linux-kernel - Re: [PATCH] padata: Remove broken queue flushing

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Message-ID: <20191119225017.mjrak2fwa5vccazl@gondor.apana.org.au>
Date:   Wed, 20 Nov 2019 06:50:17 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Daniel Jordan <daniel.m.jordan@...cle.com>
Cc:     Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] padata: Remove broken queue flushing

On Tue, Nov 19, 2019 at 05:44:32PM -0500, Daniel Jordan wrote:
> 
> I assume you mean the third patch you recently posted, "crypto: pcrypt - Avoid
> deadlock by using per-instance padata queues".  That's true, the problem is
> fixed there, and the bug being present in bisection doesn't seem like enough
> justification to implement something short-lived just to prevent it.

Right.  But as pcrypt is the only user this should still work.
 
> Makes sense to me, though I don't see how it's enforced now in pcrypt.  I'm not
> an async crypto person, but wouldn't unloading the pcrypt module when there are
> still outstanding async jobs break this rule?

It's enforced through module reference counting.  While there are
any outstanding requests, there must be allocated crypto tfms.  Each
crypto tfm maintains a module reference count on pcrypt which
prevents it from being unloaded.

> Actually, I'm working on an RFC right now to add more users for padata.  It
> should be posted in the coming week or two, and I hope it can be part of that
> discussion.

OK.

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