On Fri, Jan 04, 2019 at 08:05:06AM +0200, Leon Romanovsky wrote:
> On Thu, Jan 03, 2019 at 10:30:26PM +0000, Jason Gunthorpe wrote:
> > On Thu, Jan 03, 2019 at 10:05:59AM +0200, Leon Romanovsky wrote:
> > > From: Leon Romanovsky <leonro@xxxxxxxxxxxx>
> > >
> > > XArray uses internal lock for updates to XArray. This means that our
> > > external RW lock is not needed anymore and we can delete it.
> >
> > The xarray lock only protects the array itself - not the things it
> > points to.
> >
> > > - down_read(&res->rwsem);
> > > xa_for_each(&res->xa[type], e, index, ULONG_MAX, XA_PRESENT) {
> > > if (ns == &init_pid_ns ||
> > > (!rdma_is_kernel_res(e) &&
> >
> > So eg here, 'e' is still needs the locking to protect against
> > concurrent restrack_del causing e to be freed.
> >
> > Most likely the internal xarray locking doesn't save anything in this
> > usage..
>
> The "rwsem" protects hash lists insert/delete and we are still using
> kref to protect specific entries. And those xarray insert/deletion are
> handled by xa_lock() now.
This doesn't explain where the locking for 'e' comes from above
Jason
