prefork.c

Apache官方在今天放出产品系列2.2的最新版本2.2.11的源码包 最流行的HTTP服务器软件之一

/* 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

#define CORE_PRIVATE

#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 "unixd.h"
#include "mpm_common.h"
#include "ap_listen.h"
#include "ap_mmn.h"
#include "apr_poll.h"

#ifdef HAVE_BSTRING_H
#include <bstring.h>            /* for IRIX, FD_SET calls bzero() */
#endif
#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 */

int ap_threads_per_child=0;         /* Worker threads per child */
static apr_proc_mutex_t *accept_mutex;
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;      /* MaxClients */
static int server_limit = DEFAULT_SERVER_LIMIT;
static int first_server_limit = 0;
static int changed_limit_at_restart;
static int mpm_state = AP_MPMQ_STARTING;
static ap_pod_t *pod;

/*
 * The max child slot ever assigned, preserved across restarts.  Necessary
 * to deal with MaxClients changes across AP_SIG_GRACEFUL restarts.  We
 * use this value to optimize routines that have to scan the entire scoreboard.
 */
int ap_max_daemons_limit = -1;
server_rec *ap_server_conf;

/* 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;
#ifndef MULTITHREAD
static int my_child_num;
#endif
ap_generation_t volatile ap_my_generation=0;

#ifdef TPF
int tpf_child = 0;
char tpf_server_name[INETD_SERVNAME_LENGTH+1];
#endif /* TPF */

static volatile int die_now = 0;

#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_module_config(ap_server_conf->module_config, &core_module);
    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,
                         "gprof: error creating directory %s", dir);
        }
    }
    else {
        use_dir = ap_server_root_relative(pconf, DEFAULT_REL_RUNTIMEDIR);
    }

    chdir(use_dir);
}
#else
#define chdir_for_gprof()
#endif

/* XXX - I don't know if TPF will ever use this module or not, so leave
 * the ap_check_signals calls in but disable them - manoj */
#define ap_check_signals()

/* 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)
{
    mpm_state = AP_MPMQ_STOPPING;

    if (pchild) {
        apr_pool_destroy(pchild);
    }
    ap_mpm_pod_close(pod);
    chdir_for_gprof();
    exit(code);
}

static void accept_mutex_on(void)
{
    apr_status_t rv = apr_proc_mutex_lock(accept_mutex);
    if (rv != APR_SUCCESS) {
        const char *msg = "couldn't grab the accept mutex";

        if (ap_my_generation !=
            ap_scoreboard_image->global->running_generation) {
            ap_log_error(APLOG_MARK, APLOG_DEBUG, rv, NULL, "%s", msg);
            clean_child_exit(0);
        }
        else {
            ap_log_error(APLOG_MARK, APLOG_EMERG, rv, NULL, "%s", msg);
            exit(APEXIT_CHILDFATAL);
        }
    }
}

static void accept_mutex_off(void)
{
    apr_status_t rv = apr_proc_mutex_unlock(accept_mutex);
    if (rv != APR_SUCCESS) {
        const char *msg = "couldn't release the accept mutex";

        if (ap_my_generation !=
            ap_scoreboard_image->global->running_generation) {
            ap_log_error(APLOG_MARK, APLOG_DEBUG, rv, NULL, "%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, NULL, "%s", msg);
            exit(APEXIT_CHILDFATAL);
        }
    }
}

/* 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) do {if (ap_listeners->next) {stmt;}} while(0)
#else
#define SAFE_ACCEPT(stmt) do {stmt;} while(0)
#endif

AP_DECLARE(apr_status_t) ap_mpm_query(int query_code, int *result)
{
    switch(query_code){
    case AP_MPMQ_MAX_DAEMON_USED:
        *result = ap_daemons_limit;
        return APR_SUCCESS;
    case AP_MPMQ_IS_THREADED:
        *result = AP_MPMQ_NOT_SUPPORTED;
        return APR_SUCCESS;
    case AP_MPMQ_IS_FORKED:
        *result = AP_MPMQ_DYNAMIC;
        return APR_SUCCESS;
    case AP_MPMQ_HARD_LIMIT_DAEMONS:
        *result = server_limit;
        return APR_SUCCESS;
    case AP_MPMQ_HARD_LIMIT_THREADS:
        *result = HARD_THREAD_LIMIT;
        return APR_SUCCESS;
    case AP_MPMQ_MAX_THREADS:
        *result = 0;
        return APR_SUCCESS;
    case AP_MPMQ_MIN_SPARE_DAEMONS:
        *result = ap_daemons_min_free;
        return APR_SUCCESS;
    case AP_MPMQ_MIN_SPARE_THREADS:
        *result = 0;
        return APR_SUCCESS;
    case AP_MPMQ_MAX_SPARE_DAEMONS:
        *result = ap_daemons_max_free;
        return APR_SUCCESS;
    case AP_MPMQ_MAX_SPARE_THREADS:
        *result = 0;
        return APR_SUCCESS;
    case AP_MPMQ_MAX_REQUESTS_DAEMON:
        *result = ap_max_requests_per_child;
        return APR_SUCCESS;
    case AP_MPMQ_MAX_DAEMONS:
        *result = server_limit;
        return APR_SUCCESS;
    case AP_MPMQ_MPM_STATE:
        *result = mpm_state;
        return APR_SUCCESS;
    }
    return APR_ENOTIMPL;
}

#if defined(NEED_WAITPID)
/*
   Systems without a real waitpid sometimes lose a child's exit while waiting
   for another.  Search through the scoreboard for missing children.
 */
int reap_children(int *exitcode, apr_exit_why_e *status)
{
    int n, pid;

    for (n = 0; n < ap_max_daemons_limit; ++n) {
        if (ap_scoreboard_image->servers[n][0].status != SERVER_DEAD &&
                kill((pid = ap_scoreboard_image->parent[n].pid), 0) == -1) {
            ap_update_child_status_from_indexes(n, 0, SERVER_DEAD, NULL);
            /* just mark it as having a successful exit status */
            *status = APR_PROC_EXIT;
            *exitcode = 0;
            return(pid);
        }
    }
    return 0;
}
#endif

/*****************************************************************
 * Connection structures and accounting...
 */

static void just_die(int sig)
{
    clean_child_exit(0);
}

static void stop_listening(int sig)
{
    ap_close_listeners();

    /* For a graceful stop, we want the child to exit when done */
    die_now = 1;
}

/* volatile just in case */
static int volatile shutdown_pending;
static int volatile restart_pending;
static int volatile is_graceful;

static void sig_term(int sig)
{
    if (shutdown_pending == 1) {
        /* Um, is this _probably_ not an error, if the user has
         * tried to do a shutdown twice quickly, so we won't
         * worry about reporting it.
         */
        return;
    }
    shutdown_pending = 1;
    is_graceful = (sig == AP_SIG_GRACEFUL_STOP);
}

/* restart() is the signal handler for SIGHUP and AP_SIG_GRACEFUL
 * in the parent process, unless running in ONE_PROCESS mode
 */
static void restart(int sig)
{
    if (restart_pending == 1) {
        /* Probably not an error - don't bother reporting it */
        return;
    }
    restart_pending = 1;
    is_graceful = (sig == AP_SIG_GRACEFUL);
}

static void set_signals(void)
{
#ifndef NO_USE_SIGACTION