build: use initial-exec TLS when building seastar as shared library #2255
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quote from https://patchwork.ozlabs.org/project/glibc/patch/8734v1ieke.fsf@oldenburg.str.redhat.com/ > On the glibc side, we should recommend that intercepting mallocs and its > dependencies use initial-exec TLS because that kind of TLS does not use > malloc. If intercepting mallocs using dynamic TLS work at all, that's > totally by accident, and was in the past helped by glibc bug 19924. so instead of allocating TLS variables using malloc, let's allocate them using initial-exec TLS model. another approach is to single out the static TLS variables in the code path of malloc/free and apply `__attribute__ ((tls_model("initial-exec")))` to them, and optionally only do this when we are building shared library. but this could be overkill as 1. we build static library in the release build 2. the total size of the static TLS variables is presumably small, so the application linking against the seastar shared library should be able to afford this. see also https://patchwork.ozlabs.org/project/glibc/patch/8734v1ieke.fsf@oldenburg.str.redhat.com/ and https://sourceware.org/bugzilla/show_bug.cgi?id=19924 Fixes scylladb#2247 Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
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What's the downside of initial-exec? I guess it can't be used with dlopen(), which seems minor here. |
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Seems reasonable to me. But please verify it works with scylladb. |
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@avikivity yes, as you put. an application would not be able to dlopen tested with following steps $ cd seastar
$ git cherry-pick 6c44eed
$ git show HEAD --name-only --oneline
2ee99a7b2 (HEAD) build: use initial-exec TLS when building seastar as shared library
CMakeLists.txt
$ cd ..
$ ./configure.py --mode dev --compiler clang++ --c-compiler clang
$ ninja build/dev/scylla
$ grep CMAKE_BUILD_TYPE build/dev/seastar/CMakeCache.txt
CMAKE_BUILD_TYPE:STRING=Dev
$ cd ~/dev/scylla-dtest
$ JAVA_HOME=/usr/lib/jvm/jre-11 pytest -s --log-cli-level=debug -c $PWD/pytest.ini --cassandra-dir $HOME/dev/scylladb/build/dev repair_additional_test.py::TestRepairAdditional::test_repair_one_node_alter_rf
...
==================================================== 1 passed, 2 warnings in 59.91s ==================================================== |
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quote from
https://patchwork.ozlabs.org/project/glibc/patch/8734v1ieke.fsf@oldenburg.str.redhat.com/
so instead of allocating TLS variables using malloc, let's allocate them using initial-exec TLS model. another approach is to single out the static TLS variables in the code path of malloc/free and apply
__attribute__ ((tls_model("initial-exec")))to them, and optionally only do this when we are building shared library.but this could be overkill as
see also
https://patchwork.ozlabs.org/project/glibc/patch/8734v1ieke.fsf@oldenburg.str.redhat.com/ and
https://sourceware.org/bugzilla/show_bug.cgi?id=19924
Fixes #2247
Signed-off-by: Kefu Chai kefu.chai@scylladb.com