Hi,
I think I have identified some issues with the atomic builtins, but I want
your advises.
For instance :
A: __atomic_store_n (addr, val, __ATOMIC_SEQ_CST);
gives the armv7 code:
DMB sy
STR r1, [r0]
DMB sy
but if I have well understood, the DMBs instructions only provide the
property that the
code is sequentially consistent, but not the atomicity for which we have to
use the
LDREX/STREX instructions. Thus I think that the code should be :
DMB sy
1: LDREX r2, [r0]
STREX r1, r2, [r0]
TEQ r1, #0
BNE 1b
B: __atomic_load_n (addr, __ATOMIC_ACQUIRE);
gives the armv7 code:
DMB sy
LDR r0, [r0]
but the load-acquire semantique specifies that all loads and stores
appearing in program order
after the load-acquire will be observed after the load-acquire, thus the
DMB should be after the
LDR, no ?
--
Yvan
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