Re: [gomp4.5] Handle #pragma omp declare target link

[Ilya Verbin <iverbin at gmail dot com>]

On Mon, Nov 30, 2015 at 21:49:02 +0100, Jakub Jelinek wrote:
> On Mon, Nov 30, 2015 at 11:29:34PM +0300, Ilya Verbin wrote:
> > You're right, it doesn't deallocate memory on the device if DSO leaves nonzero
> > refcount.  And currently host compiler doesn't set MSB in host_var_table, it's
> > set only by accel compiler.  But it's possible to do splay_tree_lookup for each
> > var to determine whether is it linked or not, like in the patch bellow.
> > Or do you prefer to set the bit in host compiler too?  It requires
> > lookup_attribute ("omp declare target link") for all vars in the table during
> > compilation, but allows to do splay_tree_lookup at run-time only for vars with
> > MSB set in host_var_table.
> > Unfortunately, calling gomp_exit_data from gomp_unload_image_from_device works
> > only for DSO, but it crashed when an executable leaves nonzero refcount, because
> > target device may be already uninitialized from plugin's __run_exit_handlers
> > (and it is in case of intelmic), so gomp_exit_data cannot run free_func.
> > Is it possible do add some atexit (...) to libgomp, which will set shutting_down
> > flag, and just do nothing in gomp_unload_image_from_device if it is set?
> 
> Sorry, I didn't mean you should call gomp_exit_data, what I meant was that
> you perform the same action as would delete(var) do in that case.
> Calling gomp_exit_data e.g. looks it up again etc.
> Supposedly having the MSB in host table too is useful, so if you could
> handle that, it would be nice.  And splay_tree_lookup only if the MSB is
> set.
> So,
>     if (!host_data_has_msb_set)
>       splay_tree_remove (&devicep->mem_map, &k);
>     else
>       {
>         splay_tree_key n = splay_tree_lookup (&devicep->mem_map, &k);
>         if (n->link_key)
> 	  {
> 	    n->refcount = 0;
> 	    n->link_key = NULL;
> 	    splay_tree_remove (&devicep->mem_map, n);
> 	    if (n->tgt->refcount > 1)
> 	      n->tgt->refcount--;
> 	    else
> 	      gomp_unmap_tgt (n->tgt);
> 	  }
> 	else
> 	  splay_tree_remove (&devicep->mem_map, n);
>       }
> or so.

Ok, but it doesn't solve the issue with doing it for the executable, because
gomp_unmap_tgt (n->tgt) will want to run free_func on uninitialized device.

  -- Ilya