Re: circular locking, mirred, 2.6.24.2

Denys Fedoryshchenko
2008-03-06T15:51:18Z

On Thu, 06 Mar 2008 09:27:14 -0500, jamal wrote
> On Thu, 2008-06-03 at 15:57 +0200, Denys Fedoryshchenko wrote:
> > I am able to reproduce this warning over this relatively simple shell
script
> > on my Gentoo PC (2.6.25-rc3).
> > http://www.nuclearcat.com/files/bug_feb.txt
> >
>
> That script looks pretty sane to me - nothing super-exciting. I suspect
> you eventually want them all to look like ifb1 on the egress.
> Do you see the same issue without the ifb1 speacial case?
Well, i am able to reproduce in much more trivial script. Tested 2.6.25-rc4
also.

modprobe ifb
ifconfig ifb0 up
TC=/sbin/tc
$TC qdisc del dev eth0 ingress 1>/dev/null 2>/dev/null
$TC qdisc add dev eth0 ingress
${TC} filter add dev eth0 parent ffff: protocol ip prio 10 u32 \
match u32 0 0 flowid 1:1 \
action mirred egress redirect dev ifb0

>
> > Probably it will help to debug issue for more experienced developers.
Note:
> > it appears not immediately, second time i tested, it's appeared after
while,
> > but in matter of seconds.
>
> I wonder is there some latency from the moment you insmod ifb to the
> moment the tc rules take effect? Will it still happen if you dont
> have modules? Also note, that lock dependency is a bit strange,
> Jarek correct me if i am wrong; it seems to say: a packet received
> on ingress of some e1000 (ethx) gets acted on by mirred which ends
> grabbing lock of an ifb device - this part should be fine and no
> need for the alarm. The alarm seems to be a result of a loopback
> device that is being registered in between the two activities.
> i.e there are three devices affected with entirely different
> locks(ethx, ifbx, and loopback). Smells like lockdep is getting it wrong?
No idea, i have strange lockup's on my systems where i have ifb, and that
make me worry. And i feel it is directly related with my love to use ifb
devices and way how i am using them.

>
> > Note - it can stop traffic on PC completely. It is also seems crashed my
> > desktop PC, i am not able to execute "tc qdisc del dev eth0 root".
> > The system hang completely. I had few similar issues on my PPPoE servers
> > (with different scripts for shapers), that system hang, and even "reboot -
f"
> > doesn't work sometimes.
>
> This sounds like a different issue from above - when did this start
> to happen? Is it at the same time as above warnings showing up?

Yes, it is different issue seems, it is rare to lockup system , and i will
dig more, to understand how it is happening.

>
> cheers,
> jamal
>
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--
Denys Fedoryshchenko
Technical Manager
Virtual ISP S.A.L.