On 09/21/15 at 07:51am, Eric Dumazet wrote: > The important part here is that we rehash an item, so we need to make > sure to maintain consistent ->next field, and need to prevent compiler > from using ->next as a temporary variable. > > ptr->next = 1UL | ((base + offset) << 1); > > Is dangerous because compiler could issue : > > ptr->next = (base + offset); > > ptr->next <<= 1; > > ptr->next += 1UL; > > Frankly, all this looks like an oversight in this code. > > Not sure why the NULLS value is even recomputed.
The hash of the chain is part of the NULLS value. Since the entry might have been moved to a different chain, the NULLS value must be recalculated to contain the proper hash. However, nobody is using the hash today as far as I can see so we could as well just remove it and use the base value only for the nulls marker. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
