On Mon, Jun 30, 2008 at 07:22:17PM +0200, Manuel Bouyer wrote:
> On Mon, Jun 30, 2008 at 10:01:52AM -0700, Bill Stouder-Studenmund wrote:
> > On Sun, Jun 29, 2008 at 11:14:01PM +0200, Manuel Bouyer wrote:
> > > On Sun, Jun 29, 2008 at 02:03:18PM -0600, Greg Oster wrote:
> > > > > Its done it to me 4 or 5 times now. Trying to scp or rdist about 7GB
> > > > > of /usr/pkg and /usr/local to the domU, it gets about 1 or 2 GB
> > > > > transferred then the dom0 panics :-(
> > > >
> > > > In both xbdback_xenbus.c and xbdback.c we have this code:
> > > >
> > > > if ((xbd_io->xio_buf.b_flags & B_READ) == 0)
> > > > xbd_io->xio_buf.b_vp->v_numoutput++;
> > > >
> > > > Should this not read:
> > > >
> > > > if ((xbd_io->xio_buf.b_flags & B_READ) == 0) {
> > > > mutex_enter(&xbd_io->xio_buf.b_vp->v_interlock);
> > > > xbd_io->xio_buf.b_vp->v_numoutput++;
> > > > mutex_exit(&xbd_io->xio_buf.b_vp->v_interlock);
> > > > }
> > > >
> > > > (or somesuch) to properly update v_numoutput ? Most other changes
> > > > to v_numoutput are holding the vp->v_interlock, but if this one is,
> > > > I'm completely missing how it's doing it...
> > >
> > > I think you're right, the interlock is not taken here.
> > > But we have a problem: at this point we are in interrupt context.
> > > Can we take this mutex from interrupt context ?
> >
> > Would this be a good candidate for the atomic update operations? That way
> > you don't need a lock.
>
> Could be, but then it needs to be updated atomically everywhere.
Right.
But if you can't take a lock, then you need to do something. :-) And
either cscope or eid (probably eid) can help you change the whole tree at
once.
Take care,
Bill
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