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Date:   Thu, 22 Apr 2021 19:01:18 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc:     linux-mm@kvack.org, Tony Luck <tony.luck@intel.com>,
        Aili Yao <yaoaili@kingsoft.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oscar Salvador <osalvador@suse.de>,
        David Hildenbrand <david@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Naoya Horiguchi <naoya.horiguchi@nec.com>,
        Jue Wang <juew@google.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/3] mm/memory-failure: Use a mutex to avoid
 memory_failure() races
Message-ID: <20210422170118.GC7021@zn.tnic>
References: <20210421005728.1994268-1-nao.horiguchi@gmail.com>
 <20210421005728.1994268-2-nao.horiguchi@gmail.com>
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On Wed, Apr 21, 2021 at 09:57:26AM +0900, Naoya Horiguchi wrote:
> From: Tony Luck <tony.luck@intel.com>
> 
> There can be races when multiple CPUs consume poison from the same
> page. The first into memory_failure() atomically sets the HWPoison
> page flag and begins hunting for tasks that map this page. Eventually
> it invalidates those mappings and may send a SIGBUS to the affected
> tasks.
> 
> But while all that work is going on, other CPUs see a "success"
> return code from memory_failure() and so they believe the error
> has been handled and continue executing.
> 
> Fix by wrapping most of the internal parts of memory_failure() in
> a mutex.
> 
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
> ---
>  mm/memory-failure.c | 37 ++++++++++++++++++++++++-------------
>  1 file changed, 24 insertions(+), 13 deletions(-)

Reviewed-by: Borislav Petkov <bp@suse.de>

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette