atomic functions where they are almost identical, or have acquire/release
semantics.
While here clean these function up. The cbnz instruction doesn't change
the condition flags so drop cc, however they should have memory added to the
clobber list.
Reviewed by: kib
Sponsored by: ABT Systems Ltd
Differential Revision: https://reviews.freebsd.org/D4318
provide a semantic defined by the C11 fences with corresponding
memory_order.
atomic_thread_fence_acq() gives r | r, w, where r and w are read and
write accesses, and | denotes the fence itself.
atomic_thread_fence_rel() is r, w | w.
atomic_thread_fence_acq_rel() is the combination of the acquire and
release in single operation. Note that reads after the acq+rel fence
could be made visible before writes preceeding the fence.
atomic_thread_fence_seq_cst() orders all accesses before/after the
fence, and the fence itself is globally ordered against other
sequentially consistent atomic operations.
Reviewed by: alc
Discussed with: bde
Sponsored by: The FreeBSD Foundation
MFC after: 3 weeks
Using plain dsb()/dmb() as full system barriers is usually to much.
Adding proper options to those barriers (instead of full system - sy)
will most likely reduce the cost of the instructions and will benefit
in performance improvement.
This commit adds options to barrier macro definitions.
Obtained from: Semihalf
Reviewed by: andrew, ian
Sponsored by: The FreeBSD Foundation
no need for them to be this strong, we only need to provide one or the
other.
While here replace atomic_load_acq_* and atomic_store_rel_* with a single
instruction version, and fix the definition of atomic_clear_* to point to
the correct functions.
Sponsored by: The FreeBSD Foundation
