linux-kernel - Re: [PATCH 1/4] list: introduce list_is

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Message-ID: <20151210153540.GA27533@infradead.org>
Date:	Thu, 10 Dec 2015 07:35:40 -0800
From:	Christoph Hellwig <hch@...radead.org>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Jens Axboe <axboe@...nel.dk>, Geliang Tang <geliangtang@....com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Jan Kara <jack@...e.cz>, Josef Bacik <jbacik@...com>,
	Josh Triplett <josh@...htriplett.org>,
	Seth Jennings <sjenning@...hat.com>,
	Jiri Kosina <jikos@...nel.org>,
	Vojtech Pavlik <vojtech@...e.com>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Patrick McHardy <kaber@...sh.net>,
	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
	"David S. Miller" <davem@...emloft.net>,
	live-patching@...r.kernel.org, netfilter-devel@...r.kernel.org,
	coreteam@...filter.org, netdev@...r.kernel.org,
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] list: introduce list_is_first()

On Thu, Dec 10, 2015 at 09:23:57AM -0600, Josh Poimboeuf wrote:
> Personally I would disagree.  Something like:
> 
>   if (list_is_first(&rq->queuelist, &nd->queue))
> 
> is much more readable to me than:
> 
>   if (rq->queuelist.prev == &nd->queue)
> 
> The first one takes no effort for me -- it's almost English.  While the
> second one takes me a few seconds (and some precious brain cycles) to
> decipher.
> 
> Maybe whether it's readable depends on how many years you've been
> looking at the pattern.  But IMHO we shouldn't make "having x # of years
> staring at kernel code" a prerequisite for being able to read kernel
> code.

I think understanding the list.h semantics is a requirement for writing
(or reading) non-trivial kernel code.
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