text: /* 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 "util_time.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)
  {
      apr_signal(SIGHUP, SIG_IGN);
      apr_signal(SIGTERM, SIG_IGN);
  
      retained->mpm->mpm_state = AP_MPMQ_STOPPING;
      if (code == 0) {
          ap_run_child_stopping(pchild, 0);
      }
  
      if (pchild) {
          apr_pool_destroy(pchild);
          /*
           * Be safe in case someone still uses afterwards or we get here again.
           * Should not happen.
           */
          pchild = NULL;
      }
  
      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;
  
  #if APR_HAS_THREADS
  static void child_sigmask(sigset_t *new_mask, sigset_t *old_mask)
  {
  #if defined(SIGPROCMASK_SETS_THREAD_MASK)
      sigprocmask(SIG_SETMASK, new_mask, old_mask);
  #else
      pthread_sigmask(SIG_SETMASK, new_mask, old_mask);
  #endif
  }
  #endif
  
  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;
      sigset_t sig_mask;
  #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);
      }
  
  #if APR_HAS_THREADS
      /* Save the signal mask and block all the signals from being received by
       * threads potentially created in child_init() hooks (e.g. mod_watchdog).
       */
      child_sigmask(NULL, &sig_mask);
      {
          apr_status_t rv;
          rv = apr_setup_signal_thread();
          if (rv != APR_SUCCESS) {
              ap_log_error(APLOG_MARK, APLOG_EMERG, rv, ap_server_conf, APLOGNO(10271)
                           "Couldn't initialize signal thread");
              clean_child_exit(APEXIT_CHILDFATAL);
          }
      }
  #endif /* APR_HAS_THREADS */
  
      ap_run_child_init(pchild, ap_server_conf);
  
  #if APR_HAS_THREADS
      /* Restore the original signal mask for this main thread, the only one
       * that should possibly get interrupted by signals.
       */
      child_sigmask(&sig_mask, NULL);
  #endif
  
      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);
          }
          if (ap_accept_error_is_nonfatal(status)) {
              ap_log_error(APLOG_MARK, APLOG_DEBUG, status, ap_server_conf,
                      "accept() on client socket failed");
          }
  
          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 = slot % retained->mpm->num_buckets;
      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-conditions in signals
           * handling when httpd is running 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);
      }
  
      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) < 0) {
              break;
          }
          --number_to_start;
      }
  }
  
  static void perform_idle_server_maintenance(apr_pool_t *p)
  {
      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) {
          static int bucket_kill_child_record = -1;
          /* 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) {
                  make_child(ap_server_conf, free_slots[i]);
              }
              /* 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);
          /* 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);
                      --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), APLOGNO(03279)
                       "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), APLOGNO(03280)
                       "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), APLOGNO(03281)
                           "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), APLOGNO(03282)
                           "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, p /* == 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_force_set_tz(p);
  
      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 */
  };
  