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author | Szabolcs Nagy <szabolcs.nagy@arm.com> | 2021-02-16 12:55:13 +0000 |
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committer | Szabolcs Nagy <szabolcs.nagy@arm.com> | 2021-04-13 08:43:40 +0100 |
commit | b116855de71098ef7dd2875dd3237f8f3ecc12c2 (patch) | |
tree | 6da94b9ca548a5042d743626fdbe1990fa5221a2 /db/mpool | |
parent | f8ea2b9982e39fd950d157f5dba31121ceb51df3 (diff) | |
download | glibc-nsz/bug19329-v2.zip glibc-nsz/bug19329-v2.tar.gz glibc-nsz/bug19329-v2.tar.bz2 |
RFC elf: Fix slow tls access after dlopen [BZ #19924]nsz/bug19329-v2
In short: __tls_get_addr checks the global generation counter,
_dl_update_slotinfo updates up to the generation of the accessed
module. If the global generation is newer than geneneration of the
module then __tls_get_addr keeps hitting the slow path that updates
the dtv.
Possible approaches i can see:
1. update to global generation instead of module,
2. check the module generation in the fast path.
This patch is 1.: it needs additional sync (load acquire) so the
slotinfo list is up to date with the observed global generation.
Approach 2. would require walking the slotinfo list at all times.
I don't know how to make that fast with many modules.
Note: in the x86_64 version of dl-tls.c the generation is only loaded
once, since relaxed mo is not faster than acquire mo load.
I have not benchmarked this yet.
Diffstat (limited to 'db/mpool')
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