Re: Top 10 bugs/warnings for the week of March 23rd, 2008

From: Jan Kara
Date: Mon May 26 2008 - 12:21:01 EST


On Mon 26-05-08 12:48:32, Ingo Molnar wrote:
>
> * Theodore Tso <tytso@xxxxxxx> wrote:
>
> > On Mon, May 26, 2008 at 11:39:13AM +0200, Ingo Molnar wrote:
> > > Exactly why is pulling an USB stick considered "stupid"? Last i checked
> > > there was no physical lock preventing users from doing that.
> > >
> > > Sure, pulling a mounted USB stick is inconvenient ... for _us_
> > > kernel developers. But the user really doesnt care and shouldnt
> > > care.
> >
> > Because they could lose data? Because if the kernel wakes up and
> > tries writing to the USB stick right as they pull it out, it could
> > physically damage the flash format? I know, stupid reason... :-)
>
> user can lose data in many other ways, that's not the issue - the issue
> here is something very crutial: the kernel gets confused about a _very_
> common user-triggerable condition.
>
> That confusion must not happen in a modern OS and the kernel should be
> resilient and cope with such external events. And we must not
> deprioritize it with an incorrect "user did something stupid" tag...
> That argument might have been valid 15 years ago when floppies could be
> locked and you needed a needle to force-eject it but it is rather lame
> today when unplugging an USB stick is as easy as moving the mouse.
>
> If there's something stupid here it's the kernel not dealing with that
> condition properly. Yes, the "user action" here looks "trivial" to the
> user but what happens below is indeed very hard technically, but who
> said that writing an OS from scratch would be an easy task? ;-)
Well, Ingo, I don't know if you've noticed but the machine continues to run
just fine, as far as I understand. It only spits a dangerously looking
warning and that's it. I agree we shouldn't be doing this but I don't really
find this a critical problem.

Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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