Teach libarena's BPF atomic primitives to use compiler builtins for
load-acquire and store-release when Clang advertises
__BPF_FEATURE_LOAD_ACQ_STORE_REL. Older compilers continue to use the
existing barrier-based fallback.
Notably, as BPF programs begin running on arm64, it is better to use the
more appropriate variants since we can no longer rely on x86 TSO ordering.
Commit 880442305a ("bpf: Introduce load-acquire and store-release instructions")
introduced support, hence kernels from 6.15 onwards are needed when
compiling with compilers supporting these instructions. We have
relatively recent kernel version requirements in libarena anyway, and
have not cut first release, hence declare such a dependency.
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/bpf/20260722141003.2841007-1-puranjay@kernel.org
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
87267b8945