Based on the discussion [1], this patch series is to refine the memory
barriers for AUX ring buffer.

Patches 01 ~ 04 to address the barriers usage in the kernel.  The first
patch is to make clear comment for how to use the barriers between the
data store and aux_head store, this asks the driver to make sure the
data is visible.  Patches 02 ~ 04 is to refine the drivers for barriers
after the data store.

Patches 05 ~ 07 is to fix and clean up the memory barries in perf tool
for AUX ring buffer.

Since the 64-bit value's atomicity is not promised on 32-bit perf, the
last patch is to report error and let perf to directly exit for this
case.

Have testes the patches on Arm64 Juno platform.

[1] https://lore.kernel.org/patchwork/patch/1431867/


Leo Yan (8):
  perf/ring_buffer: Add comment for barriers on AUX ring buffer
  coresight: tmc-etr: Add barrier after updating AUX ring buffer
  coresight: tmc-etf: Add comment for store ordering
  perf/x86: Add barrier after updating bts
  perf auxtrace: Change to use SMP memory barriers
  perf auxtrace: Drop legacy __sync functions
  perf auxtrace: Use WRITE_ONCE() for updating aux_tail
  perf record: Directly bail out for compat case

 arch/x86/events/intel/bts.c                   |  3 +++
 .../hwtracing/coresight/coresight-tmc-etf.c   |  6 +++++
 .../hwtracing/coresight/coresight-tmc-etr.c   |  8 ++++++
 kernel/events/ring_buffer.c                   |  9 +++++++
 tools/perf/builtin-record.c                   | 17 ++++++++++++
 tools/perf/util/auxtrace.h                    | 27 +++----------------
 6 files changed, 47 insertions(+), 23 deletions(-)

-- 
2.25.1


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