From: Michael Ellerman <mpe@ellerman.id.au>
To: Christophe Leroy <christophe.leroy@c-s.fr>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
aneesh.kumar@linux.ibm.com
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2 01/17] powerpc/mm: Don't BUG() in hugepd_page()
Date: Thu, 02 May 2019 22:02:05 +1000 [thread overview]
Message-ID: <87o94lxdxe.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <ff4366d14b3ef4de6af835a880a772477577139f.1556258135.git.christophe.leroy@c-s.fr>
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
next prev parent reply other threads:[~2019-05-02 12:02 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-26 5:59 [PATCH v2 00/17] Reduce ifdef mess in hugetlbpage.c Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 01/17] powerpc/mm: Don't BUG() in hugepd_page() Christophe Leroy
2019-05-02 12:02 ` Michael Ellerman [this message]
2019-05-02 12:11 ` Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 02/17] powerpc/mm: don't BUG in add_huge_page_size() Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 03/17] powerpc/book3e: drop mmu_get_tsize() Christophe Leroy
2019-05-03 6:59 ` Michael Ellerman
2019-04-26 5:59 ` [PATCH v2 04/17] powerpc/64: only book3s/64 supports CONFIG_PPC_64K_PAGES Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 05/17] powerpc/book3e: hugetlbpage is only for CONFIG_PPC_FSL_BOOK3E Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 06/17] powerpc/mm: move __find_linux_pte() out of hugetlbpage.c Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 07/17] powerpc/mm: make hugetlbpage.c depend on CONFIG_HUGETLB_PAGE Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 08/17] powerpc/mm: make gup_hugepte() static Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 09/17] powerpc/mm: split asm/hugetlb.h into dedicated subarch files Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 10/17] powerpc/mm: add a helper to populate hugepd Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 11/17] powerpc/mm: cleanup ifdef mess in add_huge_page_size() Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 12/17] powerpc/mm: move hugetlb_disabled into asm/hugetlb.h Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 13/17] powerpc/mm: cleanup HPAGE_SHIFT setup Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 14/17] powerpc/mm: cleanup remaining ifdef mess in hugetlbpage.c Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 15/17] powerpc/mm: flatten function __find_linux_pte() step 1 Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 16/17] powerpc/mm: flatten function __find_linux_pte() step 2 Christophe Leroy
2019-04-26 5:59 ` [PATCH v2 17/17] powerpc/mm: flatten function __find_linux_pte() step 3 Christophe Leroy
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