Re: [PATCH 2.6.28-rc6] ACPICA: don't cond_resched() when irqs_disabled()

[Len Brown <lenb@kernel.org>]

On Fri, 19 Dec 2008, Wu Fengguang wrote:

> On Fri, Dec 19, 2008 at 10:38:18AM +0200, Len Brown wrote:
> > >     The issue on Fengguang's laptop is different with that on the box of
> > > T61.  On Fengguang's laptop after evaluating one ACPI object(GPE
> > > _L18object), the irq is disabled mystically. After some investigations
> > > we find that it is caused by SMI(The SMI will be triggered while
> > > evaluating the ACPI object. And this issue is also related with Video). 
> > 
> > Interesting.
> > I hadn't realized you root-caused that failure.
> > This is good to know, but the fact that SMM can
> > leave interrupts disabled is frightening.
> 
> > If the BIOS SMM on that box disables interrupts when
> > random AML is run, then it is going to run into
> > all kinds of other problems in addition to this one...
> 
> Exactly. This is another warning:
> 
> [ 6559.754331] irq status before SMI: enable
> [ 6559.757388] irq status after SMI: disable, value: 0xF3
> [ 6599.816127] Corrupted low memory at ffff88000000fe08 (fe08 phys) = 01007062
> [ 6599.816253] Corrupted low memory at ffff88000000fe10 (fe10 phys) = 7ba83066
> [ 6599.816376] Corrupted low memory at ffff88000000fe18 (fe18 phys) = 00010062
> [ 6599.816492] Corrupted low memory at ffff88000000fe20 (fe20 phys) = 01006062

I proposed a long term fix for this years ago.
If it had been implemented, this insanity would not be possible.

Every time a BIOS writer uses SMM, they should be rewarded
by having a digit severed.

This is a very simple proposal, very easy to understand.
Further, with "10-strikes and you're out", it comprehends that
there may be some BIOS writerse that take a while to catch on...

However, when they run out of fingers I'd draw the line
and insist that they find a new line of work.

-Len