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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
arch Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-10-12 21:38:46 -07:00
block
certs
crypto
Documentation FDDI: defza: Add support for DEC FDDIcontroller 700 TURBOchannel adapter 2018-10-15 21:46:06 -07:00
drivers nfp: bpf: double check vNIC capabilities after object sharing 2018-10-16 15:23:58 -07:00
firmware
fs Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-10-12 21:38:46 -07:00
include bpf: add MAP_LOOKUP_AND_DELETE_ELEM syscall 2018-10-19 13:24:31 -07:00
init
ipc
kernel bpf: add MAP_LOOKUP_AND_DELETE_ELEM syscall 2018-10-19 13:24:31 -07:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-10-12 21:38:46 -07:00
LICENSES
mm Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-10-11 12:27:47 +02:00
net bpf: add queue and stack maps 2018-10-19 13:24:31 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-10-12 21:38:46 -07:00
scripts Kbuild fixes for v4.19 (2nd) 2018-10-11 19:23:07 +02:00
security
sound
tools bpf, libbpf: use correct barriers in perf ring buffer walk 2018-10-19 13:43:08 -07:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2018-10-15 23:21:07 -07:00
Makefile Kbuild fixes for v4.19 (2nd) 2018-10-11 19:23:07 +02:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.