linux-kernel - Re: [PATCH] x86/nmi: remove the irqwork from long duration nmi handler

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Message-ID: <20200109210225.GK5603@zn.tnic>
Date:   Thu, 9 Jan 2020 22:02:25 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Changbin Du <changbin.du@...il.com>,
        Ingo Molnar <mingo@...hat.com>, hpa@...or.com, x86@...nel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/nmi: remove the irqwork from long duration nmi
 handler

On Thu, Jan 09, 2020 at 09:55:51PM +0100, Thomas Gleixner wrote:
> Changbin Du <changbin.du@...il.com> writes:
> 
> > First, printk is NMI context safe now since the safe printk has been
> > implemented. The safe printk already has an irqwork to make NMI context
> > safe.
> >
> > Second, the NMI irqwork actually does not work if a NMI handler causes
> > panic by watchdog timeout. This NMI irqwork have no chance to run in such
> > case, while the safe printk will flush its per-cpu buffer before panic.
> >
> > Signed-off-by: Changbin Du <changbin.du@...il.com>
> 
> Looks about right.
> 
> Acked-by: Thomas Gleixner <tglx@...utronix.de>

I'm wondering why is this thing being moved:

-             if (delta < nmi_longest_ns || delta < a->max_duration)
-                     continue;

into nmi_check_duration() and not remaining where it is?

-- 
Regards/Gruss,
    Boris.

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