Re: [PATCH 1/2] vhost: reference count fix for nb_started_ports

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Wed, Dec 28, 2016 at 04:10:51PM -0500, Charles (Chas) Williams wrote:
> From: Wen Chiu <wchiu@brocade.com>
> 
> Only increment and decrement nb_started_ports on the first and last
> device start and stop.  Otherwise, nb_started_ports can become negative
> if a device is stopped multiple times.

How could you be able to stop dev (precisely, invoke eth_dev_stop)
multiple times, judging that eth_dev_stop() will be invoked once
only?

    void
    rte_eth_dev_stop(uint8_t port_id)
    {
            struct rte_eth_dev *dev;
    
            RTE_ETH_VALID_PORTID_OR_RET(port_id);
            dev = &rte_eth_devices[port_id];
    
            RTE_FUNC_PTR_OR_RET(*dev->dev_ops->dev_stop);
    
==>         if (dev->data->dev_started == 0) {
                    RTE_PMD_DEBUG_TRACE("Device with port_id=%" PRIu8
                            " already stopped\n",
                            port_id);
                    return;
            }
    
==>         dev->data->dev_started = 0;
            (*dev->dev_ops->dev_stop)(dev);
    }

Multiple threads?

	--yliu