From: Jarkko Sakkinen <jarkko@kernel.org>
To: keyrings@vger.kernel.org
Cc: David Howells <dhowells@redhat.com>,
Lukas Wunner <lukas@wunner.de>,
Ignat Korchagin <ignat@cloudflare.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
"David S. Miller" <davem@davemloft.net>,
Peter Huewe <peterhuewe@gmx.de>, Jason Gunthorpe <jgg@ziepe.ca>,
Paul Moore <paul@paul-moore.com>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
Mimi Zohar <zohar@linux.ibm.com>,
linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org
Subject: Re: [PATCH] KEYS: Reduce smp_mb() calls in key_put()
Date: Sat, 3 May 2025 17:39:16 +0300 [thread overview]
Message-ID: <aBYqlBoSq4FwiDKD@kernel.org> (raw)
In-Reply-To: <20250430152554.23646-1-jarkko@kernel.org>
On Wed, Apr 30, 2025 at 06:25:53PM +0300, Jarkko Sakkinen wrote:
> Rely only on the memory ordering of spin_unlock() when setting
> KEY_FLAG_FINAL_PUT under key->user->lock in key_put().
>
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
> security/keys/key.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/security/keys/key.c b/security/keys/key.c
> index 7198cd2ac3a3..aecbd624612d 100644
> --- a/security/keys/key.c
> +++ b/security/keys/key.c
> @@ -656,10 +656,12 @@ void key_put(struct key *key)
> spin_lock_irqsave(&key->user->lock, flags);
> key->user->qnkeys--;
> key->user->qnbytes -= key->quotalen;
> + set_bit(KEY_FLAG_FINAL_PUT, &key->flags);
> spin_unlock_irqrestore(&key->user->lock, flags);
> + } else {
> + set_bit(KEY_FLAG_FINAL_PUT, &key->flags);
> + smp_mb(); /* key->user before FINAL_PUT set. */
> }
> - smp_mb(); /* key->user before FINAL_PUT set. */
> - set_bit(KEY_FLAG_FINAL_PUT, &key->flags);
Oops, my bad (order swap), sorry. Should have been:
spin_unlock_irqrestore(&key->user->lock, flags);
} else {
smp_mb(); /* key->user before FINAL_PUT set. */
}
set_bit(KEY_FLAG_FINAL_PUT, &key->flags);
Should spin_lock()/unlock() be good enough or what good does smp_mb() do
in that branch? Just checking if I'm missing something before sending
fixed version.
BR, Jarkko
next prev parent reply other threads:[~2025-05-03 14:39 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-30 15:25 [PATCH] KEYS: Reduce smp_mb() calls in key_put() Jarkko Sakkinen
2025-05-03 14:39 ` Jarkko Sakkinen [this message]
2025-05-03 15:02 ` Herbert Xu
2025-05-04 16:55 ` Jarkko Sakkinen
2025-05-03 22:19 ` David Howells
2025-05-04 0:35 ` Herbert Xu
2025-05-04 5:36 ` [PATCH] KEYS: Invert FINAL_PUT bit Herbert Xu
2025-05-04 7:44 ` David Howells
2025-05-04 7:52 ` [v2 PATCH] " Herbert Xu
2025-05-09 9:34 ` kernel test robot
2025-05-09 9:45 ` [v3 " Herbert Xu
2025-05-12 9:19 ` David Howells
2025-05-12 11:42 ` Jarkko Sakkinen
2025-05-12 12:01 ` David Howells
2025-05-12 12:07 ` Herbert Xu
2025-05-04 16:42 ` [PATCH] KEYS: Reduce smp_mb() calls in key_put() Jarkko Sakkinen
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