[Xen-devel] Re: [PATCH] gntdev: switch back to rwlocks

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 9 Jul 2010, Jeremy Fitzhardinge wrote:
> On 07/09/2010 07:32 AM, Stefano Stabellini wrote:
> > Hi Jeremy,
> > this patch switches back from spinlocks to rwlocks in gntdev, solving
> > the locking issue that was preventing stubdoms from working.
> > In particular the problem is that gntdev_mmap calls apply_to_page_range
> > after acquiring the spinlock. apply_to_page_range causes the mmu
> > notifiers to be called, so mn_invl_range_start will be called that will
> > try to acquire again the same spinlock.
> >   
> 
> I think the problem is that apply_to_page_range is calling the mmu
> notifiers at all.  It seems to be plain bogus; it should be up to the
> callers of apply_to_page_range to call the mmu notifiers if necessary.
> 
> Does removing those calls fix the problem?
> 

yep


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