Re: iwlwifi warn_slowpath with 3.*

[Antonio Quartulli <ordex@autistici.org>]

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On Tue, May 01, 2012 at 08:13:46PM +0300, Emmanuel Grumbach wrote:
> Hi,
> 
> I am not sure the patch will help because the race is _very_ unlikely.
> But I would be glad to know if you can reproduce on latest
> compat-wireless.
> How reproducible is that on 3.3.3 ? Is that 100% ?

it seems so. It happens at least once at boot time.
I will try wireless-testing and see what happens. Then I will apply your patch.

Thanks a lot!

> 
> I guess my machine doesn't have IOMMU, but honestly, I am not sure I
> know how to check.
> 
> On Tue, May 1, 2012 at 19:52, Venkataraman, Meenakshi
> <meenakshi.venkataraman@intel.com> wrote:
> >
> > Hi John, Antonio,
> >
> > Emmanuel found a race condition in rx buffer allocation/deallocation, and
> > attached is a patch that fixes it.
> >
> > >> > since linux-3.0 (I don't remember if it was the case even before),
> > >> > I'm getting this output in dmesg:
> > >> >
> > >> > [   53.662990] ------------[ cut here ]------------
> > >> > [   53.663016] WARNING: at drivers/iommu/intel-iommu.c:2911
> > >> > intel_unmap_page+0x14b/0x180()
> > >> > [   53.663047] Hardware name: Latitude E5420
> > >> > [   53.663066] Driver unmaps unmatched page at PFN ffd1a000
> > >>
> > >>
> > >> I see that I always get the same addr passed to the unmap function:
> > >>
> > >> [   23.950535] Driver unmaps unmatched page at PFN ffd1a000
> > >>
> > >> is it a coincidence?
> > >> I'm running linux-3.3.3 right now. I can try wireless-testing if it
> > >> would help.
> >
> > [MV] Antonio -- can you try out the patch attached and let us know if you
> > continue to see the problem?
> >
> > >Just for the record, we are seeing a similar problem on RHEL 6.3 (which
> > > has an
> > >iwlwifi driver derived from linux-3.2).
> > >
> > >       https://bugzilla.redhat.com/show_bug.cgi?id=815998
> >
> > [MV] John -- I'll update the redhat bugzilla as well.
> >
> > Thanks
> > Meenakshi

-- 
Antonio Quartulli

..each of us alone is worth nothing..
Ernesto "Che" Guevara

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