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Date:   Wed, 8 Jul 2020 18:18:00 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     "Ahmed S. Darwish" <a.darwish@linutronix.de>
Cc:     Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        "Sebastian A. Siewior" <bigeasy@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 06/20] seqlock: Extend seqcount API with associated
 locks
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On Wed, Jul 08, 2020 at 05:58:13PM +0200, Ahmed S. Darwish wrote:
> > I even considered:
> >
> > #define __SEQPROP(name, prop, expr) \
> > static __always_inline __seqprop_##prop##_t \
> > __seqprop##name##_##prop(seqcount##name##_t *s) \
> > { \
> > 	expr; \
> > }
> >
> > Such that we could write:
> >
> > __SEQPROP(, ptr, return s)
> > __SEQPROP(, preempt, return false)
> > __SEQPROP(, assert, )
> >
> > __SEQPROP(_##locktype, ptr, return &s->seqcount) \
> > __SEQPROP(_##locktype, preempt, return preempt) \
> > __SEQPROP(_##locktype, assert, __SEQCOUNT_LOCKDEP(lockdep_assert_held(s->lockmember))) \
> >
> > But I figured _that_ might've been one step too far ;-)
> 
> Initially I implemented something like this during internal,
> pre-upstream, versions of this patch series. We've decided afterwards
> that the macro compression level is so high that the whole thing is not
> so easily understandable.

I've been reading too much tracing code lately... :-) This is only 2
levels of expansion and fits on a single screen.