Adding upstream version 2.4.38.upstream/2.4.38upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1513 insertions, 0 deletions

diff --git a/server/mpm/prefork/prefork.c b/server/mpm/prefork/prefork.c
new file mode 100644
index 0000000..8efda72
--- /dev/null
+++ b/server/mpm/prefork/prefork.c
@@ -0,0 +1,1513 @@
+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "apr.h"
+#include "apr_portable.h"
+#include "apr_strings.h"
+#include "apr_thread_proc.h"
+#include "apr_signal.h"
+
+#define APR_WANT_STDIO
+#define APR_WANT_STRFUNC
+#include "apr_want.h"
+
+#if APR_HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#if APR_HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+
+#include "ap_config.h"
+#include "httpd.h"
+#include "mpm_default.h"
+#include "http_main.h"
+#include "http_log.h"
+#include "http_config.h"
+#include "http_core.h"          /* for get_remote_host */
+#include "http_connection.h"
+#include "scoreboard.h"
+#include "ap_mpm.h"
+#include "util_mutex.h"
+#include "unixd.h"
+#include "mpm_common.h"
+#include "ap_listen.h"
+#include "ap_mmn.h"
+#include "apr_poll.h"
+
+#include <stdlib.h>
+
+#ifdef HAVE_TIME_H
+#include <time.h>
+#endif
+#ifdef HAVE_SYS_PROCESSOR_H
+#include <sys/processor.h> /* for bindprocessor() */
+#endif
+
+#include <signal.h>
+#include <sys/times.h>
+
+/* Limit on the total --- clients will be locked out if more servers than
+ * this are needed.  It is intended solely to keep the server from crashing
+ * when things get out of hand.
+ *
+ * We keep a hard maximum number of servers, for two reasons --- first off,
+ * in case something goes seriously wrong, we want to stop the fork bomb
+ * short of actually crashing the machine we're running on by filling some
+ * kernel table.  Secondly, it keeps the size of the scoreboard file small
+ * enough that we can read the whole thing without worrying too much about
+ * the overhead.
+ */
+#ifndef DEFAULT_SERVER_LIMIT
+#define DEFAULT_SERVER_LIMIT 256
+#endif
+
+/* Admin can't tune ServerLimit beyond MAX_SERVER_LIMIT.  We want
+ * some sort of compile-time limit to help catch typos.
+ */
+#ifndef MAX_SERVER_LIMIT
+#define MAX_SERVER_LIMIT 200000
+#endif
+
+#ifndef HARD_THREAD_LIMIT
+#define HARD_THREAD_LIMIT 1
+#endif
+
+/* config globals */
+
+static int ap_daemons_to_start=0;
+static int ap_daemons_min_free=0;
+static int ap_daemons_max_free=0;
+static int ap_daemons_limit=0;      /* MaxRequestWorkers */
+static int server_limit = 0;
+
+/* data retained by prefork across load/unload of the module
+ * allocated on first call to pre-config hook; located on
+ * subsequent calls to pre-config hook
+ */
+typedef struct prefork_retained_data {
+    ap_unixd_mpm_retained_data *mpm;
+
+    int first_server_limit;
+    int maxclients_reported;
+    /*
+     * The max child slot ever assigned, preserved across restarts.  Necessary
+     * to deal with MaxRequestWorkers changes across AP_SIG_GRACEFUL restarts.  We
+     * use this value to optimize routines that have to scan the entire scoreboard.
+     */
+    int max_daemons_limit;
+    /*
+     * idle_spawn_rate is the number of children that will be spawned on the
+     * next maintenance cycle if there aren't enough idle servers.  It is
+     * doubled up to MAX_SPAWN_RATE, and reset only when a cycle goes by
+     * without the need to spawn.
+     */
+    int idle_spawn_rate;
+#ifndef MAX_SPAWN_RATE
+#define MAX_SPAWN_RATE  (32)
+#endif
+    int hold_off_on_exponential_spawning;
+} prefork_retained_data;
+static prefork_retained_data *retained;
+
+typedef struct prefork_child_bucket {
+    ap_pod_t *pod;
+    ap_listen_rec *listeners;
+    apr_proc_mutex_t *mutex;
+} prefork_child_bucket;
+static prefork_child_bucket *all_buckets, /* All listeners buckets */
+                            *my_bucket;   /* Current child bucket */
+
+#define MPM_CHILD_PID(i) (ap_scoreboard_image->parent[i].pid)
+
+/* one_process --- debugging mode variable; can be set from the command line
+ * with the -X flag.  If set, this gets you the child_main loop running
+ * in the process which originally started up (no detach, no make_child),
+ * which is a pretty nice debugging environment.  (You'll get a SIGHUP
+ * early in standalone_main; just continue through.  This is the server
+ * trying to kill off any child processes which it might have lying
+ * around --- Apache doesn't keep track of their pids, it just sends
+ * SIGHUP to the process group, ignoring it in the root process.
+ * Continue through and you'll be fine.).
+ */
+
+static int one_process = 0;
+
+static apr_pool_t *pconf;               /* Pool for config stuff */
+static apr_pool_t *pchild;              /* Pool for httpd child stuff */
+
+static pid_t ap_my_pid; /* it seems silly to call getpid all the time */
+static pid_t parent_pid;
+static int my_child_num;
+
+#ifdef GPROF
+/*
+ * change directory for gprof to plop the gmon.out file
+ * configure in httpd.conf:
+ * GprofDir $RuntimeDir/   -> $ServerRoot/$RuntimeDir/gmon.out
+ * GprofDir $RuntimeDir/%  -> $ServerRoot/$RuntimeDir/gprof.$pid/gmon.out
+ */
+static void chdir_for_gprof(void)
+{
+    core_server_config *sconf =
+        ap_get_core_module_config(ap_server_conf->module_config);
+    char *dir = sconf->gprof_dir;
+    const char *use_dir;
+
+    if(dir) {
+        apr_status_t res;
+        char *buf = NULL ;
+        int len = strlen(sconf->gprof_dir) - 1;
+        if(*(dir + len) == '%') {
+            dir[len] = '\0';
+            buf = ap_append_pid(pconf, dir, "gprof.");
+        }
+        use_dir = ap_server_root_relative(pconf, buf ? buf : dir);
+        res = apr_dir_make(use_dir,
+                           APR_UREAD | APR_UWRITE | APR_UEXECUTE |
+                           APR_GREAD | APR_GEXECUTE |
+                           APR_WREAD | APR_WEXECUTE, pconf);
+        if(res != APR_SUCCESS && !APR_STATUS_IS_EEXIST(res)) {
+            ap_log_error(APLOG_MARK, APLOG_ERR, res, ap_server_conf, APLOGNO(00142)
+                         "gprof: error creating directory %s", dir);
+        }
+    }
+    else {
+        use_dir = ap_runtime_dir_relative(pconf, "");
+    }
+
+    chdir(use_dir);
+}
+#else
+#define chdir_for_gprof()
+#endif
+
+static void prefork_note_child_killed(int childnum, pid_t pid,
+                                      ap_generation_t gen)
+{
+    AP_DEBUG_ASSERT(childnum != -1); /* no scoreboard squatting with this MPM */
+    ap_run_child_status(ap_server_conf,
+                        ap_scoreboard_image->parent[childnum].pid,
+                        ap_scoreboard_image->parent[childnum].generation,
+                        childnum, MPM_CHILD_EXITED);
+    ap_scoreboard_image->parent[childnum].pid = 0;
+}
+
+static void prefork_note_child_started(int slot, pid_t pid)
+{
+    ap_generation_t gen = retained->mpm->my_generation;
+    ap_scoreboard_image->parent[slot].pid = pid;
+    ap_scoreboard_image->parent[slot].generation = gen;
+    ap_run_child_status(ap_server_conf, pid, gen, slot, MPM_CHILD_STARTED);
+}
+
+/* a clean exit from a child with proper cleanup */
+static void clean_child_exit(int code) __attribute__ ((noreturn));
+static void clean_child_exit(int code)
+{
+    retained->mpm->mpm_state = AP_MPMQ_STOPPING;
+
+    apr_signal(SIGHUP, SIG_IGN);
+    apr_signal(SIGTERM, SIG_IGN);
+
+    if (pchild) {
+        apr_pool_destroy(pchild);
+    }
+
+    if (one_process) {
+        prefork_note_child_killed(/* slot */ 0, 0, 0);
+    }
+
+    ap_mpm_pod_close(my_bucket->pod);
+    chdir_for_gprof();
+    exit(code);
+}
+
+static apr_status_t accept_mutex_on(void)
+{
+    apr_status_t rv = apr_proc_mutex_lock(my_bucket->mutex);
+    if (rv != APR_SUCCESS) {
+        const char *msg = "couldn't grab the accept mutex";
+
+        if (retained->mpm->my_generation !=
+            ap_scoreboard_image->global->running_generation) {
+            ap_log_error(APLOG_MARK, APLOG_DEBUG, rv, ap_server_conf, APLOGNO(00143) "%s", msg);
+            clean_child_exit(0);
+        }
+        else {
+            ap_log_error(APLOG_MARK, APLOG_EMERG, rv, ap_server_conf, APLOGNO(00144) "%s", msg);
+            exit(APEXIT_CHILDFATAL);
+        }
+    }
+    return APR_SUCCESS;
+}
+
+static apr_status_t accept_mutex_off(void)
+{
+    apr_status_t rv = apr_proc_mutex_unlock(my_bucket->mutex);
+    if (rv != APR_SUCCESS) {
+        const char *msg = "couldn't release the accept mutex";
+
+        if (retained->mpm->my_generation !=
+            ap_scoreboard_image->global->running_generation) {
+            ap_log_error(APLOG_MARK, APLOG_DEBUG, rv, ap_server_conf, APLOGNO(00145) "%s", msg);
+            /* don't exit here... we have a connection to
+             * process, after which point we'll see that the
+             * generation changed and we'll exit cleanly
+             */
+        }
+        else {
+            ap_log_error(APLOG_MARK, APLOG_EMERG, rv, ap_server_conf, APLOGNO(00146) "%s", msg);
+            exit(APEXIT_CHILDFATAL);
+        }
+    }
+    return APR_SUCCESS;
+}
+
+/* On some architectures it's safe to do unserialized accept()s in the single
+ * Listen case.  But it's never safe to do it in the case where there's
+ * multiple Listen statements.  Define SINGLE_LISTEN_UNSERIALIZED_ACCEPT
+ * when it's safe in the single Listen case.
+ */
+#ifdef SINGLE_LISTEN_UNSERIALIZED_ACCEPT
+#define SAFE_ACCEPT(stmt) (ap_listeners->next ? (stmt) : APR_SUCCESS)
+#else
+#define SAFE_ACCEPT(stmt) (stmt)
+#endif
+
+static int prefork_query(int query_code, int *result, apr_status_t *rv)
+{
+    *rv = APR_SUCCESS;
+    switch(query_code){
+    case AP_MPMQ_MAX_DAEMON_USED:
+        *result = ap_daemons_limit;
+        break;
+    case AP_MPMQ_IS_THREADED:
+        *result = AP_MPMQ_NOT_SUPPORTED;
+        break;
+    case AP_MPMQ_IS_FORKED:
+        *result = AP_MPMQ_DYNAMIC;
+        break;
+    case AP_MPMQ_HARD_LIMIT_DAEMONS:
+        *result = server_limit;
+        break;
+    case AP_MPMQ_HARD_LIMIT_THREADS:
+        *result = HARD_THREAD_LIMIT;
+        break;
+    case AP_MPMQ_MAX_THREADS:
+        *result = 1;
+        break;
+    case AP_MPMQ_MIN_SPARE_DAEMONS:
+        *result = ap_daemons_min_free;
+        break;
+    case AP_MPMQ_MIN_SPARE_THREADS:
+        *result = 0;
+        break;
+    case AP_MPMQ_MAX_SPARE_DAEMONS:
+        *result = ap_daemons_max_free;
+        break;
+    case AP_MPMQ_MAX_SPARE_THREADS:
+        *result = 0;
+        break;
+    case AP_MPMQ_MAX_REQUESTS_DAEMON:
+        *result = ap_max_requests_per_child;
+        break;
+    case AP_MPMQ_MAX_DAEMONS:
+        *result = ap_daemons_limit;
+        break;
+    case AP_MPMQ_MPM_STATE:
+        *result = retained->mpm->mpm_state;
+        break;
+    case AP_MPMQ_GENERATION:
+        *result = retained->mpm->my_generation;
+        break;
+    default:
+        *rv = APR_ENOTIMPL;
+        break;
+    }
+    return OK;
+}
+
+static const char *prefork_get_name(void)
+{
+    return "prefork";
+}
+
+/*****************************************************************
+ * Connection structures and accounting...
+ */
+
+static void just_die(int sig)
+{
+    clean_child_exit(0);
+}
+
+/* volatile because it's updated from a signal handler */
+static int volatile die_now = 0;
+
+static void stop_listening(int sig)
+{
+    retained->mpm->mpm_state = AP_MPMQ_STOPPING;
+    ap_close_listeners_ex(my_bucket->listeners);
+
+    /* For a graceful stop, we want the child to exit when done */
+    die_now = 1;
+}
+
+/*****************************************************************
+ * Child process main loop.
+ * The following vars are static to avoid getting clobbered by longjmp();
+ * they are really private to child_main.
+ */
+
+static int requests_this_child;
+static int num_listensocks = 0;
+
+static void child_main(int child_num_arg, int child_bucket)
+{
+#if APR_HAS_THREADS
+    apr_thread_t *thd = NULL;
+    apr_os_thread_t osthd;
+#endif
+    apr_pool_t *ptrans;
+    apr_allocator_t *allocator;
+    apr_status_t status;
+    int i;
+    ap_listen_rec *lr;
+    apr_pollset_t *pollset;
+    ap_sb_handle_t *sbh;
+    apr_bucket_alloc_t *bucket_alloc;
+    int last_poll_idx = 0;
+    const char *lockfile;
+
+    /* for benefit of any hooks that run as this child initializes */
+    retained->mpm->mpm_state = AP_MPMQ_STARTING;
+
+    my_child_num = child_num_arg;
+    ap_my_pid = getpid();
+    requests_this_child = 0;
+
+    ap_fatal_signal_child_setup(ap_server_conf);
+
+    /* Get a sub context for global allocations in this child, so that
+     * we can have cleanups occur when the child exits.
+     */
+    apr_allocator_create(&allocator);
+    apr_allocator_max_free_set(allocator, ap_max_mem_free);
+    apr_pool_create_ex(&pchild, pconf, NULL, allocator);
+    apr_allocator_owner_set(allocator, pchild);
+    apr_pool_tag(pchild, "pchild");
+
+#if APR_HAS_THREADS
+    osthd = apr_os_thread_current();
+    apr_os_thread_put(&thd, &osthd, pchild);
+#endif
+
+    apr_pool_create(&ptrans, pchild);
+    apr_pool_tag(ptrans, "transaction");
+
+    /* close unused listeners and pods */
+    for (i = 0; i < retained->mpm->num_buckets; i++) {
+        if (i != child_bucket) {
+            ap_close_listeners_ex(all_buckets[i].listeners);
+            ap_mpm_pod_close(all_buckets[i].pod);
+        }
+    }
+
+    /* needs to be done before we switch UIDs so we have permissions */
+    ap_reopen_scoreboard(pchild, NULL, 0);
+    status = SAFE_ACCEPT(apr_proc_mutex_child_init(&my_bucket->mutex,
+                                    apr_proc_mutex_lockfile(my_bucket->mutex),
+                                    pchild));
+    if (status != APR_SUCCESS) {
+        lockfile = apr_proc_mutex_lockfile(my_bucket->mutex);
+        ap_log_error(APLOG_MARK, APLOG_EMERG, status, ap_server_conf, APLOGNO(00155)
+                     "Couldn't initialize cross-process lock in child "
+                     "(%s) (%s)",
+                     lockfile ? lockfile : "none",
+                     apr_proc_mutex_name(my_bucket->mutex));
+        clean_child_exit(APEXIT_CHILDFATAL);
+    }
+
+    if (ap_run_drop_privileges(pchild, ap_server_conf)) {
+        clean_child_exit(APEXIT_CHILDFATAL);
+    }
+
+    ap_run_child_init(pchild, ap_server_conf);
+
+    ap_create_sb_handle(&sbh, pchild, my_child_num, 0);
+
+    (void) ap_update_child_status(sbh, SERVER_READY, (request_rec *) NULL);
+
+    /* Set up the pollfd array */
+    status = apr_pollset_create(&pollset, num_listensocks, pchild,
+                                APR_POLLSET_NOCOPY);
+    if (status != APR_SUCCESS) {
+        ap_log_error(APLOG_MARK, APLOG_EMERG, status, ap_server_conf, APLOGNO(00156)
+                     "Couldn't create pollset in child; check system or user limits");
+        clean_child_exit(APEXIT_CHILDSICK); /* assume temporary resource issue */
+    }
+
+    for (lr = my_bucket->listeners, i = num_listensocks; i--; lr = lr->next) {
+        apr_pollfd_t *pfd = apr_pcalloc(pchild, sizeof *pfd);
+
+        pfd->desc_type = APR_POLL_SOCKET;
+        pfd->desc.s = lr->sd;
+        pfd->reqevents = APR_POLLIN;
+        pfd->client_data = lr;
+
+        status = apr_pollset_add(pollset, pfd);
+        if (status != APR_SUCCESS) {
+            /* If the child processed a SIGWINCH before setting up the
+             * pollset, this error path is expected and harmless,
+             * since the listener fd was already closed; so don't
+             * pollute the logs in that case. */
+            if (!die_now) {
+                ap_log_error(APLOG_MARK, APLOG_EMERG, status, ap_server_conf, APLOGNO(00157)
+                             "Couldn't add listener to pollset; check system or user limits");
+                clean_child_exit(APEXIT_CHILDSICK);
+            }
+            clean_child_exit(0);
+        }
+
+        lr->accept_func = ap_unixd_accept;
+    }
+
+    retained->mpm->mpm_state = AP_MPMQ_RUNNING;
+
+    bucket_alloc = apr_bucket_alloc_create(pchild);
+
+    /* die_now is set when AP_SIG_GRACEFUL is received in the child;
+     * {shutdown,restart}_pending are set when a signal is received while
+     * running in single process mode.
+     */
+    while (!die_now
+           && !retained->mpm->shutdown_pending
+           && !retained->mpm->restart_pending) {
+        conn_rec *current_conn;
+        void *csd;
+
+        /*
+         * (Re)initialize this child to a pre-connection state.
+         */
+
+        apr_pool_clear(ptrans);
+
+        if ((ap_max_requests_per_child > 0
+             && requests_this_child++ >= ap_max_requests_per_child)) {
+            clean_child_exit(0);
+        }
+
+        (void) ap_update_child_status(sbh, SERVER_READY, (request_rec *) NULL);
+
+        /*
+         * Wait for an acceptable connection to arrive.
+         */
+
+        /* Lock around "accept", if necessary */
+        SAFE_ACCEPT(accept_mutex_on());
+
+        if (num_listensocks == 1) {
+            /* There is only one listener record, so refer to that one. */
+            lr = my_bucket->listeners;
+        }
+        else {
+            /* multiple listening sockets - need to poll */
+            for (;;) {
+                apr_int32_t numdesc;
+                const apr_pollfd_t *pdesc;
+
+                /* check for termination first so we don't sleep for a while in
+                 * poll if already signalled
+                 */
+                if (die_now         /* in graceful stop/restart */
+                        || retained->mpm->shutdown_pending
+                        || retained->mpm->restart_pending) {
+                    SAFE_ACCEPT(accept_mutex_off());
+                    clean_child_exit(0);
+                }
+
+                /* timeout == 10 seconds to avoid a hang at graceful restart/stop
+                 * caused by the closing of sockets by the signal handler
+                 */
+                status = apr_pollset_poll(pollset, apr_time_from_sec(10),
+                                          &numdesc, &pdesc);
+                if (status != APR_SUCCESS) {
+                    if (APR_STATUS_IS_TIMEUP(status) ||
+                        APR_STATUS_IS_EINTR(status)) {
+                        continue;
+                    }
+                    /* Single Unix documents select as returning errnos
+                     * EBADF, EINTR, and EINVAL... and in none of those
+                     * cases does it make sense to continue.  In fact
+                     * on Linux 2.0.x we seem to end up with EFAULT
+                     * occasionally, and we'd loop forever due to it.
+                     */
+                    ap_log_error(APLOG_MARK, APLOG_ERR, status,
+                                 ap_server_conf, APLOGNO(00158) "apr_pollset_poll: (listen)");
+                    SAFE_ACCEPT(accept_mutex_off());
+                    clean_child_exit(APEXIT_CHILDSICK);
+                }
+
+                /* We can always use pdesc[0], but sockets at position N
+                 * could end up completely starved of attention in a very
+                 * busy server. Therefore, we round-robin across the
+                 * returned set of descriptors. While it is possible that
+                 * the returned set of descriptors might flip around and
+                 * continue to starve some sockets, we happen to know the
+                 * internal pollset implementation retains ordering
+                 * stability of the sockets. Thus, the round-robin should
+                 * ensure that a socket will eventually be serviced.
+                 */
+                if (last_poll_idx >= numdesc)
+                    last_poll_idx = 0;
+
+                /* Grab a listener record from the client_data of the poll
+                 * descriptor, and advance our saved index to round-robin
+                 * the next fetch.
+                 *
+                 * ### hmm... this descriptor might have POLLERR rather
+                 * ### than POLLIN
+                 */
+                lr = pdesc[last_poll_idx++].client_data;
+                goto got_fd;
+            }
+        }
+    got_fd:
+        /* if we accept() something we don't want to die, so we have to
+         * defer the exit
+         */
+        status = lr->accept_func(&csd, lr, ptrans);
+
+        SAFE_ACCEPT(accept_mutex_off());      /* unlock after "accept" */
+
+        if (status == APR_EGENERAL) {
+            /* resource shortage or should-not-occur occurred */
+            clean_child_exit(APEXIT_CHILDSICK);
+        }
+        else if (status != APR_SUCCESS) {
+            continue;
+        }
+
+        /*
+         * We now have a connection, so set it up with the appropriate
+         * socket options, file descriptors, and read/write buffers.
+         */
+
+        current_conn = ap_run_create_connection(ptrans, ap_server_conf, csd, my_child_num, sbh, bucket_alloc);
+        if (current_conn) {
+#if APR_HAS_THREADS
+            current_conn->current_thread = thd;
+#endif
+            ap_process_connection(current_conn, csd);
+            ap_lingering_close(current_conn);
+        }
+
+        /* Check the pod and the generation number after processing a
+         * connection so that we'll go away if a graceful restart occurred
+         * while we were processing the connection or we are the lucky
+         * idle server process that gets to die.
+         */
+        if (ap_mpm_pod_check(my_bucket->pod) == APR_SUCCESS) { /* selected as idle? */
+            die_now = 1;
+        }
+        else if (retained->mpm->my_generation !=
+                 ap_scoreboard_image->global->running_generation) { /* restart? */
+            /* yeah, this could be non-graceful restart, in which case the
+             * parent will kill us soon enough, but why bother checking?
+             */
+            die_now = 1;
+        }
+    }
+    apr_pool_clear(ptrans); /* kludge to avoid crash in APR reslist cleanup code */
+    clean_child_exit(0);
+}
+
+
+static int make_child(server_rec *s, int slot, int bucket)
+{
+    int pid;
+
+    if (slot + 1 > retained->max_daemons_limit) {
+        retained->max_daemons_limit = slot + 1;
+    }
+
+    if (one_process) {
+        my_bucket = &all_buckets[0];
+
+        prefork_note_child_started(slot, getpid());
+        child_main(slot, 0);
+        /* NOTREACHED */
+        ap_assert(0);
+        return -1;
+    }
+
+    (void) ap_update_child_status_from_indexes(slot, 0, SERVER_STARTING,
+                                               (request_rec *) NULL);
+
+#ifdef _OSD_POSIX
+    /* BS2000 requires a "special" version of fork() before a setuid() call */
+    if ((pid = os_fork(ap_unixd_config.user_name)) == -1) {
+#else
+    if ((pid = fork()) == -1) {
+#endif
+        ap_log_error(APLOG_MARK, APLOG_ERR, errno, s, APLOGNO(00159) "fork: Unable to fork new process");
+
+        /* fork didn't succeed. Fix the scoreboard or else
+         * it will say SERVER_STARTING forever and ever
+         */
+        (void) ap_update_child_status_from_indexes(slot, 0, SERVER_DEAD,
+                                                   (request_rec *) NULL);
+
+        /* In case system resources are maxxed out, we don't want
+         * Apache running away with the CPU trying to fork over and
+         * over and over again.
+         */
+        sleep(10);
+
+        return -1;
+    }
+
+    if (!pid) {
+        my_bucket = &all_buckets[bucket];
+
+#ifdef HAVE_BINDPROCESSOR
+        /* by default AIX binds to a single processor
+         * this bit unbinds children which will then bind to another cpu
+         */
+        int status = bindprocessor(BINDPROCESS, (int)getpid(),
+                                   PROCESSOR_CLASS_ANY);
+        if (status != OK) {
+            ap_log_error(APLOG_MARK, APLOG_DEBUG, errno,
+                         ap_server_conf, APLOGNO(00160) "processor unbind failed");
+        }
+#endif
+        RAISE_SIGSTOP(MAKE_CHILD);
+        AP_MONCONTROL(1);
+        /* Disable the parent's signal handlers and set up proper handling in
+         * the child.
+         */
+        apr_signal(SIGHUP, just_die);
+        apr_signal(SIGTERM, just_die);
+        /* Ignore SIGINT in child. This fixes race-condition in signals
+         * handling when httpd is runnning on foreground and user hits ctrl+c.
+         * In this case, SIGINT is sent to all children followed by SIGTERM
+         * from the main process, which interrupts the SIGINT handler and
+         * leads to inconsistency.
+         */
+        apr_signal(SIGINT, SIG_IGN);
+        /* The child process just closes listeners on AP_SIG_GRACEFUL.
+         * The pod is used for signalling the graceful restart.
+         */
+        apr_signal(AP_SIG_GRACEFUL, stop_listening);
+        child_main(slot, bucket);
+    }
+
+    ap_scoreboard_image->parent[slot].bucket = bucket;
+    prefork_note_child_started(slot, pid);
+
+    return 0;
+}
+
+
+/* start up a bunch of children */
+static void startup_children(int number_to_start)
+{
+    int i;
+
+    for (i = 0; number_to_start && i < ap_daemons_limit; ++i) {
+        if (ap_scoreboard_image->servers[i][0].status != SERVER_DEAD) {
+            continue;
+        }
+        if (make_child(ap_server_conf, i, i % retained->mpm->num_buckets) < 0) {
+            break;
+        }
+        --number_to_start;
+    }
+}
+
+static void perform_idle_server_maintenance(apr_pool_t *p)
+{
+    static int bucket_make_child_record = -1;
+    static int bucket_kill_child_record = -1;
+    int i;
+    int idle_count;
+    worker_score *ws;
+    int free_length;
+    int free_slots[MAX_SPAWN_RATE];
+    int last_non_dead;
+    int total_non_dead;
+
+    /* initialize the free_list */
+    free_length = 0;
+
+    idle_count = 0;
+    last_non_dead = -1;
+    total_non_dead = 0;
+
+    for (i = 0; i < ap_daemons_limit; ++i) {
+        int status;
+
+        if (i >= retained->max_daemons_limit && free_length == retained->idle_spawn_rate)
+            break;
+        ws = &ap_scoreboard_image->servers[i][0];
+        status = ws->status;
+        if (status == SERVER_DEAD) {
+            /* try to keep children numbers as low as possible */
+            if (free_length < retained->idle_spawn_rate) {
+                free_slots[free_length] = i;
+                ++free_length;
+            }
+        }
+        else {
+            /* We consider a starting server as idle because we started it
+             * at least a cycle ago, and if it still hasn't finished starting
+             * then we're just going to swamp things worse by forking more.
+             * So we hopefully won't need to fork more if we count it.
+             * This depends on the ordering of SERVER_READY and SERVER_STARTING.
+             */
+            if (status <= SERVER_READY) {
+                ++ idle_count;
+            }
+
+            ++total_non_dead;
+            last_non_dead = i;
+        }
+    }
+    retained->max_daemons_limit = last_non_dead + 1;
+    if (idle_count > ap_daemons_max_free) {
+        /* kill off one child... we use the pod because that'll cause it to
+         * shut down gracefully, in case it happened to pick up a request
+         * while we were counting
+         */
+        bucket_kill_child_record = (bucket_kill_child_record + 1) % retained->mpm->num_buckets;
+        ap_mpm_pod_signal(all_buckets[bucket_kill_child_record].pod);
+        retained->idle_spawn_rate = 1;
+    }
+    else if (idle_count < ap_daemons_min_free) {
+        /* terminate the free list */
+        if (free_length == 0) {
+            /* only report this condition once */
+            if (!retained->maxclients_reported) {
+                ap_log_error(APLOG_MARK, APLOG_ERR, 0, ap_server_conf, APLOGNO(00161)
+                            "server reached MaxRequestWorkers setting, consider"
+                            " raising the MaxRequestWorkers setting");
+                retained->maxclients_reported = 1;
+            }
+            retained->idle_spawn_rate = 1;
+        }
+        else {
+            if (retained->idle_spawn_rate >= 8) {
+                ap_log_error(APLOG_MARK, APLOG_INFO, 0, ap_server_conf, APLOGNO(00162)
+                    "server seems busy, (you may need "
+                    "to increase StartServers, or Min/MaxSpareServers), "
+                    "spawning %d children, there are %d idle, and "
+                    "%d total children", retained->idle_spawn_rate,
+                    idle_count, total_non_dead);
+            }
+            for (i = 0; i < free_length; ++i) {
+                bucket_make_child_record++;
+                bucket_make_child_record %= retained->mpm->num_buckets;
+                make_child(ap_server_conf, free_slots[i],
+                           bucket_make_child_record);
+            }
+            /* the next time around we want to spawn twice as many if this
+             * wasn't good enough, but not if we've just done a graceful
+             */
+            if (retained->hold_off_on_exponential_spawning) {
+                --retained->hold_off_on_exponential_spawning;
+            }
+            else if (retained->idle_spawn_rate < MAX_SPAWN_RATE) {
+                retained->idle_spawn_rate *= 2;
+            }
+        }
+    }
+    else {
+        retained->idle_spawn_rate = 1;
+    }
+}
+
+/*****************************************************************
+ * Executive routines.
+ */
+
+static int prefork_run(apr_pool_t *_pconf, apr_pool_t *plog, server_rec *s)
+{
+    int index;
+    int remaining_children_to_start;
+    int i;
+
+    ap_log_pid(pconf, ap_pid_fname);
+
+    if (!retained->mpm->was_graceful) {
+        if (ap_run_pre_mpm(s->process->pool, SB_SHARED) != OK) {
+            retained->mpm->mpm_state = AP_MPMQ_STOPPING;
+            return !OK;
+        }
+        /* fix the generation number in the global score; we just got a new,
+         * cleared scoreboard
+         */
+        ap_scoreboard_image->global->running_generation = retained->mpm->my_generation;
+    }
+
+    ap_unixd_mpm_set_signals(pconf, one_process);
+
+    if (one_process) {
+        AP_MONCONTROL(1);
+        make_child(ap_server_conf, 0, 0);
+        /* NOTREACHED */
+        ap_assert(0);
+        return !OK;
+    }
+
+    /* Don't thrash since num_buckets depends on the
+     * system and the number of online CPU cores...
+     */
+    if (ap_daemons_limit < retained->mpm->num_buckets)
+        ap_daemons_limit = retained->mpm->num_buckets;
+    if (ap_daemons_to_start < retained->mpm->num_buckets)
+        ap_daemons_to_start = retained->mpm->num_buckets;
+    if (ap_daemons_min_free < retained->mpm->num_buckets)
+        ap_daemons_min_free = retained->mpm->num_buckets;
+    if (ap_daemons_max_free < ap_daemons_min_free + retained->mpm->num_buckets)
+        ap_daemons_max_free = ap_daemons_min_free + retained->mpm->num_buckets;
+
+    /* If we're doing a graceful_restart then we're going to see a lot
+     * of children exiting immediately when we get into the main loop
+     * below (because we just sent them AP_SIG_GRACEFUL).  This happens pretty
+     * rapidly... and for each one that exits we'll start a new one until
+     * we reach at least daemons_min_free.  But we may be permitted to
+     * start more than that, so we'll just keep track of how many we're
+     * supposed to start up without the 1 second penalty between each fork.
+     */
+    remaining_children_to_start = ap_daemons_to_start;
+    if (remaining_children_to_start > ap_daemons_limit) {
+        remaining_children_to_start = ap_daemons_limit;
+    }
+    if (!retained->mpm->was_graceful) {
+        startup_children(remaining_children_to_start);
+        remaining_children_to_start = 0;
+    }
+    else {
+        /* give the system some time to recover before kicking into
+         * exponential mode
+         */
+        retained->hold_off_on_exponential_spawning = 10;
+    }
+
+    ap_log_error(APLOG_MARK, APLOG_NOTICE, 0, ap_server_conf, APLOGNO(00163)
+                "%s configured -- resuming normal operations",
+                ap_get_server_description());
+    ap_log_error(APLOG_MARK, APLOG_INFO, 0, ap_server_conf, APLOGNO(00164)
+                "Server built: %s", ap_get_server_built());
+    ap_log_command_line(plog, s);
+    ap_log_mpm_common(s);
+    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ap_server_conf, APLOGNO(00165)
+                "Accept mutex: %s (default: %s)",
+                (all_buckets[0].mutex)
+                    ? apr_proc_mutex_name(all_buckets[0].mutex)
+                    : "none",
+                apr_proc_mutex_defname());
+
+    retained->mpm->mpm_state = AP_MPMQ_RUNNING;
+
+    while (!retained->mpm->restart_pending && !retained->mpm->shutdown_pending) {
+        int child_slot;
+        apr_exit_why_e exitwhy;
+        int status, processed_status;
+        /* this is a memory leak, but I'll fix it later. */
+        apr_proc_t pid;
+
+        ap_wait_or_timeout(&exitwhy, &status, &pid, pconf, ap_server_conf);
+
+        /* XXX: if it takes longer than 1 second for all our children
+         * to start up and get into IDLE state then we may spawn an
+         * extra child
+         */
+        if (pid.pid != -1) {
+            processed_status = ap_process_child_status(&pid, exitwhy, status);
+            child_slot = ap_find_child_by_pid(&pid);
+            if (processed_status == APEXIT_CHILDFATAL) {
+                /* fix race condition found in PR 39311
+                 * A child created at the same time as a graceful happens 
+                 * can find the lock missing and create a fatal error.
+                 * It is not fatal for the last generation to be in this state.
+                 */
+                if (child_slot < 0
+                    || ap_get_scoreboard_process(child_slot)->generation
+                       == retained->mpm->my_generation) {
+                    retained->mpm->mpm_state = AP_MPMQ_STOPPING;
+                    return !OK;
+                }
+                else {
+                    ap_log_error(APLOG_MARK, APLOG_WARNING, 0, ap_server_conf, APLOGNO(00166)
+                                 "Ignoring fatal error in child of previous "
+                                 "generation (pid %ld).",
+                                 (long)pid.pid);
+                }
+            }
+
+            /* non-fatal death... note that it's gone in the scoreboard. */
+            if (child_slot >= 0) {
+                (void) ap_update_child_status_from_indexes(child_slot, 0, SERVER_DEAD,
+                                                           (request_rec *) NULL);
+                prefork_note_child_killed(child_slot, 0, 0);
+                if (processed_status == APEXIT_CHILDSICK) {
+                    /* child detected a resource shortage (E[NM]FILE, ENOBUFS, etc)
+                     * cut the fork rate to the minimum
+                     */
+                    retained->idle_spawn_rate = 1;
+                }
+                else if (remaining_children_to_start
+                    && child_slot < ap_daemons_limit) {
+                    /* we're still doing a 1-for-1 replacement of dead
+                     * children with new children
+                     */
+                    make_child(ap_server_conf, child_slot,
+                               ap_get_scoreboard_process(child_slot)->bucket);
+                    --remaining_children_to_start;
+                }
+#if APR_HAS_OTHER_CHILD
+            }
+            else if (apr_proc_other_child_alert(&pid, APR_OC_REASON_DEATH, status) == APR_SUCCESS) {
+                /* handled */
+#endif
+            }
+            else if (retained->mpm->was_graceful) {
+                /* Great, we've probably just lost a slot in the
+                 * scoreboard.  Somehow we don't know about this
+                 * child.
+                 */
+                ap_log_error(APLOG_MARK, APLOG_WARNING,
+                            0, ap_server_conf, APLOGNO(00167)
+                            "long lost child came home! (pid %ld)", (long)pid.pid);
+            }
+            /* Don't perform idle maintenance when a child dies,
+             * only do it when there's a timeout.  Remember only a
+             * finite number of children can die, and it's pretty
+             * pathological for a lot to die suddenly.
+             */
+            continue;
+        }
+        else if (remaining_children_to_start) {
+            /* we hit a 1 second timeout in which none of the previous
+             * generation of children needed to be reaped... so assume
+             * they're all done, and pick up the slack if any is left.
+             */
+            startup_children(remaining_children_to_start);
+            remaining_children_to_start = 0;
+            /* In any event we really shouldn't do the code below because
+             * few of the servers we just started are in the IDLE state
+             * yet, so we'd mistakenly create an extra server.
+             */
+            continue;
+        }
+
+        perform_idle_server_maintenance(pconf);
+    }
+
+    retained->mpm->mpm_state = AP_MPMQ_STOPPING;
+
+    if (retained->mpm->shutdown_pending && retained->mpm->is_ungraceful) {
+        /* Time to shut down:
+         * Kill child processes, tell them to call child_exit, etc...
+         */
+        if (ap_unixd_killpg(getpgrp(), SIGTERM) < 0) {
+            ap_log_error(APLOG_MARK, APLOG_WARNING, errno, ap_server_conf, APLOGNO(00168) "killpg SIGTERM");
+        }
+        ap_reclaim_child_processes(1, /* Start with SIGTERM */
+                                   prefork_note_child_killed);
+
+        /* cleanup pid file on normal shutdown */
+        ap_remove_pid(pconf, ap_pid_fname);
+        ap_log_error(APLOG_MARK, APLOG_NOTICE, 0, ap_server_conf, APLOGNO(00169)
+                    "caught SIGTERM, shutting down");
+
+        return DONE;
+    }
+
+    if (retained->mpm->shutdown_pending) {
+        /* Time to perform a graceful shut down:
+         * Reap the inactive children, and ask the active ones
+         * to close their listeners, then wait until they are
+         * all done to exit.
+         */
+        int active_children;
+        apr_time_t cutoff = 0;
+
+        /* Stop listening */
+        ap_close_listeners();
+
+        /* kill off the idle ones */
+        for (i = 0; i < retained->mpm->num_buckets; i++) {
+            ap_mpm_pod_killpg(all_buckets[i].pod, retained->max_daemons_limit);
+        }
+
+        /* Send SIGUSR1 to the active children */
+        active_children = 0;
+        for (index = 0; index < ap_daemons_limit; ++index) {
+            if (ap_scoreboard_image->servers[index][0].status != SERVER_DEAD) {
+                /* Ask each child to close its listeners. */
+                ap_mpm_safe_kill(MPM_CHILD_PID(index), AP_SIG_GRACEFUL);
+                active_children++;
+            }
+        }
+
+        /* Allow each child which actually finished to exit */
+        ap_relieve_child_processes(prefork_note_child_killed);
+
+        /* cleanup pid file */
+        ap_remove_pid(pconf, ap_pid_fname);
+        ap_log_error(APLOG_MARK, APLOG_NOTICE, 0, ap_server_conf, APLOGNO(00170)
+           "caught " AP_SIG_GRACEFUL_STOP_STRING ", shutting down gracefully");
+
+        if (ap_graceful_shutdown_timeout) {
+            cutoff = apr_time_now() +
+                     apr_time_from_sec(ap_graceful_shutdown_timeout);
+        }
+
+        /* Don't really exit until each child has finished */
+        retained->mpm->shutdown_pending = 0;
+        do {
+            /* Pause for a second */
+            sleep(1);
+
+            /* Relieve any children which have now exited */
+            ap_relieve_child_processes(prefork_note_child_killed);
+
+            active_children = 0;
+            for (index = 0; index < ap_daemons_limit; ++index) {
+                if (ap_mpm_safe_kill(MPM_CHILD_PID(index), 0) == APR_SUCCESS) {
+                    active_children = 1;
+                    /* Having just one child is enough to stay around */
+                    break;
+                }
+            }
+        } while (!retained->mpm->shutdown_pending && active_children &&
+                 (!ap_graceful_shutdown_timeout || apr_time_now() < cutoff));
+
+        /* We might be here because we received SIGTERM, either
+         * way, try and make sure that all of our processes are
+         * really dead.
+         */
+        ap_unixd_killpg(getpgrp(), SIGTERM);
+
+        return DONE;
+    }
+
+    /* we've been told to restart */
+    if (one_process) {
+        /* not worth thinking about */
+        return DONE;
+    }
+
+    /* advance to the next generation */
+    /* XXX: we really need to make sure this new generation number isn't in
+     * use by any of the children.
+     */
+    ++retained->mpm->my_generation;
+    ap_scoreboard_image->global->running_generation = retained->mpm->my_generation;
+
+    if (!retained->mpm->is_ungraceful) {
+        ap_log_error(APLOG_MARK, APLOG_NOTICE, 0, ap_server_conf, APLOGNO(00171)
+                    "Graceful restart requested, doing restart");
+
+        /* kill off the idle ones */
+        for (i = 0; i < retained->mpm->num_buckets; i++) {
+            ap_mpm_pod_killpg(all_buckets[i].pod, retained->max_daemons_limit);
+        }
+
+        /* This is mostly for debugging... so that we know what is still
+         * gracefully dealing with existing request.  This will break
+         * in a very nasty way if we ever have the scoreboard totally
+         * file-based (no shared memory)
+         */
+        for (index = 0; index < ap_daemons_limit; ++index) {
+            if (ap_scoreboard_image->servers[index][0].status != SERVER_DEAD) {
+                ap_scoreboard_image->servers[index][0].status = SERVER_GRACEFUL;
+                /* Ask each child to close its listeners.
+                 *
+                 * NOTE: we use the scoreboard, because if we send SIGUSR1
+                 * to every process in the group, this may include CGI's,
+                 * piped loggers, etc. They almost certainly won't handle
+                 * it gracefully.
+                 */
+                ap_mpm_safe_kill(ap_scoreboard_image->parent[index].pid, AP_SIG_GRACEFUL);
+            }
+        }
+    }
+    else {
+        /* Kill 'em off */
+        if (ap_unixd_killpg(getpgrp(), SIGHUP) < 0) {
+            ap_log_error(APLOG_MARK, APLOG_WARNING, errno, ap_server_conf, APLOGNO(00172) "killpg SIGHUP");
+        }
+        ap_reclaim_child_processes(0, /* Not when just starting up */
+                                   prefork_note_child_killed);
+        ap_log_error(APLOG_MARK, APLOG_NOTICE, 0, ap_server_conf, APLOGNO(00173)
+                    "SIGHUP received.  Attempting to restart");
+    }
+
+    return OK;
+}
+
+/* This really should be a post_config hook, but the error log is already
+ * redirected by that point, so we need to do this in the open_logs phase.
+ */
+static int prefork_open_logs(apr_pool_t *p, apr_pool_t *plog, apr_pool_t *ptemp, server_rec *s)
+{
+    int startup = 0;
+    int level_flags = 0;
+    ap_listen_rec **listen_buckets;
+    apr_status_t rv;
+    char id[16];
+    int i;
+
+    pconf = p;
+
+    /* the reverse of pre_config, we want this only the first time around */
+    if (retained->mpm->module_loads == 1) {
+        startup = 1;
+        level_flags |= APLOG_STARTUP;
+    }
+
+    if ((num_listensocks = ap_setup_listeners(ap_server_conf)) < 1) {
+        ap_log_error(APLOG_MARK, APLOG_ALERT | level_flags, 0,
+                     (startup ? NULL : s),
+                     "no listening sockets available, shutting down");
+        return !OK;
+    }
+
+    if (one_process) {
+        retained->mpm->num_buckets = 1;
+    }
+    else if (!retained->mpm->was_graceful) {
+        /* Preserve the number of buckets on graceful restarts. */
+        retained->mpm->num_buckets = 0;
+    }
+    if ((rv = ap_duplicate_listeners(pconf, ap_server_conf,
+                                     &listen_buckets, &retained->mpm->num_buckets))) {
+        ap_log_error(APLOG_MARK, APLOG_CRIT | level_flags, rv,
+                     (startup ? NULL : s),
+                     "could not duplicate listeners");
+        return !OK;
+    }
+    all_buckets = apr_pcalloc(pconf, retained->mpm->num_buckets *
+                                     sizeof(prefork_child_bucket));
+    for (i = 0; i < retained->mpm->num_buckets; i++) {
+        if ((rv = ap_mpm_pod_open(pconf, &all_buckets[i].pod))) {
+            ap_log_error(APLOG_MARK, APLOG_CRIT | level_flags, rv,
+                         (startup ? NULL : s),
+                         "could not open pipe-of-death");
+            return !OK;
+        }
+        /* Initialize cross-process accept lock (safe accept needed only) */
+        if ((rv = SAFE_ACCEPT((apr_snprintf(id, sizeof id, "%i", i),
+                               ap_proc_mutex_create(&all_buckets[i].mutex,
+                                                    NULL, AP_ACCEPT_MUTEX_TYPE,
+                                                    id, s, pconf, 0))))) {
+            ap_log_error(APLOG_MARK, APLOG_CRIT | level_flags, rv,
+                         (startup ? NULL : s),
+                         "could not create accept mutex");
+            return !OK;
+        }
+        all_buckets[i].listeners = listen_buckets[i];
+    }
+
+    return OK;
+}
+
+static int prefork_pre_config(apr_pool_t *p, apr_pool_t *plog, apr_pool_t *ptemp)
+{
+    int no_detach, debug, foreground;
+    apr_status_t rv;
+    const char *userdata_key = "mpm_prefork_module";
+
+    debug = ap_exists_config_define("DEBUG");
+
+    if (debug) {
+        foreground = one_process = 1;
+        no_detach = 0;
+    }
+    else
+    {
+        no_detach = ap_exists_config_define("NO_DETACH");
+        one_process = ap_exists_config_define("ONE_PROCESS");
+        foreground = ap_exists_config_define("FOREGROUND");
+    }
+
+    ap_mutex_register(p, AP_ACCEPT_MUTEX_TYPE, NULL, APR_LOCK_DEFAULT, 0);
+
+    retained = ap_retained_data_get(userdata_key);
+    if (!retained) {
+        retained = ap_retained_data_create(userdata_key, sizeof(*retained));
+        retained->mpm = ap_unixd_mpm_get_retained_data();
+        retained->max_daemons_limit = -1;
+        retained->idle_spawn_rate = 1;
+    }
+    retained->mpm->mpm_state = AP_MPMQ_STARTING;
+    if (retained->mpm->baton != retained) {
+        retained->mpm->was_graceful = 0;
+        retained->mpm->baton = retained;
+    }
+    ++retained->mpm->module_loads;
+
+    /* sigh, want this only the second time around */
+    if (retained->mpm->module_loads == 2) {
+        if (!one_process && !foreground) {
+            /* before we detach, setup crash handlers to log to errorlog */
+            ap_fatal_signal_setup(ap_server_conf, pconf);
+            rv = apr_proc_detach(no_detach ? APR_PROC_DETACH_FOREGROUND
+                                           : APR_PROC_DETACH_DAEMONIZE);
+            if (rv != APR_SUCCESS) {
+                ap_log_error(APLOG_MARK, APLOG_CRIT, rv, NULL, APLOGNO(00174)
+                             "apr_proc_detach failed");
+                return HTTP_INTERNAL_SERVER_ERROR;
+            }
+        }
+    }
+
+    parent_pid = ap_my_pid = getpid();
+
+    ap_listen_pre_config();
+    ap_daemons_to_start = DEFAULT_START_DAEMON;
+    ap_daemons_min_free = DEFAULT_MIN_FREE_DAEMON;
+    ap_daemons_max_free = DEFAULT_MAX_FREE_DAEMON;
+    server_limit = DEFAULT_SERVER_LIMIT;
+    ap_daemons_limit = server_limit;
+    ap_extended_status = 0;
+
+    return OK;
+}
+
+static int prefork_check_config(apr_pool_t *p, apr_pool_t *plog,
+                                apr_pool_t *ptemp, server_rec *s)
+{
+    int startup = 0;
+
+    /* the reverse of pre_config, we want this only the first time around */
+    if (retained->mpm->module_loads == 1) {
+        startup = 1;
+    }
+
+    if (server_limit > MAX_SERVER_LIMIT) {
+        if (startup) {
+            ap_log_error(APLOG_MARK, APLOG_WARNING | APLOG_STARTUP, 0, NULL, APLOGNO(00175)
+                         "WARNING: ServerLimit of %d exceeds compile-time "
+                         "limit of %d servers, decreasing to %d.",
+                         server_limit, MAX_SERVER_LIMIT, MAX_SERVER_LIMIT);
+        } else {
+            ap_log_error(APLOG_MARK, APLOG_WARNING, 0, s, APLOGNO(00176)
+                         "ServerLimit of %d exceeds compile-time limit "
+                         "of %d, decreasing to match",
+                         server_limit, MAX_SERVER_LIMIT);
+        }
+        server_limit = MAX_SERVER_LIMIT;
+    }
+    else if (server_limit < 1) {
+        if (startup) {
+            ap_log_error(APLOG_MARK, APLOG_WARNING | APLOG_STARTUP, 0, NULL, APLOGNO(00177)
+                         "WARNING: ServerLimit of %d not allowed, "
+                         "increasing to 1.", server_limit);
+        } else {
+            ap_log_error(APLOG_MARK, APLOG_WARNING, 0, s, APLOGNO(00178)
+                         "ServerLimit of %d not allowed, increasing to 1",
+                         server_limit);
+        }
+        server_limit = 1;
+    }
+
+    /* you cannot change ServerLimit across a restart; ignore
+     * any such attempts
+     */
+    if (!retained->first_server_limit) {
+        retained->first_server_limit = server_limit;
+    }
+    else if (server_limit != retained->first_server_limit) {
+        /* don't need a startup console version here */
+        ap_log_error(APLOG_MARK, APLOG_WARNING, 0, s, APLOGNO(00179)
+                     "changing ServerLimit to %d from original value of %d "
+                     "not allowed during restart",
+                     server_limit, retained->first_server_limit);
+        server_limit = retained->first_server_limit;
+    }
+
+    if (ap_daemons_limit > server_limit) {
+        if (startup) {
+            ap_log_error(APLOG_MARK, APLOG_WARNING | APLOG_STARTUP, 0, NULL, APLOGNO(00180)
+                         "WARNING: MaxRequestWorkers of %d exceeds ServerLimit "
+                         "value of %d servers, decreasing MaxRequestWorkers to %d. "
+                         "To increase, please see the ServerLimit directive.",
+                         ap_daemons_limit, server_limit, server_limit);
+        } else {
+            ap_log_error(APLOG_MARK, APLOG_WARNING, 0, s, APLOGNO(00181)
+                         "MaxRequestWorkers of %d exceeds ServerLimit value "
+                         "of %d, decreasing to match",
+                         ap_daemons_limit, server_limit);
+        }
+        ap_daemons_limit = server_limit;
+    }
+    else if (ap_daemons_limit < 1) {
+        if (startup) {
+            ap_log_error(APLOG_MARK, APLOG_WARNING | APLOG_STARTUP, 0, NULL, APLOGNO(00182)
+                         "WARNING: MaxRequestWorkers of %d not allowed, "
+                         "increasing to 1.", ap_daemons_limit);
+        } else {
+            ap_log_error(APLOG_MARK, APLOG_WARNING, 0, s, APLOGNO(00183)
+                         "MaxRequestWorkers of %d not allowed, increasing to 1",
+                         ap_daemons_limit);
+        }
+        ap_daemons_limit = 1;
+    }
+
+    /* ap_daemons_to_start > ap_daemons_limit checked in prefork_run() */
+    if (ap_daemons_to_start < 1) {
+        if (startup) {
+            ap_log_error(APLOG_MARK, APLOG_WARNING | APLOG_STARTUP, 0, NULL, APLOGNO(00184)
+                         "WARNING: StartServers of %d not allowed, "
+                         "increasing to 1.", ap_daemons_to_start);
+        } else {
+            ap_log_error(APLOG_MARK, APLOG_WARNING, 0, s, APLOGNO(00185)
+                         "StartServers of %d not allowed, increasing to 1",
+                         ap_daemons_to_start);
+        }
+        ap_daemons_to_start = 1;
+    }
+
+    if (ap_daemons_min_free < 1) {
+        if (startup) {
+            ap_log_error(APLOG_MARK, APLOG_WARNING | APLOG_STARTUP, 0, NULL, APLOGNO(00186)
+                         "WARNING: MinSpareServers of %d not allowed, "
+                         "increasing to 1 to avoid almost certain server failure. "
+                         "Please read the documentation.", ap_daemons_min_free);
+        } else {
+            ap_log_error(APLOG_MARK, APLOG_WARNING, 0, s, APLOGNO(00187)
+                         "MinSpareServers of %d not allowed, increasing to 1",
+                         ap_daemons_min_free);
+        }
+        ap_daemons_min_free = 1;
+    }
+
+    /* ap_daemons_max_free < ap_daemons_min_free + 1 checked in prefork_run() */
+
+    return OK;
+}
+
+static void prefork_hooks(apr_pool_t *p)
+{
+    /* Our open_logs hook function must run before the core's, or stderr
+     * will be redirected to a file, and the messages won't print to the
+     * console.
+     */
+    static const char *const aszSucc[] = {"core.c", NULL};
+
+    ap_hook_open_logs(prefork_open_logs, NULL, aszSucc, APR_HOOK_REALLY_FIRST);
+    /* we need to set the MPM state before other pre-config hooks use MPM query
+     * to retrieve it, so register as REALLY_FIRST
+     */
+    ap_hook_pre_config(prefork_pre_config, NULL, NULL, APR_HOOK_REALLY_FIRST);
+    ap_hook_check_config(prefork_check_config, NULL, NULL, APR_HOOK_MIDDLE);
+    ap_hook_mpm(prefork_run, NULL, NULL, APR_HOOK_MIDDLE);
+    ap_hook_mpm_query(prefork_query, NULL, NULL, APR_HOOK_MIDDLE);
+    ap_hook_mpm_get_name(prefork_get_name, NULL, NULL, APR_HOOK_MIDDLE);
+}
+
+static const char *set_daemons_to_start(cmd_parms *cmd, void *dummy, const char *arg)
+{
+    const char *err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
+    if (err != NULL) {
+        return err;
+    }
+
+    ap_daemons_to_start = atoi(arg);
+    return NULL;
+}
+
+static const char *set_min_free_servers(cmd_parms *cmd, void *dummy, const char *arg)
+{
+    const char *err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
+    if (err != NULL) {
+        return err;
+    }
+
+    ap_daemons_min_free = atoi(arg);
+    return NULL;
+}
+
+static const char *set_max_free_servers(cmd_parms *cmd, void *dummy, const char *arg)
+{
+    const char *err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
+    if (err != NULL) {
+        return err;
+    }
+
+    ap_daemons_max_free = atoi(arg);
+    return NULL;
+}
+
+static const char *set_max_clients (cmd_parms *cmd, void *dummy, const char *arg)
+{
+    const char *err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
+    if (err != NULL) {
+        return err;
+    }
+    if (!strcasecmp(cmd->cmd->name, "MaxClients")) {
+        ap_log_error(APLOG_MARK, APLOG_INFO, 0, NULL, APLOGNO(00188)
+                     "MaxClients is deprecated, use MaxRequestWorkers "
+                     "instead.");
+    }
+    ap_daemons_limit = atoi(arg);
+    return NULL;
+}
+
+static const char *set_server_limit (cmd_parms *cmd, void *dummy, const char *arg)
+{
+    const char *err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
+    if (err != NULL) {
+        return err;
+    }
+
+    server_limit = atoi(arg);
+    return NULL;
+}
+
+static const command_rec prefork_cmds[] = {
+LISTEN_COMMANDS,
+AP_INIT_TAKE1("StartServers", set_daemons_to_start, NULL, RSRC_CONF,
+              "Number of child processes launched at server startup"),
+AP_INIT_TAKE1("MinSpareServers", set_min_free_servers, NULL, RSRC_CONF,
+              "Minimum number of idle children, to handle request spikes"),
+AP_INIT_TAKE1("MaxSpareServers", set_max_free_servers, NULL, RSRC_CONF,
+              "Maximum number of idle children"),
+AP_INIT_TAKE1("MaxClients", set_max_clients, NULL, RSRC_CONF,
+              "Deprecated name of MaxRequestWorkers"),
+AP_INIT_TAKE1("MaxRequestWorkers", set_max_clients, NULL, RSRC_CONF,
+              "Maximum number of children alive at the same time"),
+AP_INIT_TAKE1("ServerLimit", set_server_limit, NULL, RSRC_CONF,
+              "Maximum value of MaxRequestWorkers for this run of Apache"),
+AP_GRACEFUL_SHUTDOWN_TIMEOUT_COMMAND,
+{ NULL }
+};
+
+AP_DECLARE_MODULE(mpm_prefork) = {
+    MPM20_MODULE_STUFF,
+    NULL,                       /* hook to run before apache parses args */
+    NULL,                       /* create per-directory config structure */
+    NULL,                       /* merge per-directory config structures */
+    NULL,                       /* create per-server config structure */
+    NULL,                       /* merge per-server config structures */
+    prefork_cmds,               /* command apr_table_t */
+    prefork_hooks,              /* register hooks */
+};