Segher Boessenkool wrote:
The hardware must not see that is given ownership of a buffer until it is
completely written, and when the driver receives ownership of a buffer,
it must ensure that any other reads to the buffer reflect its final
state. Thus, I/O barriers are added where required.
Without this patch, I have observed GCC reordering the setting of
bdp->length and bdp->status in gfar_new_skb.
The :::"memory" in the barriers you used prevent GCC
from reordering accesses around the barriers.
Sure... it was just an example to point out that it's actually
happening, rather than a theoretical concern.
AFAICS you need stronger barriers though; {w,r,}mb(),
to prevent _any_ reordering of those memory accesses,
not just the compiler-generated ones.
My impression was that the eieio used by iobarrier would be sufficient
for that, as we're not trying to synchronize between accesses to
different types of memory. Is sync really required here?
-Scott
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