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

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Message-ID: <20190716135010.GC3402@hirez.programming.kicks-ass.net>
Date:   Tue, 16 Jul 2019 15:50:10 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        andrea.parri@...rulasolutions.com, boqun.feng@...il.com,
        paulmck@...ux.ibm.com, 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 09:18:07PM +0800, Herbert Xu wrote:
> On Tue, Jul 16, 2019 at 03:15:20PM +0200, Peter Zijlstra wrote:
> >
> > > @@ -367,7 +368,7 @@ void padata_do_serial(struct padata_priv *padata)
> > >  	struct parallel_data *pd;
> > >  	int reorder_via_wq = 0;
> > >  
> > > -	pd = padata->pd;
> > > +	pd = rcu_dereference_bh(padata->inst->pd);
> > >  
> > >  	cpu = get_cpu();
> > >  
> > 
> > That's weird for not having a matching assign and lacking comments to
> > explain that.
> 
> There is a matching rcu_assign_pointer.  But we should add some
> RCU markers.
> 
> Or perhaps you're misreading the level of indirections :)

Could well be, I'm not much familiar with this code; I'll look more
careful.