linux-kernel - Re: [PATCH] padata: Replace delayed timer with immediate workqueue in padata

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Date:   Thu, 18 Jul 2019 22:56:34 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Daniel Jordan <daniel.m.jordan@...cle.com>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        Andrea Parri <andrea.parri@...rulasolutions.com>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E . McKenney" <paulmck@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-arch@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Mathias Krause <minipli@...glemail.com>
Subject: Re: [PATCH] padata: Replace delayed timer with immediate workqueue
 in padata_reorder

On Thu, Jul 18, 2019 at 10:27:30AM -0400, Daniel Jordan wrote:
>
> That's what I expected when I first saw it too, but nr_cpumask_bits is returned
> to signal the end of the iteration.  The patch always passes 0 for the 'start'
> argument, so when cpumask_next_wrap is called with the last cpu in the mask,
> the end-of-iteration case is triggered.  To reassure you and myself :) I ran it
> and got the expected crash.
> 
> Passing pd->cpu for the start argument instead avoids that problem, but the
> one-cpu-in-mask case still needs handling because cpumask_next_wrap always
> signals end of iteration for that, hence the cpumask_weight check.

My bad.  I should have set start to -1 to make it do the right thing.

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