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

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Message-ID: <ZjnuJgUVVnwYrr5p@localhost.localdomain>
Date: Tue, 7 May 2024 11:02:30 +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 Wed, May 01, 2024 at 05:24:56PM -0600, Jane Chu wrote:
> For years when it comes down to kill a process due to hwpoison,
> a SIGBUS is delivered only if unmap has been successful.
> Otherwise, a SIGKILL is delivered. And the reason for that is
> to prevent the involved process from accessing the hwpoisoned
> page again.
> 
> Since then a lot has changed, a hwpoisoned page is marked and
> upon being re-accessed, the process will be killed immediately.
> So let's take out the '!unmap_success' factor and try to deliver
> SIGBUS if possible.

I am missing some details here.
An unmapped hwpoison page will trigger a fault and will return
VM_FAULT_HWPOISON all the way down and then deliver SIGBUS,
but if the page was not unmapped, how will this be catch upon
re-accessing? Will the system deliver a MCE event? 


-- 
Oscar Salvador
SUSE Labs