linux-kernel - Re: [PATCH] KEYS: Reduce smp_mb() calls in key

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Message-ID: <aBa2bZGnJ2kRJJpa@gondor.apana.org.au>
Date: Sun, 4 May 2025 08:35:57 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: David Howells <dhowells@...hat.com>
Cc: Jarkko Sakkinen <jarkko@...nel.org>, keyrings@...r.kernel.org,
	Lukas Wunner <lukas@...ner.de>,
	Ignat Korchagin <ignat@...udflare.com>,
	"David S. Miller" <davem@...emloft.net>,
	Peter Huewe <peterhuewe@....de>, Jason Gunthorpe <jgg@...pe.ca>,
	Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Mimi Zohar <zohar@...ux.ibm.com>, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH] KEYS: Reduce smp_mb() calls in key_put()

On Sat, May 03, 2025 at 11:19:21PM +0100, David Howells wrote:
>
> Possibly we only need smp_mb() in the IN_QUOTA branch in key_put().

Just change the smp_mb to smp_mb__before_atomic, at least on x86
it just disappears because set_bit is already a serialising operation.

Or even better, reverse the FINAL_PUT bit and call it ALIVE, so
that you can use test_bit_acquire and clear_bit_unlock.

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