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

[Jacob Pan]

Hi Jason,

On Fri, 15 Oct 2021 08:18:07 -0300, Jason Gunthorpe <jgg@xxxxxxxxxx> 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