deadlock in PowerPC VM system

[Duncan Missimer <dmissimer%rhapsodynetworks.com@localhost>]

Anybody else seen this one?

        sys__sysctl ->
        kern_sysctl ->
        sysctl_procargs ->
        uvm_io -> # creates kernel mapping
        uiomove ->
        kcopy ->
        bcopy ->
        trap ->
        uvm_fault ->  # acquires shared lock for kernel map
        pmap_enter ->
        pmap_enter_pv ->
        pmap_alloc_pv ->  # but pv_nfree is 0, so.....
        uvm_km_zalloc (== uvm_km_alloc1) ->
        uvm_map ->
        uvm_map_lock ->
        lockmgr(kernel_map, LK_EXCLUSIVE # hangs forever waiting for above
shared lock to go away

        Note that the WEHOLDIT test under LK_EXCLUSIVE doesn't help because
it is
        impossible to identify the owner[s] of shared locks.

Got any good ideas? I understand that the kernel is based on current as of
7/17.

thanks,
Duncan