linux-kernel - Re: [PATCH] padata: Use RCU when fetching pd from do

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Message-ID: <20190716130928.ga4acvxipsdzyzlp@gondor.apana.org.au>
Date:   Tue, 16 Jul 2019 21:09:28 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Steffen Klassert <steffen.klassert@...unet.com>
Cc:     Daniel Jordan <daniel.m.jordan@...cle.com>,
        andrea.parri@...rulasolutions.com, boqun.feng@...il.com,
        paulmck@...ux.ibm.com, peterz@...radead.org,
        linux-arch@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] padata: Use RCU when fetching pd from do_serial

On Tue, Jul 16, 2019 at 08:57:04PM +0800, Herbert Xu wrote:
>
> How about using RCU?
> 
> We still need to fix up the refcnt if it's supposed to limit the
> overall number of outstanding requests.

Hmm, it doesn't work because the refcnt is attached to the old
pd.  That shouldn't be a problem though as we could simply ignore
the refcnt in padata_flush_queue.

However, I think this leads to another bug in that pcrypt doesn't
support dm-crypt properly.  It never does the backlog stuff and
therefore can't guarantee reliable processing which dm-crypt requires.

Is it intentional to only allow pcrypt for IPsec?

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