> On Thu, Oct 18, 2001 at 07:50:31PM +0300, Richard Earnshaw wrote:
> 
>  > However, even with this step having more than a small number of
>  > processes searching for a L1 pt can still be enough to bring the system
>  > down, since they all run at high priority and sleep for very little time,
>  > thus blocking out user code from completing.  So implement an exponential
>  > backoff when waiting for a page table, so that we don't hog the CPU when
>  > memory is scarce.
> 
> This is a good improvement, but...
> 
> The pmap isn't really supposed to be sleeping -- there could be locks
> held by the caller (UVM).  The fact that other pmaps currently sleep
> is not meant to suggest that such behavior is correct :-) I should
> probably clarify this in the pmap(9) manual page.
> 
> The right thing to do is to return an error to the caller of pmap_enter()
> if PMAP_CANFAIL is set in the flags argument.  The caller will then unlock
> and wait for more memory.

We aren't in pmap_enter.  This is pmap_pinit, which is called from 
pmap_create().  As far as I can tell, there is no mechanism for this to 
fail.