svn commit: r239395 - head/sys/netinet
Robert Watson
rwatson at FreeBSD.org
Sun Aug 19 11:58:08 UTC 2012
On Sun, 19 Aug 2012, Randall Stewart wrote:
> Though I disagree, I conceed to jhb & Rui. Note
> that we still have a problem with this whole structure of
> locks and in_input.c [it does not lock which it should not, but
> this *can* lead to crashes]. (I have seen it in our SQA
> testbed.. besides the one with a refcnt issue that I will
> have SQA work on next week ;-)
I agree with John here -- these are seperate issues, and we need to get each
part correct in isolation, not just in composition.
Bjoern and I have been plotting a lock reduction exercise in the network stack
for some time, based on a model Jeff Roberson and the Nokia guys used -- a
global "config" lock, which would use our rmlock primitive. This would make
address list synchronisation sufficiently affordable to use in ip_input().
However, it comes with a number of other issues that we need to consider, such
as potential latency impacts of reconfiguration events, which have to be
characterised before we commit to it, as well as potential issues with lock
order. Recent rmlock improvements (e.g., with respect to WITNESS) make doing
this work much more plausible. Hopefully this is something we'll get to in
September.
Robert
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