[dpdk-dev] rte_eal_hotplug_remove() generates error message

[Hideyuki Yamashita]

> On 17-Dec-18 10:45 AM, Hideyuki Yamashita wrote:
> >> 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
> > Hello Anatoly,
> >
> > Thanks for your reply for my newbie question.
> > Now I understand that this error is harmless from DPDK application(SPP)
> > point of view in practice. Thanks.
> > But anyway if there is a double free logic, it is a bug and should be
> > fixed.
> > The remaining issues are
> > 1. If it is really a bug (or my mis-understanding)
> > 2. If is is a bug which function should remove rte_free(mac_addrs)
> 
>  From description, it looks like a bug. Correct usage of API (rte_dev_close() followed by rte_dev_remove()) should not trigger any errors. You might want to create a BugZilla entry describing the issue.
> 
> >
> > Thanks,
> > Hideyuki Yamashita
> > NTT TechnoCross
> >
> >
> 
> --Thanks,
> Anatoly
Hello 

Thanks for your reply again.
I would like to wait for a while(at least a day) to hear 
opnion from other people including Thomas or maintainer.
In addition I have to learn how to file bug in Bugzzilla
for DPDK.

Thanks,
Hideyuki Yamashita
NTT TechnoCross