Hi!

On 2020-12-04T22:15:46+0800, Chung-Lin Tang <cltang@codesourcery.com> wrote:
> this is a new version of the structure element mapping patch for OpenMP 5.0 requirement
> changes.

>       (gomp_exit_data): [...]
>       adjust to queue splay-tree keys for removal
>       after main loop.

> --- a/libgomp/target.c
> +++ b/libgomp/target.c

> @@ -2485,14 +2714,17 @@ gomp_exit_data (struct gomp_device_descr *devicep, size_t mapnum,

> +  int nrmvars = 0;
> +  splay_tree_key remove_vars[mapnum];
> +
>    for (i = 0; i < mapnum; i++)
>      {

> -       if (k->refcount == 0)
> -         gomp_remove_var (devicep, k);
> +
> +       /* Structure elements lists are removed altogether at once, which
> +          may cause immediate deallocation of the target_mem_desc, causing
> +          errors if we still have following element siblings to copy back.
> +          While we're at it, it also seems more disciplined to simply
> +          queue all removals together for processing below.
> +
> +          Structured block unmapping (i.e. gomp_unmap_vars_internal) should
> +          not have this problem, since they maintain an additional
> +          tgt->refcount = 1 reference to the target_mem_desc to start with.
> +       */
> +       if (do_remove)
> +         remove_vars[nrmvars++] = k;

>      }
>
> +  for (int i = 0; i < nrmvars; i++)
> +    gomp_remove_var (devicep, remove_vars[i]);
> +
>    gomp_mutex_unlock (&devicep->lock);
>  }

Upcoming work of mine actually now does require this change also for
'gomp_unmap_vars_internal', such that 'gomp_remove_var' be deferred until
after all 'gomp_copy_dev2host' calls have been handled.
I've pushed to devel/omp/gcc-12
commit 65037818987ffce7d6f466fa8bde13e9f59a3218
"In 'libgomp/target.c:gomp_unmap_vars_internal', defer 'gomp_remove_var'",
see attached.


Grüße
 Thomas


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