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a64af0ef1c
linux-next/tools/lib/bpf
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Daniel Borkmann a64af0ef1c bpf, libbpf: use correct barriers in perf ring buffer walk 
Given libbpf is a generic library and not restricted to x86-64 only,
the compiler barrier in bpf_perf_event_read_simple() after fetching
the head needs to be replaced with smp_rmb() at minimum. Also, writing
out the tail we should use WRITE_ONCE() to avoid store tearing.

Now that we have the logic in place in ring_buffer_read_head() and
ring_buffer_write_tail() helper also used by perf tool which would
select the correct and best variant for a given architecture (e.g.
x86-64 can avoid CPU barriers entirely), make use of these in order
to fix bpf_perf_event_read_simple().

Fixes: d0cabbb021 ("tools: bpf: move the event reading loop to libbpf")
Fixes: 39111695b1 ("samples: bpf: add bpf_perf_event_output example")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-10-19 13:43:08 -07:00
..
.gitignore tools lib bpf: Change FEATURE-DUMP to FEATURE-DUMP.libbpf 2015-11-05 12:47:51 -03:00
bpf.c selftests/bpf: add test cases for queue and stack maps 2018-10-19 13:24:31 -07:00
bpf.h selftests/bpf: add test cases for queue and stack maps 2018-10-19 13:24:31 -07:00
btf.c libbpf: relicense libbpf as LGPL-2.1 OR BSD-2-Clause 2018-10-08 10:09:48 +02:00
btf.h libbpf: Per-symbol visibility for DSO 2018-10-16 15:16:47 -07:00
Build Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2018-09-25 20:29:38 -07:00
libbpf_errno.c libbpf: relicense libbpf as LGPL-2.1 OR BSD-2-Clause 2018-10-08 10:09:48 +02:00
libbpf.c bpf, libbpf: use correct barriers in perf ring buffer walk 2018-10-19 13:43:08 -07:00
libbpf.h libbpf: Per-symbol visibility for DSO 2018-10-16 15:16:47 -07:00
Makefile libbpf: Per-symbol visibility for DSO 2018-10-16 15:16:47 -07:00
netlink.c libbpf: relicense libbpf as LGPL-2.1 OR BSD-2-Clause 2018-10-08 10:09:48 +02:00
nlattr.c libbpf: relicense libbpf as LGPL-2.1 OR BSD-2-Clause 2018-10-08 10:09:48 +02:00
nlattr.h libbpf: relicense libbpf as LGPL-2.1 OR BSD-2-Clause 2018-10-08 10:09:48 +02:00
str_error.c libbpf: relicense libbpf as LGPL-2.1 OR BSD-2-Clause 2018-10-08 10:09:48 +02:00
str_error.h libbpf: relicense libbpf as LGPL-2.1 OR BSD-2-Clause 2018-10-08 10:09:48 +02:00