isc/unix/app.c

	app.c revision 91cd0f93ad34d23e8b09dca337120f64fbe8f0a1
/*
 * Copyright (C) 1999-2001  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
 * DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
 * INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
 * FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
 * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: app.c,v 1.46 2001/11/27 01:56:13 gson Exp $ */

#include <config.h>

#include <sys/types.h>

#include <stddef.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <sys/time.h>

#include <isc/app.h>
#include <isc/boolean.h>
#include <isc/condition.h>
#include <isc/msgs.h>
#include <isc/mutex.h>
#include <isc/event.h>
#include <isc/platform.h>
#include <isc/strerror.h>
#include <isc/string.h>
#include <isc/task.h>
#include <isc/time.h>
#include <isc/util.h>

#ifdef ISC_PLATFORM_USETHREADS
#include <pthread.h>
#else /* ISC_PLATFORM_USETHREADS */
#include "../timer_p.h"
#include "../task_p.h"
#include "socket_p.h"
#endif /* ISC_PLATFORM_USETHREADS */

static isc_eventlist_t      on_run;
static isc_mutex_t      lock;
static isc_boolean_t        shutdown_requested = ISC_FALSE;
static isc_boolean_t        running = ISC_FALSE;
/*
 * We assume that 'want_shutdown' can be read and written atomically.
 */
static isc_boolean_t        want_shutdown = ISC_FALSE;
/*
 * We assume that 'want_reload' can be read and written atomically.
 */
static isc_boolean_t        want_reload = ISC_FALSE;

static isc_boolean_t        blocked  = ISC_FALSE;
#ifdef ISC_PLATFORM_USETHREADS
static pthread_t        blockedthread;
#endif /* ISC_PLATFORM_USETHREADS */

#ifdef HAVE_LINUXTHREADS
/*
 * Linux has sigwait(), but it appears to prevent signal handlers from
 * running, even if they're not in the set being waited for.  This makes
 * it impossible to get the default actions for SIGILL, SIGSEGV, etc.
 * Instead of messing with it, we just use sigsuspend() instead.
 */
#undef HAVE_SIGWAIT
/*
 * We need to remember which thread is the main thread...
 */
static pthread_t        main_thread;
#endif

#ifndef HAVE_SIGWAIT
static void
exit_action(int arg) {
        UNUSED(arg);
    want_shutdown = ISC_TRUE;
}

static void
reload_action(int arg) {
        UNUSED(arg);
    want_reload = ISC_TRUE;
}
#endif

static isc_result_t
handle_signal(int sig, void (*handler)(int)) {
    struct sigaction sa;
    char strbuf[ISC_STRERRORSIZE];

    memset(&sa, 0, sizeof(sa));
    sa.sa_handler = handler;

    if (sigfillset(&sa.sa_mask) != 0 ||
        sigaction(sig, &sa, NULL) < 0) {
        isc__strerror(errno, strbuf, sizeof(strbuf));
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 isc_msgcat_get(isc_msgcat, ISC_MSGSET_APP,
                           ISC_MSG_SIGNALSETUP,
                           "handle_signal() %d setup: %s"),
                 sig, strbuf);
        return (ISC_R_UNEXPECTED);
    }

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_app_start(void) {
    isc_result_t result;
    int presult;
    sigset_t sset;
    char strbuf[ISC_STRERRORSIZE];

    /*
     * Start an ISC library application.
     */

#ifdef NEED_PTHREAD_INIT
    /*
     * BSDI 3.1 seg faults in pthread_sigmask() if we don't do this.
     */
    presult = pthread_init();
    if (presult != 0) {
        isc__strerror(presult, strbuf, sizeof(strbuf));
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_app_start() pthread_init: %s", strbuf);
        return (ISC_R_UNEXPECTED);
    }
#endif

#ifdef HAVE_LINUXTHREADS
    main_thread = pthread_self();
#endif

    result = isc_mutex_init(&lock);
    if (result != ISC_R_SUCCESS)
        return (result);

#ifndef HAVE_SIGWAIT
    /*
     * Install do-nothing handlers for SIGINT and SIGTERM.
     *
     * We install them now because BSDI 3.1 won't block
     * the default actions, regardless of what we do with
     * pthread_sigmask().
     */
    result = handle_signal(SIGINT, exit_action);
    if (result != ISC_R_SUCCESS)
        return (result);
    result = handle_signal(SIGTERM, exit_action);
    if (result != ISC_R_SUCCESS)
        return (result);
#endif

    /*
     * Always ignore SIGPIPE.
     */
    result = handle_signal(SIGPIPE, SIG_IGN);
    if (result != ISC_R_SUCCESS)
        return (result);

    /*
     * On Solaris 2, delivery of a signal whose action is SIG_IGN
     * will not cause sigwait() to return. We may have inherited
     * unexpected actions for SIGHUP, SIGINT, and SIGTERM from our parent
     * process (e.g, Solaris cron).  Set an action of SIG_DFL to make
     * sure sigwait() works as expected.  Only do this for SIGTERM and
     * SIGINT if we don't have sigwait(), since a different handler is
     * installed above.
     */
    result = handle_signal(SIGHUP, SIG_DFL);
    if (result != ISC_R_SUCCESS)
        return (result);

#ifdef HAVE_SIGWAIT
    result = handle_signal(SIGTERM, SIG_DFL);
    if (result != ISC_R_SUCCESS)
        return (result);
    result = handle_signal(SIGINT, SIG_DFL);
    if (result != ISC_R_SUCCESS)
        return (result);
#endif

#ifdef ISC_PLATFORM_USETHREADS
    /*
     * Block SIGHUP, SIGINT, SIGTERM.
     *
     * If isc_app_start() is called from the main thread before any other
     * threads have been created, then the pthread_sigmask() call below
     * will result in all threads having SIGHUP, SIGINT and SIGTERM
     * blocked by default, ensuring that only the thread that calls
     * sigwait() for them will get those signals.
     */
    if (sigemptyset(&sset) != 0 ||
        sigaddset(&sset, SIGHUP) != 0 ||
        sigaddset(&sset, SIGINT) != 0 ||
        sigaddset(&sset, SIGTERM) != 0) {
        isc__strerror(errno, strbuf, sizeof(strbuf));
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_app_start() sigsetops: %s", strbuf);
        return (ISC_R_UNEXPECTED);
    }
    presult = pthread_sigmask(SIG_BLOCK, &sset, NULL);
    if (presult != 0) {
        isc__strerror(presult, strbuf, sizeof(strbuf));
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_app_start() pthread_sigmask: %s",
                 strbuf);
        return (ISC_R_UNEXPECTED);
    }
#else /* ISC_PLATFORM_USETHREADS */
    /*
     * Unblock SIGHUP, SIGINT, SIGTERM.
     *
     * If we're not using threads, we need to make sure that SIGHUP,
     * SIGINT and SIGTERM are not inherited as blocked from the parent
     * process.
     */
    if (sigemptyset(&sset) != 0 ||
        sigaddset(&sset, SIGHUP) != 0 ||
        sigaddset(&sset, SIGINT) != 0 ||
        sigaddset(&sset, SIGTERM) != 0) {
        isc__strerror(errno, strbuf, sizeof(strbuf));
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_app_start() sigsetops: %s", strbuf);
        return (ISC_R_UNEXPECTED);
    }
    presult = sigprocmask(SIG_UNBLOCK, &sset, NULL);
    if (presult != 0) {
        isc__strerror(presult, strbuf, sizeof(strbuf));
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_app_start() sigprocmask: %s", strbuf);
        return (ISC_R_UNEXPECTED);
    }
#endif /* ISC_PLATFORM_USETHREADS */

    ISC_LIST_INIT(on_run);

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_app_onrun(isc_mem_t *mctx, isc_task_t *task, isc_taskaction_t action,
          void *arg)
{
    isc_event_t *event;
    isc_task_t *cloned_task = NULL;
    isc_result_t result;

    LOCK(&lock);

    if (running) {
        result = ISC_R_ALREADYRUNNING;
        goto unlock;
    }

    /*
     * Note that we store the task to which we're going to send the event
     * in the event's "sender" field.
     */
    isc_task_attach(task, &cloned_task);
    event = isc_event_allocate(mctx, cloned_task, ISC_APPEVENT_SHUTDOWN,
                   action, arg, sizeof(*event));
    if (event == NULL) {
        result = ISC_R_NOMEMORY;
        goto unlock;
    }

    ISC_LIST_APPEND(on_run, event, ev_link);

    result = ISC_R_SUCCESS;

 unlock:
    UNLOCK(&lock);

    return (result);
}

#ifndef ISC_PLATFORM_USETHREADS
/*
 * Event loop for nonthreaded programs.
 */
static isc_result_t
evloop() {
    isc_result_t result;
    while (!want_shutdown) {
        int n;
        isc_time_t when, now;
        struct timeval tv, *tvp;
        fd_set readfds, writefds;
        int maxfd;
        isc_boolean_t readytasks;

        readytasks = isc__taskmgr_ready();
        if (readytasks) {
            tv.tv_sec = 0;
            tv.tv_usec = 0;
            tvp = &tv;
        } else {
            result = isc__timermgr_nextevent(&when);
            if (result != ISC_R_SUCCESS)
                tvp = NULL;
            else {
                isc_uint64_t us;

                (void)isc_time_now(&now);
                us = isc_time_microdiff(&when, &now);
                tv.tv_sec = us / 1000000;
                tv.tv_usec = us % 1000000;
                tvp = &tv;
            }
        }

        isc__socketmgr_getfdsets(&readfds, &writefds, &maxfd);
        n = select(maxfd, &readfds, &writefds, NULL, tvp);

        (void)isc__timermgr_dispatch();
        if (n > 0)
            (void)isc__socketmgr_dispatch(&readfds, &writefds,
                              maxfd);
        (void)isc__taskmgr_dispatch();

        if (want_reload) {
            want_reload = ISC_FALSE;
            return (ISC_R_RELOAD);
        }
    }
    return (ISC_R_SUCCESS);
}

/*
 * This is a gross hack to support waiting for condition
 * variables in nonthreaded programs in a limited way;
 * see lib/isc/nothreads/include/isc/condition.h.
 * We implement isc_condition_wait() by entering the
 * event loop recursively until the want_shutdown flag
 * is set by isc_condition_signal().
 */

/*
 * True iff we are currently executing in the recursive
 * event loop.
 */
static isc_boolean_t in_recursive_evloop = ISC_FALSE;

/*
 * True iff we are exiting the event loop as the result of
 * a call to isc_condition_signal() rather than a shutdown
 * or reload.
 */
static isc_boolean_t signalled = ISC_FALSE;

isc_result_t
isc__nothread_wait_hack(isc_condition_t *cp, isc_mutex_t *mp) {
    isc_result_t result;

    UNUSED(cp);
    UNUSED(mp);

    INSIST(!in_recursive_evloop);
    in_recursive_evloop = ISC_TRUE;

    INSIST(*mp == 1); /* Mutex must be locked on entry. */
    --*mp;

    result = evloop();
    if (result == ISC_R_RELOAD)
        want_reload = ISC_TRUE;
    if (signalled) {
        want_shutdown = ISC_FALSE;
        signalled = ISC_FALSE;
    }

    ++*mp;
    in_recursive_evloop = ISC_FALSE;
    return (ISC_R_SUCCESS);
}

isc_result_t
isc__nothread_signal_hack(isc_condition_t *cp) {

    UNUSED(cp);

    INSIST(in_recursive_evloop);

    want_shutdown = ISC_TRUE;
    signalled = ISC_TRUE;
    return (ISC_R_SUCCESS);
}

#endif /* ISC_PLATFORM_USETHREADS */

isc_result_t
isc_app_run(void) {
    int result;
    isc_event_t *event, *next_event;
    isc_task_t *task;
#ifdef ISC_PLATFORM_USETHREADS
    sigset_t sset;
    char strbuf[ISC_STRERRORSIZE];
#endif /* ISC_PLATFORM_USETHREADS */
#ifdef HAVE_SIGWAIT
    int sig;
#endif

#ifdef HAVE_LINUXTHREADS
    REQUIRE(main_thread == pthread_self());
#endif

    LOCK(&lock);

    if (!running) {
        running = ISC_TRUE;

        /*
         * Post any on-run events (in FIFO order).
         */
        for (event = ISC_LIST_HEAD(on_run);
             event != NULL;
             event = next_event) {
            next_event = ISC_LIST_NEXT(event, ev_link);
            ISC_LIST_UNLINK(on_run, event, ev_link);
            task = event->ev_sender;
            event->ev_sender = NULL;
            isc_task_sendanddetach(&task, &event);
        }

    }

    UNLOCK(&lock);

#ifndef HAVE_SIGWAIT
    /*
     * Catch SIGHUP.
     *
     * We do this here to ensure that the signal handler is installed
     * (i.e. that it wasn't a "one-shot" handler).
     */
    result = handle_signal(SIGHUP, reload_action);
    if (result != ISC_R_SUCCESS)
        return (ISC_R_SUCCESS);
#endif

#ifdef ISC_PLATFORM_USETHREADS
    /*
     * There is no danger if isc_app_shutdown() is called before we wait
     * for signals.  Signals are blocked, so any such signal will simply
     * be made pending and we will get it when we call sigwait().
     */

    while (!want_shutdown) {
#ifdef HAVE_SIGWAIT
        /*
         * Wait for SIGHUP, SIGINT, or SIGTERM.
         */
        if (sigemptyset(&sset) != 0 ||
            sigaddset(&sset, SIGHUP) != 0 ||
            sigaddset(&sset, SIGINT) != 0 ||
            sigaddset(&sset, SIGTERM) != 0) {
            isc__strerror(errno, strbuf, sizeof(strbuf));
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "isc_app_run() sigsetops: %s", strbuf);
            return (ISC_R_UNEXPECTED);
        }

#ifndef HAVE_UNIXWARE_SIGWAIT
        result = sigwait(&sset, &sig);
        if (result == 0) {
            if (sig == SIGINT ||
                sig == SIGTERM)
                want_shutdown = ISC_TRUE;
            else if (sig == SIGHUP)
                want_reload = ISC_TRUE;
        }

#else /* Using UnixWare sigwait semantics. */
        sig = sigwait(&sset);
        if (sig >= 0) {
            if (sig == SIGINT ||
                sig == SIGTERM)
                want_shutdown = ISC_TRUE;
            else if (sig == SIGHUP)
                want_reload = ISC_TRUE;
        }

#endif /* HAVE_UNIXWARE_SIGWAIT */
#else  /* Don't have sigwait(). */
        /*
         * Listen for all signals.
         */
        if (sigemptyset(&sset) != 0) {
            isc__strerror(errno, strbuf, sizeof(strbuf));
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "isc_app_run() sigsetops: %s", strbuf);
            return (ISC_R_UNEXPECTED);
        }
        result = sigsuspend(&sset);
#endif /* HAVE_SIGWAIT */

        if (want_reload) {
            want_reload = ISC_FALSE;
            return (ISC_R_RELOAD);
        }

        if (want_shutdown && blocked)
            exit(1);
    }

#else /* ISC_PLATFORM_USETHREADS */

    (void)isc__taskmgr_dispatch();

    result = evloop();
    if (result != ISC_R_SUCCESS)
        return (result);

#endif /* ISC_PLATFORM_USETHREADS */

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_app_shutdown(void) {
    isc_boolean_t want_kill = ISC_TRUE;
    char strbuf[ISC_STRERRORSIZE];

    LOCK(&lock);

    REQUIRE(running);

    if (shutdown_requested)
        want_kill = ISC_FALSE;
    else
        shutdown_requested = ISC_TRUE;

    UNLOCK(&lock);

    if (want_kill) {
#ifdef HAVE_LINUXTHREADS
        int result;

        result = pthread_kill(main_thread, SIGTERM);
        if (result != 0) {
            isc__strerror(result, strbuf, sizeof(strbuf));
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "isc_app_shutdown() pthread_kill: %s",
                     strbuf);
            return (ISC_R_UNEXPECTED);
        }
#else
        if (kill(getpid(), SIGTERM) < 0) {
            isc__strerror(errno, strbuf, sizeof(strbuf));
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "isc_app_shutdown() kill: %s", strbuf);
            return (ISC_R_UNEXPECTED);
        }
#endif
    }

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_app_reload(void) {
    isc_boolean_t want_kill = ISC_TRUE;
    char strbuf[ISC_STRERRORSIZE];

    LOCK(&lock);

    REQUIRE(running);

    /*
     * Don't send the reload signal if we're shutting down.
     */
    if (shutdown_requested)
        want_kill = ISC_FALSE;

    UNLOCK(&lock);

    if (want_kill) {
#ifdef HAVE_LINUXTHREADS
        int result;

        result = pthread_kill(main_thread, SIGHUP);
        if (result != 0) {
            isc__strerror(result, strbuf, sizeof(strbuf));
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "isc_app_reload() pthread_kill: %s",
                     strbuf);
            return (ISC_R_UNEXPECTED);
        }
#else
        if (kill(getpid(), SIGHUP) < 0) {
            isc__strerror(errno, strbuf, sizeof(strbuf));
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "isc_app_reload() kill: %s", strbuf);
            return (ISC_R_UNEXPECTED);
        }
#endif
    }

    return (ISC_R_SUCCESS);
}

void
isc_app_finish(void) {
    DESTROYLOCK(&lock);
}

void
isc_app_block(void) {
#ifdef ISC_PLATFORM_USETHREADS
    sigset_t sset;
#endif /* ISC_PLATFORM_USETHREADS */
    REQUIRE(running);
    REQUIRE(!blocked);

    blocked = ISC_TRUE;
#ifdef ISC_PLATFORM_USETHREADS
    blockedthread = pthread_self();
    RUNTIME_CHECK(sigemptyset(&sset) == 0 &&
              sigaddset(&sset, SIGINT) == 0 &&
              sigaddset(&sset, SIGTERM) == 0);
    RUNTIME_CHECK(pthread_sigmask(SIG_UNBLOCK, &sset, NULL) == 0);
#endif /* ISC_PLATFORM_USETHREADS */
}

void
isc_app_unblock(void) {
#ifdef ISC_PLATFORM_USETHREADS
    sigset_t sset;
#endif /* ISC_PLATFORM_USETHREADS */

    REQUIRE(running);
    REQUIRE(blocked);

    blocked = ISC_FALSE;

#ifdef ISC_PLATFORM_USETHREADS
    REQUIRE(blockedthread == pthread_self());

    RUNTIME_CHECK(sigemptyset(&sset) == 0 &&
              sigaddset(&sset, SIGINT) == 0 &&
              sigaddset(&sset, SIGTERM) == 0);
    RUNTIME_CHECK(pthread_sigmask(SIG_BLOCK, &sset, NULL) == 0);
#endif /* ISC_PLATFORM_USETHREADS */
}