linux-kernel - Re: linux-next: tree build failure

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Message-Id: <1254182409.15622.154.camel@slab.beaverton.ibm.com>
Date:	Mon, 28 Sep 2009 17:00:09 -0700
From:	Hollis Blanchard <hollisb@...ibm.com>
To:	Stephen Rothwell <sfr@...b.auug.org.au>
Cc:	ppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jan Beulich <JBeulich@...ell.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	kvm-ppc@...r.kernel.org
Subject: Re: linux-next: tree build failure

On Thu, 2009-09-24 at 15:21 +1000, Stephen Rothwell wrote:
> Hi all,
> 
> Today's linux-next build (powerpc ppc44x_defconfig) failed like this:
> 
> In file included from arch/powerpc/kvm/booke.c:31:
> arch/powerpc/kvm/timing.h: In function 'kvmppc_account_exit_stat':
> arch/powerpc/kvm/timing.h:51: error: bit-field '<anonymous>' width not an integer constant
> In file included from arch/powerpc/kvm/booke.h:26,
>                  from arch/powerpc/kvm/booke_emulate.c:23:
> arch/powerpc/kvm/timing.h: In function 'kvmppc_account_exit_stat':
> arch/powerpc/kvm/timing.h:51: error: bit-field '<anonymous>' width not an integer constant
> 
> Presumably caused by commit 8c87df457cb58fe75b9b893007917cf8095660a0
> ("BUILD_BUG_ON(): fix it and a couple of bogus uses of it").

First, I think there is a real bug here, and the code should read like
this (to match the comment):
 	/* type has to be known at build time for optimization */
-	BUILD_BUG_ON(__builtin_constant_p(type));
+	BUILD_BUG_ON(!__builtin_constant_p(type));

However, I get the same build error *both* ways, i.e.
__builtin_constant_p(type) evaluates to both 0 and 1? Either that, or
the new BUILD_BUG_ON() macro isn't working...

> I applied the following patch for today.  This inline function is
> only called from one place in one file ...

It's also called via kvmppc_account_exit() from a number of places.

-- 
Hollis Blanchard
IBM Linux Technology Center

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