linux-kernel - Re: [PATCH] rculist: fix borked __list_for_each

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Message-ID: <20101217101039.GC8413@cr0.nay.redhat.com>
Date:	Fri, 17 Dec 2010 18:10:39 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Am??rico Wang <xiyou.wangcong@...il.com>,
	Mariusz Kozlowski <mk@....zgora.pl>,
	Dipankar Sarma <dipankar@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rculist: fix borked __list_for_each_rcu() macro

On Thu, Dec 16, 2010 at 07:50:54AM -0800, Paul E. McKenney wrote:
>On Thu, Dec 16, 2010 at 03:38:40PM +0800, Américo Wang wrote:
>> On Thu, Dec 16, 2010 at 07:02:36AM +0100, Mariusz Kozlowski wrote:
>> >On Wed, Dec 15, 2010 at 03:20:05PM -0800, Paul E. McKenney wrote:
>> >> On Wed, Dec 15, 2010 at 11:11:12PM +0100, Mariusz Kozlowski wrote:
>> >> > This restores parentheses blance.
>> >> 
>> >> Good catch, queued!!!
>> >> 
>> >> This does not actually appear to be in use anywhere in the kernel any
>> >> more, so I queued this for 2.6.38 rather than in the 2.6.37 urgent queue.
>> >> So, just out of curiosity, how did you find this one?
>> >
>> >Some years ago I wrote a dumb script that walks trees of () and {}.
>> >It catches unbalanced trees. It's dumb enough to fail with #ifdef etc,
>> >but most of the time it does its job. It reaches unreachable code
>> >and unused one too.
>> 
>> gcc will complain about this, however, in this case, it is used.
>
>Hello, Américo!
>
>I did a "git grep -l __list_for_each_rcu" and its output was only:
>
>	include/linux/rculist.h:#define __list_for_each_rcu(pos, head) \
>
>This was in Linus's tree.  And gcc certainly would have failed if
>this macro had been used in any recent build.
>

Yeah, my bad, actually I meant to say "unused"... :-(
Sorry for confusing!

My point is that gcc should do this basic lexical check, no need
to invent another tool. :)

Thanks.
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