[PATCH 4/4] mm, notifier: Catch sleeping/blocking for !blockable
daniel at ffwll.ch
Thu Aug 22 08:42:39 UTC 2019
On Thu, Aug 22, 2019 at 10:16 AM Jason Gunthorpe <jgg at ziepe.ca> wrote:
> On Wed, Aug 21, 2019 at 05:41:51PM +0200, Daniel Vetter wrote:
> > > Hm, I thought the page table locks we're holding there already prevent any
> > > sleeping, so would be redundant? But reading through code I think that's
> > > not guaranteed, so yeah makes sense to add it for invalidate_range_end
> > > too. I'll respin once I have the ack/nack from scheduler people.
> > So I started to look into this, and I'm a bit confused. There's no
> > _nonblock version of this, so does this means blocking is never allowed,
> > or always allowed?
> RDMA has a mutex:
> I'm working to delete this path though!
> nonblocking or not follows the start, the same flag gets placed into
> the mmu_notifier_range struct passed to end.
Ok, makes sense.
I guess that also means the might_sleep (I started on that) in
invalidate_range_end also needs to be conditional? Or not bother with
a might_sleep in invalidate_range_end since you're working on removing
the last sleep in there?
> > From a quick look through implementations I've only seen spinlocks, and
> > one up_read. So I guess I should wrape this callback in some unconditional
> > non_block_start/end, but I'm not sure.
> For now, we should keep it the same as start, conditionally blocking.
> Hopefully before LPC I can send a RFC series that eliminates most
> invalidate_range_end users in favor of common locking..
Software Engineer, Intel Corporation
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