Re: getting uninterruptible sleep processes after upgrade from 2.6.20.20 to 2.6.24.2

[allied internet ag- Stefan Priebe <s.priebe@allied-internet.ag>]

 >> One week ago we upgraded about 300 servers from 2.6.20.20 to 2.6.24.2.
 >
 > Painfull.

OK not really - i've tested the new kernel on all models. And it works 
fine... the DN state only comes sometimes - absolutely not reproducable. 
So my tests went OK and then we've done the update. I've now seen 5 
servers in 7 days having this problem.

 >> Now we get sometimes dozent of processes in state DN. The system is
 >> completely idle - but the load is 20 or 90 or whatever. And it can
 >> only be "repaired" by rebooting the system.
 >
 > please post sysrq-t (echo t > /proc/sysrq-trigger) output.
Sorry what key is sysrq? Can i also do this via SSH Console?

 > Did you test with *one* server before upgrading all 300? If not, please
 > do and try to upgrade in smaller steps, e.g. 2.6.20->2.6.21 and see when
 > it breaks. Add a few *DEBUG .config options, they may help narrowing
 > down the problem...
Problem here is that it is not reproducable...

Stefan