Re: [dpdk-dev] [PATCH v6 3/4] bond mode 4: allow external state machine

[Eric Kinzie <ehkinzie@gmail.com>]

On Tue Nov 03 10:30:56 +0200 2015, Panu Matilainen wrote:
> On 11/03/2015 10:16 AM, Thomas Monjalon wrote:
> >2015-11-03 08:48, Panu Matilainen:
> >>On 11/02/2015 06:42 PM, Eric Kinzie wrote:
> >>>On Mon Nov 02 12:23:47 +0200 2015, Panu Matilainen wrote:
> >>>>On 11/01/2015 08:17 PM, Thomas Monjalon wrote:
> >>>>>2015-10-19 08:36, Eric Kinzie:
> >>>>>>    Size of struct rte_eth_bond_8023ad_conf changed.  Increment LIBABIVER
> >>>>>>    and version bond_mode_8023ad_setup and bond_mode_8023ad_conf_get
> >>>>>>    functions.
> >>>>>[...]
> >>>>>>+VERSION_SYMBOL(bond_mode_8023ad_setup, _v20, 2.0);
> >>>>>[...]
> >>>>>>+BIND_DEFAULT_SYMBOL(bond_mode_8023ad_setup, _v22, 2.2);
> >>>>>>+MAP_STATIC_SYMBOL(void bond_mode_8023ad_setup(struct rte_eth_dev *dev, struct rte_eth_bond_8023ad_conf *conf), \
> >>>>>>+		  bond_mode_8023ad_setup_v22);
> >>>>>
> >>>>>I'm sorry it doesn't work well when trying to build a combined lib:
> >>>>>
> >>>>>ld: libdpdk.so: version node not found for symbol bond_mode_8023ad_setup@@DPDK_2.2
> >>>>>
> >>>>>The symbols are OK in the .o file:
> >>>>>0000000000002340 g     F .text  0000000000000171 bond_mode_8023ad_setup@@DPDK_2.2
> >>>>>0000000000002260 g     F .text  00000000000000da bond_mode_8023ad_setup@DPDK_2.0
> >>>>>0000000000002260 g     F .text  00000000000000da bond_mode_8023ad_setup_v20
> >>>>>0000000000002340 g     F .text  0000000000000171 bond_mode_8023ad_setup_v22
> >>>>>0000000000000000         *UND*  0000000000000000 bond_mode_8023ad_setup
> >>>>>
> >>>>>I don't understand the problem and I am considering disabling versioning in
> >>>>>combined library.
> >>>>>
> >>>>>Any idea?
> >>>>>
> >>>>
> >>>>The .map additions look incorrect to me:
> >>>>
> >>>>>diff --git a/drivers/net/bonding/rte_eth_bond_version.map b/drivers/net/bonding/rte_eth_bond_version.map
> >>>>>index 22bd920..7f78717 100644
> >>>>>--- a/drivers/net/bonding/rte_eth_bond_version.map
> >>>>>+++ b/drivers/net/bonding/rte_eth_bond_version.map
> >>>>>@@ -17,6 +17,9 @@  DPDK_2.0 {
> >>>>>	rte_eth_bond_slaves_get;
> >>>>>	rte_eth_bond_xmit_policy_get;
> >>>>>	rte_eth_bond_xmit_policy_set;
> >>>>>+	rte_eth_bond_8023ad_ext_collect;
> >>>>>+	rte_eth_bond_8023ad_ext_distrib;
> >>>>>+	rte_eth_bond_8023ad_ext_slowtx;
> >>>>
> >>>>These symbols didn't exist in DPDK 2.0 but are only being added
> >>>>here. So why are they being added to the 2.0 section?
> >>>
> >>>Yes, I think these should probably be moved.
> >>>
> >>>
> >>>>>
> >>>>>	local: *;
> >>>>>};
> >>>>>@@ -27,3 +30,10 @@  DPDK_2.1 {
> >>>>>	rte_eth_bond_free;
> >>>>>
> >>>>>} DPDK_2.0;
> >>>>>+
> >>>>>+DPDK_2.2 {
> >>>>>+	local
> >>>>>+
> >>>>>+	bond_mode_8023ad_conf_get;
> >>>>>+	bond_mode_8023ad_setup;
> >>>>>+} DPDK_2.1;
> >>>>
> >>>>These are marked local, as in, "not exported" which doesn't seem
> >>>>right. Also they're lacking the rte_eth_ prefix. AFAICS this is what
> >>>>the symbol export map should look like here:
> >>>
> >>>
> >>>These were not exported to begin with.  But after versioning these
> >>>functions, they are exported unless explicitly declared to be local here.
> >>>
> >>
> >>And this does not ring any warning bells? :)
> >>
> >>Sorry, I was not looking at the patch as a whole. You're declaring these
> >>symbols as exported with the versioning macros, eg
> >>
> >>BIND_DEFAULT_SYMBOL(bond_mode_8023ad_setup, _v22, 2.2);
> >>
> >>...and then explicitly telling it to not export them by declaring local,
> >>and then we wonder why it has trouble finding the symbols.
> >>The versioning macros wont invent the librte_ prefix for you, you need
> >>to rename the functions accordingly.
> >>
> >>But all this versioning gymnastics is moot anyway because you declare
> >>the ABI incompatible:
> >>
> >>-LIBABIVER := 1
> >>+LIBABIVER := 2
> >>
> >>This changes the library soname, so no binary compiled against the
> >>previous version can possibly use it anymore. As in, by definition there
> >>can be no callers of the _v20 variants after this ABI version bump.
> >
> >Panu, thanks for your careful review.
> >We must remove the private functions from the export map.and not bump LIBABIVER.
> >
> 
> Actually the LIBABIVER bump seems appropriate since a public struct
> (rte_eth_bond_8023ad_conf) changes size.
> 
> As for the rest, I'm not quite sure what the patch is trying to
> achieve. I initially assumed its trying to add a new incompatible
> version of rte_bond_mode_8023ad_setup() and
> rte_eth_bond_8023ad_conf_get() which could be a perfectly reasonable
> thing to do in some circumstances. As it is, the patch actually adds
> versioning to an internal symbol which just doesn't make sense at
> all. Symbol versioning is only meaningful for public symbols.
> 
> 	- Panu -

It's likely I misintepreted some advice from an ealier review of
this code.  The intention was to prevent an application accidentally
reading/writing past the end of a struct rte_eth_bond_8023ad_conf after
upgrading the library.

I can send another version of these patches that, instead,
adds new versions of rte_bond_mode_8023ad_setup() and
rte_eth_bond_8023ad_conf_get().

Eric