Re: [ PATCH] Add suspend/resume for HPET was: Re: [3/6] 2.6.21-rc4: known regressions

Linus Torvalds
2007-03-29T16:35:21Z

On Thu, 29 Mar 2007, Maxim wrote:

> On Thursday 29 March 2007 07:08:58 Linus Torvalds wrote:
> >
> > (Or, better yet, shouldn't we set "boot_hpet_disable" when we decide not
> > to use the HPET, and set hpet_virt_address to NULL?)
>
> This is done here
>
> out_nohpet:
> iounmap(hpet_virt_address);
> hpet_virt_address = NULL;

No, that only clears hpet_virt_address, and thus makes all subsequent
"hpet_readl()" and "hpet_writel()" calls oops.

But it doesn't actually *tell* anybody that the HPET is disabled, so if
you later on do

if (is_hpet_capable()) {
time = hpet_readl(..);
..

you will just Oops!

So as far as I can see, even with your latest patch, if hpet_enable()
fails (and triggers the "goto out_nohpet" cases), you'll just oops
immediately when you try to suspend/resume the HPET.

THAT was what I meant - when we clear hpet_virt_address, we should also
tell all potential subsequent users that the HPET is not there!

Linus