Messages in this thread | | | Date | Mon, 19 Dec 2011 11:52:47 -0800 | From | David Daney <> | Subject | Re: [PATCH] mm: Fix BUILD_BUG assertion in pmdp_clear_flush_young() |
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On 12/19/2011 11:29 AM, David Rientjes wrote: > On Mon, 19 Dec 2011, David Daney wrote: > >> From: David Daney<david.daney@cavium.com> >> >> It has been reported that when building for sh: >> >> mm/pgtable-generic.c: In function 'pmdp_clear_flush_young': >> mm/pgtable-generic.c:76: error: call to '__build_bug_failed' declared with attribute error: BUILD_BUG failed >> >> Adding some ugle #ifdeffery will probably fix this issue. >> > > It won't, CONFIG_HUGETLB_PAGE has nothing at all to do with this. >
Sorry for the noise. You are correct.
>> Signed-off-by: David Daney<david.daney@cavium.com> >> --- >> >> This is completely untested, but may be the best fix for this. Linus >> and others have expressed a dislike for using BUG() to detect what >> should be dead code paths at runtime, but it seems to be the state of >> the art here. >> > > 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.
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.
David Daney
>> mm/pgtable-generic.c | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c >> index eb663fb..73784c8 100644 >> --- a/mm/pgtable-generic.c >> +++ b/mm/pgtable-generic.c >> @@ -70,7 +70,7 @@ int pmdp_clear_flush_young(struct vm_area_struct *vma, >> unsigned long address, pmd_t *pmdp) >> { >> int young; >> -#ifndef CONFIG_TRANSPARENT_HUGEPAGE >> +#if !defined(CONFIG_HUGETLB_PAGE) || !defined(CONFIG_TRANSPARENT_HUGEPAGE) >> BUG(); >> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ >> VM_BUG_ON(address& ~HPAGE_PMD_MASK);
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