linux-kernel - Re: [PATCH] crypto: iaa - Fix race condition when probing IAA devices

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Message-ID: <aEpn0B6CrMNcD-Oj@gondor.apana.org.au>
Date: Thu, 12 Jun 2025 13:38:24 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Vinicius Costa Gomes <vinicius.gomes@...el.com>
Cc: Kristen Accardi <kristen.c.accardi@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crypto: iaa - Fix race condition when probing IAA devices

On Wed, Jun 11, 2025 at 02:17:49PM -0700, Vinicius Costa Gomes wrote:
>
> >From what I could gather, the idea of the per-cpu workqueue table ("map"
> really) is more to "spread" the workqueues to different CPUS than to
> reduce contention.
> 
> If the question is more about the choice of using per-cpu variables, I
> can look for alternatives.

Prior to your patch, the compress/decompress paths simply did a
lockless per-cpu lookup to find the wq.  Now you're taking a global
spinlock to do the same lookup.

That makes no sense.  Either it should be redesigned to not use
a spinlock, or the per-cpu data structure should be removed since
it serves no purpose as you're always taking a global spinlock.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt