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.
Patch 05 is to use WRITE_ONCE() for updating aux_tail.
Patches 06 ~ 09 is to drop the legacy __sync functions, and polish for duplicate code and cleanup the build and feature test after SYNC_COMPARE_AND_SWAP is not used.
Patch 10 introduces a new global variable to indicate the kernel runs in 64-bit mode which can be used to confirm if in compat mode; patch 11 introduces variant functions for accessing AUX head/tail, it resolves the aotmicity for reading head pointer, and returns error for the tail is bigger than 4GB.
Have testes the patches on Arm64 Juno platform.
Changes from v3: - Removed the inapprocate paragraph in the commit log for patch "perf auxtrace: Drop legacy __sync functions" (Adrian); - Added new patch to remove feature-sync-compare-and-swap test (Adrian); - Th patch for "perf auxtrace: Use WRITE_ONCE() for updating aux_tail", is a standlone and simple change, so moved it ahead in the patch set for better ordering; - Minor improvement for commit logs in the last two patches.
Changes from v2: - Removed auxtrace_mmap__read_snapshot_head(), which has the duplicated code with auxtrace_mmap__read_head(); - Cleanuped the build for HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT (Adrian); - Added global variable "kernel_is_64_bit" (Adrian); - Added compat variants compat_auxtrace_mmap__{read_head|write_tail} (Adrian).
Leo Yan (11): 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: Use WRITE_ONCE() for updating aux_tail perf auxtrace: Drop legacy __sync functions perf auxtrace: Remove auxtrace_mmap__read_snapshot_head() perf: Cleanup for HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT tools: Remove feature-sync-compare-and-swap feature detection perf env: Set flag for kernel is 64-bit mode perf auxtrace: Add compat_auxtrace_mmap__{read_head|write_tail}
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/build/Makefile.feature | 1 - tools/build/feature/Makefile | 4 - tools/build/feature/test-all.c | 4 - .../feature/test-sync-compare-and-swap.c | 15 --- tools/perf/Makefile.config | 4 - tools/perf/util/auxtrace.c | 19 ++- tools/perf/util/auxtrace.h | 109 ++++++++++++++---- tools/perf/util/env.c | 17 ++- tools/perf/util/env.h | 1 + 13 files changed, 136 insertions(+), 64 deletions(-) delete mode 100644 tools/build/feature/test-sync-compare-and-swap.c