Re: [RFC 01/20] iommu/iommufd: Add /dev/iommu core

Jacob Pan
2021-10-19T16:53:56Z

Hi Jason,

On Fri, 15 Oct 2021 08:18:07 -0300, Jason Gunthorpe <jgg@nvidia.com> wrote:

> On Fri, Oct 15, 2021 at 09:18:06AM +0000, Liu, Yi L wrote:
>
> > > Acquire from the xarray is
> > > rcu_lock()
> > > ioas = xa_load()
> > > if (ioas)
> > > if (down_read_trylock(&ioas->destroying_lock))
> >
> > all good suggestions, will refine accordingly. Here destroying_lock is a
> > rw_semaphore. right? Since down_read_trylock() accepts a rwsem.
>
> Yes, you probably need a sleeping lock
>
I am not following why we want a sleeping lock inside RCU protected
section?

For ioas, do we really care about the stale data to choose rw_lock vs RCU?
Destroying can be kfree_rcu?
> Jason

Thanks,

Jacob