I don't know if this is worth reporting - please let me know what your
thoughts are on the following email. Recipients are from
'get_maintainer.pl -f tools/testing/selftests/x86/fsgsbase.c'.
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To: Shuah Khan <shuah(a)kernel.org>,
Ingo Molnar <mingo(a)kernel.org>,
Andy Lutomirski <luto(a)kernel.org>,
Dmitry Safonov <dsafonov(a)virtuozzo.com>,
linux-kselftest(a)vger.kernel.org,
linux-kernel(a)vger.kernel.org
Subject: selftests/x86/fsgsbase_64 test problem
We've noticed that fsgsbase_64 can fail periodically with the following
error:
[RUN] ARCH_SET_GS(0x0) and clear gs, then schedule to 0x1
Before schedule, set selector to 0x1
other thread: ARCH_SET_GS(0x1) -- sel is 0x0
[FAIL] GS/BASE changed from 0x1/0x0 to 0x0/0x0
This can be reliably reproduced by running fsgsbase_64 in a loop. i.e.
for i in $(seq 1 10000); do ./fsgsbase_64 || break; done
This problem isn't new - I've reproduced it on latest mainline and every
release going back to v4.12 (I did not try earlier).
Thanks,
Dan