proc_mutex.c

Apache 2.0.63 is the current stable version of the 2.0 series, and is recommended over any previous

/* 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_strings.h"
#include "apr_arch_proc_mutex.h"
#include "apr_arch_file_io.h" /* for apr_mkstemp() */

APR_DECLARE(apr_status_t) apr_proc_mutex_destroy(apr_proc_mutex_t *mutex)
{
    return apr_pool_cleanup_run(mutex->pool, mutex, apr_proc_mutex_cleanup);
}

static apr_status_t proc_mutex_no_tryacquire(apr_proc_mutex_t *new_mutex)
{
    return APR_ENOTIMPL;
}

#if APR_HAS_POSIXSEM_SERIALIZE

#ifndef SEM_FAILED
#define SEM_FAILED (-1)
#endif

static void proc_mutex_posix_setup(void)
{
}

static apr_status_t proc_mutex_posix_cleanup(void *mutex_)
{
    apr_proc_mutex_t *mutex=mutex_;
    apr_status_t stat = APR_SUCCESS;
    
    if (mutex->interproc->filedes != -1) {
        if (sem_close((sem_t *)mutex->interproc->filedes) < 0) {
            stat = errno;
        }
    }
    return stat;
}    

static apr_status_t proc_mutex_posix_create(apr_proc_mutex_t *new_mutex,
                                            const char *fname)
{
    sem_t *psem;
    apr_status_t stat;
    char semname[31];
    apr_time_t now;
    unsigned long sec;
    unsigned long usec;
    
    new_mutex->interproc = apr_palloc(new_mutex->pool,
                                      sizeof(*new_mutex->interproc));
    new_mutex->interproc->filedes = -1;
    /*
     * This bogusness is to follow what appears to be the
     * lowest common denominator in Posix semaphore naming:
     *   - start with '/'
     *   - be at most 14 chars
     *   - be unique and not match anything on the filesystem
     *
     * Because of this, we ignore fname, and try our
     * own naming system. We tuck the name away, since it might
     * be useful for debugging. to  make this as robust as possible,
     * we initially try something larger (and hopefully more unique)
     * and gracefully fail down to the LCD above.
     *
     * NOTE: Darwin (Mac OS X) seems to be the most restrictive
     * implementation. Versions previous to Darwin 6.2 had the 14
     * char limit, but later rev's allow up to 31 characters.
     *
     * FIXME: There is a small window of opportunity where
     * instead of getting a new semaphore descriptor, we get
     * a previously obtained one. This can happen if the requests
     * are made at the "same time" and in the small span of time between
     * the sem_open and the sem_unlink. Use of O_EXCL does not
     * help here however...
     *
     */
    now = apr_time_now();
    sec = apr_time_sec(now);
    usec = apr_time_usec(now);
    apr_snprintf(semname, sizeof(semname), "/ApR.%lxZ%lx", sec, usec);
    psem = sem_open((const char *) semname, O_CREAT, 0644, 1);
    if ((psem == (sem_t *)SEM_FAILED) && (errno == ENAMETOOLONG)) {
        /* Oh well, good try */
        semname[13] = '\0';
        psem = sem_open((const char *) semname, O_CREAT, 0644, 1);
    }

    if (psem == (sem_t *)SEM_FAILED) {
        stat = errno;
        proc_mutex_posix_cleanup(new_mutex);
        return stat;
    }
    /* Ahhh. The joys of Posix sems. Predelete it... */
    sem_unlink((const char *) semname);
    new_mutex->interproc->filedes = (int)psem;	/* Ugg */
    new_mutex->fname = apr_pstrdup(new_mutex->pool, semname);
    apr_pool_cleanup_register(new_mutex->pool, (void *)new_mutex,
                              apr_proc_mutex_cleanup, 
                              apr_pool_cleanup_null);
    return APR_SUCCESS;
}

static apr_status_t proc_mutex_posix_acquire(apr_proc_mutex_t *mutex)
{
    int rc;

    if ((rc = sem_wait((sem_t *)mutex->interproc->filedes)) < 0) {
        return errno;
    }
    mutex->curr_locked = 1;
    return APR_SUCCESS;
}

static apr_status_t proc_mutex_posix_release(apr_proc_mutex_t *mutex)
{
    int rc;

    mutex->curr_locked = 0;
    if ((rc = sem_post((sem_t *)mutex->interproc->filedes)) < 0) {
        return errno;
    }
    return APR_SUCCESS;
}

static apr_status_t proc_mutex_posix_child_init(apr_proc_mutex_t **mutex,
                                                apr_pool_t *cont,
                                                const char *fname)
{
    return APR_SUCCESS;
}

const apr_proc_mutex_unix_lock_methods_t apr_proc_mutex_unix_posix_methods =
{
#if APR_PROCESS_LOCK_IS_GLOBAL || !APR_HAS_THREADS || defined(POSIXSEM_IS_GLOBAL)
    APR_PROCESS_LOCK_MECH_IS_GLOBAL,
#else
    0,
#endif
    proc_mutex_posix_create,
    proc_mutex_posix_acquire,
    proc_mutex_no_tryacquire,
    proc_mutex_posix_release,
    proc_mutex_posix_cleanup,
    proc_mutex_posix_child_init,
    "posixsem"
};

#endif /* Posix sem implementation */

#if APR_HAS_SYSVSEM_SERIALIZE

static struct sembuf proc_mutex_op_on;
static struct sembuf proc_mutex_op_off;

static void proc_mutex_sysv_setup(void)
{
    proc_mutex_op_on.sem_num = 0;
    proc_mutex_op_on.sem_op = -1;
    proc_mutex_op_on.sem_flg = SEM_UNDO;
    proc_mutex_op_off.sem_num = 0;
    proc_mutex_op_off.sem_op = 1;
    proc_mutex_op_off.sem_flg = SEM_UNDO;
}

static apr_status_t proc_mutex_sysv_cleanup(void *mutex_)
{
    apr_proc_mutex_t *mutex=mutex_;
    union semun ick;
    
    if (mutex->interproc->filedes != -1) {
        ick.val = 0;
        semctl(mutex->interproc->filedes, 0, IPC_RMID, ick);
    }
    return APR_SUCCESS;
}    

static apr_status_t proc_mutex_sysv_create(apr_proc_mutex_t *new_mutex,
                                           const char *fname)
{
    union semun ick;
    apr_status_t rv;
    
    new_mutex->interproc = apr_palloc(new_mutex->pool, sizeof(*new_mutex->interproc));
    new_mutex->interproc->filedes = semget(IPC_PRIVATE, 1, IPC_CREAT | 0600);

    if (new_mutex->interproc->filedes < 0) {
        rv = errno;
        proc_mutex_sysv_cleanup(new_mutex);
        return rv;
    }
    ick.val = 1;
    if (semctl(new_mutex->interproc->filedes, 0, SETVAL, ick) < 0) {
        rv = errno;
        proc_mutex_sysv_cleanup(new_mutex);
        return rv;
    }
    new_mutex->curr_locked = 0;
    apr_pool_cleanup_register(new_mutex->pool,
                              (void *)new_mutex, apr_proc_mutex_cleanup, 
                              apr_pool_cleanup_null);
    return APR_SUCCESS;
}

static apr_status_t proc_mutex_sysv_acquire(apr_proc_mutex_t *mutex)
{
    int rc;

    do {
        rc = semop(mutex->interproc->filedes, &proc_mutex_op_on, 1);
    } while (rc < 0 && errno == EINTR);
    if (rc < 0) {
        return errno;
    }
    mutex->curr_locked = 1;
    return APR_SUCCESS;
}

static apr_status_t proc_mutex_sysv_release(apr_proc_mutex_t *mutex)
{
    int rc;

    mutex->curr_locked = 0;
    do {
        rc = semop(mutex->interproc->filedes, &proc_mutex_op_off, 1);
    } while (rc < 0 && errno == EINTR);
    if (rc < 0) {
        return errno;
    }
    return APR_SUCCESS;
}

static apr_status_t proc_mutex_sysv_child_init(apr_proc_mutex_t **mutex, apr_pool_t *cont, const char *fname)
{
    return APR_SUCCESS;
}

const apr_proc_mutex_unix_lock_methods_t apr_proc_mutex_unix_sysv_methods =
{
#if APR_PROCESS_LOCK_IS_GLOBAL || !APR_HAS_THREADS || defined(SYSVSEM_IS_GLOBAL)
    APR_PROCESS_LOCK_MECH_IS_GLOBAL,
#else
    0,
#endif
    proc_mutex_sysv_create,
    proc_mutex_sysv_acquire,
    proc_mutex_no_tryacquire,
    proc_mutex_sysv_release,
    proc_mutex_sysv_cleanup,
    proc_mutex_sysv_child_init,
    "sysvsem"
};

#endif /* SysV sem implementation */

#if APR_HAS_PROC_PTHREAD_SERIALIZE

static void proc_mutex_proc_pthread_setup(void)
{
}

static apr_status_t proc_mutex_proc_pthread_cleanup(void *mutex_)
{
    apr_proc_mutex_t *mutex=mutex_;
    apr_status_t rv;

    if (mutex->curr_locked == 1) {
        if ((rv = pthread_mutex_unlock(mutex->pthread_interproc))) {
#ifdef PTHREAD_SETS_ERRNO
            rv = errno;
#endif
            return rv;
        } 
        if (munmap((caddr_t)mutex->pthread_interproc, sizeof(pthread_mutex_t))){
            return errno;
        }
    }
    return APR_SUCCESS;
}    

static apr_status_t proc_mutex_proc_pthread_create(apr_proc_mutex_t *new_mutex,
                                                   const char *fname)
{
    apr_status_t rv;
    int fd;
    pthread_mutexattr_t mattr;

    fd = open("/dev/zero", O_RDWR);
    if (fd < 0) {
        return errno;
    }

    new_mutex->pthread_interproc = (pthread_mutex_t *)mmap(
                                       (caddr_t) 0, 
                                       sizeof(pthread_mutex_t), 
                                       PROT_READ | PROT_WRITE, MAP_SHARED,
                                       fd, 0); 
    if (new_mutex->pthread_interproc == (pthread_mutex_t *) (caddr_t) -1) {
        return errno;
    }
    close(fd);
    if ((rv = pthread_mutexattr_init(&mattr))) {
#ifdef PTHREAD_SETS_ERRNO
        rv = errno;
#endif
        proc_mutex_proc_pthread_cleanup(new_mutex);
        return rv;
    }
    if ((rv = pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED))) {
#ifdef PTHREAD_SETS_ERRNO
        rv = errno;
#endif
        proc_mutex_proc_pthread_cleanup(new_mutex);
        return rv;
    }

#ifdef HAVE_PTHREAD_MUTEX_ROBUST
    if ((rv = pthread_mutexattr_setrobust_np(&mattr, 
                                               PTHREAD_MUTEX_ROBUST_NP))) {
#ifdef PTHREAD_SETS_ERRNO
        rv = errno;
#endif
        proc_mutex_proc_pthread_cleanup(new_mutex);
        return rv;
    }
    if ((rv = pthread_mutexattr_setprotocol(&mattr, PTHREAD_PRIO_INHERIT))) {
#ifdef PTHREAD_SETS_ERRNO
        rv = errno;
#endif
        proc_mutex_proc_pthread_cleanup(new_mutex);
        return rv;
    }
#endif /* HAVE_PTHREAD_MUTEX_ROBUST */

    if ((rv = pthread_mutex_init(new_mutex->pthread_interproc, &mattr))) {
#ifdef PTHREAD_SETS_ERRNO
        rv = errno;
#endif
        proc_mutex_proc_pthread_cleanup(new_mutex);
        return rv;
    }

    if ((rv = pthread_mutexattr_destroy(&mattr))) {
#ifdef PTHREAD_SETS_ERRNO
        rv = errno;
#endif
        proc_mutex_proc_pthread_cleanup(new_mutex);
        return rv;
    }

    new_mutex->curr_locked = 0;
    apr_pool_cleanup_register(new_mutex->pool,
                              (void *)new_mutex,
                              apr_proc_mutex_cleanup, 
                              apr_pool_cleanup_null);
    return APR_SUCCESS;
}

static apr_status_t proc_mutex_proc_pthread_acquire(apr_proc_mutex_t *mutex)
{
    apr_status_t rv;

    if ((rv = pthread_mutex_lock(mutex->pthread_interproc))) {
#ifdef PTHREAD_SETS_ERRNO
        rv = errno;
#endif
#ifdef HAVE_PTHREAD_MUTEX_ROBUST
        /* Okay, our owner died.  Let's try to make it consistent again. */
        if (rv == EOWNERDEAD) {
            pthread_mutex_consistent_np(mutex->pthread_interproc);
        }
        else
            return rv;
#else
        return rv;
#endif
    }
    mutex->curr_locked = 1;
    return APR_SUCCESS;
}

/* TODO: Add proc_mutex_proc_pthread_tryacquire(apr_proc_mutex_t *mutex) */

static apr_status_t proc_mutex_proc_pthread_release(apr_proc_mutex_t *mutex)
{
    apr_status_t rv;

    mutex->curr_locked = 0;
    if ((rv = pthread_mutex_unlock(mutex->pthread_interproc))) {
#ifdef PTHREAD_SETS_ERRNO
        rv = errno;
#endif
        return rv;
    }
    return APR_SUCCESS;
}

static apr_status_t proc_mutex_proc_pthread_child_init(apr_proc_mutex_t **mutex,
                                            apr_pool_t *cont, 
                                            const char *fname)
{
    return APR_SUCCESS;
}

const apr_proc_mutex_unix_lock_methods_t apr_proc_mutex_unix_proc_pthread_methods =
{
    APR_PROCESS_LOCK_MECH_IS_GLOBAL,
    proc_mutex_proc_pthread_create,
    proc_mutex_proc_pthread_acquire,
    proc_mutex_no_tryacquire,
    proc_mutex_proc_pthread_release,
    proc_mutex_proc_pthread_cleanup,
    proc_mutex_proc_pthread_child_init,
    "pthread"
};

#endif

#if APR_HAS_FCNTL_SERIALIZE

static struct flock proc_mutex_lock_it;
static struct flock proc_mutex_unlock_it;

static apr_status_t proc_mutex_fcntl_release(apr_proc_mutex_t *);

static void proc_mutex_fcntl_setup(void)
{
    proc_mutex_lock_it.l_whence = SEEK_SET;   /* from current point */
    proc_mutex_lock_it.l_start = 0;           /* -"- */
    proc_mutex_lock_it.l_len = 0;             /* until end of file */
    proc_mutex_lock_it.l_type = F_WRLCK;      /* set exclusive/write lock */
    proc_mutex_lock_it.l_pid = 0;             /* pid not actually interesting */
    proc_mutex_unlock_it.l_whence = SEEK_SET; /* from current point */