7.1-PRERELEASE freezes (IPFW related)

Robert Watson rwatson at FreeBSD.org
Sat Sep 27 10:14:22 UTC 2008

On Sat, 27 Sep 2008, Christian Laursen wrote:

> I am now back to running with everything I usually have running on this 
> machine (my primary desktop) but without the ipfw uid rules and the machine 
> is rock stable.
> I have been running with debug.mpsafenet="0" most likely because I have been 
> using ipfw uid matching. Has RELENG_7 had significant changes in this area?
> Since I don't need these rules anymore I have just removed them.

In the last few days, some previously undiscovered interactions have been 
discovered between the rwlock work for udp/tcp performance and ipfw 
uid/gid/jail rules.  In essence, there were a number of edge cases where it 
turned out ipfw was relying on lock recursion on those locks, and that's no 
longer possible.

I've fixed two such edge cases in HEAD and will MFC them shortly, but there is 
at least one other known case.  I'm on the fence about whether to continue 
playing whack-a-mole knocking off the bugs as they are discovered, and fixing 
it with a hammer (having ipfw and friends check for the lock held before 
trying to acquire it) -- if this keeps up it's the latter for -STABLE and 
continuing to fix them as one-off bugs in HEAD.

Robert N M Watson
Computer Laboratory
University of Cambridge

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