openacc: Deep copy attach/detach should not affect reference counts

Attach and detach operations are not supposed to affect structural or
dynamic reference counts for OpenACC. Previously they did so, which led to
subtle problems in some circumstances. We can avoid reference-counting
attach/detach operations by extending and slightly repurposing the
do_detach field in target_var_desc. It is now called is_attach to better
reflect its new role.

2020-07-27  Julian Brown  <julian@codesourcery.com>
	    Thomas Schwinge  <thomas@codesourcery.com>

libgomp/
	* libgomp.h (struct target_var_desc): Rename do_detach field to
	is_attach.
	* oacc-mem.c (goacc_exit_datum_1): Add assert.  Don't set finalize for
	GOMP_MAP_FORCE_DETACH. Update checking to use is_attach field.
	(goacc_enter_data_internal): Don't affect reference counts
	for attach mappings.
	(goacc_exit_data_internal): Don't affect reference counts for detach
	mappings.
	* target.c (gomp_map_vars_existing): Don't affect reference counts for
	attach mappings.
	(gomp_map_vars_internal): Set renamed is_attach flag unconditionally to
	mark attach mappings.
	(gomp_unmap_vars_internal): Use is_attach flag to prevent affecting
	reference count for attach mappings.
	* testsuite/libgomp.oacc-c-c++-common/mdc-refcount-1.c: New test.
	* testsuite/libgomp.oacc-c-c++-common/mdc-refcount-2.c: New test.
	* testsuite/libgomp.oacc-c-c++-common/mdc-refcount-2.c: New test.
	* testsuite/libgomp.oacc-fortran/deep-copy-6-no_finalize.F90: Mark
	test as shouldfail.
	* testsuite/libgomp.oacc-fortran/deep-copy-6.f90: Adjust to fail
	gracefully in no-finalize mode.

Co-Authored-By: Thomas Schwinge <thomas@codesourcery.com>

1 files changed, 25 insertions, 15 deletions

diff --git a/libgomp/oacc-mem.c b/libgomp/oacc-mem.c
index 855cad8..65757ab 100644
--- a/libgomp/oacc-mem.c
+++ b/libgomp/oacc-mem.c
@@ -667,6 +667,9 @@ static void
 goacc_exit_datum_1 (struct gomp_device_descr *acc_dev, void *h, size_t s,
 		    unsigned short kind, splay_tree_key n, goacc_aq aq)
 {
+  assert (kind != GOMP_MAP_DETACH
+	  && kind != GOMP_MAP_FORCE_DETACH);
+
   if ((uintptr_t) h < n->host_start || (uintptr_t) h + s > n->host_end)
     {
       size_t host_size = n->host_end - n->host_start;
@@ -676,8 +679,7 @@ goacc_exit_datum_1 (struct gomp_device_descr *acc_dev, void *h, size_t s,
     }
 
   bool finalize = (kind == GOMP_MAP_FORCE_FROM
-		   || kind == GOMP_MAP_DELETE
-		   || kind == GOMP_MAP_FORCE_DETACH);
+		   || kind == GOMP_MAP_DELETE);
 
   assert (n->refcount != REFCOUNT_LINK);
   if (n->refcount != REFCOUNT_INFINITY
@@ -725,7 +727,8 @@ goacc_exit_datum_1 (struct gomp_device_descr *acc_dev, void *h, size_t s,
 	     zero.  Otherwise (e.g. for a 'GOMP_MAP_STRUCT' mapping with
 	     multiple members), fall back to skipping the test.  */
 	  for (size_t l_i = 0; l_i < n->tgt->list_count; ++l_i)
-	    if (n->tgt->list[l_i].key)
+	    if (n->tgt->list[l_i].key
+		&& !n->tgt->list[l_i].is_attach)
 	      ++num_mappings;
 	  bool is_tgt_unmapped = gomp_remove_var (acc_dev, n);
 	  assert (is_tgt_unmapped || num_mappings > 1);
@@ -1135,12 +1138,15 @@ goacc_enter_data_internal (struct gomp_device_descr *acc_dev, size_t mapnum,
 	  void *h = hostaddrs[i];
 	  size_t s = sizes[i];
 
-	  /* A standalone attach clause.  */
 	  if ((kinds[i] & 0xff) == GOMP_MAP_ATTACH)
-	    gomp_attach_pointer (acc_dev, aq, &acc_dev->mem_map, n,
-				 (uintptr_t) h, s, NULL);
-
-	  goacc_map_var_existing (acc_dev, h, s, n);
+	    {
+	      gomp_attach_pointer (acc_dev, aq, &acc_dev->mem_map, n,
+				   (uintptr_t) h, s, NULL);
+	      /* OpenACC 'attach'/'detach' doesn't affect structured/dynamic
+		 reference counts ('n->refcount', 'n->dynamic_refcount').  */
+	    }
+	  else
+	    goacc_map_var_existing (acc_dev, h, s, n);
 	}
       else if (n && groupnum > 1)
 	{
@@ -1168,7 +1174,9 @@ goacc_enter_data_internal (struct gomp_device_descr *acc_dev, size_t mapnum,
 		   list, and increment the refcounts for each item in that
 		   group.  */
 		for (size_t k = 0; k < groupnum; k++)
-		  if (j + k < tgt->list_count && tgt->list[j + k].key)
+		  if (j + k < tgt->list_count
+		      && tgt->list[j + k].key
+		      && !tgt->list[j + k].is_attach)
 		    {
 		      tgt->list[j + k].key->refcount++;
 		      tgt->list[j + k].key->dynamic_refcount++;
@@ -1202,7 +1210,7 @@ goacc_enter_data_internal (struct gomp_device_descr *acc_dev, size_t mapnum,
 	  for (size_t j = 0; j < tgt->list_count; j++)
 	    {
 	      n = tgt->list[j].key;
-	      if (n)
+	      if (n && !tgt->list[j].is_attach)
 		n->dynamic_refcount++;
 	    }
 	}
@@ -1268,14 +1276,10 @@ goacc_exit_data_internal (struct gomp_device_descr *acc_dev, size_t mapnum,
 	case GOMP_MAP_POINTER:
 	case GOMP_MAP_DELETE:
 	case GOMP_MAP_RELEASE:
-	case GOMP_MAP_DETACH:
-	case GOMP_MAP_FORCE_DETACH:
 	  {
 	    struct splay_tree_key_s cur_node;
 	    size_t size;
-	    if (kind == GOMP_MAP_POINTER
-		|| kind == GOMP_MAP_DETACH
-		|| kind == GOMP_MAP_FORCE_DETACH)
+	    if (kind == GOMP_MAP_POINTER)
 	      size = sizeof (void *);
 	    else
 	      size = sizes[i];
@@ -1298,6 +1302,12 @@ goacc_exit_data_internal (struct gomp_device_descr *acc_dev, size_t mapnum,
 	     'GOMP_MAP_STRUCT's anymore.  */
 	  break;
 
+	case GOMP_MAP_DETACH:
+	case GOMP_MAP_FORCE_DETACH:
+	  /* OpenACC 'attach'/'detach' doesn't affect structured/dynamic
+	     reference counts ('n->refcount', 'n->dynamic_refcount').  */
+	  break;
+
 	default:
 	  gomp_fatal (">>>> goacc_exit_data_internal UNHANDLED kind 0x%.2x",
 			  kind);