linux-kernel - Re: [PATCH 1/3] mm/memory-failure: try to send SIGBUS even if unmap failed

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Message-ID: <7fd20d16-066d-4ec3-9ca1-e99ff39d3d86@oracle.com>
Date: Wed, 8 May 2024 09:51:51 -0700
From: Jane Chu <jane.chu@...cle.com>
To: Oscar Salvador <osalvador@...e.de>
Cc: linmiaohe@...wei.com, nao.horiguchi@...il.com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] mm/memory-failure: try to send SIGBUS even if unmap
 failed

On 5/8/2024 5:06 AM, Oscar Salvador wrote:

> On Tue, May 07, 2024 at 10:54:10AM -0700, Jane Chu wrote:
>> I actually managed to hit the re-access case with an older version of Linux
>> -
>>
>> MCE occurred, but unmap failed,  no SIGBUS and test process re-access
>>
>> the same address over and over (hence MCE after MCE), as the CPU
>>
>> was unable to make forward progress.   In reality, this issue is fixed with
>>
>> kill_accessing_processes().  The comment for this patch refers to comment
>> made
> So we get a faulty page and we try to unmap it from all processes that
> might have it mapped in their pgtables.
> Prior to this patch we would kill the processes right away and now we
> deliver a SIGBUS.
>
> Seems safe as upon-reaccesing kill_accessing_process() will be called
> for already hwpoisoned pages.
>
> I think the changelog could be made more explicit about this scenario
> and state the role of kill_accessing_process more clear.
>
> With that: Reviewed-by: Oscar Salvador <osalvador@...e.de>
>   

I will revise the changelog and mention kill_accessing_process().

Thanks!

-jane

>