On Thu, Jun 13, 2024 at 07:17:38AM -0700, Jakub Kicinski wrote:

On Wed, 12 Jun 2024 20:38:02 -0700 Paul E. McKenney wrote:

quoted

o	Make rcu_barrier() wait for kfree_rcu() objects.  (This is
	surprisingly complex and will wait unnecessarily in some cases.
	However, it does preserve current code.)

Not sure how much mental capacity for API variations we expect from
people using caches, but I feel like this would score the highest
on Rusty's API scale. I'd even venture an opinion that it's less
confusing to require cache users to have their own (trivial) callbacks
than add API variants we can't error check even at runtime...

Fair point, though please see Jason's emails.

And the underlying within-RCU mechanism is the same either way, so that
API decision can be deferred for some time.

But the within-slab mechanism does have the advantage of also possibly
simplifying reference-counting and the potential upcoming hazard pointers.
On the other hand, I currently have no idea what level of violence this
change would make to the slab subsystem.

							Thanx, Paul