Re: floppy driver assumes INITIAL_JIFFIES == 0

From: Linus Torvalds
Date: Thu Jun 03 2010 - 18:03:09 EST




On Thu, 3 Jun 2010, Stephen Hemminger wrote:
>
> It seems it isn't related to initial jiffies.
> Initializing the values (though a good idea), doesn't solve the
> problem. Still failed. So dazed and confused, went back and reran
> kernel with jiffies=0 showed same problem, just took multiple boots
> to reproduce.

Ahh, ok. That really ends up limiting us. At least having a "it's related
to jiffy wraparound" was a big clue.

> So still a race that shows up with KVM (fast floppy?) and manifests
> as floppy_ready or reset_interrupt OOPS.

Yes, it's quite possible that the Linux floppy driver is simply broken by
any floppy device that basically responds immediately to a command with an
interrupt. And considering how few people use floppies, I do expect that
driver to get _worse_ rather than better in the future.

Don't get me wrong - I'm sure it could be fixed. I'm just not sure that
anybody is going to spend the effort.

I'd love to be proven wrong. Anybody?

Linus
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