Kernel failure while writing DVD-RAM
Gilboa Davara
gilboad at gmail.com
Tue Nov 24 18:22:38 UTC 2009
On Wed, 2009-11-18 at 10:43 +0000, Dave Higton wrote:
Hello Dave,
Sorry for the late reply.
Somehow missed you message due to excessive F12-release noise. :)
> OK. I've just been Googling for warn_slowpath, but although I've
> found lots of examples, I don't know what it means. My guess is
> that it's used as a diagnostic by some code, probably kernel code,
> so the next challenge is to find where it was called from. Yes?
I tried tracking down the kernel code...
>
> > Are you getting a real crash or some kind of failure.
>
> More information since my original posting: fillDVD2 is a test app
> that I wrote as part of an effort to test the ability of Fedora to
> write DVD-RAM discs. We have experienced numerous failures, but
> we don't yet understand why.
>
> fillDVD2 wasn't testing for errors. An error occurred somewhere,
> but fillDVD2 carried on trying to write to the DVD-RAM disc. This
> doesn't work; once DVD-RAM writing has failed, no subsequent
> attempts will succeed. The disc has to be ejected.
>
> I revised fillDVD2 to stop on an error. A subsequent test showed
> that the first error, at a similar point (when the disc was within
> a few hundred MB of getting full), was "I/O error". Not very
> meaningful to me.
Other than the WARN_ON, are you seeing anything useful in the kernel
log?
> uname -a says:
> 2.6.27.38-170.2.113.fc10.i686 #1 SMP Wed Nov 4 17:55:39 EST 2009
> i686 i686 i386 GNULinux
> We originally wanted to use CentOS but were never able to solve
> a real-time problem it gave us: we need to service interrupts from
> our cards every 32 ms. Normally the IRQ is active for no more than
> 8 us before it's serviced; under CentOS this would often exceed 20 ms
> and we would lose data.
>
Weird. 8us sounds right under both RHEL and Fedora.
Care to take it off ML?
- Gilboa
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