linux-kernel - Re: [PATCH] mm,hwpoison: return -EBUSY when page already poisoned

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Date:   Thu, 25 Feb 2021 19:26:47 -0800
From:   Tony Luck <tony.luck@...il.com>
To:     HORIGUCHI NAOYA(堀口 直也) 
        <naoya.horiguchi@....com>
Cc:     Oscar Salvador <osalvador@...e.de>,
        Aili Yao <yaoaili@...gsoft.com>,
        "david@...hat.com" <david@...hat.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "bp@...en8.de" <bp@...en8.de>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "inux-edac@...r.kernel.org" <inux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "yangfeng1@...gsoft.com" <yangfeng1@...gsoft.com>
Subject: Re: [PATCH] mm,hwpoison: return -EBUSY when page already poisoned

On Thu, Feb 25, 2021 at 6:23 PM HORIGUCHI NAOYA(堀口　直也)
<naoya.horiguchi@....com> wrote:
>
> On Thu, Feb 25, 2021 at 10:15:42AM -0800, Luck, Tony wrote:

> > CPU3 reads the poison and starts along same path that CPU2
> > did.
>
> I think that the MCE loop happening on CPU2 and CPU3 is unexpected
> and these threads should immediately kill the current process on
> each CPU.  force_sig_mceerr() in kill_me_maybe() is supposed to do it,
> so Aili's patch would fix this issue too?

It would stop the looping. But for the case where the error came from
user code we don't have
the virtual address that was accessed at this point (normally this
address is found during the
reverse lokup from the physical address inside memory_failure()).

So we can send a generic SIGBUS, but not one with the usual extra
information about the
location of the error.

-Tony