On Mon, 24 Jun 1996 16:39:23 +0200 (MET DST) 
 Matthias Drochner <drochner@zelux6.zel.kfa-juelich.de> wrote:

 > If the machine is heavily loaded (esp. process creation) the
 > "vsunlock()" occasionaly causes a panic in "vm_fault_unwire()":
 > "unwire: page not in pmap". The reason is (I checked it explicitely
 > before calling "vsunlock()") that the page directory entry for
 > the user buffer became zero in the meantime.
 > (The check tests
 > vm_map_pmap(&curproc->p_vmspace->vm_map)->pm_pdir[((vm_offset_t)(buf) >>
 > PDSHIFT)&1023]
 > )
 > The system is NetBSD-1.1.
 > 
 > Can anybody explain this?

Paul Kranenburg recently dealt with some race conditions in this area.  
You might consider upgrading your system to -current (which is currently 
following the 1.2 release sources).

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