

apr_status_t ap_queue_interrupt_all(fd_queue_t *queue)
{
    apr_status_t rv;

    if ((rv = apr_thread_mutex_lock(queue->one_big_mutex)) != APR_SUCCESS) {
        return rv;
    }
    apr_thread_cond_broadcast(queue->not_empty);
    /* We shouldn't have multiple threads sitting in not_full, but
     * broadcast just in case. */
    apr_thread_cond_broadcast(queue->not_full);
    if ((rv = apr_thread_mutex_unlock(queue->one_big_mutex)) != APR_SUCCESS) {
        return rv;
    }
    return APR_SUCCESS;
}

apr_status_t ap_queue_term(fd_queue_t *queue)
{
    apr_status_t rv;

    if ((rv = apr_thread_mutex_lock(queue->one_big_mutex)) != APR_SUCCESS) {
        return rv;
    }
    /* we must hold one_big_mutex when setting this... otherwise,
     * we could end up setting it and waking everybody up just after a
     * would-be popper checks it but right before they block
     */
    queue->terminated = 1;
    if ((rv = apr_thread_mutex_unlock(queue->one_big_mutex)) != APR_SUCCESS) {
        return rv;
    }
    return ap_queue_interrupt_all(queue);
}