[dpdk-dev] [PATCH v4 0/4] fix race condition in enqueue/dequeue because of cpu reorder

[Jia He <hejianet@gmail.com>]

We watched a rte panic of mbuf_autotest in our qualcomm arm64 server due
to a possible race condition.

To fix this race, there are 2 options as suggested by Jerin:
1. use rte_smp_rmb
2. use load_acquire/store_release(refer to [2]).
CONFIG_RTE_RING_USE_C11_MEM_MODEL is provided, and by default it is "y"
only on arm64 so far.

The reason why providing 2 options is due to the performance benchmark
difference in different arm machines.

Already fuctionally tested on the machines as follows:
- on X86
- on arm64 with CONFIG_RTE_RING_USE_C11_MEM_MODEL=y
- on arm64 with CONFIG_RTE_RING_USE_C11_MEM_MODEL=n

---
Changelog:
V4: split into small patches
V3: arch specific implementation for enqueue/dequeue barrier
V2: let users choose whether using load_acquire/store_release
V1: rte_smp_rmb() between 2 loads

Jia He (4):
  eal/arm64: remove the braces {} for dmb() and dsb()
  ring: guarantee load/load order in enqueue and dequeue
  ring: introduce new header file to include common functions
  ring: introduce new header file to support C11 memory model

 config/common_armv8a_linuxapp                      |   2 +
 .../common/include/arch/arm/rte_atomic_64.h        |   4 +-
 lib/librte_eventdev/rte_event_ring.h               |   6 +-
 lib/librte_ring/Makefile                           |   4 +-
 lib/librte_ring/rte_ring.h                         | 161 ++---------------
 lib/librte_ring/rte_ring_c11_mem.h                 | 185 ++++++++++++++++++++
 lib/librte_ring/rte_ring_generic.h                 | 194 +++++++++++++++++++++
 7 files changed, 404 insertions(+), 152 deletions(-)
 create mode 100644 lib/librte_ring/rte_ring_c11_mem.h
 create mode 100644 lib/librte_ring/rte_ring_generic.h

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2.7.4