Re: [Xen-devel] vbd devices stuck in Initialising/InitWait

["Christopher S. Aker" <caker@xxxxxxxxxxxx>]

Ewan Mellor wrote:
> That sounds to me like the guest kernel is crashing or deadlocking.  Do you
> see anything on the guest console?  Perhaps you could put #define DEBUG 1 at
> the top of blkfront/block.h and xenbus/xenbus_probe.c for your guest kernel,
> and try and figure out where it is getting stuck.
The domains aren't crashing since they will boot, provided the root 
device isn't among the missing...
I've added DEBUG a bunch of printk's to talk_to_backend() and 
xenbus_switch_state().  The outputs are here:
http://www.theshore.net/~caker/xen/InitWait/dmesg-working.txt
http://www.theshore.net/~caker/xen/InitWait/dmesg-not_working.txt

At the bottom of both of those files, I've pasted in just the debugging 
messages in order.
There are two main differences:

When devices are missing, talk_to_backend() is making duplicate calls 
for the same vbd to xenbus_switch_state(), and on the second call 
xenbus_switch_state avoids writing to xenstore an identical value (which 
it's supposed to).  Why the duplicate calls?
Second difference: even though there were two calls to 
xenbus_switch_state) to set the state to 3, later on xenbus_probe only 
detects the state as 2.
talk_to_backend - about to call xenbus_switch_state
xenbus_switch_state() nodename=device/vbd/770 state=3 - entering
xenbus_switch_state() nodename=device/vbd/770 state=3 - finished
talk_to_backend - about to call xenbus_switch_state
xenbus_switch_state() nodename=device/vbd/770 state=3 - entering
xenbus_switch_state() nodename=device/vbd/770 state=3 - state == dev->state

but then:
xenbus_probe (otherend_changed:302) state is 2, 
/local/domain/0/backend/vbd/151/770/state, 
/local/domain/0/backend/vbd/151/770/state.
So, is this a deadlock or locking issue like you suspected?

Thanks,
-Chris

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