> -----Original Message----- > From: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com> > Sent: Saturday, March 9, 2019 7:48 AM > To: tho...@monjalon.net; Ananyev, Konstantin > <konstantin.anan...@intel.com>; Gavin Hu (Arm Technology China) > <gavin...@arm.com> > Cc: Ilya Maximets <i.maxim...@samsung.com>; dev@dpdk.org; nd > <n...@arm.com>; jer...@marvell.com; hemant.agra...@nxp.com; > nipun.gu...@nxp.com; olivier.m...@6wind.com; Richardson, Bruce > <bruce.richard...@intel.com>; chao...@linux.vnet.ibm.com; nd > <n...@arm.com> > Subject: RE: [PATCH v2] ring: enforce reading the tails before ring > operations > > > 08/03/2019 16:50, Ananyev, Konstantin: > > > 08/03/2019 16:05, Gavin Hu (Arm Technology China): > > > > Anyway, on x86, smp_rmb, as a compiler barrier, applies to > load/store, not > > only load/load. > > > > > > Yes, that's true, but I think that's happened by coincidence, not > > > intentionally. > > > > > > > This is the case also for arm, arm64, ppc32, ppc64. > > > > I will submit a patch to expand the definition of this API. > > > > > > I understand your intention, but that does mean we would also need > to > > > change not only rte_smp_rmb() but rte_rmb() too (to keep things > consistent)? > > > That sounds worring. > > > Might be better to keep smp_rmb() definition as it is, and introduce > > > new function that fits your purposes (smp_rwmb or > smp_load_store_barrier)? > Looking at rte_rmb, rte_io_rmb, rte_cio_rmb implementations for Arm, > they all provide load/store barrier as well. If other architectures also > provide load/store barrier with rte_xxx_rmb, then we could extend the > meaning of the existing APIs. Further looking at rte_rmb, rte_io_rmb, rte_cio_rmb implementations for PPC64 and x86, They also provide load/store barrier. It is safe to extend the meaning of the existing rte_XXX_rmb API. > > Even if a new API is provided, we need to do provide the same APIs for IO > and CIO variants. Since rte_XXX_rmbs API for all architectures already provide the desired load/store ordering, a new API is redundant and not needed.
> > > > How is it managed in other projects? > In my experience, I usually have been changing the algorithms to use C11 > memory model. So, I have not come across this issue yet. Others can > comment. > > >
