From: Patrick McHardy > On 16.01, Thomas Graf wrote: > > On 01/16/15 at 04:03pm, Patrick McHardy wrote: > > > On 16.01, Thomas Graf wrote: > > > > A walker may not see insertions that occur after the walker was started > > > > if resizing is enabled. Is that a problem for nftables? > > > > > > No, that would be Ok. The case I'm wondering about is: > > > > > > - insertion > > > - resize starts > > > - another insertion > > > - walker, resize not finished yet > > > > Correct, walker may not see "another insertion". The window for this > > behavior to occur is not the full resize operation, just the linking > > period, but it may occur. The length of the window is typically > > equal to a grace period. > > > > We can provide a synchronization function to block the dumper or the > > insertion/removal until the linking is complete. The latter would > > give the old runtime behaviour back (variable runtime of insert), > > the blocked dumper might be preferred. What do you think? > > If we have to block, the dumper if of course preferred. Taking the > mutex should do fine I guess? > > I suppose walking both tables without any races would be rather > complicated. The walker is unlikely to see items that get inserted early in the hash table even without a resize. I'd be more worried about the walker missing big blocks of entries or getting duplicate entries during a resize. This might be a problem if the walker is a user-process table dump, in which case you can't assume it will finish in any finite time. David -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
