TAIXIN/sdk/lib/posix/pthread_rwlock.c

#include "sys_config.h"
#include "typesdef.h"
#include "errno.h"
#include "osal/semaphore.h"
#include "osal/task.h"
#include "osal/string.h"
#include "osal/timer.h"
#include "osal/mutex.h"
#include "lib/common/rbuffer.h"
#include "lib/posix/pthread.h"

#ifdef TXWSDK_POSIX

int pthread_rwlockattr_init(pthread_rwlockattr_t *attr)
{
    if (!attr) {
        return -EINVAL;
    }

    *attr = PTHREAD_PROCESS_PRIVATE;
    return 0;
}

int pthread_rwlockattr_destroy(pthread_rwlockattr_t *attr)
{
    if (!attr) {
        return -EINVAL;
    }
    return 0;
}

int pthread_rwlockattr_getpshared(const pthread_rwlockattr_t *attr,
                                  int                        *pshared)
{
    if (!attr || !pshared) {
        return -EINVAL;
    }
    *pshared = PTHREAD_PROCESS_PRIVATE;
    return 0;
}

int pthread_rwlockattr_setpshared(pthread_rwlockattr_t *attr, int pshared)
{
    if (!attr || pshared != PTHREAD_PROCESS_PRIVATE) {
        return -EINVAL;
    }
    return 0;
}

int pthread_rwlock_init(pthread_rwlock_t           *rwlock,
                        const pthread_rwlockattr_t *attr)
{
    if (!rwlock) {
        return -EINVAL;
    }

    rwlock->attr = PTHREAD_PROCESS_PRIVATE;
    pthread_mutex_init(&(rwlock->rw_mutex), NULL);
    pthread_cond_init(&(rwlock->rw_condreaders), NULL);
    pthread_cond_init(&(rwlock->rw_condwriters), NULL);

    rwlock->rw_nwaitwriters = 0;
    rwlock->rw_nwaitreaders = 0;
    rwlock->rw_refcount = 0;
    return 0;
}

int pthread_rwlock_destroy(pthread_rwlock_t *rwlock)
{
    int result;

    if (!rwlock) {
        return -EINVAL;
    }

    if (rwlock->attr == -1) {
        return 0; /* rwlock is not initialized */
    }

    if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0) {
        return (result);
    }

    if (rwlock->rw_refcount != 0 ||
        rwlock->rw_nwaitreaders != 0 ||
        rwlock->rw_nwaitwriters != 0) {
        return -EBUSY;
    } else {
        pthread_cond_destroy(&rwlock->rw_condreaders);
        pthread_cond_destroy(&rwlock->rw_condwriters);
    }

    pthread_mutex_unlock(&rwlock->rw_mutex);
    if (result == 0) {
        pthread_mutex_destroy(&rwlock->rw_mutex);
    }
    return result;
}

int pthread_rwlock_rdlock(pthread_rwlock_t *rwlock)
{
    int result;

    if (!rwlock) {
        return -EINVAL;
    }

    if (rwlock->attr == -1) {
        pthread_rwlock_init(rwlock, NULL);
    }

    if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0) {
        return (result);
    }

    /* give preference to waiting writers */
    while (rwlock->rw_refcount < 0 || rwlock->rw_nwaitwriters > 0) {
        rwlock->rw_nwaitreaders++;
        /* rw_mutex will be released when waiting for rw_condreaders */
        result = pthread_cond_wait(&rwlock->rw_condreaders, &rwlock->rw_mutex);
        /* rw_mutex should have been taken again when returned from waiting */
        rwlock->rw_nwaitreaders--;
        if (result != 0) { /* wait error */
            break;
        }
    }

    /* another reader has a read lock */
    if (result == 0) {
        rwlock->rw_refcount++;
    }

    pthread_mutex_unlock(&rwlock->rw_mutex);

    return (result);
}

int pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock)
{
    int result;

    if (!rwlock) {
        return -EINVAL;
    }

    if (rwlock->attr == -1) {
        pthread_rwlock_init(rwlock, NULL);
    }

    if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0) {
        return (result);
    }

    if (rwlock->rw_refcount < 0 || rwlock->rw_nwaitwriters > 0) {
        result = -EBUSY; /* held by a writer or waiting writers */
    } else {
        rwlock->rw_refcount++; /* increment count of reader locks */
    }

    pthread_mutex_unlock(&rwlock->rw_mutex);

    return (result);
}

int pthread_rwlock_timedrdlock(pthread_rwlock_t      *rwlock,
                               const struct timespec *abstime)
{
    int result;

    if (!rwlock) {
        return -EINVAL;
    }

    if (rwlock->attr == -1) {
        pthread_rwlock_init(rwlock, NULL);
    }

    if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0) {
        return (result);
    }

    /* give preference to waiting writers */
    while (rwlock->rw_refcount < 0 || rwlock->rw_nwaitwriters > 0) {
        rwlock->rw_nwaitreaders++;
        /* rw_mutex will be released when waiting for rw_condreaders */
        result = pthread_cond_timedwait(&rwlock->rw_condreaders, &rwlock->rw_mutex, abstime);
        /* rw_mutex should have been taken again when returned from waiting */
        rwlock->rw_nwaitreaders--;
        if (result != 0) {
            break;
        }
    }

    /* another reader has a read lock */
    if (result == 0) {
        rwlock->rw_refcount++;
    }

    pthread_mutex_unlock(&rwlock->rw_mutex);

    return (result);
}

int pthread_rwlock_timedwrlock(pthread_rwlock_t      *rwlock,
                               const struct timespec *abstime)
{
    int result;

    if (!rwlock) {
        return -EINVAL;
    }

    if (rwlock->attr == -1) {
        pthread_rwlock_init(rwlock, NULL);
    }

    if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0) {
        return (result);
    }

    while (rwlock->rw_refcount != 0) {
        rwlock->rw_nwaitwriters++;
        /* rw_mutex will be released when waiting for rw_condwriters */
        result = pthread_cond_timedwait(&rwlock->rw_condwriters, &rwlock->rw_mutex, abstime);
        /* rw_mutex should have been taken again when returned from waiting */
        rwlock->rw_nwaitwriters--;

        if (result != 0) {
            break;
        }
    }

    if (result == 0) {
        rwlock->rw_refcount = -1;
    }

    pthread_mutex_unlock(&rwlock->rw_mutex);

    return (result);
}

int pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock)
{
    int result;

    if (!rwlock) {
        return -EINVAL;
    }

    if (rwlock->attr == -1) {
        pthread_rwlock_init(rwlock, NULL);
    }

    if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0) {
        return (result);
    }

    if (rwlock->rw_refcount != 0) {
        result = -EBUSY; /* held by either writer or reader(s) */
    } else {
        rwlock->rw_refcount = -1; /* available, indicate a writer has it */

    }
    pthread_mutex_unlock(&rwlock->rw_mutex);

    return (result);
}

int pthread_rwlock_unlock(pthread_rwlock_t *rwlock)
{
    int result;

    if (!rwlock) {
        return -EINVAL;
    }

    if (rwlock->attr == -1) {
        pthread_rwlock_init(rwlock, NULL);
    }

    if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0) {
        return (result);
    }

    if (rwlock->rw_refcount > 0) {
        rwlock->rw_refcount--; /* releasing a reader */
    } else if (rwlock->rw_refcount == -1) {
        rwlock->rw_refcount = 0; /* releasing a writer */
    }

    /* give preference to waiting writers over waiting readers */
    if (rwlock->rw_nwaitwriters > 0) {
        if (rwlock->rw_refcount == 0) {
            result = pthread_cond_signal(&rwlock->rw_condwriters);
        }
    } else if (rwlock->rw_nwaitreaders > 0) {
        result = pthread_cond_broadcast(&rwlock->rw_condreaders);
    }

    pthread_mutex_unlock(&rwlock->rw_mutex);

    return (result);
}

int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock)
{
    int result;

    if (!rwlock) {
        return -EINVAL;
    }

    if (rwlock->attr == -1) {
        pthread_rwlock_init(rwlock, NULL);
    }

    if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0) {
        return (result);
    }

    while (rwlock->rw_refcount != 0) {
        rwlock->rw_nwaitwriters++;
        /* rw_mutex will be released when waiting for rw_condwriters */
        result = pthread_cond_wait(&rwlock->rw_condwriters, &rwlock->rw_mutex);
        /* rw_mutex should have been taken again when returned from waiting */
        rwlock->rw_nwaitwriters--;

        if (result != 0) {
            break;
        }
    }

    if (result == 0) {
        rwlock->rw_refcount = -1;
    }

    pthread_mutex_unlock(&rwlock->rw_mutex);

    return (result);
}

#endif