Commit c166cb72 authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Anthony Liguori
Browse files

semaphore: implement fallback counting semaphores with mutex+condvar 



OpenBSD and Darwin do not have sem_timedwait.  Implement a fallback
for them.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarAnthony Liguori <aliguori@us.ibm.com>
parent 1f001dc7

qemu-thread-posix.c

+82 −10
Original line number Diff line number Diff line
@@ -122,36 +122,106 @@ void qemu_sem_init(QemuSemaphore *sem, int init) 
{

    int rc;



#if defined(__OpenBSD__) || defined(__APPLE__) || defined(__NetBSD__)

    rc = pthread_mutex_init(&sem->lock, NULL);

    if (rc != 0) {

        error_exit(rc, __func__);

    }

    rc = pthread_cond_init(&sem->cond, NULL);

    if (rc != 0) {

        error_exit(rc, __func__);

    }

    if (init < 0) {

        error_exit(EINVAL, __func__);

    }

    sem->count = init;

#else

    rc = sem_init(&sem->sem, 0, init);

    if (rc < 0) {

        error_exit(errno, __func__);

    }

#endif

}



void qemu_sem_destroy(QemuSemaphore *sem)

{

    int rc;



#if defined(__OpenBSD__) || defined(__APPLE__) || defined(__NetBSD__)

    rc = pthread_cond_destroy(&sem->cond);

    if (rc < 0) {

        error_exit(rc, __func__);

    }

    rc = pthread_mutex_destroy(&sem->lock);

    if (rc < 0) {

        error_exit(rc, __func__);

    }

#else

    rc = sem_destroy(&sem->sem);

    if (rc < 0) {

        error_exit(errno, __func__);

    }

#endif

}



void qemu_sem_post(QemuSemaphore *sem)

{

    int rc;



#if defined(__OpenBSD__) || defined(__APPLE__) || defined(__NetBSD__)

    pthread_mutex_lock(&sem->lock);

    if (sem->count == INT_MAX) {

        rc = EINVAL;

    } else if (sem->count++ < 0) {

        rc = pthread_cond_signal(&sem->cond);

    } else {

        rc = 0;

    }

    pthread_mutex_unlock(&sem->lock);

    if (rc != 0) {

        error_exit(rc, __func__);

    }

#else

    rc = sem_post(&sem->sem);

    if (rc < 0) {

        error_exit(errno, __func__);

    }

#endif

}



static void compute_abs_deadline(struct timespec *ts, int ms)

{

    struct timeval tv;

    gettimeofday(&tv, NULL);

    ts->tv_nsec = tv.tv_usec * 1000 + (ms % 1000) * 1000000;

    ts->tv_sec = tv.tv_sec + ms / 1000;

    if (ts->tv_nsec >= 1000000000) {

        ts->tv_sec++;

        ts->tv_nsec -= 1000000000;

    }

}



int qemu_sem_timedwait(QemuSemaphore *sem, int ms)

{

    int rc;

    struct timespec ts;



#if defined(__OpenBSD__) || defined(__APPLE__) || defined(__NetBSD__)

    compute_abs_deadline(&ts, ms);

    pthread_mutex_lock(&sem->lock);

    --sem->count;

    while (sem->count < 0) {

        rc = pthread_cond_timedwait(&sem->cond, &sem->lock, &ts);

        if (rc == ETIMEDOUT) {

            break;

        }

        if (rc != 0) {

            error_exit(rc, __func__);

        }

    }

    pthread_mutex_unlock(&sem->lock);

    return (rc == ETIMEDOUT ? -1 : 0);

#else

    if (ms <= 0) {

        /* This is cheaper than sem_timedwait.  */

        do {
@@ -161,15 +231,7 @@ int qemu_sem_timedwait(QemuSemaphore *sem, int ms) 
            return -1;

        }

    } else {

        struct timeval tv;

        struct timespec ts;

        gettimeofday(&tv, NULL);

        ts.tv_nsec = tv.tv_usec * 1000 + (ms % 1000) * 1000000;

        ts.tv_sec = tv.tv_sec + ms / 1000;

        if (ts.tv_nsec >= 1000000000) {

            ts.tv_sec++;

            ts.tv_nsec -= 1000000000;

        }

        compute_abs_deadline(&ts, ms);

        do {

            rc = sem_timedwait(&sem->sem, &ts);

        } while (rc == -1 && errno == EINTR);
@@ -181,10 +243,19 @@ int qemu_sem_timedwait(QemuSemaphore *sem, int ms) 
        error_exit(errno, __func__);

    }

    return 0;

#endif

}



void qemu_sem_wait(QemuSemaphore *sem)

{

#if defined(__OpenBSD__) || defined(__APPLE__) || defined(__NetBSD__)

    pthread_mutex_lock(&sem->lock);

    --sem->count;

    while (sem->count < 0) {

        pthread_cond_wait(&sem->cond, &sem->lock);

    }

    pthread_mutex_unlock(&sem->lock);

#else

    int rc;



    do {
@@ -193,6 +264,7 @@ void qemu_sem_wait(QemuSemaphore *sem) 
    if (rc < 0) {

        error_exit(errno, __func__);

    }

#endif

}



void qemu_thread_create(QemuThread *thread,

qemu-thread-posix.h

+6 −0
Original line number Diff line number Diff line
@@ -12,7 +12,13 @@ struct QemuCond { 
};



struct QemuSemaphore {

#if defined(__OpenBSD__) || defined(__APPLE__) || defined(__NetBSD__)

    pthread_mutex_t lock;

    pthread_cond_t cond;

    int count;

#else

    sem_t sem;

#endif

};



struct QemuThread {