linux-kernel - Re: [RFC] mmiotrace full patch, preview 2

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Message-ID: <19f34abd0803271613vc6d6e9ic0491643eb25a3e8@mail.gmail.com>
Date:	Fri, 28 Mar 2008 00:13:48 +0100
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Pekka Paalanen" <pq@....fi>
Cc:	linux-kernel@...r.kernel.org, "Ingo Molnar" <mingo@...e.hu>,
	"Christoph Hellwig" <hch@...radead.org>,
	"Arjan van de Ven" <arjan@...radead.org>,
	"Pavel Roskin" <proski@....org>,
	"Steven Rostedt" <rostedt@...dmis.org>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Subject: Re: [RFC] mmiotrace full patch, preview 2

Hi,

I may of course be wrong, but... Shouldn't the post_kmmio_handler(),
called from the die notifier chain, check for the DR_STEP condition?
This makes sure that the function is not called in the cases where the
source of the debug exception was not a single-stepping event. Though
I guess you'll also have other checks in place to notice that the
interrupt was not the one you were expecting. I guess a little extra
safety won't hurt though?

On Sun, Mar 9, 2008 at 3:40 PM, Pekka Paalanen <pq@....fi> wrote:
>  +/*
>  + * Interrupts are disabled on entry as trap1 is an interrupt gate
>  + * and they remain disabled thorough out this function.
>  + * This must always get called as the pair to kmmio_handler().
>  + */
>  +static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs)
>  +{
>  +       int ret = 0;
>  +       struct kmmio_context *ctx = &get_cpu_var(kmmio_ctx);

if (!(condition & DR_STEP))
    return;


Vegard
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