linux-kernel - Re: [PATCH v3 1/3] mm/memory-failure: Use a mutex to avoid memory

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Date:   Thu, 22 Apr 2021 19:01:18 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Naoya Horiguchi <nao.horiguchi@...il.com>
Cc:     linux-mm@...ck.org, Tony Luck <tony.luck@...el.com>,
        Aili Yao <yaoaili@...gsoft.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Jue Wang <juew@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] mm/memory-failure: Use a mutex to avoid
 memory_failure() races

On Wed, Apr 21, 2021 at 09:57:26AM +0900, Naoya Horiguchi wrote:
> From: Tony Luck <tony.luck@...el.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@...el.com>
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@....com>
> ---
>  mm/memory-failure.c | 37 ++++++++++++++++++++++++-------------
>  1 file changed, 24 insertions(+), 13 deletions(-)

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

-- 
Regards/Gruss,
    Boris.

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