From: Jeff Moyer <jmoyer@redhat.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Justin He <Justin.He@arm.com>,
Catalin Marinas <Catalin.Marinas@arm.com>,
"Kirill A.Shutemov" <kirill.shutemov@linux.intel.com>,
"linux-mm\@kvack.org" <linux-mm@kvack.org>
Subject: Re: bug: data corruption introduced by commit 83d116c53058 ("mm: fix double page fault on arm64 if PTE_AF is cleared")
Date: Tue, 11 Feb 2020 12:55:50 -0500 [thread overview]
Message-ID: <x49k14tnh3t.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <20200211173352.wjm6govzcqy355y7@box> (Kirill A. Shutemov's message of "Tue, 11 Feb 2020 20:33:52 +0300")
"Kirill A. Shutemov" <kirill@shutemov.name> writes:
> On Tue, Feb 11, 2020 at 11:44:06AM -0500, Jeff Moyer wrote:
>> Hi, Justin,
>>
>> Justin He <Justin.He@arm.com> writes:
>> >> Thanks for the report. But this commit 83d116c53058 doesn't add the
>> >> new clear_page code path. Besides the pte_mkyoung part, It just refines
>> >> the codes(no functional change) and add a WARN_ON_ONCE to indicate
>> >> there is any obscure case before.
>> >
>> > I can't reproduce it with your provided test file on my arm64 qemu with
>> > a pmem device.
>> > Could you do me a favor that just revert 83d116c53058 but keep that
>> > WARN_ON_ONCE after clear_page()? Is there any difference?
>> > Thanks for your help
>>
>> Below is the patch I used to put the WARN_ON_ONCE after the clear_page,
>> just to be sure that's what you intended. So with 83d116c53058
>> reverted, and the below patch applied, the WARN_ON_ONCE does not
>> trigger.
>
> I cannot explain this. There is no locking to prevent the same scenario
> before. It might be an timing difference.
>
> Could try to put a delay before the copy to make race window larger?
I reverted my change to the reproducer, and now it triggers the warning.
-Jeff
next prev parent reply other threads:[~2020-02-11 17:55 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-10 22:51 bug: data corruption introduced by commit 83d116c53058 ("mm: fix double page fault on arm64 if PTE_AF is cleared") Jeff Moyer
2020-02-11 4:17 ` Justin He
2020-02-11 4:29 ` Justin He
2020-02-11 16:44 ` Jeff Moyer
2020-02-11 17:33 ` Kirill A. Shutemov
2020-02-11 17:55 ` Jeff Moyer [this message]
2020-02-11 21:44 ` Kirill A. Shutemov
2020-02-11 22:01 ` Jeff Moyer
2020-02-11 22:15 ` Kirill A. Shutemov
2020-02-11 14:51 ` Kirill A. Shutemov
2020-02-11 16:27 ` Jeff Moyer
2020-02-11 22:40 ` Kirill A. Shutemov
2020-02-12 14:22 ` Jeff Moyer
2020-02-13 12:14 ` Kirill A. Shutemov
2020-02-14 21:07 ` Jeff Moyer
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