Re: [RFC: 2.6.19 patch] let PCI_MULTITHREAD_PROBE depend on BROKEN

Adrian Bunk
2006-10-27T22:23:28Z

On Fri, Oct 27, 2006 at 10:07:48AM -0700, Greg KH wrote:
> On Thu, Oct 26, 2006 at 07:11:31PM -0700, Stephen Hemminger wrote:
> > On Thu, 26 Oct 2006 18:28:38 -0700
> > Andrew Morton <akpm@osdl.org> wrote:
> >
> > > On Thu, 26 Oct 2006 19:20:58 -0600
> > > Matthew Wilcox <matthew@wil.cx> wrote:
> > >
> > > > On Fri, Oct 27, 2006 at 03:02:52AM +0200, Adrian Bunk wrote:
> > > > > PCI_MULTITHREAD_PROBE is an interesting feature, but in it's current
> > > > > state it seems to be more of a trap for users who accidentally
> > > > > enable it.
> > > > >
> > > > > This patch lets PCI_MULTITHREAD_PROBE depend on BROKEN for 2.6.19.
> > > > >
> > > > > The intention is to get this patch reversed in -mm as soon as it's in
> > > > > Linus' tree, and reverse it for 2.6.20 or 2.6.21 after the fallout of
> > > > > in-kernel problems PCI_MULTITHREAD_PROBE causes got fixed.
> > > >
> > > > People who enable features clearly marked as EXPERIMENTAL deserve what
> > > > they get, IMO.
> > >
> > > It's not the impact on "people" which is of concern - it's the impact on
> > > kernel developers - specifically those who spend time looking at bug
> > > reports :(
> >
> > Either it is broken and should be removed, or is barely working and
> > should be fixed. If Greg wants to take bug reports then it can stay.
>
> I want to keep taking bug reports.
>
> I've found only 1 real bug from all of this. The pci MSI initialization
> issue. It's on my queue of things to fix. Andrew has also sent me
> another "interesting" patch about making sure devices are found by the
> time we hit another init level which I'll see about adding too.
>
> But that MSI bug was a real bug, which is good to have found. It's also
> found other real bugs in other subsystems that could easily be hit by
> other users.
>
> So no, this should not be marked BROKEN.
>
> It's a very experimental feature, as the help text says. If you can
> think of any harsher language to put in that text, please let me know.

The problem is that if only 1 out of 100 people who are compiling a
kernel accidentally enable this option, linux-kernel will be swamped
with bug reports...

If it shouldn't be enabled by users, the only correct language is a
dependency on BROKEN.

And it doesn't matter whether PCI_MULTITHREAD_PROBE itself is buggy or
whether it only exposes latent bugs in other subsystems - the effect is
the same.

> And yes, there also has been a proposed change to the driver core to fix
> up how the multi-thread stuff works that looks very good, but it's down
> in my queue that I'm trying to catch up on right now.
>
> So consider this a NAK for this change.
>
> thanks,
>
> greg k-h

cu
Adrian

--

"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed