Fix potential race condition in OpenACC "exit data" operations

	PR libgomp/92881

	libgomp/
	* libgomp.h (gomp_remove_var_async): Add prototype.
	* oacc-mem.c (delete_copyout): Call gomp_remove_var_async instead of
	gomp_remove_var.
	* target.c (gomp_unref_tgt): Change return type to bool, indicating
	whether target_mem_desc was unmapped.
	(gomp_unref_tgt_void): New.
	(gomp_remove_var): Reimplement in terms of...
	(gomp_remove_var_internal): ...this new helper function.
	(gomp_remove_var_async): New, implemented using above helper function.
	(gomp_unmap_vars_internal): Use gomp_unref_tgt_void instead of
	gomp_unref_tgt.

Reviewed-by: Thomas Schwinge <thomas@codesourcery.com>

From-SVN: r279388

1 files changed, 45 insertions, 14 deletions

diff --git a/libgomp/target.c b/libgomp/target.c
index 1151debf256..82ed38c01ec 100644
--- a/libgomp/target.c
+++ b/libgomp/target.c
@@ -1116,32 +1116,63 @@ gomp_unmap_tgt (struct target_mem_desc *tgt)
   free (tgt);
 }
 
-attribute_hidden bool
-gomp_remove_var (struct gomp_device_descr *devicep, splay_tree_key k)
+static bool
+gomp_unref_tgt (void *ptr)
 {
   bool is_tgt_unmapped = false;
-  splay_tree_remove (&devicep->mem_map, k);
-  if (k->link_key)
-    splay_tree_insert (&devicep->mem_map, (splay_tree_node) k->link_key);
-  if (k->tgt->refcount > 1)
-    k->tgt->refcount--;
+
+  struct target_mem_desc *tgt = (struct target_mem_desc *) ptr;
+
+  if (tgt->refcount > 1)
+    tgt->refcount--;
   else
     {
+      gomp_unmap_tgt (tgt);
       is_tgt_unmapped = true;
-      gomp_unmap_tgt (k->tgt);
     }
+
   return is_tgt_unmapped;
 }
 
 static void
-gomp_unref_tgt (void *ptr)
+gomp_unref_tgt_void (void *ptr)
 {
-  struct target_mem_desc *tgt = (struct target_mem_desc *) ptr;
+  (void) gomp_unref_tgt (ptr);
+}
 
-  if (tgt->refcount > 1)
-    tgt->refcount--;
+static inline __attribute__((always_inline)) bool
+gomp_remove_var_internal (struct gomp_device_descr *devicep, splay_tree_key k,
+			  struct goacc_asyncqueue *aq)
+{
+  bool is_tgt_unmapped = false;
+  splay_tree_remove (&devicep->mem_map, k);
+  if (k->link_key)
+    splay_tree_insert (&devicep->mem_map, (splay_tree_node) k->link_key);
+  if (aq)
+    devicep->openacc.async.queue_callback_func (aq, gomp_unref_tgt_void,
+						(void *) k->tgt);
   else
-    gomp_unmap_tgt (tgt);
+    is_tgt_unmapped = gomp_unref_tgt ((void *) k->tgt);
+  return is_tgt_unmapped;
+}
+
+attribute_hidden bool
+gomp_remove_var (struct gomp_device_descr *devicep, splay_tree_key k)
+{
+  return gomp_remove_var_internal (devicep, k, NULL);
+}
+
+/* Remove a variable asynchronously.  This actually removes the variable
+   mapping immediately, but retains the linked target_mem_desc until the
+   asynchronous operation has completed (as it may still refer to target
+   memory).  The device lock must be held before entry, and remains locked on
+   exit.  */
+
+attribute_hidden void
+gomp_remove_var_async (struct gomp_device_descr *devicep, splay_tree_key k,
+		       struct goacc_asyncqueue *aq)
+{
+  (void) gomp_remove_var_internal (devicep, k, aq);
 }
 
 /* Unmap variables described by TGT.  If DO_COPYFROM is true, copy relevant
@@ -1197,7 +1228,7 @@ gomp_unmap_vars_internal (struct target_mem_desc *tgt, bool do_copyfrom,
     }
 
   if (aq)
-    devicep->openacc.async.queue_callback_func (aq, gomp_unref_tgt,
+    devicep->openacc.async.queue_callback_func (aq, gomp_unref_tgt_void,
 						(void *) tgt);
   else
     gomp_unref_tgt ((void *) tgt);