Re: [PATCH] Revert "batman-adv: prefer kfree_rcu() over call_rcu() with free-only callbacks"

On Wednesday, 12 June 2024 18:31:57 CEST Linus Lüssing wrote:

On Wed, Jun 12, 2024 at 09:06:25AM -0700, Paul E. McKenney wrote:

quoted

We are looking into nice ways of solving this, but in the meantime,
yes, if you are RCU-freeing slab objects into a slab that is destroyed
at module-unload time, you currently need to stick with call_rcu()
and rcu_barrier().

We do have some potential solutions to allow use of kfree_rcu() with
this sort of slab, but they are still strictly potential.

Apologies for my having failed to foresee this particular trap!

No worries, thanks for the help and clarification! This at least
restored my sanity, was starting to doubt my understanding of RCU
and the batman-adv code the longer I tried to find the issue in
batman-adv :D.

Thanks Linus and Paul. I've queued up the revert. But feel free to submit a 
version with updated text in case you want to incorporate information from 
this thread.

Kind regards,
	Sven