On Thursday 26 February 2009, Linus Torvalds wrote:
>
> On Thu, 26 Feb 2009, Rafael J. Wysocki wrote:
> >
> > Well, how exactly the $subject patch does cause this problem to happen?
>
> Rafael, the problem is that if an interrupt happens while it's disabled -
> but before the CPU has actually turned all interrupts off - the CPU will
> ACK the interrupt (but just set a flag for it being PENDING), so now the
> chipset logic around it will not see it as pending any more, so now the
> chipset won't auto-wake the CPU immediately (or more likely, it won't
> even suspend it).
Ah, I see now, thanks.
> It's trivial to fix multiple ways, so I wouldn't worry. The most trivial
> way is to just have some sysdev drievr code simply do something like
>
> static int sysdev_suspend()
> {
> for_each_irq(irq,desc) {
> if (!(desc->flags & IRQF_WAKE))
> continue;
> if (desc->flags & IRQ_PENDING)
> return -EBUSY;
> }
> return 0;
> }
>
> and that should automatically mean that if any irq is pending, the suspend
> will fail and we'll immediately wake up again.
Yeah.
Thanks,
Rafael
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