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Date:   Fri, 20 Nov 2020 11:20:32 +0100
From:   Florian Westphal <fw@strlen.de>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     subashab@codeaurora.org, Florian Westphal <fw@strlen.de>,
        Will Deacon <will@kernel.org>, pablo@netfilter.org,
        Sean Tranchetti <stranche@codeaurora.org>,
        netfilter-devel@vger.kernel.org, tglx@linutronix.de
Subject: Re: [PATCH nf] x_tables: Properly close read section with
 read_seqcount_retry
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Peter Zijlstra <peterz@infradead.org> wrote:
> On Fri, Nov 20, 2020 at 10:44:13AM +0100, Peter Zijlstra wrote:
> > On Thu, Nov 19, 2020 at 10:53:13PM -0700, subashab@codeaurora.org wrote:
> > > +struct xt_table_info
> > > +*xt_table_get_private_protected(const struct xt_table *table)
> > > +{
> > > +	return rcu_dereference_protected(table->private,
> > > +					 mutex_is_locked(&xt[table->af].mutex));
> > > +}
> > > +EXPORT_SYMBOL(xt_table_get_private_protected);
> > 
> > In all debug builds this function compiles to a single memory
> 
> ! went missing... :/

? Not sure about "!".

> > dereference. Do you really want that out-of-line?

Its the lesser of two evils, the other solution would be to export
xt[] from x_tables.c; its static right now.

Or we just use a rcu primitive that does no checking but I'd prefer
avoid that.