Re: [PATCH, RFC] Driver for reading HP laptop LCD brightness

[Arjan van de Ven]

On Sun, 2006-02-05 at 14:34 +0000, Matthew Garrett wrote:
> On Sun, Feb 05, 2006 at 03:27:26PM +0100, Arjan van de Ven wrote:
> 
> > disable_irq() and enable_irq() are really really evil. Are you sure you
> > need these? To me on first sight it looks like a bug (think of shared
> > interrupts for example), can you explain what you are trying to achieve
> > with these?
> 
> We're talking to the hardware directly. There's a potential race where 
> the BIOS will try to access the cmos at the same time, with potentially 
> interesting results (We set the address we want to read with the outb. 
> The BIOS runs, outbs its own address, and then reads. We then read from 
> the address the BIOS was looking at, rather than what we were looking 
> at).

.. and just disabling interrupts isn't going to work? Ok sure there is
an SMP issue, but a spinlock ought to be able to fix that properly,
instead of something this evil....


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/