Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH v2 01/17] powerpc/mm: Don't BUG() in hugepd_page() | Date | Thu, 02 May 2019 22:02:05 +1000 |
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Christophe Leroy <christophe.leroy@c-s.fr> writes: > Use VM_BUG_ON() instead of BUG_ON(), as those BUG_ON() > are not there to catch runtime errors but to catch errors > during development cycle only.
I've dropped this one and the next, because I don't like VM_BUG_ON().
Why not? Because it's contradictory. It's a condition that's so important that we should BUG, but only if the kernel has been built specially for debugging.
I don't really buy the development cycle distinction, it's not like we have a rigorous test suite that we run and then we declare everything's gold and ship a product. We often don't find bugs until they're hit in the wild.
For example the recent corruption Joel discovered with STRICT_KERNEL_RWX could have been caught by a BUG_ON() to check we weren't patching kernel text in radix__change_memory_range(), but he wouldn't have been using CONFIG_DEBUG_VM. (See 8adddf349fda)
I know Aneesh disagrees with me on this, so maybe you two can convince me otherwise.
cheers
> diff --git a/arch/powerpc/include/asm/hugetlb.h b/arch/powerpc/include/asm/hugetlb.h > index 8d40565ad0c3..7f1867e428c0 100644 > --- a/arch/powerpc/include/asm/hugetlb.h > +++ b/arch/powerpc/include/asm/hugetlb.h > @@ -14,7 +14,7 @@ > */ > static inline pte_t *hugepd_page(hugepd_t hpd) > { > - BUG_ON(!hugepd_ok(hpd)); > + VM_BUG_ON(!hugepd_ok(hpd)); > /* > * We have only four bits to encode, MMU page size > */ > @@ -42,7 +42,7 @@ static inline void flush_hugetlb_page(struct vm_area_struct *vma, > > static inline pte_t *hugepd_page(hugepd_t hpd) > { > - BUG_ON(!hugepd_ok(hpd)); > + VM_BUG_ON(!hugepd_ok(hpd)); > #ifdef CONFIG_PPC_8xx > return (pte_t *)__va(hpd_val(hpd) & ~HUGEPD_SHIFT_MASK); > #else > -- > 2.13.3
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