On Fri, Aug 26, 2016 at 12:16 PM, Eric Dumazet <eric.duma...@gmail.com> wrote: > On Fri, 2016-08-26 at 11:26 -0700, Cong Wang wrote: >> 1) Currently there are only a few actions using lockless, and they are >> questionable, as we already discussed before, there could be some >> race condition when you modify an existing action. > > There is no fundamental issue with a race condition.
For mirred action, maybe. As we already discussed, the more complex an action is, the harder to make it lockless in your way (that is, not using RCU) > > Sure, there are races, but they have no serious effect. > > Feel free to send a fix if you really have time to spare. It's because the code is written by you? I am surprised how you try to hide your own problem in such a way... > >> >> 2) We need to change the tc action API in order to fully support RCU, >> which is what I have been working on these days. I should come up >> with something next Monday (if not this weekend). >> >> So for this patchset, using spinlock is fine, just as many other actions. >> I will take care of it later. > > This is _not_ fine. OK, so where are your patches to make the rest actions lockless? > > We are in 2016, not in 1995 anymore. > Fair enough, sounds like all actions are already lockless in fast path now in 2016, you know this is not true... > We are not adding a spinlock in a hot path unless absolutely needed. If it is bug-free, yes, I am totally with you. I care about corretness more than any performance. > > With multi queue NIC, this spinlock is going to hurt performance so much > that this action wont be used by any serious user. We have used mirred action even before you make it lockless. > > Here, it is absolutely trivial to use RCU and/or percpu counters. Sounds like we don't need any API change, why not go ahead and try it? Please do teach me how to modify an existing action in a lockless way without changing any API (and of course needs to be bug-free), I am very happy to learn your "trivial" way to fix this, since I don't have any trivial fix. Please, stop bullsh*t, show me your trivial code.
