[Xen-devel] Unplugging a dom0 vcpu and domain destruction

[George Dunlap <dunlapg@xxxxxxxxx>]

In the course of developing the new scheduler, I noticed something
rather strange.

If I bring dom0's second cpu offline (echo "0" >
/sys/devices/system/cpu/cpu1/online), and then create and destroy a
number of domains, xen/common/domain.c:domain_destroy() is not called
(nor vcpu_destroy, and the scheduler domain destruction
functionality).  If I bring the cpu back online (echo 1 > ...), the
domains are destroyed almost immediately.

domain_destroy() is only called from put_domain(), so presumably
there's somehow reference counts held somewhere which aren't released
when the second cpu is offline.

I've duplicated this using the standard credit scheduler on
xen-unstable tip.  I'm using a Debian dom0 filesystem, and a
linux-2.6.18-xen0 build from a month ago.

My box has 2 cores, so dom0 has only 2 cpus; disabling the second
causes it to switch to UP primitives.

I'm looking into it, but I thought it might ring some bells with someone...

 -George

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