On Mon, Apr 25, 2016 at 11:52:04AM -0700, Andres Freund wrote: > On 2016-04-23 21:54:07 -0400, Noah Misch wrote: > > The bug is that the pg_atomic_compare_exchange_*() specifications > > grant "full barrier semantics", but generic-xlc.h provided only the > > semantics of an acquire barrier. > > I find the docs at > http://www-01.ibm.com/support/knowledgecenter/SSGH3R_13.1.2/com.ibm.xlcpp131.aix.doc/compiler_ref/bifs_sync_atomic.html > to be be awfully silent about that matter. I guess you just looked at > the assembler code? It's nice that one can figure out stuff like that > from an architecture manual, but it's sad that the docs for the > intrinsics is silent about that matter.
Right. The intrinsics provide little value as abstractions if one checks the generated code to deduce how to use them. I was tempted to replace the intrinsics calls with inline asm. At least these functions are unlikely to change over time. > Except that I didn't verify the rs6000_pre_atomic_barrier() and > __fetch_and_add() internals about emitted sync/isync, the patch looks > good. We've so far not referred to "sequential consistency", but given > it's rise in popularity, I don't think it hurts. Thanks; committed. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
