isc/win32/condition.c

/*
 * Copyright (C) 1998-2001, 2004, 2006, 2007, 2016  Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

/* $Id: condition.c,v 1.23 2007/06/18 23:47:49 tbox Exp $ */

#include <config.h>

#include <isc/condition.h>
#include <isc/assertions.h>
#include <isc/util.h>
#include <isc/thread.h>
#include <isc/time.h>

#define LSIGNAL     0
#define LBROADCAST  1

isc_result_t
isc_condition_init(isc_condition_t *cond) {
    HANDLE h;

    REQUIRE(cond != NULL);

    cond->waiters = 0;
    /*
     * This handle is shared across all threads
     */
    h = CreateEvent(NULL, FALSE, FALSE, NULL);
    if (h == NULL) {
        /* XXX */
        return (ISC_R_UNEXPECTED);
    }
    cond->events[LSIGNAL] = h;

    /*
     * The threadlist will hold the actual events needed
     * for the wait condition
     */
    ISC_LIST_INIT(cond->threadlist);

    return (ISC_R_SUCCESS);
}

/*
 * Add the thread to the threadlist along with the required events
 */
static isc_result_t
register_thread(unsigned long thrd, isc_condition_t *gblcond,
        isc_condition_thread_t **localcond)
{
    HANDLE hc;
    isc_condition_thread_t *newthread;

    REQUIRE(localcond != NULL && *localcond == NULL);

    newthread = malloc(sizeof(isc_condition_thread_t));
    if (newthread == NULL)
        return (ISC_R_NOMEMORY);

    /*
     * Create the thread-specific handle
     */
    hc = CreateEvent(NULL, FALSE, FALSE, NULL);
    if (hc == NULL) {
        free(newthread);
        return (ISC_R_UNEXPECTED);
    }

    /*
     * Add the thread ID and handles to list of threads for broadcast
     */
    newthread->handle[LSIGNAL] = gblcond->events[LSIGNAL];
    newthread->handle[LBROADCAST] = hc;
    newthread->th = thrd;

    /*
     * The thread is holding the manager lock so this is safe
     */
    ISC_LINK_INIT(newthread, link);
    ISC_LIST_APPEND(gblcond->threadlist, newthread, link);
    *localcond = newthread;
    return (ISC_R_SUCCESS);
}

static isc_result_t
find_thread_condition(unsigned long thrd, isc_condition_t *cond,
              isc_condition_thread_t **threadcondp)
{
    isc_condition_thread_t *threadcond;

    REQUIRE(threadcondp != NULL && *threadcondp == NULL);

    /*
     * Look for the thread ID.
     */
    for (threadcond = ISC_LIST_HEAD(cond->threadlist);
         threadcond != NULL;
         threadcond = ISC_LIST_NEXT(threadcond, link)) {

        if (threadcond->th == thrd) {
            *threadcondp = threadcond;
            return (ISC_R_SUCCESS);
        }
    }

    /*
     * Not found, so add it.
     */
    return (register_thread(thrd, cond, threadcondp));
}

isc_result_t
isc_condition_signal(isc_condition_t *cond) {

    /*
     * Unlike pthreads, the caller MUST hold the lock associated with
     * the condition variable when calling us.
     */
    REQUIRE(cond != NULL);

    if (!SetEvent(cond->events[LSIGNAL])) {
        /* XXX */
        return (ISC_R_UNEXPECTED);
    }

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_condition_broadcast(isc_condition_t *cond) {

    isc_condition_thread_t *threadcond;
    isc_boolean_t failed = ISC_FALSE;

    /*
     * Unlike pthreads, the caller MUST hold the lock associated with
     * the condition variable when calling us.
     */
    REQUIRE(cond != NULL);

    /*
     * Notify every thread registered for this
     */
    for (threadcond = ISC_LIST_HEAD(cond->threadlist);
         threadcond != NULL;
         threadcond = ISC_LIST_NEXT(threadcond, link)) {

        if (!SetEvent(threadcond->handle[LBROADCAST]))
            failed = ISC_TRUE;
    }

    if (failed)
        return (ISC_R_UNEXPECTED);

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_condition_destroy(isc_condition_t *cond) {

    isc_condition_thread_t *next, *threadcond;

    REQUIRE(cond != NULL);
    REQUIRE(cond->waiters == 0);

    (void)CloseHandle(cond->events[LSIGNAL]);

    /*
     * Delete the threadlist
     */
    threadcond = ISC_LIST_HEAD(cond->threadlist);

    while (threadcond != NULL) {
        next = ISC_LIST_NEXT(threadcond, link);
        DEQUEUE(cond->threadlist, threadcond, link);
        (void) CloseHandle(threadcond->handle[LBROADCAST]);
        free(threadcond);
        threadcond = next;
    }

    return (ISC_R_SUCCESS);
}

/*
 * This is always called when the mutex (lock) is held, but because
 * we are waiting we need to release it and reacquire it as soon as the wait
 * is over. This allows other threads to make use of the object guarded
 * by the mutex but it should never try to delete it as long as the
 * number of waiters > 0. Always reacquire the mutex regardless of the
 * result of the wait. Note that EnterCriticalSection will wait to acquire
 * the mutex.
 */
static isc_result_t
wait(isc_condition_t *cond, isc_mutex_t *mutex, DWORD milliseconds) {
    DWORD result;
    isc_result_t tresult;
    isc_condition_thread_t *threadcond = NULL;

    /*
     * Get the thread events needed for the wait
     */
    tresult = find_thread_condition(isc_thread_self(), cond, &threadcond);
    if (tresult !=  ISC_R_SUCCESS)
        return (tresult);

    cond->waiters++;
    LeaveCriticalSection(mutex);
    result = WaitForMultipleObjects(2, threadcond->handle, FALSE,
                    milliseconds);
    EnterCriticalSection(mutex);
    cond->waiters--;
    if (result == WAIT_FAILED) {
        /* XXX */
        return (ISC_R_UNEXPECTED);
    }
    if (result == WAIT_TIMEOUT)
        return (ISC_R_TIMEDOUT);

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_condition_wait(isc_condition_t *cond, isc_mutex_t *mutex) {
    return (wait(cond, mutex, INFINITE));
}

isc_result_t
isc_condition_waituntil(isc_condition_t *cond, isc_mutex_t *mutex,
            isc_time_t *t) {
    DWORD milliseconds;
    isc_uint64_t microseconds;
    isc_time_t now;

    if (isc_time_now(&now) != ISC_R_SUCCESS) {
        /* XXX */
        return (ISC_R_UNEXPECTED);
    }

    microseconds = isc_time_microdiff(t, &now);
    if (microseconds > 0xFFFFFFFFi64 * 1000)
        milliseconds = 0xFFFFFFFF;
    else
        milliseconds = (DWORD)(microseconds / 1000);

    return (wait(cond, mutex, milliseconds));
}