[Xen-devel] event_lock not initialized in the idle domain (permitted actions in a tasklet?)

["Byrne, John (HP Labs)" <john.l.byrne@xxxxxx>]

I am playing with the xenpaging code that was checked into xen 4.0 and I hit a 
bug because it sends an event channel notification from a tasklet which was 
getting run from the idle domain on my box. Since domain_create() does not 
perform the evtchn_init for the idle domain, the event_lock was not initialized 
and the tasklet would hang the cpu when it tried to acquire the lock.

While my immediate problem seems easy enough to work around --- I really can't 
see the reason for the tasklet in the first place, so I just got rid of it --- 
the underlying issue needs a look. Should domain_create() simply initialize all 
of the idle_domain structure?  As far as I can tell, the only reason it doesn't 
is to save a little memory. While the event_lock issue can be dealt with simply 
enough by breaking out the initialization separately, it seems that having the 
special-case code for the idle domain opens up the possibility for bugs with 
respect to operations from tasklets.

Thanks,

John Byrne

 

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