Messages in this thread | | | Date | Mon, 19 Dec 2011 12:34:16 -0800 (PST) | From | David Rientjes <> | Subject | Re: [PATCH] mm: Fix BUILD_BUG assertion in pmdp_clear_flush_young() |
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On Mon, 19 Dec 2011, David Daney wrote:
> > The problem here is that HPAGE_PMD_MASK is being referenced without > > CONFIG_TRANSPARENT_HUGEPAGE. pmdp_clear_flush_young() is only applicable > > with that config option enabled. So rather than trying to minimize lines > > captured under an #ifdef by placing the BUG() directly in the function for > > asm-generic, you'll need to wrap pmd_clear_flush_young() with > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE and define its equivalent for > > CONFIG_TRANSPARENT_HUGEPAGE=n that breaks the build if not enabled. > > > > That does sound like a better option. > > I still think having the BUILD_BUG defined as we do in Andrew Morton's tree is > the correct approach, and I don't want to see that reverted because of this > ugliness. >
Agreed, the problem here is that we have existing code, such as pmdp_clear_flush_young() that is calling BUG() at runtime for non-supported configurations. So when BUILD_BUG_ON() for HPAGE_PMD_MASK and friends was introduced, it detects improper use that needs to be fixed and you've found one of those cases.
> Really this is hackery that should be cleaned up as you suggest, instead of > being papered over with this BUG() thing. I can't test SH things, otherwise I > might look at it. The SH maintainers should probably take a look instead. >
It's not only about sh, this will affect any architecture that uses the generic version of pmdp_clear_flush_young(), which is everything except x86.
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