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Date: Fri, 24 Jul 2015 13:22:11 -0700
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Subject: Re: Dealing with the NMI mess
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Willy Tarreau <w@1wt.eu>, Steven Rostedt <rostedt@goodmis.org>,
        Andy Lutomirski <luto@amacapital.net>, X86 ML <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Borislav Petkov <bp@alien8.de>, Thomas Gleixner <tglx@linutronix.de>,
        Brian Gerst <brgerst@gmail.com>
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On Fri, Jul 24, 2015 at 12:55 PM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> I worry that we'll end up running the do_debug() handlers from effective
> NMI context.
>
> The NMI might have preempted locks which these handlers require etc..

If #DB takes any locks like that, then #DB is broken.

Pretty much by definition, a data breakpoint can happen on pretty much
absolutely any code. This is in no way NMI-specific as far as I can
tell.

Do we really take locks in the #DB handler?

                     Linus
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