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

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Message-ID: <2328482.ElGaqSPkdT@sven-l14>
Date: Wed, 12 Jun 2024 20:22:49 +0200
From: Sven Eckelmann <sven@...fation.org>
To: "Paul E. McKenney" <paulmck@...nel.org>, b.a.t.m.a.n@...ts.open-mesh.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,
 Linus Lüssing <linus.luessing@...3.blue>
Subject:
 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:
> > 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
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