[RFC][PATCH 0/2] Make sparcv8 work again on cas enabled hardware

[Andreas Larsson <andreas at gaisler dot com>]

This patch series:

1) Fixes a sparcv8 bug introduced since the #error was added to
sysdeps/sparc/sparc32/pthread_barrier_wait.c in 2.23. This fix stops
incorrect usage of sendmsg and recvmsg Linux system calls for sparcv8.

2) Makes use of the CASA compare and swap instruction for atomic_*
functions sparcv8, that is available for most LEON3 and LEON4 designs
and implied by -mcpu=leon3, but not part of the sparcv8 standard. To
allow for easy kernel emulation on systems that lack the instruction,
the CASA instruction is used for all writing atomic_* functions. This
approach is discussed in thread [1].

Any comments are most welcome. The spin lock based sparcv8 semaphore
implementation is currently unchanged by this patchset, but I would say
that that should go as well. I will look into that as well, but I have
not tested that yet.

[1] https://sourceware.org/ml/libc-alpha/2016-10/msg00344.html

Andreas Larsson (2):
  sparc32: Mark sendmsg and recvmsg system calls as unsupported
  sparc32: Use cas for atomic_* operations and use general
    pthread_barrier_wait

 sysdeps/sparc/sparc32/atomic-machine.h          |  228 +++++------------------
 sysdeps/sparc/sparc32/pthread_barrier_wait.c    |    1 -
 sysdeps/unix/sysv/linux/sparc/kernel-features.h |    4 +-
 3 files changed, 53 insertions(+), 180 deletions(-)
 delete mode 100644 sysdeps/sparc/sparc32/pthread_barrier_wait.c