Merged. Sorry for delay. Maxim.
On 09/06/17 19:37, Brian Brooks wrote: > ping > > On Sat, Aug 26, 2017 at 9:52 AM, Bill Fischofer > <bill.fischo...@linaro.org> wrote: >> On Sat, Aug 26, 2017 at 12:40 AM, Brian Brooks <brian.bro...@arm.com> wrote: >> >>> Memory accesses that happen-before, in program order, a call to >>> odp_barrier_wait() cannot be reordered to after the call. Similarly, >>> memory accesses that happen-after, in program order, a call to >>> odp_barrier_wait() cannot be reordered to before the call. >>> >>> The current implementation of barriers uses sequentially consistent >>> fences on either side of odp_barrier_wait(). >>> >>> The correct memory ordering for barriers is release upon entering >>> odp_barrier_wait(), to prevent reordering to after the barrier, and >>> acquire upon exiting odp_barrier_wait(), to prevent reordering to >>> before the barrier. >>> >>> The measurable performance difference is negligible on weakly ordered >>> architectures such as ARM, so the highlight of this change is correctness. >>> >>> Signed-off-by: Brian Brooks <brian.bro...@arm.com> >>> >> >> Reviewed-by: Bill Fischofer <bill.fischo...@linaro.org> >> >> >>> --- >>> platform/linux-generic/odp_barrier.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/platform/linux-generic/odp_barrier.c >>> b/platform/linux-generic/odp_barrier.c >>> index 5eb354de..f70bdbf8 100644 >>> --- a/platform/linux-generic/odp_barrier.c >>> +++ b/platform/linux-generic/odp_barrier.c >>> @@ -34,7 +34,7 @@ void odp_barrier_wait(odp_barrier_t *barrier) >>> uint32_t count; >>> int wasless; >>> >>> - odp_mb_full(); >>> + odp_mb_release(); >>> >>> count = odp_atomic_fetch_inc_u32(&barrier->bar); >>> wasless = count < barrier->count; >>> @@ -48,5 +48,5 @@ void odp_barrier_wait(odp_barrier_t *barrier) >>> odp_cpu_pause(); >>> } >>> >>> - odp_mb_full(); >>> + odp_mb_acquire(); >>> } >>> -- >>> 2.14.1 >>> >>>
