linux-kernel - Re: [PATCH v3 0/3] mm,hwpoison: fix sending SIGBUS for Action Required MCE

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Date:   Fri, 7 May 2021 05:24:22 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     "Luck, Tony" <tony.luck@...el.com>
CC:     Naoya Horiguchi <nao.horiguchi@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Aili Yao <yaoaili@...gsoft.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>, Jue Wang <juew@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 0/3] mm,hwpoison: fix sending SIGBUS for Action
 Required MCE

On Fri, May 07, 2021 at 03:37:07AM +0000, Luck, Tony wrote:
> >> I updated the series based on previous feedbacks/discussions.
> >
> > Tested-by: Tony Luck <tony.luck@...el.com>
> 
> Maybe this series should get a "Cc: stable" tag too?

The second patch (I squashed 2/3 and 3/3 into one in v4) is a little
too large (more than 100 lines of change), which doesn't meet stable rule.
But the first patch looks suitable to me for stable.

> 
> I don't have a specific commit to provide for Fixes:, but it deals
> with an issue where sometimes processes return from the machine
> check handler and hit the same machine check again.

If we consider that this issue is visible after LMCE is supported,
the following commit could be the target of Fixes tag.

    commit 243d657eaf540db882f73497060da5a4f7d86a90
    Author: Ashok Raj <ashok.raj@...el.com>
    Date:   Thu Jun 4 18:55:24 2015 +0200

        x86/mce: Handle Local MCE events

but according to your test result, any other factor might affect when
the issue actually got reproducible.

> 
> It's hard[1] to hit in v5.8, but somehow gets progressively easier in
> newer versions.
> 
> -Tony
> 
> [1] Initially I thought it didn't happen at all in v5.8. Then wasted a bunch
> of time trying to bisect. But my "git bisect good" responses turned out to
> be randomly assigned when I just hadn't tried enough times to make the
> problem show up.

Thanks for time and effort for testing.

- Naoya