linux-kernel - Re: [PATCH 00/14] replace call_rcu by kfree_rcu for simple kmem_cache

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Message-ID: <20240613071738.0655ff4f@kernel.org>
Date: Thu, 13 Jun 2024 07:17:38 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: "Paul E. McKenney" <paulmck@...nel.org>
Cc: "Jason A. Donenfeld" <Jason@...c4.com>, Julia Lawall
 <Julia.Lawall@...ia.fr>, linux-block@...r.kernel.org,
 kernel-janitors@...r.kernel.org, bridge@...ts.linux.dev,
 linux-trace-kernel@...r.kernel.org, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, kvm@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, "Naveen N. Rao"
 <naveen.n.rao@...ux.ibm.com>, Christophe Leroy
 <christophe.leroy@...roup.eu>, Nicholas Piggin <npiggin@...il.com>,
 netdev@...r.kernel.org, wireguard@...ts.zx2c4.com,
 linux-kernel@...r.kernel.org, ecryptfs@...r.kernel.org, Neil Brown
 <neilb@...e.de>, Olga Kornievskaia <kolga@...app.com>, Dai Ngo
 <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
 linux-nfs@...r.kernel.org, linux-can@...r.kernel.org, Lai Jiangshan
 <jiangshanlai@...il.com>, netfilter-devel@...r.kernel.org,
 coreteam@...filter.org, Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH 00/14] replace call_rcu by kfree_rcu for simple
 kmem_cache_free callback

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