Hi All,

Because I could not find a solution for the cpu stall problem on kernel 
3.2.18-rt29. I thought I might try an older kernel. So I download 
linux-2.6.33.9 and patch-2.6.33.9-rt31. But 2.6.33 doesn't have 
vhost_net, so I ported vhost_net from 2.6.34 back to 2.6.33.9.

The kernel was patched and built successfully. But when I boot, I got 
kernel NULL pointer dereference error. After the error, my system seems 
stable, I can start KVM client without CPU stalls. But very frequently, 
processes will locked up for long time, the wchan displayed by ps is 
either sync_page or synchronize_rcu. It looks that rcu still causes 
problem in the rt-kernel.

The dmesg out of NULL pointer is attached.

Thanks!

Dong