Re: Adding pool_cache_invalidate_local() to pool_cache(9) API

[Andrew Doran <ad%NetBSD.org@localhost>]

On Tue, Oct 13, 2009 at 11:19:11AM -0700, Jason Thorpe wrote:
> 
> On Oct 9, 2009, at 7:35 AM, Matt Thomas wrote:
> 
> > Do it lazily.  Set a flag in each per-cpu queue and next time an item that
> > cpu accesses its per-cpu cache, it can see the cache is invalid and discard 
> > it.
> > This doesn't solve the window of that cpu already actively using the pool
> > while the flag is set but it could that could solved by get testing the 
> > test on
> > exit, if set discarding the item, and retrying.
> > 
> > No reason for exposing the mechanics of how to do this to the users of the
> > poll APIs.
> 
> It actually turned out to be very trivial to fix pool_cache_invalidate() to 
> DTRT with per-CPU caches.  I'll provide a patch for Jean-Yves to try in the 
> situation where he required pool_cache_invalidate_local().  While I was at 
> it, I discovered that the two existing uses of pool_cache_invalidate() don't 
> do proper synchronization wrt. the constructor.  I'll write up a patch for 
> the alpha and x86 pmaps separately.

x86 used pmap_list_lock (pmaps_lock?) to do this at one point, it's possible
that somebody broke it.