Eric Dumazet <[email protected]> wrote: > On Wed, 2017-07-26 at 02:09 +0200, Florian Westphal wrote: > > switch to lockless lockup. write side now also increments sequence > > counter. On lookup, sample counter value and only take the lock > > if we did not find a match and the counter has changed. > > > > This avoids need to write to private area in normal (lookup) cases. > > > > Note that we take the non-blocking variant (raw_seqcount_begin), i.e. > > read side will not wait for writer to finish. > > > > If we did not find a result we will fall back to use of read-lock. > > > > The readlock is also used during dumps to ensure we get a consistent > > tree walk. > > > > Similar technique (rbtree+seqlock) was used by David Howells in rxrpc. > > Please note that in commit b145425f269a17ed344d737f746b844dfac60c82 > ("inetpeer: remove AVL implementation in favor of RB tree") > > I chose to also pass the sequence so that the lookup could abort. > I am not sure that during rb tree write operations, some nodes could be > left with some kind of loop.
I see. Ok, I will spin a v2 and will pass the sequence too, thanks Eric. If we have to abort on seqretry anyway then I can also use read_seqcount_begin to force readers to wait until writer is done, so I will change that as well. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
