usb/46176: Let's save the horse! [was: HEADSUP new usb code coming in.]

Fabian Keil freebsd-listen at
Thu Aug 21 16:45:12 UTC 2008

"Alexey Shuvaev" <shuvaev at> wrote:

> On Wed, Aug 20, 2008 at 11:43:35PM +0200, Fabian Keil wrote:
> > Warner Losh <imp at> wrote:
> > 
> > > From: Bakul Shah <bakul at>

> > > > Accidentally unplugging a mounted USB disk (without
> > > > unmounting it) resulted in a hang or a crash.  Is this fixed?
> > > 
> > > That's fixed in -current right now with the old stack.  It isn't a usb
> > > issue at all, but a buffer cache issue.
> > 
> > I can't confirm this for either msdosfs or geli (with ZFS).
> > 
> > In case of msdosfs the situation has been vastly improved
> > and the panic seems to be no longer guaranteed, but there's
> > still a fair chance it'll happen eventually.
> > 
> It was discussed now and then on freebsd-usb mailing list.

I'm not subscribed to freebsd-usb so I'm not sure
what was or wasn't discussed there, but I also don't
see how it's relevant here.

All I'm saying is that unplugging a mounted USB
disk is very likely to panic my system running
FreeBSD 8.0-CURRENT #2: Fri Aug 15 23:35:09 CEST 2008
eventually and thus I wouldn't call the problem fixed
just yet.

> Have a look at

It seems to be mainly about patches against FreeBSD 7.0-BETA1.5,
I'm talking about CURRENT without additional patches.

> As for the non-msdosfs formatted media, I am quite sure it is a really bad
> idea to unplug media before unmounting it (there is actually no difference
> between "removable" and "stationary" drives).

That's besides the point.

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