On Thu, Feb 12, 2015 at 09:17:39AM +0000, Gonzalez Monroy, Sergio wrote: > On 12/02/2015 05:41, Neil Horman wrote: > >On Wed, Feb 11, 2015 at 11:11:13AM +0000, Gonzalez Monroy, Sergio wrote: > >>>From: Neil Horman [mailto:nhorman at tuxdriver.com] > >>>Sent: Friday, January 30, 2015 6:13 PM > >>>To: Gonzalez Monroy, Sergio > >>>Cc: Thomas Monjalon; dev at dpdk.org > >>>Subject: Re: [dpdk-dev] [PATCH 0/8] Improve build process > >>> > >>>On Fri, Jan 30, 2015 at 05:38:49PM +0000, Gonzalez Monroy, Sergio wrote: > >>[snip] > >> > >>>>So would it be reasonable to add DT_NEEDED entries to all DPDK libraries > >>>but EAL? > >>>>If I understood what you were saying right, we could enforce the > >>>>'dependency' in the linker script with something like this: > >>>>$ cat librte_eal.so > >>>>INPUT( librte_eal.so.1 -lrte_mempool -lrte_malloc) We could have such > >>>>linker script for librte_eal.so instead of the soft link once > >>>>versioning is in place. > >>>> > >>>Correct. > >>> > >>>>Things that would be missing versus the proposed patch: > >>>> - As I have mention in previous post, ldd info for EAL library would not > >>>reflect > >>>> its dependency to other DPDK libs. > >>>librte_eal.so would no show those dependencies, as far as I know (though I > >>>haven't explicitly checked). The subordunate libraries included in the > >>>input > >>>line, may or may not show dependencies among themselves, depending on > >>>your build setup (and the use of --no-as-needed and -l when linking the > >>>individual .so libraries. > >>> > >>>> - I was enforcing resolving all references when building the libraries > >>>> (-z > >>>defs), so > >>>> we either remove it altogether or skip eal. > >>>I think thats correct, yes. > >>> > >>>> - All apps would show DT_NEEDED entries for a set of DPDK libraries that > >>>> in most cases are required (eal, mempool, malloc, mbuf, ring VS > >>>>dpdk_core) > >>>> > >>>I think apps linked to libdpdk_core would have DT_NEEDED entries for > >>>libdpdk_core, not the subordonate libraries (though check me on that to be > >>>sure). > >>> > >>Just checked on this and they do link against the subordinate libraries, > >>although > >>It does not really matter as we are dropping the 'core' library approach > >>anyway. > >> > >ok, understood. > > > >>>>I think that the linker script approach is reasonable if we prefer to > >>>>go that way instead of creating a core library. > >>>> > >>>I think it would make sense from a build environment point of view, in > >>>that it > >>>allows library specific flags to be incorporated properly. I think the > >>>only > >>>downside is that the individual libraries still need to be carried around > >>>(though they can be ignored from an application build/run standpoint). > >>>You're question should probably be asked of people using COMBINED_LIBS > >>>currently to make sure that meets their needs, though I think it will. > >>> > >>>Neil > >>> > >>So I just realized that I was not having into account a possible scenario, > >>where > >>we have an app built with static dpdk libs then loading a dso with -d > >>option. > >> > >This is very true, but I was under the impression that the only things that > >were > >dlopen-able were PMD's, which would not be part of the core library. Was I > >mistaken? > As far as I know you are right that only PMDs are being dlopen. > The proposed patch though, added DT_NEEDED entries for PMDs too, so they > would need to be > left empty for them to work in such scenario. > > Is that reasonable? > Ah, I see now. What you're saying is that, in our proposed scenario, a PMD that requires, say librte_ether, will have a DT_NEEDED entry explicitly for that library, as opposed to libdpdk_core, is that correct? If it is, I think thats ok. We will still need to have the librte_ether library around, because the libdpdk_core DSO will reference it on its INPUT line, and in fact it should already be loaded because of that, rendering the DT_NEEDED entry moot. That is to say, and requirements from a PMD codified in a DT_NEEDED entry should already be satisfied by the application if it properly linked against libdpdk_core.
That said, it should also be safe to remove the DT_NEEDED entry from the PMD for the same reason (the fact that any dependent libraries should already be loaded makes it non-useful). I would personally just leave them in place, as they are harmless, and doing so is really just more work, but if you want to remove the DT_NEEDED's from the PMD's it won't hurt anything Or is there another facet to this that I'm missing? Best Neil > Regards, > Sergio > >>In such case, because the pmd would have DT_NEEDED entries, dlopen will > >>fail. > >>So to enable such scenario we would need to build PMDs without DT_NEEDED > >>entries. > >> > >>Thoughts? > >> > >As I mentioned above I thought the only thing that would typically be > >referenced > >via dlopen would be libraries that were not part of the unified core library. > >if thats not the case, then yes, we need a little more thought here > >Neil > > > >>Regards, > >>Sergio > >> > >
