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Date: Thu, 21 Jul 2016 20:48:12 -0500
From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
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        Frederic Weisbecker <fweisbec@gmail.com>,
        Byungchul Park <byungchul.park@lge.com>
Subject: Re: [PATCH 07/19] x86/dumpstack: add IRQ_USABLE_STACK_SIZE define
Message-ID: <20160722014812.3adsrej7zj4qpbff@treble>
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On Thu, Jul 21, 2016 at 03:01:10PM -0700, Andy Lutomirski wrote:
> On Thu, Jul 21, 2016 at 2:21 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > For reasons unknown, the x86_64 irq stack starts at an offset 64 bytes
> > from the end of the page.  At least make that explicit.
> 
> This is a change in behavior -- see below.  Please mention this in the
> changelog.

Ah, right.

> 
> >
> > FIXME: Can we just remove the 64 byte gap?  If not, at least document
> > why.
> 
> I have no clue.
> 
> >
> >         irq_stack_end   = (unsigned long *)(per_cpu(irq_stack_ptr, cpu));
> > -       irq_stack       = (unsigned long *)(per_cpu(irq_stack_ptr, cpu) - IRQ_STACK_SIZE);
> > +       irq_stack       = (unsigned long *)(per_cpu(irq_stack_ptr, cpu) -
> > +                         IRQ_USABLE_STACK_SIZE);
> 
> This is different.

If nobody knows the reason for it, I may just remove it.  It doesn't
seem to blow anything up on my system.  I tried digging through the git
history but it's been there since the beginning of git time.

-- 
Josh