> -----Original Message----- > From: Tyler Retzlaff <roret...@linux.microsoft.com> > Sent: Saturday, June 24, 2023 5:51 AM > To: Mattias Rönnblom <hof...@lysator.liu.se> > Cc: Ruifeng Wang <ruifeng.w...@arm.com>; tho...@monjalon.net; > david.march...@redhat.com; > dev@dpdk.org; konstantin.v.anan...@yandex.ru; Honnappa Nagarahalli > <honnappa.nagaraha...@arm.com>; nd <n...@arm.com> > Subject: Re: [PATCH] eal: add notes to SMP memory barrier APIs > > On Thu, Jun 22, 2023 at 08:19:30PM +0200, Mattias R�nnblom wrote: > > On 2023-06-21 08:44, Ruifeng Wang wrote: > > >The rte_smp_xx() APIs are deprecated. But it is not mentioned in the > > >function header. > > >Added notes in function header for clarification. > > > > > >Signed-off-by: Ruifeng Wang <ruifeng.w...@arm.com> > > >--- > > > lib/eal/include/generic/rte_atomic.h | 15 +++++++++++++++ > > > 1 file changed, 15 insertions(+) > > > > > >diff --git a/lib/eal/include/generic/rte_atomic.h > > >b/lib/eal/include/generic/rte_atomic.h > > >index 58df843c54..542a2c16ff 100644 > > >--- a/lib/eal/include/generic/rte_atomic.h > > >+++ b/lib/eal/include/generic/rte_atomic.h > > >@@ -55,6 +55,11 @@ static inline void rte_rmb(void); > > > * Guarantees that the LOAD and STORE operations that precede the > > > * rte_smp_mb() call are globally visible across the lcores > > > * before the LOAD and STORE operations that follows it. > > >+ * > > >+ * @note > > >+ * This function is deprecated. It adds complexity to the memory > > >+ model > > >+ * used by this project. C11 memory model should always be used. > > >+ * rte_atomic_thread_fence() should be used instead. > > > > It's somewhat confusing to learn I should use the C11 memory model, > > and then in the next sentence that I should call a function which is > > not in C11. > > i wonder if we can just do without the comments until we begin to adopt > changes for 23.11 > release because the guidance will be short lived. > > in 23.07 we want to say that only gcc builtins that align with the standard > C++ memory > model should be used. > > in 23.11 we want to say that only standard C11 atomics should be used.
Good point. The memory order parameter will change in 23.11. > > my suggestion i guess is just adapt the patch to be appropriate for > 23.11 and only merge it after 23.07 release? might be easier to manage. Agree to only merge it after 23.07. I will update the comment for standard C11 atomics. > > > > > I think it would be helpful to say which memory_model parameters > > should be used to replace the rte_smp_*mb() calls, and if there are > > any difference in semantics between the Linux kernel-style barriers > > and their C11 (near-)equivalents. > > > > Is there some particular reason these functions aren't marked > > __rte_deprecated? Too many warnings? > > > > > */ > > > static inline void rte_smp_mb(void); @@ -64,6 +69,11 @@ static > > >inline void rte_smp_mb(void); > > > * Guarantees that the STORE operations that precede the > > > * rte_smp_wmb() call are globally visible across the lcores > > > * before the STORE operations that follows it. > > >+ * > > >+ * @note > > >+ * This function is deprecated. It adds complexity to the memory > > >+ model > > >+ * used by this project. C11 memory model should always be used. > > >+ * rte_atomic_thread_fence() should be used instead. > > > */ > > > static inline void rte_smp_wmb(void); @@ -73,6 +83,11 @@ static > > >inline void rte_smp_wmb(void); > > > * Guarantees that the LOAD operations that precede the > > > * rte_smp_rmb() call are globally visible across the lcores > > > * before the LOAD operations that follows it. > > >+ * > > >+ * @note > > >+ * This function is deprecated. It adds complexity to the memory > > >+ model > > >+ * used by this project. C11 memory model should always be used. > > >+ * rte_atomic_thread_fence() should be used instead. > > > */ > > > static inline void rte_smp_rmb(void); ///@}
