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SubjectRe: Add support for checking before-the-fact whether an IRQ is


On Mon, 29 Dec 2003, Arjan van de Ven wrote:
> On Mon, 2003-12-29 at 19:18, Linux Kernel Mailing List wrote:
> > ChangeSet 1.1552, 2003/12/29 10:18:11-08:00, torvalds@home.osdl.org
> >
> > Add support for checking before-the-fact whether an IRQ is
> > already registered or not. The x86 PCI layer wants this for
> > its availability testing.
> >
> > Doing a request_irq()/free_irq() pair to check this condition
> > like we used to do can lock the machine if the irq happens to
> > be screaming.
>
>
> question; which lock prevents someone else claiming the irq and making
> it unsharable/unclaimable between can_request_irq() and the eventual
> request_irq() ????

Nothing. It never did. This is basically a heuristic: "find the irq that
looks the least used".

I just fixed the heuristic so that it shouldn't cause problems if the
system comes up with the BIOS having done something silly like leaving an
irq pending..

Linus
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