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Daniel Borkmann 6b7a21140f tools: add smp_* barrier variants to include infrastructure Add the definition for smp_rmb(), smp_wmb(), and smp_mb() to the tools include infrastructure: this patch adds the implementation for x86-64 and arm64, and have it fall back as currently is for other archs which do not have it implemented at this point. The x86-64 one uses lock + add combination for smp_mb() with address below red zone. This is on top of `09d62154f6` ("tools, perf: add and use optimized ring_buffer_{read_head, write_tail} helpers"), which didn't touch smp_* barrier implementations. Magnus recently rightfully reported however that the latter on x86-64 still wrongly falls back to sfence, lfence and mfence respectively, thus fix that for applications under tools making use of these to avoid such ugly surprises. The main header under tools (include/asm/barrier.h) will in that case not select the fallback implementation. Reported-by: Magnus Karlsson <magnus.karlsson@intel.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>	History 2019-04-11 14:45:50 -07:00
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barrier.h	tools: add smp_* barrier variants to include infrastructure	2019-04-11 14:45:50 -07:00

Daniel Borkmann 6b7a21140f tools: add smp_* barrier variants to include infrastructure

Add the definition for smp_rmb(), smp_wmb(), and smp_mb() to the
tools include infrastructure: this patch adds the implementation
for x86-64 and arm64, and have it fall back as currently is for
other archs which do not have it implemented at this point. The
x86-64 one uses lock + add combination for smp_mb() with address
below red zone.

This is on top of 09d62154f6 ("tools, perf: add and use optimized
ring_buffer_{read_head, write_tail} helpers"), which didn't touch
smp_* barrier implementations. Magnus recently rightfully reported
however that the latter on x86-64 still wrongly falls back to sfence,
lfence and mfence respectively, thus fix that for applications under
tools making use of these to avoid such ugly surprises. The main
header under tools (include/asm/barrier.h) will in that case not
select the fallback implementation.

Reported-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

History

2019-04-11 14:45:50 -07:00

barrier.h tools: add smp_* barrier variants to include infrastructure 2019-04-11 14:45:50 -07:00