Linux SMP Problems
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Fellow IPv6 Experimenters,
today I upgraded my (so far pretty stable) IPv6 router from one to two CPUs.
The Kernel (2.2.25) didn't change, it was SMP-enabled before.
Right after the update strange behaviour has begun:
After running my IPv6 setup script for the first time, ifconfig dropped a segmentation fault on any kind of action (but did the requested action correctly)
After a few minutes of IPv6 being up, the kernel panics with "tried to kill idle task".
I tried to upgrade to 2.4.21 with basically the same behaviour (2.4.21 just reboots without notice :> )
The system has been up without IPv6 now for over an hour, with various "make -j8" tests and seems to run as stable as before, so I'm far away from blaming the new processors.
I am still examining this strange behaviour and would be very thankful for any kind of suggestion ...
Kind regards,
Michael Beck
Linux SMP Problems
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Michael,
I'm running Red Hat 9.0 on a dual Athlon MP 2000+ system with the following kernel:
[tez@cybernoid tez]$ uname -a
Linux cybernoid.spilsby.net 2.4.20-18.9smp #1 SMP Wed Jun 25 11:19:23 BST 2003 i686 athlon i386 GNU/Linux
The only difference between the stock Red Hat kernel and my own version is the addition of NeTraverse's Win4Lin patches. Nothing else added or taken away.
Unfortunately, I don't have a 2.2.x machine to test with... but I can confirm that IPv6 *does* work with current 2.4.x kernels.
If you have a broadband connection, you might want to consider downloading an ISO of Knoppix (http://www.knoppix.net/) and booting your SMP machine with that to see if you can replicate the issue with a 2.4.x-based kernel. Knoppix doesn't touch your hard disk in any way so it won't break your existing setup.
I suggest you try it - at least you will know then if it is kernel-related or SMP-related, eh ?
Linux SMP Problems
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Terry,
thanks for your message and the confirmation that IPv6 in linux is SMP-safe.
I guess I have to blame myself for the odd system - it's a RedHat 6.2 which has been updated over the years so there must be some kind of undesired interaction :( I've had different other problems with 2.4 kernels with this particular machine, perhaps it's time for an update.
Let's see if I can solve it without upgrading the whole box to RH9 :)
And thanks for the knoppix hint, it's on the way through my not-so-broadband pipe :)
To be continued...
Linux SMP Problems
IMHO you will be better off reporting this behaviour to the smp list along with the oops etc.
I would almost have guessed it was a motherboard (apic, procs) problem, but apparently you can do a make -j8, which should cause it to die either way. I know of several smp boxes using SMP and IPv6 on Linux without any problems. I do even recall running a dual p2 266 in 1998 or something along with IPv6 enabled which was prolly a early 2.2.x then. But that was on a p2b-ds ;)
Linux SMP Problems
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sure, I'll report everything I have as soon as the problem is solved ...
Linux SMP Problems
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Update:
The problem was solved - one of the new processors was indeed defective and failed very unpredictively, which I really didn't suspect. (Murphy ..)
Anyways, there's still one useful conclusion from this dilemma:
*never* try to compile ipv6 as a module on SMP systems with 2.2.25.
It crashes the machine within minutes. Compiled into the kernel it works like a charm.
Michael
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