On Thu, Dec 31, 2015 at 09:09:47PM +0200, Michael S. Tsirkin wrote: > At the moment, xchg on sh only supports 4 and 1 byte values, so using it > from smp_store_mb means attempts to store a 2 byte value using this > macro fail. > > And happens to be exactly what virtio drivers want to do. > > Check size and fall back to a slower, but safe, WRITE_ONCE+smp_mb.
Can you please do this for size 1 as well (i.e. all sizes != 4)? If you check the source, the code for size-1 xchg in sh cmpxchg-llsc.h is completely wrong and operates on a 32-bit object at the address passed to it. This code is presently unused anyway and I plan to submit a patch to remove the size 1 case. Rich -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/