netdev - Re: [PATCH] can: gw: prefer kfree_rcu() over call_rcu() with cgw_job_free

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Date: Wed, 13 Mar 2024 17:01:57 +0300
From: Dmitry Antipov <dmantipov@...dex.ru>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Oliver Hartkopp <socketcan@...tkopp.net>,
 Marc Kleine-Budde <mkl@...gutronix.de>, linux-can@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH] can: gw: prefer kfree_rcu() over call_rcu() with
 cgw_job_free_rcu()

On 3/13/24 13:55, Eric Dumazet wrote:

> kmem_cache_free(struct kmem_cache *s, void *x) has additional checks
> to make sure the object @x was allocated
> from the @s kmem_cache.
> 
> Look for SLAB_CONSISTENCY_CHECKS and CONFIG_SLAB_FREELIST_HARDENED

Yes. Using kfree_rcu() bypasses these (optional) debugging/consistency
checks.

> Your patch is not 'trivial' as you think.

You're shifting from "not going to work" to "not trivial" so nicely.

> Otherwise, we will soon have dozen of patches submissions replacing
> kmem_cache_free() with kfree()

No. The question is about freeing on some (where the freeing callback
function is trivial) RCU-protected paths only.

Dmitry