doc: announce adoption of C11 atomic operations semantics

As agreed in the DPDK tech board [1], after 20.05 release, patches must
use C11 atomic operations semantics with the help of wrappers.

[1] http://mails.dpdk.org/archives/dev/2020-April/165143.html

Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>
Acked-by: David Christensen <drc@linux.vnet.ibm.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>

diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
index 2e2ed92..2d11bae 100644 (file)
--- a/doc/guides/rel_notes/deprecation.rst
+++ b/doc/guides/rel_notes/deprecation.rst
@@ -38,6 +38,19 @@ Deprecation Notices
   remove it from the externally visible ABI and allow it to be updated in the
   future.
 
+* rte_atomicNN_xxx: These APIs do not take memory order parameter. This does
+  not allow for writing optimized code for all the CPU architectures supported
+  in DPDK. DPDK will adopt C11 atomic operations semantics and provide wrappers
+  using C11 atomic built-ins. These wrappers must be used for patches that
+  need to be merged in 20.08 onwards. This change will not introduce any
+  performance degradation.
+
+* rte_smp_*mb: These APIs provide full barrier functionality. However, many
+  use cases do not require full barriers. To support such use cases, DPDK will
+  adopt C11 barrier semantics and provide wrappers using C11 atomic built-ins.
+  These wrappers must be used for patches that need to be merged in 20.08
+  onwards. This change will not introduce any performance degradation.
+
 * igb_uio: In the view of reducing the kernel dependency from the main tree,
   as a first step, the Technical Board decided to move ``igb_uio``
   kernel module to the dpdk-kmods repository in the /linux/igb_uio/ directory