On Fri, Sep 9, 2016 at 5:23 AM, Eric Dumazet <eric.duma...@gmail.com> wrote: > On Thu, 2016-09-08 at 22:24 -0700, Cong Wang wrote: >> On Thu, Sep 8, 2016 at 8:35 AM, Eric Dumazet <eric.duma...@gmail.com> wrote: >> > From: Eric Dumazet <eduma...@google.com> >> > >> > As reported by Cong Wang, I was lazy when I did initial RCU conversion >> > of tc_mirred, as I thought I could avoid allocation/freeing of a >> > parameter block. >> >> Quote from Eric Dumazet: >> >> https://www.mail-archive.com/netdev@vger.kernel.org/msg115482.html >> >> <Quote> >> Well, I added a READ_ONCE() to read tcf_action once. >> >> Adding rcu here would mean adding a pointer and extra cache line, to >> deref the values. >> >> IMHO the race here has no effect . You either read the old or new value. >> </Quote> >> >> Me with facepalm... ;-) > > > Point is still valid. Show me a real case where it was a serious > problem, instead of simply theoretical. > > tc_mirred + ifb patches allowed us to reach a milestone, removing the > last contended spinlocks, and you are catching up with this one year > later. > > I wont backport this fix in Google prod kernels, because there is > absolutely no way we need it, and the extra memory cache line might hurt > latencies. > > Since you did not write a fix on your side since June 17th, I presume > you do not care that much.
Sounds like I were the author of this patch.... Why are you questioning your own patch? Did I ask you to care about it? ;-) Please drop this patch. Thanks.
