isc/unix/app.c

	app.c revision 0e58c0998df1ccd1a289b2c3f078e7d03d9331d3
/*
 * Copyright (C) 1999, 2000  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.
 */

#include <config.h>

#include <pthread.h>

#include <sys/types.h>

#include <stddef.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <signal.h>

#include <isc/app.h>
#include <isc/assertions.h>
#include <isc/error.h>
#include <isc/boolean.h>
#include <isc/mutex.h>
#include <isc/event.h>
#include <isc/util.h>

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;

#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) {
        (void)arg;
    want_shutdown = ISC_TRUE;
}

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

static isc_result_t
handle_signal(int sig, void (*handler)(int)) {
    struct sigaction sa;

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

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

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_app_start(void) {
    isc_result_t result;
    int presult;
    sigset_t sset;

    /*
     * 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) {
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_app_start() pthread_init: %s",
                 strerror(presult));
        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);

    /*
     * 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) {
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_app_start() sigsetops: %s",
                 strerror(errno));
        return (ISC_R_UNEXPECTED);
    }
    presult = pthread_sigmask(SIG_BLOCK, &sset, NULL);
    if (presult != 0) {
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_app_start() pthread_sigmask: %s",
                 strerror(presult));
        return (ISC_R_UNEXPECTED);
    }

    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;

    /*
     * Request delivery of an event when the application is run.
     */

    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, link);

    result = ISC_R_SUCCESS;

 unlock:
    UNLOCK(&lock);

    return (result);
}

isc_result_t
isc_app_run(void) {
    int result;
    sigset_t sset;
    isc_event_t *event, *next_event;
    isc_task_t *task;
#ifdef HAVE_SIGWAIT
    int sig;
#endif

    /*
     * Run an ISC library application.
     */

#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, link);
            ISC_LIST_UNLINK(on_run, event, link);
            task = event->sender;
            event->sender = (void *)&running;
            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

    /*
     * 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) {
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "isc_app_run() sigsetops: %s",
                     strerror(errno));
            return (ISC_R_UNEXPECTED);
        }
        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
        /*
         * Listen for all signals.
         */
        if (sigemptyset(&sset) != 0) {
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "isc_app_run() sigsetops: %s",
                     strerror(errno));
            return (ISC_R_UNEXPECTED);
        }
        result = sigsuspend(&sset);
#endif

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

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_app_shutdown(void) {
    isc_boolean_t want_kill = ISC_TRUE;

    /*
     * Request application shutdown.
     */

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

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_app_reload(void) {
    isc_boolean_t want_kill = ISC_TRUE;

    /*
     * Request application reload.
     */

    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) {
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "isc_app_shutdown() pthread_kill: %s",
                     strerror(result));
            return (ISC_R_UNEXPECTED);
        }
#else
        if (kill(getpid(), SIGHUP) < 0) {
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "isc_app_shutdown() kill: %s",
                     strerror(errno));
            return (ISC_R_UNEXPECTED);
        }
#endif
    }

    return (ISC_R_SUCCESS);
}

void
isc_app_finish(void) {
    /*
     * Finish an ISC library application.
     */

    (void)isc_mutex_destroy(&lock);
}