On Tue, 2019-12-10 at 15:46 +0000, Bruce Richardson wrote: > On Tue, Dec 10, 2019 at 03:03:51PM +0000, Luca Boccassi wrote: > > On Tue, 2019-12-10 at 14:36 +0000, Bruce Richardson wrote: > > > On Tue, Dec 10, 2019 at 12:40:53PM +0000, Ferruh Yigit wrote: > > > > On 12/10/2019 12:04 PM, Bruce Richardson wrote: > > > > > On Tue, Dec 10, 2019 at 11:56:28AM +0000, Ferruh Yigit wrote: > > > > > > Hi, > > > > > > > > > > > > With new process, the major ABI releases will be compatible > > > > > > until it is > > > > > > deprecated (until next LTS for now), > > > > > > like current ABI version is 20 in DPDK_19.11 and DPDK > > > > > > versions > > > > > > until DPDK_20.11 > > > > > > will be ABI compatible with this version. > > > > > > > > > > > > But if we introduce a new API after major ABI, say in 20.02 > > > > > > release, are we > > > > > > allowed to break the ABI for that API before DPDK_20.11? > > > > > > > > > > > > If we allow it break, following problem will be observed: > > > > > > Assume an application using .so.20.1 library, and using the > > > > > > new > > > > > > API introduced > > > > > > in 20.02, lets say foo(), > > > > > > but when application switches to .so.20.2 (released via > > > > > > DPDK_20.05), application > > > > > > will fail because of ABI breakage in foo(). > > > > > > > > > > > > I think it is fair that application expects forward > > > > > > compatibility in minor > > > > > > versions of a shared library. > > > > > > Like if application linked against .so.20.2, fair to expect > > > > > > .so.20.3, .so.20.4 > > > > > > etc will work fine. I think currently only .so.20.0 is > > > > > > fully > > > > > > forward compatible. > > > > > > > > > > > > If we all agree on this, we may need to tweak the process a > > > > > > little, but before > > > > > > diving into implementation details, I would like to be sure > > > > > > we > > > > > > are in same page. > > > > > > > > > > > > > > > > Well, any new API's generally come in as experimental, in > > > > > which > > > > > case > > > > > changes are allowed, and breakage can be expected. If they > > > > > are > > > > > not > > > > > experiemental, then the ABI policy applies to them in that > > > > > they > > > > > cannot > > > > > change since they are part of the .21 ABI, even if that ABI > > > > > is > > > > > not fully > > > > > complete yet. For any application only using stable, non- > > > > > experimental > > > > > functions, forward compatibility must be maintained IMHO. > > > > > > > > > > > > > Talking about not experimental APIs, experimental ones free > > > > from > > > > the process. > > > > > > > > And when and API added in 20.02 (ABI_20.1) it is kind of still > > > > ABI_20, because > > > > it should be supported for following ABI_20.x, instead of > > > > calling > > > > it ABI_21, and > > > > this minor tweak (and mind shift) in .map files can be our > > > > solution. > > > > > > Related at what to do with adding versions between major ABI > > > versions, when > > > investigating with Kevin the ABI checking we have made an > > > unpleasant > > > discovery: > > > > > > This minor version bumping from 20.0 to 20.1 has apparently > > > already > > > broken > > > our ABI according to libabigail. > > > > > > The Gory Details [skip to the end for suggestions to fix] > > > ------------------------------------------------------------ > > > > > > The reason for this is that the soversion encoded in each library > > > - > > > whether > > > built with meson or make - is the full 20.0 version, not just the > > > major ABI > > > .20 part. Then when apps link against DPDK, they actually encode > > > the > > > 20.0. > > > > > > So what this means is that currently - using a make build as an > > > example > > > here - ldd on the latest head build gives: > > > > > > LD_LIBRARY_PATH=$(pwd)/x86_64-native-linux-gcc/lib ldd x86_64- > > > native-linux-gcc/app/testpmd | head > > > linux-vdso.so.1 (0x00007fff6813d000) > > > librte_pmd_bond.so.20.1 => /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc/lib/librte_pmd_bond.so.20.1 (0x00007f36d723c000) > > > librte_pmd_dpaa.so.20.1 => /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc/lib/librte_pmd_dpaa.so.20.1 (0x00007f36d7229000) > > > librte_mempool_dpaa.so.20.1 => > > > /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc/lib/librte_mempool_dpaa.so.20.1 > > > (0x00007f36d7224000) > > > librte_pmd_ixgbe.so.20.1 => /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc/lib/librte_pmd_ixgbe.so.20.1 > > > (0x00007f36d71ba000) > > > librte_pmd_i40e.so.20.1 => /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc/lib/librte_pmd_i40e.so.20.1 (0x00007f36d7126000) > > > librte_pmd_bnxt.so.20.1 => /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc/lib/librte_pmd_bnxt.so.20.1 (0x00007f36d70e5000) > > > librte_pmd_softnic.so.20.1 => > > > /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc/lib/librte_pmd_softnic.so.20.1 > > > (0x00007f36d70b7000) > > > librte_flow_classify.so.0.201 => > > > /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc/lib/librte_flow_classify.so.0.201 > > > (0x00007f36d70b1000) > > > librte_pipeline.so.20.1 => /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc/lib/librte_pipeline.so.20.1 (0x00007f36d7088000) > > > ... > > > > > > Similarly ldd on a 19.11 checkout gives: > > > > > > LD_LIBRARY_PATH=$(pwd)/x86_64-native-linux-gcc_v19.11/lib ldd > > > x86_64- > > > native-linux-gcc_v19.11/app/testpmd | head > > > linux-vdso.so.1 (0x00007ffc2a964000) > > > librte_pmd_bond.so.20.0 => /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc_v19.11/lib/librte_pmd_bond.so.20.0 > > > (0x00007fd4dc6b6000) > > > librte_pmd_dpaa.so.20.0 => /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc_v19.11/lib/librte_pmd_dpaa.so.20.0 > > > (0x00007fd4dc6a3000) > > > librte_mempool_dpaa.so.20.0 => > > > /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc_v19.11/lib/librte_mempool_dpaa.so.20.0 > > > (0x00007fd4dc69e000) > > > librte_pmd_ixgbe.so.20.0 => /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc_v19.11/lib/librte_pmd_ixgbe.so.20.0 > > > (0x00007fd4dc634000) > > > librte_pmd_i40e.so.20.0 => /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc_v19.11/lib/librte_pmd_i40e.so.20.0 > > > (0x00007fd4dc5a0000) > > > librte_pmd_bnxt.so.20.0 => /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc_v19.11/lib/librte_pmd_bnxt.so.20.0 > > > (0x00007fd4dc55d000) > > > librte_pmd_softnic.so.20.0 => > > > /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc_v19.11/lib/librte_pmd_softnic.so.20.0 > > > (0x00007fd4dc531000) > > > librte_flow_classify.so.0.200 => > > > /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc_v19.11/lib/librte_flow_classify.so.0.200 > > > (0x00007fd4dc52b000) > > > librte_pipeline.so.20.0 => /home/bruce/dpdk.org/x86_64- > > > native-linux-gcc_v19.11/lib/librte_pipeline.so.20.0 > > > (0x00007fd4dc502000) > > > > > > The final check - using the 19.11 compiled testpmd with the > > > library > > > path > > > set to 20.02 versionned libs: > > > > > > LD_LIBRARY_PATH=$(pwd)/x86_64-native-linux-gcc/lib ldd x86_64- > > > native- > > > linux-gcc_v19.11/app/testpmd | head > > > linux-vdso.so.1 (0x00007ffc711fc000) > > > librte_pmd_bond.so.20.0 => not found > > > librte_pmd_dpaa.so.20.0 => not found > > > librte_mempool_dpaa.so.20.0 => not found > > > librte_pmd_ixgbe.so.20.0 => not found > > > librte_pmd_i40e.so.20.0 => not found > > > librte_pmd_bnxt.so.20.0 => not found > > > librte_pmd_softnic.so.20.0 => not found > > > librte_flow_classify.so.0.200 => not found > > > librte_pipeline.so.20.0 => not found > > > > > > Fixing This > > > ----------- > > > > > > To fix this, we need to ensure that the SONAME remains constant > > > across the > > > releases. Therefore, I currently see two options: > > > > > > 1. keep 20.0 as the version and soname across all releases in > > > 2020, > > > i.e. > > > just revert the ABIVERSION change patch. Trouble there is how > > > to > > > track > > > 20.02 vs 20.05 etc. etc. > > > > > > 2. remove the .0, .1 from the SONAMES stored in the libraries. > > > This > > > has the > > > advantage of keeping the existing planned schemes, but has the > > > really big > > > downside of breaking ABI compatibility with anyone who has > > > already > > > compiled with 19.11. > > > > > > Personally, of the two options - unless someone can come up with > > > a > > > third > > > option - I'd tend towards the second, fixing the builds to remove > > > the > > > .0 in > > > the soname, and releasing that ASAP as 19.11.1 before 19.11 gets > > > widespread > > > adoption. Since this ABI stability is new, teething problems may > > > be > > > expected. > > > > > > Thoughts and comments? > > > /Bruce > > > > > > BTW: For meson, the patch for option 2 is just to remove the > > > so_version > > > variable and all references to it from lib/meson.build and > > > drivers/meson.build. Haven't looked into a "make" fix yet. > > > > Hi, > > > > With libtool and its (arguably arcane) format, only the first digit > > is > > the ABI current version and gets encoded in the elf header. The > > other > > digits can be used to track compatible minor increments, and are > > mostly > > ignored. On the system a symlink libfoo.so.major -> > > libfoo.so.major.minor is added. > > > > Eg: > > > > $ readelf -d /usr/lib/x86_64-linux-gnu/libzmq.so.5.2.3 | grep > > SONAME > > 0x000000000000000e (SONAME) Library soname: > > [libzmq.so.5] > > $ ls -l /usr/lib/x86_64-linux-gnu/libzmq.so.5 > > lrwxrwxrwx 1 root root 15 Dec 31 2014 /usr/lib/x86_64-linux- > > gnu/libzmq.so.5 -> libzmq.so.5.2.3 > > > > Can we do the same? Not sure what the right incantation is for > > Meson, > > but it should be possibly. > > > > That's essentially option 2, and it's still an ABI break because > existing > builds of 19.11 have the soname will the full version number in it. > The > default behaviour for meson is exactly how you described it, except > that > previously we needed more exact control over the version info (for > your > dpdk-specific versions in the sonames) and so overrode the soversion > explicitly. The fix for meson is to remove this overriding i.e. > remove > "soversion:" parameter for each shared_library() call. > > > > Also, we should leave the current at 20.0 - let's not break > > compatibility already, please :-) > > > > If we do this, maybe we can use 20.0.1 and 20.0.2 version numbers?
Yes, that's what I meant - IMHO we should just take the hit and use the slightly weird 20.0 format until next year, and add a third digit for compatible updates. Then for v21 we can drop it. -- Kind regards, Luca Boccassi
