Hi David, You wrote: > 2) We can't turn sk_forward_alloc easily into an atomic_t. The > masking operation in __sk_stream_mem_reclaim() does not translate > readily into an atomic_t op: > > sk->sk_forward_alloc &= SK_STREAM_MEM_QUANTUM - 1; > > That line has always driven me nuts, but I know that it is there > to handle partial page allocations existing when that function > is called. > > I guess for #2 we could change those two lines into: > > int n = atomic_read(&sk->sk_forward_alloc) / > SK_STREAM_MEM_QUANTUM; > > atomic_sub(n, sk->sk_prot->memory_allocated); > sk->sk_forward_alloc -= n * SK_STREAM_MEM_QUANTUM; > > in order to make it "atomic_t op" translatable.
It is possible. Just view this as an register with size SK_STREAM_MEM_QUANTUM. Mask on every read and always after the read. Always add/subtract the intended value. Wraparound happens within the modulo/mask value. This works without problems as long as SK_STREAM_MEM_QUANTUM is a power of two. If not, just use modulo arithmetics. The non-atomic wrapround doesn't change the atomic nature of read, add, sub. Only problem is atomic_dec_and_test() or similiar ops. Regards Ingo Oeser - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
