Log Message:
-----------
Seems I was too optimistic in supposing that sinval's maxMsgNum could be
read and written without a lock. The value itself is atomic, sure, but on
processors with weak memory ordering it's possible for a reader to see the
value change before it sees the associated message written into the buffer
array. Fix by introducing a spinlock that's used just to read and write
maxMsgNum. (We could do this with less overhead if we recognized a concept
of "memory access barrier"; is it worth introducing such a thing? At the
moment probably not --- I can't measure any clear slowdown from adding the
spinlock, so this solution is probably fine.) Per buildfarm results.
Modified Files:
--------------
pgsql/src/backend/storage/ipc:
sinvaladt.c (r1.71 -> r1.72)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/ipc/sinvaladt.c?r1=1.71&r2=1.72)