linux-kernel - Re: 2.6.33 bugs (USBFS, Intel graphic)

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Date:	Fri, 26 Feb 2010 21:48:08 -0800
From:	Greg KH <greg@...ah.com>
To:	Markus Rechberger <mrechberger@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-usb@...r.kernel.org, werner@...ane.dyn-o-saur.com,
	Marcus Meissner <meissner@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.33 bugs (USBFS, Intel graphic)

On Sat, Feb 27, 2010 at 06:38:09AM +0100, Markus Rechberger wrote:
> On Sat, Feb 27, 2010 at 6:26 AM, Greg KH <greg@...ah.com> wrote:
> > On Fri, Feb 26, 2010 at 09:17:37PM -0800, Greg KH wrote:
> >> On Sat, Feb 27, 2010 at 05:34:27AM +0100, Markus Rechberger wrote:
> >> > On Sat, Feb 27, 2010 at 5:29 AM, Linus Torvalds
> >> > <torvalds@...ux-foundation.org> wrote:
> >> > >
> >> > >
> >> > > On Fri, 26 Feb 2010, Greg KH wrote:
> >> > >>
> >> > >> Yes, and that patch didn't touch the iso frames. ?That happens later on
> >> > >> in the functions that were modified. ?The patch should not have had any
> >> > >> affect on iso transfers. ?Unless I'm missing something?
> >> > >
> >> > > Hmm. What seems to happen is that for an isochronous transfer, the buffer
> >> > > is split for each microframe. No?
> >> > >
> >> >
> >> > exactly. and each microframe has its own buffer length identifier.
> >> >
> >> > the current behaviour breaks VMware, QEMU and virtualbox .. probably
> >> > other things too.
> >> >
> >> >
> >> > > So the total length may be in 'urb->actual_length', but the actual data in
> >> > > the buffer may not be contiguous, because it's created from multiple
> >> > > smaller frames, some of which might not be full length?
> >> > >
> >> >
> >> > yes, it's only contiguous for BULK.
> >> >
> >> > > I dunno. That would explain the problem - actual_length is correct, but
> >> > > the 'copy_to_user()' still doesn't copy all the data, because it's
> >> > > fragmented.
> >> > >
> >> >
> >> > no you got it, but your patch does not work. The best way would be to
> >> > revert it if someone wants to speed up BULK it should go down another
> >> > path, leaving the old working implementation untouched.
> >>
> >> Hm, so it's back to the original idea of just doing a kzalloc of the
> >> initial buffer, that should solve the problem that Marcus found.
> >>
> >> I'll go dig that back up and if you could test it, that would be most
> >> appreciated.
> >
> > Here, can you try this on top of everything?
> >
> 
> just tested it, everything's back to normal again now!

Thanks for testing, I'll queue it up for Linus and then add it back to
.32-stable.

Linus, I know you didn't want to do a kzalloc, but it looks like this is
the easiest/simplest thing to do, unless you can think of something
else?

thanks,

greg k-h
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