Hi,
IIRC Paul relies on schedule() implying a full memory barrier with
strong transitivity for RCU.
If not, ignore this email.
If so, however, I suspect AARGH64 is borken and would need (just like
PPC):
#define smp_mb__before_spinlock() smp_mb()
The problem is that schedule() (when a NO-OP) does:
smp_mb__before_spinlock();
LOCK rq->lock
clear_bit()
UNLOCK rq->lock
And nothing there implies a full barrier on AARGH64, since
smp_mb__before_spinlock() defaults to WMB, LOCK is an "ldaxr" or
load-acquire, UNLOCK is "stlrh" or store-release and clear_bit() isn't
anything.
Pretty much every other arch has LOCK implying a full barrier, either
because its strongly ordered or because it needs one for the ACQUIRE
semantics.
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