Re: [dpdk-dev] rte_eal_hotplug_remove() generates error message

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 17-Dec-18 10:02 AM, Hideyuki Yamashita wrote:
> Dear Thomas and all,
> 
> I took a look on dpdk code.
> I firstly write qustions and my analisys
> on the current dpdk code follows after that.
> 
> [1.Questions]
> I have several questions to ask again.
> Is my understanding correct about followings
> 
> Q1: "EAL:ERROR, Invalid memory" is ignorable
> 
> Q2: there is no big difference between calling
> rte_eal_hotplug_remove(bus->name, dev->name)
> and
> rte_dev_remove(dev) because anyway it
> reaches to rte_pmd_vhost_remove and encounter
> the same error.
> 
> [2.snip from my code]
> .....
>          rte_eth_dev_close(port_id);
>          ret = rte_dev_remove(dev);
>          if (ret < 0)
>                  return ret;
>          rte_eth_dev_release_port(&rte_eth_devices[port_id]);
> 
> [3. My analysis on dpdk code]
> static int
>    rte_pmd_vhost_remove(struct rte_vdev_device *dev)
>    {
>     ...........
>          　eth_dev_close(eth_dev);
> 
>            rte_free(vring_states[eth_dev->data->port_id]);
>            vring_states[eth_dev->data->port_id] = NULL;
> 
>            rte_eth_dev_release_port(eth_dev);
> 
> As you can see in rte_eth_vhost.c
> It calls both eth_dev_close and rte_eth_dev_release_port.
> And inside both functions, it tries to free mac_addrs.
>          rte_free(dev->data->mac_addrs);       //in rth_dev_close
>          rte_free(eth_dev->data->mac_addrs);  //in rte_eth_dev_release_port
> 
> I understand that is the reason why
> /* Free the memory space back to heap */
> void rte_free(void *addr)
> {
>          if (addr == NULL) return;
>          if (malloc_heap_free(malloc_elem_from_data(addr)) < 0)
>                  RTE_LOG(ERR, EAL, "Error: Invalid memory\n");
> }
> encounter the error.
> As an experiment, I commented out one of them, "ERR, Invalid memory"
> disappered.
> 
> Thanks and BR,
> Hideyuki Yamashita
> NTT TechnoCross
> 
>> Adding my colleague Yasufumi and Hiroyuki as CC.
>>
>> We are waiting valuable advice from you.
>>
>> Thanks in advance,
>> Hideyuki Yamashita
>> NTT TechnoCross
>>
>>>
>>> Dear Thomas and all,
>>>
>>> I hope you all get safely back home after DPDK summit.
>>> (When I get back Japan, it is chilling. (start of winter))
>>>
>>> On DPDK 18.11.0, we tried to remove vhost device by using rte_eal_hotplug_remove().
>>> However, following syslog message is printed.
>>> “EAL: Error: Invalid memory”
>>>
>>> At DPDK summit San Jose, we had chance to ask Thomas how to handle the error message, and he gave us following advice:
>>> Replace “rte_eal_hotplug_add()” to “rte_dev_probe(devargs)” and
>>> “rte_eal_hotplug_remove()” to “rte_eth_dev_close() and rte_dev_remove(rte_dev)”
>>>
>>> We tested above changes, but the result is the same (i.e., same error message is printed).
>>> The debug log message says:
>>> ---
>>> [primary]
>>> VHOST_CONFIG: vhost-user server: socket created, fd: 17
>>> VHOST_CONFIG: bind to /tmp/sock0
>>> EAL: Error: Invalid memory
>>> VHOST_CONFIG: vhost-user server: socket created, fd: 17
>>> VHOST_CONFIG: bind to /tmp/sock0
>>>
>>> [secondary]
>>> APP: devargs=eth_vhost0,iface=/tmp/sock0,queues=1
>>> EAL: request: eal_dev_mp_request
>>> EAL: msg: eal_dev_mp_request
>>> EAL: request: bus_vdev_mp
>>> EAL: msg: bus_vdev_mp
>>> EAL: msg: bus_vdev_mp
>>> EAL: reply: eal_dev_mp_request
>>> EAL: msg: eal_dev_mp_request
>>> rte_eth_promiscuous_disable: Function not supported
>>> rte_eth_allmulticast_disable: Function not supported
>>> APP: To Server: add
>>> EAL: request: eal_dev_mp_request
>>> EAL: msg: eal_dev_mp_request
>>> EAL: reply: eal_dev_mp_request
>>> EAL: msg: eal_dev_mp_request
>>> APP: To Server: del
>>> APP: devargs=eth_vhost0,iface=/tmp/sock0,queues=1
>>> EAL: request: eal_dev_mp_request
>>> EAL: msg: eal_dev_mp_request
>>> EAL: request: bus_vdev_mp
>>> EAL: msg: bus_vdev_mp
>>> EAL: msg: bus_vdev_mp
>>> EAL: reply: eal_dev_mp_request
>>> EAL: msg: eal_dev_mp_request
>>> rte_eth_promiscuous_disable: Function not supported
>>> rte_eth_allmulticast_disable: Function not supported
>>> APP: To Server: add
>>> ---
>>>
>>> We would like to ask:
>>> 1)	Is the message “EAL: Error: Invalid memory” ignorable or not? There is no obstacle except this message to re-add the vhost device.
>>> 2)	Which is the better(best?) way to add/del vhost device “rte_eal_hotplug_add/remove()” or the way Thomas suggested?
>>>
>>> Thanks in advance and have a nice day.
>>>
>>> BR,
>>> Hideyuki Yamashita
>>> NTT TechnoCross
>>
> 
> 
> 

Hi Hideyuki,

The error you're referring to (about invalid memory) means that you're  
trying to free a pointer that points to invalid memory. Meaning, either  
the pointer itself is not pointing to an allocated area, or it points to  
memory that has already been freed.

If dev->data->mac_addrs and eth_dev->data->mac_addrs point to the same  
area, this is a bug, because this would lead to double free, and  
rte_malloc will rightly complain about invalid memory. Now, malloc won't  
try to do anything with the invalid memory, so the error itself is  
harmless *as far as malloc is concerned*, but these attempts to free the  
memory twice should be fixed whereever they happen.

I'm not well-versed in dev infrastructure, so i wouldn't be able to say  
which one of the rte_free calls is an extra, unneeded one. This is  
something e.g. Thomas could help with, or the driver maintainer.

-- 
Thanks,
Anatoly