On Mon, 2018-12-03 at 13:25 -0500, Mathieu Desnoyers wrote: > ----- On Dec 3, 2018, at 12:58 PM, Jeff Layton jlay...@redhat.com wrote: > > > On Wed, 2018-11-28 at 17:06 -0500, Mathieu Desnoyers wrote: > > > ----- On Nov 27, 2018, at 1:17 PM, Jeff Layton jlay...@redhat.com wrote: > > > > > > > The nfs-ganesha project has used lttng for quite some time to handle > > > > tracing. Recently though, we decided to start building liburcu in as a > > > > mandatory component, with an eye toward using it in certain areas. > > > > > > > > Before this change, the code linked in liburcu-bp directly, but now we > > > > just use liburcu. Unfortunately, when we enable tracepoints in the build > > > > now, we get errors like this at link time: > > > > > > > > --------------------8<---------------- > > > > [ 96%] Linking C executable ganesha.nfsd > > > > /usr/bin/ld: libMainServices.a(nfs_worker_thread.c.o): undefined > > > > reference to > > > > symbol 'rcu_gp_bp' > > > > /usr/bin/ld: //usr/lib64/liburcu-bp.so.6: error adding symbols: DSO > > > > missing from > > > > command line > > > > collect2: error: ld returned 1 exit status > > > > make[2]: *** [MainNFSD/CMakeFiles/ganesha.nfsd.dir/build.make:308: > > > > MainNFSD/ganesha.nfsd] Error 1 > > > > make[1]: *** [CMakeFiles/Makefile2:2740: > > > > MainNFSD/CMakeFiles/ganesha.nfsd.dir/all] Error 2 > > > > make: *** [Makefile:152: all] Error 2 > > > > --------------------8<---------------- > > > > > > > > nfs-ganesha defines _LGPL_SOURCE, and that makes lttng use the > > > > redefinitions in tracepoint-rcu.h. If I disable _LGPL_SOURCE, it all > > > > builds as expected. > > > > > > > > I found a similar bug here: > > > > > > > > https://bugs.lttng.org/issues/1156 > > > > > > > > Any thoughts on the right fix for this? We'd like to eat our cake and > > > > have it too, so that we can have _LGPL_SOURCE defined, lttng enabled, > > > > and the urcu flavor be determined at runtime. > > > > > > Hi! > > > > > > It's great to hear that feedback. Indeed you are not the first one > > > to hit this unfortunate limitation of liburcu API. > > > > > > The use-case involves using many liburcu flavors within the same > > > compile unit _with_ _LGPL_SOURCE defined. All the tricks done > > > in urcu/map/*.h to map all flavors to a single API conflict > > > with that use-case. And the fact that the "mb", memb", and > > > signal flavors all share the same header prevents this > > > even further. This becomes a real issue when trying to use > > > the lttng-ust tracer instrumentation (which includes urcu-bp.h) > > > along with other liburcu flavors in a compile unit. > > > > > > So, I took the day to hack something out: beware, it's a complete > > > overhaul of the liburcu tree. You can try it out in this private > > > development branch: > > > > > > https://github.com/compudj/userspace-rcu-dev/tree/multiflavor > > > > > > Note: don't even try to follow the git commit history at the > > > moment, this will need editing. ;) > > > > > > A new unit test shows how it works: > > > > > > https://github.com/compudj/userspace-rcu-dev/blob/multiflavor/tests/unit/test_urcu_multiflavor_single_unit.c > > > > > > And while I was there, I did a lot of namespacing cleanups for the > > > APIs, so we'll _definitely_ need to bump the major soname for this. > > > However, I'm keeping the main use-cases of the API backward compatible > > > (those which relied on the API mapping). Here is a dev branch of > > > lttng-ust adapting to those API changes: > > > > > > https://github.com/compudj/lttng-ust-dev/tree/urcu-multiflavor > > > > > > Those who want to be able to use many liburcu flavors in a single > > > compile unit would need to define URCU_NO_API_MAP, and use each flavor > > > namespace directly, as done in the new unit test. I'm not particularly > > > fond of the URCU_NO_API_MAP name. We could perhaps name it > > > "URCU_MULTI_FLAVOR" > > > or something else... > > By the way, with the updated liburcu tree, there is no more need to > define URCU_NO_API_MAP. > > > > Please try it out and let me know how it goes. > > > > > > Thanks, > > > > > > Mathieu > > > > > > > Thanks Mathieu, > > > > Sorry for the delay, but this was rather difficult to test. I ended up > > building a userspace-rcu package from this tree, but was unable to > > build lttng-ust as a package from your tree, and so had to just do a > > make/make install of it on the build host. Ditto for lttng-tools. > > You will need lttng-ust from this tree: > > https://github.com/compudj/lttng-ust-dev/tree/urcu-multiflavor > > to build against the liburcu branch. This is causing your missing symbol > error. > > Thanks, > > Mathieu >
That's the branch I'm using [1]. I basically checked out that branch, and did: configure --prefix=/usr make make install ...and then did the same with lttng-tools (which ganesha also requires). After that, I pulled down nfs-ganesha tree, checked out the "next" branch and tried to build it, and got that same error. It's certainly possible that we don't have something right in nfs- ganesha that's causing this. [1]: note that your lttng-ust branch also requires the attached patch. Feel free to squash it in w/o attribution. > With all of that, I reran the ganesha build and got the same error: > > > > [ 97%] Linking C executable ganesha.nfsd > > /usr/bin/ld: libMainServices.a(nfs_worker_thread.c.o): undefined reference > > to > > symbol 'urcu_bp_register' > > /usr/bin/ld: //usr/lib64/liburcu-bp.so.7: error adding symbols: DSO missing > > from > > command line > > collect2: error: ld returned 1 exit status > > make[2]: *** [MainNFSD/CMakeFiles/ganesha.nfsd.dir/build.make:288: > > MainNFSD/ganesha.nfsd] Error 1 > > make[1]: *** [CMakeFiles/Makefile2:2396: > > MainNFSD/CMakeFiles/ganesha.nfsd.dir/all] Error 2 > > make: *** [Makefile:152: all] Error 2 > > > > Should we be passing in both -lurcu and -lurcu-bp on the link here? > > -- > > Jeff Layton <jlay...@redhat.com> -- Jeff Layton <jlay...@redhat.com>
From 21bdf45a43c8d66ddd25b4348bca9f33f747d74b Mon Sep 17 00:00:00 2001 From: Jeff Layton <jlay...@kernel.org> Date: Mon, 3 Dec 2018 11:29:05 -0500 Subject: [PATCH] Fix configure.ac Signed-off-by: Jeff Layton <jlay...@kernel.org> --- configure.ac | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/configure.ac b/configure.ac index a3e1e238ce47..65e025a42e24 100644 --- a/configure.ac +++ b/configure.ac @@ -275,10 +275,10 @@ AC_COMPILE_IFELSE([AC_LANG_SOURCE([[ ]) # urcu - check that URCU lib is available to compilation -AC_CHECK_LIB([urcu-bp], [synchronize_rcu_bp], [], [AC_MSG_ERROR([Cannot find liburcu-bp lib. Use [LDFLAGS]=-Ldir to specify its location.])]) +AC_CHECK_LIB([urcu-bp], [urcu_bp_synchronize_rcu], [], [AC_MSG_ERROR([Cannot find liburcu-bp lib. Use [LDFLAGS]=-Ldir to specify its location.])]) # urcu - check that URCU lib is at least version 0.6 -AC_CHECK_LIB([urcu-bp], [call_rcu_bp], [], [AC_MSG_ERROR([liburcu 0.6 or newer is needed, please update your version or use [LDFLAGS]=-Ldir to specify the right location.])]) +AC_CHECK_LIB([urcu-bp], [urcu_bp_call_rcu], [], [AC_MSG_ERROR([liburcu 0.6 or newer is needed, please update your version or use [LDFLAGS]=-Ldir to specify the right location.])]) # numa.h integration AS_IF([test "x$NO_NUMA" = "x1"],[ -- 2.19.2
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