linux-kernel - Re: Question about qspinlock nest

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Message-ID: <20190110200303.GG2861@worktop.programming.kicks-ass.net>
Date:   Thu, 10 Jan 2019 21:03:03 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Zhenzhong Duan <zhenzhong.duan@...cle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, longman@...hat.com,
        SRINIVAS <srinivas.eeda@...cle.com>
Subject: Re: Question about qspinlock nest

On Thu, Jan 10, 2019 at 04:02:53PM +0800, Zhenzhong Duan wrote:
> Hi Maintainer,
> 
> 
> There is a question confused me for days. Appreciate an answer.
> 
> In below code, the comment says we never have more than 4 nested contexts.
> 
> What happen if debug and mce exceptions nest with the four, or we ensure it
> never happen?

MCE and NMI really should not use spinlocks at all since they cannot be
masked.