Re: Reminder: NET_NEEDS_GIANT, debug.mpsafenet going away in 7.0

From: Max Laier <max_at_love2party.net>
Date: Tue, 17 Jul 2007 23:42:14 +0200
[ Excess CC-list ... testers needed!!! ]

On Tuesday 17 July 2007, Robert Watson wrote:
> Dear all:
>
> This is a reminder e-mail that, in the very near future, Giant
> compatibility shims for network protocols will be removed.

<...>

> The *only* remaining case I am aware of where removing debug.mpsafenet
> presents an issue is credential-related firewall rules (uid, gid,
> jail).  I'm am currently in an active e-mail discussion with the
> various firewall maintainers about how to address this issue; as the
> implementations of these rules violate the global lock order, deadlocks
> occur if debug.mpsafenet isn't set to 1, which causes Giant to act as a
> guard lock preventing parallel lock acquisition in the firewall. 
> Hopefully we will have this resolved, in some form, soon.

What we really need right now, is real understanding of the problem (if 
there even is any).  So we would like to ask everybody who is able to - 
to stress test user/group rules (in pf) or uid/gid/jail rules (in ipfw) 
with debug.mpsafenet=1  It is normal that (in an WITNESS enabled kernel) 
you get a LOR similar to 14-17 and 32 from [1].  Everything different to 
those should be reported.

If you indeed get a deadlock, please let us know and provide as much 
debugging information as you can.  DDB's "ps", "show locks", "show 
alllocks" would be perfect, but detailed information how to repeat would 
be a good start to already.

Thanks a lot!  If you are unable to provoke a deadlock, please let us know 
as well.  Include a few setup details (ruleset, SMP, special sysctl 
settings ...) so we can look for patterns.

[1] http://sources.zabbadoz.net/freebsd/lor.html

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Received on Tue Jul 17 2007 - 19:42:52 UTC

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