Re: [CFT]: ClangBSD is selfhosting, we need testers now

Roman Divacky schrieb am 2010-04-21:
> On Wed, Apr 21, 2010 at 07:22:00PM +0200, Alexander Best wrote:
> > Roman Divacky schrieb am 2010-04-21:
> > > On Wed, Apr 21, 2010 at 05:20:57PM +0200, Alexander Best wrote:
> > > > i might have stumbled upon a problem with clang. i've compiled
> > > > a
> > > > kernel from
> > > > the clang branch using `make kernel INSTKERNNAME=clang` and
> > > > booted
> > > > from it.
> > > > i'm now experiencing audio problems with mp3s and certain video
> > > > files.
> > > > playback is awfully slow and the audio output gets distorted
> > > > massively. `top`
> > > > however reports no high cpu load and `vmstat -i` doesn't report
> > > > anything
> > > > unusual either.

> > > > this problem doesn't occur with a regular gcc-kernel.

> > > > both kernels are running under a regular (gcc) world.

> > > > i thought it might be a problem with acpi, but disabling acpi
> > > > (hint.acpi.0.disabled=1) gives me a system freeze.

> > > I've heard about this problem but did not manage to reproduce
> > > that.

> > > can you try to bisect what file is being miscompiled? ie. compile
> > > half of the kernel with gcc and half with clang and bisect this
> > > way to a single file.

> > > we can work from there...

> > i've identified the problem to be somewhere in sys/dev/sound. i've
> > removed
> > "device sound" and "device hda_snd" from my kernel config and
> > rebuild/reinstalled both kernels (gcc and clang). i then booted the
> > clang
> > kernel and loaded various sound.ko and snd_hda.ko combination.
> > here're the
> > results:

> > sound.ko (clang) snd_hda.ko (clang) => BROKEN
> > sound.ko (clang) snd_hda.ko (gcc)   => BROKEN
> > sound.ko (gcc) snd_hda.ko (gcc)     => OK
> > sound.ko (gcc) snd_hda.ko (clang)   => OK

> great work! it looks like sound.ko is the culprit..

> this is amd64 because my i386 kernel plays sound just fine.

> could you try to bisect the sound.ko ?

> you can do it this way:

> 1) cd modules/sound/sound && make CC=gcc

> 2) make -V SRCS | tr " " "\n" | grep -v \.h | sort | grep "^[a-m].*"
>    | xargs touch

>                                                             ^^^^^
>                                                             this is
>                                                             your
>                                                             bisect
>                                                             pattern

> 3) make CC=clang && make install

> 4) reload the module && test the sound

> 5) if the sound works you swap your bisect pattern (ie. [a-m] ->
>    [n-z] etc.)
>    if not you know that you that the miscompiled file is in you
>    pattern and
>    you can narrow it (ie. [a-m] -> [a-g] etc.)

> 6) goto 1 until you compile a single file

> I am pretty sure you can understand this and reduce this to a single
> file.
> once we get single file that is being miscompiled we can do some
> slightly
> \more educated guess on whats going on and structure our testing a
> little
> smarter...

hmmm...this gives me

link_elf_obj: symbol feeder_matrix_default_format undefined
linker_load_file: Unsupported file type

when trying to load sound.ko :( something's not working. this is not related
to clang. if i do `make CC=gcc && make install` in step 3) i'm getting the
same error.

> thnx! roman

-- 
Alexander Best