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

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Date: Wed, 8 May 2024 14:06:02 +0200
From: Oscar Salvador <osalvador@...e.de>
To: Jane Chu <jane.chu@...cle.com>
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 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>

-- 
Oscar Salvador
SUSE Labs