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Date:   Wed, 20 Jan 2021 13:18:12 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     "Luck, Tony" <tony.luck@intel.com>
Cc:     x86@kernel.org, Andrew Morton <akpm@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Darren Hart <dvhart@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH v4] x86/mce: Avoid infinite loop for copy from user
 recovery
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On Tue, Jan 19, 2021 at 03:57:59PM -0800, Luck, Tony wrote:
> But the real validation folks took my patch and found that it has
> destabilized cases 1 & 2 (and case 3 also chokes if you repeat a few
> more times). System either hangs or panics. Generally before 100
> injection/conumption cycles.

Hmm, that mce_count increment and check stuff might turn out to be
fragile in the face of a race condition. But I don't see it...

> So if you see anything obviously broken, let me know. Otherwise I'll
> be poking around at the patch to figure out what is wrong.

Yah, some printk sprinkling might be a good start. But debugging in that
atomic context is always nasty. ;-\

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette