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

[Hideyuki Yamashita <yamashita.hideyuki@po.ntt-tx.co.jp>]

> 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)

Thanks,
Hideyuki Yamashita
NTT TechnoCross