linux-kernel - Re: [PATCH] padata: upgrade smp_mb__after_atomic to smp_mb in padata_do

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Message-ID: <20200618075734.GH10091@gondor.apana.org.au>
Date:   Thu, 18 Jun 2020 17:57:35 +1000
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Daniel Jordan <daniel.m.jordan@...cle.com>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] padata: upgrade smp_mb__after_atomic to smp_mb in
 padata_do_serial

On Mon, Jun 08, 2020 at 05:26:52PM -0400, Daniel Jordan wrote:
> A 5.7 kernel hangs during a tcrypt test of padata that waits for an AEAD
> request to finish.  This is only seen on large machines running many
> concurrent requests.
> 
> The issue is that padata never serializes the request.  The removal of
> the reorder_objects atomic missed that the memory barrier in
> padata_do_serial() depends on it.
> 
> Upgrade the barrier from smp_mb__after_atomic to smp_mb to get correct
> ordering again.
> 
> Fixes: 3facced7aeed1 ("padata: remove reorder_objects")
> Signed-off-by: Daniel Jordan <daniel.m.jordan@...cle.com>
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Cc: Steffen Klassert <steffen.klassert@...unet.com>
> Cc: linux-crypto@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  kernel/padata.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Patch applied.  Thanks.
-- 
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