netdev - Re: [PATCH] Revert "batman-adv: prefer kfree_rcu() over call

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Message-ID: <ZmnNfU44NekafjA_@sellars>
Date: Wed, 12 Jun 2024 18:31:57 +0200
From: Linus Lüssing <linus.luessing@...3.blue>
To: "Paul E. McKenney" <paulmck@...nel.org>
Cc: b.a.t.m.a.n@...ts.open-mesh.org, Dmitry Antipov <dmantipov@...dex.ru>,
	netdev@...r.kernel.org, rcu@...r.kernel.org
Subject: Re: [PATCH] Revert "batman-adv: prefer kfree_rcu() over call_rcu()
 with free-only callbacks"

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

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.