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Re: kern/39052: assertion "!ISSET(bp->b_cflags, BC_BUSY)" failed

Subject: Re: kern/39052: assertion "!ISSET(bp->b_cflags, BC_BUSY)" failed
From: Manuel Bouyer
Date: Fri, 27 Jun 2008 14:50:14 UTC
Newsgroups: fa.netbsd.bugs

On Fri, Jun 27, 2008 at 04:06:53PM +0200, Manuel Bouyer wrote:
> [...]
> > Michael van Elst suggested it could be related to locking issues in vnd,
> > but I don't have more details. Note that the xen backend block device
> > calls bdev_strategy() from interrupt context, I don't know if it
> > can have a bad effect. AFAIK, this will cal vndstrategy() which will
> > enqueue the buffer and wakeup a kernel thread to handle it. This shouldn't
> > interract at all with the buffer cache.
> Another parameter is that this box is using a amr(4) controller. It's
> my only system with an amr(4) running -current, and I can't reproduce this
> on onther -current Xen dom0.
> The amr(4) interrupt routine can be called from interrupt context,
> or a kernel thread. Under heavy I/O load some of the I/O request completion
> could be handled from thread context and not interrupt context.

I've been able to reproduce it without any domU running. So it's not related
to vnd or xbdback. As I can't reproduce it on any system but this one,
the problem may be within amr(4) or ld(4).

Manuel Bouyer, LIP6, Universite Paris VI.           Manuel.Bouyer@xxxxxxx
     NetBSD: 26 ans d'experience feront toujours la difference

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