linux-kernel - Re: [PATCH 2/3] crypto: aead/shash

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Date:   Tue, 20 Dec 2022 11:55:19 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Robert Elliott <elliott@....com>
Cc:     davem@...emloft.net, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] crypto: aead/shash - yield at end of operations

On Mon, Dec 19, 2022 at 02:37:32PM -0600, Robert Elliott wrote:
> Add crypto_yield() calls at the end of all the encrypt and decrypt
> functions to let the scheduler use the CPU after possibly a long
> tenure by the crypto driver.
> 
> This reduces RCU stalls and soft lockups when running crypto
> functions back-to-back that don't have their own yield calls
> (e.g., aligned generic functions).
> 
> Signed-off-by: Robert Elliott <elliott@....com>
> ---
>  crypto/aead.c  |  4 ++++
>  crypto/shash.c | 32 ++++++++++++++++++++++++--------
>  2 files changed, 28 insertions(+), 8 deletions(-)
> 
> diff --git a/crypto/aead.c b/crypto/aead.c
> index 16991095270d..f88378f4d4f5 100644
> --- a/crypto/aead.c
> +++ b/crypto/aead.c
> @@ -93,6 +93,8 @@ int crypto_aead_encrypt(struct aead_request *req)
>  	else
>  		ret = crypto_aead_alg(aead)->encrypt(req);
>  	crypto_stats_aead_encrypt(cryptlen, alg, ret);
> +
> +	crypto_yield(crypto_aead_get_flags(aead));

This is the wrong place to do it.  It should be done by the code
that's actually doing the work, just like skcipher.

> diff --git a/crypto/shash.c b/crypto/shash.c
> index 868b6ba2b3b7..6fea17a50048 100644
> --- a/crypto/shash.c
> +++ b/crypto/shash.c
> @@ -114,11 +114,15 @@ int crypto_shash_update(struct shash_desc *desc, const u8 *data,
>  	struct crypto_shash *tfm = desc->tfm;
>  	struct shash_alg *shash = crypto_shash_alg(tfm);
>  	unsigned long alignmask = crypto_shash_alignmask(tfm);
> +	int ret;
>  
>  	if ((unsigned long)data & alignmask)
> -		return shash_update_unaligned(desc, data, len);
> +		ret = shash_update_unaligned(desc, data, len);
> +	else
> +		ret = shash->update(desc, data, len);
>  
> -	return shash->update(desc, data, len);
> +	crypto_yield(crypto_shash_get_flags(tfm));
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(crypto_shash_update);

Ditto.

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