c
int spi_sync(struct spi_device *spi, struct spi_message *message)
{
    int ret;

    mutex_lock(&spi->controller->bus_lock_mutex);
    int do_unlock = 1; // Flag to control unlocking
    defer(if (do_unlock) mutex_unlock(&spi->controller->bus_lock_mutex)); // Hypothetical 'defer'

    ret = __spi_sync(spi, message);
    if (ret != 0) {
        do_unlock = 0; // Prevent unlock if error
        // Handle the error
    }
    return ret;
}
