[dpdk-dev] [PATCH v6 0/6] use c11 atomics for service core lib

[Phil Yang <phil.yang@arm.com>]

The rte_atomic ops and rte_smp barriers enforce DMB barriers on aarch64.
Using c11 atomics with explicit memory ordering instead of the rte_atomic
ops and rte_smp barriers for inter-threads synchronization can uplift the
performance on aarch64 and no performance loss on x86.

This patchset contains:
1) fix race condition for MT unsafe service.
2) clean up redundant code.
3) use c11 atomics for service core lib to avoid unnecessary barriers.

v2:
Still waiting on Harry for the final solution on the MT unsafe race
condition issue. But I have incorporated the comments so far.
1. add 'Fixes' tag for bug-fix patches.
2. remove 'Fixes' tag for code cleanup patches.
3. remove unused parameter for service_dump_one function.
4. replace the execute_lock atomic CAS operation to spinlock_try_lock.
5. use c11 atomics with RELAXED memory ordering for num_mapped_cores.
6. relax barriers for guard variables runstate, comp_runstate and
   app_runstate with c11 one-way barriers.

v3:
Sending this version since Phil is on holiday.
1. Updated the API documentation to indicate how the locking
   can be avoided.

v4:
1. Fix the nits in 2/6 commit message and comments in code.

v5:
1. Remove redundant libatomic clang dependency claim code as it has been
added in global. (The commit da4eae278b56)

v6:
1. Fix coding style issue. Remove illegal Change-ID tag in patch 5/6.

Honnappa Nagarahalli (2):
  service: fix race condition for MT unsafe service
  service: fix identification of service running on other lcore

Phil Yang (4):
  service: remove rte prefix from static functions
  service: remove redundant code
  service: optimize with c11 atomics
  service: relax barriers with C11 atomics

 lib/librte_eal/common/rte_service.c            | 234 +++++++++++++------------
 lib/librte_eal/include/rte_service.h           |   8 +-
 lib/librte_eal/include/rte_service_component.h |   6 +-
 3 files changed, 137 insertions(+), 111 deletions(-)

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2.7.4