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SubjectRe: Circular dependency between <linux/kernel.h> and <asm/bug.h> on ARM
Hi Ben, Olof,

On Sun, Jan 1, 2012 at 11:01 PM, Olof Johansson <> wrote:
> On Sun, Jan 1, 2012 at 6:44 PM, Ben Hutchings <> wrote:
>> Commit 87e040b6456fd3416a1f6831c1eedaef5c0a94ff ("ARM: 7017/1: Use
>> generic BUG() handler") makes BUG() use BUILD_BUG_ON().  However,
>> BUILD_BUG_ON() is not defined in <linux/bug.h> but in <linux/kernel.h>.
>> arch/include/asm/bug.h does not include <linux/kernel.h> and *cannot* do
>> so because the latter already includes <asm/bug.h>.
> Sure it can, but it's not ideal. Since the BUILD_BUG_ON is only used
> in bug.h in a #define, it will be resolved below the includes of
> either so there should be no ordering issue between the two.
> I coincidentally posted a patch earlier to do just that, I didn't see
> your email until later.
>> Maybe BUILD_BUG_ON() should be moved out to a header of its own, or else
>> this particular use should be moved to some other file.  This needs to
>> be fixed somehow, as it obviously leads to build failures, e.g.:
> Or perhaps moving BUILD_BUG_ON to include/linux/bug.h?
> The quickest fix for now might be to take out the BUILD_BUG_ON(),
> especially so close to 3.2-final.

Yes I like that idea as the check isn't funtional. Perhaps ultimately
the BUILD_BUG_ON check for sizeof(struct bug_entry) should really go
in lib/bug.c. Something like, in the header:


and then in lib/bug.c:

BUILD_BUG_ON(GENERIC_BUG_ENTRY_SIZE != sizeof(struct bug_entry))

The other more fragile option might be to make sure all files include


> -Olof
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