It seems that the following error occurs whenever kernel option 
LOCKDEBUG is turned on - this happens by default on the XEN* kernels.

Sources are up-to-the-minute (well, maybe 15 or 20 minutes old!)

kern_rwlock.o: In function `rw_vector_enter':
/usr/src/sys/kern/kern_rwlock.c:257: undefined reference to `cpu_intr_p'

If LOCKDEBUG is not enabled, the RW_ASSERT gets #defined to nothing.


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