linux-kernel - Re: [PATCH 1/4] compiler.h: introduce unused

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Message-Id: <20120427145302.64f50e5c.akpm@linux-foundation.org>
Date:	Fri, 27 Apr 2012 14:53:02 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 1/4] compiler.h: introduce unused_expression() macro

On Fri, 27 Apr 2012 13:55:06 +0400
Konstantin Khlebnikov <khlebnikov@...nvz.org> wrote:

> Andrew Morton wrote:
> > On Wed, 25 Apr 2012 15:26:23 +0400
> > Konstantin Khlebnikov<khlebnikov@...nvz.org>  wrote:
> 
> for example  VM_BUG_ON(!PageCompound(page) || !PageHead(page)); in
> do_huge_pmd_wp_page() generates 114 bytes.
> 
> But they mostly disappears if I replace it with
> -VM_BUG_ON(!PageCompound(page) || !PageHead(page));
> +VM_BUG_ON(!PageCompound(page));
> +VM_BUG_ON(!PageHead(page));
> weird...
> 
> add/remove: 0/0 grow/shrink: 7/97 up/down: 135/-1784 (-1649)

OK, thanks.  I'm inclined to apply the patchset as-is.  If the
apparently mythical use of side-effects in VM_BUG_ON() really exist
then we deserve everything which happens to us as a result ;)

Please update the changelogs so they cover all the points which have been
discussed, add my little code comment then send out a v2, being sure to
cc everyone who has been involved in the discussion?

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