From mboxrd@z Thu Jan 1 00:00:00 1970 From: xieyisheng1@huawei.com (Yisheng Xie) Date: Wed, 13 Dec 2017 17:42:40 +0800 Subject: [PATCH] arm64: mm: Fix false positives in set_pte_at access/dirty race detection In-Reply-To: <20171213092119.GB27222@arm.com> References: <1513079030-8557-1-git-send-email-will.deacon@arm.com> <8761ce54-ad67-1113-44e1-0d1606d12dbf@huawei.com> <20171213092119.GB27222@arm.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Will, On 2017/12/13 17:21, Will Deacon wrote: > Hi Yisheng, > > On Wed, Dec 13, 2017 at 09:01:23AM +0800, Yisheng Xie wrote: >> On 2017/12/12 19:43, Will Deacon wrote: >>> Jiankang reports that our race detection in set_pte_at is firing when >>> copying the page tables in dup_mmap as a result of a fork(). In this >>> situation, the page table isn't actually live and so there is no way >>> that we can race with a concurrent update from the hardware page table >>> walker. >>> >>> This patch reworks the race detection so that we require either the >>> mm to match the current active_mm (i.e. currently installed in our TTBR0) >>> or the mm_users count to be greater than 1, implying that the page table >>> could be live in another CPU. The mm_users check might still be racy, >>> but we'll avoid false positives and it's not realistic to validate that >>> all the necessary locks are held as part of this assertion. >>> >>> Cc: Yisheng Xie >>> Reported-by: Jiankang Chen >>> Tested-by: Jiankang Chen >>> Signed-off-by: Will Deacon >>> --- >>> arch/arm64/include/asm/pgtable.h | 8 ++++---- >>> 1 file changed, 4 insertions(+), 4 deletions(-) >>> >>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h >>> index 3ff03a755c32..bdcc7f1c9d06 100644 >>> --- a/arch/arm64/include/asm/pgtable.h >>> +++ b/arch/arm64/include/asm/pgtable.h >>> @@ -42,6 +42,8 @@ >>> #include >>> #include >>> #include >>> +#include >>> +#include >>> >> >> Do you have compiled kernel after apply this patch? In our environment, it will >> fail to compile kernel if include file here(I will attach some log later). >> Instead, we move these included file after mmdebug.h, and I do not know whether >> this is just my compiler's problem: > > It compiles fine for me. Are you seeing a problem building this on top of > mainline? If so, what is your .config? Oh, you have already moved it after #ifndef __ASSEMBLY__ , sorry for not finding this when review this patch. And I also have just compiled with this patch in mainline, is ok. Thanks for your help. Thanks Yisheng Xie > >> --- a/arch/arm64/include/asm/pgtable.h >> +++ b/arch/arm64/include/asm/pgtable.h >> @@ -42,6 +42,8 @@ >> #include >> #include >> #include >> +#include >> +#include >> >> Sorry for not having told you this information. >> >> Thanks >> Yisheng Xie >> >> compiler err log: ========== >> [...] >> include/linux/mm_types_task.h:60: Error: unknown mnemonic `struct' -- `struct page_frag{' >> include/asm-generic/preempt.h:9: Error: unknown mnemonic `static' -- `static inline int preempt_count(void)' >> include/linux/mm_types_task.h:61: Error: unknown mnemonic `struct' -- `struct page*page' >> include/asm-generic/preempt.h:10: Error: junk at end of line, first unrecognized character is `{' >> include/linux/mm_types_task.h:63: Error: unknown mnemonic `__u32' -- `__u32 offset' >> include/asm-generic/preempt.h:11: Error: unknown mnemonic `return' -- `return READ_ONCE(((struct thread_info*)current)->preempt_count)' >> include/linux/mm_types_task.h:64: Error: unknown mnemonic `__u32' -- `__u32 size' >> [...] > > This looks like the includes are being pulled into an assembly file, but > this part is guarded by #ifndef __ASSEMBLY__ so I can't see how that could > happen. > > Will > > . >