[gcc/devel/c++-modules] libgomp: adjust nvptx_free callback context checking

[gcc/devel/c++-modules] libgomp: adjust nvptx_free callback context checking

[Nathan Sidwell]

https://gcc.gnu.org/g:f9b9832837b65046a8f01c18597cf615ff61db40

commit f9b9832837b65046a8f01c18597cf615ff61db40
Author: Chung-Lin Tang <cltang@codesourcery.com>
Date:   Thu Aug 20 07:18:51 2020 -0700

    libgomp: adjust nvptx_free callback context checking
    
    Change test for CUDA callback context in nvptx_free() from using
    GOMP_PLUGIN_acc_thread () into checking for CUDA_ERROR_NOT_PERMITTED,
    for the former only works for OpenACC, but not OpenMP offloading.
    
    2020-08-20  Chung-Lin Tang  <cltang@codesourcery.com>
    
            libgomp/
            * plugin/plugin-nvptx.c (nvptx_free):
            Change "GOMP_PLUGIN_acc_thread () == NULL" test into check of
            CUDA_ERROR_NOT_PERMITTED status for cuMemGetAddressRange. Adjust
            comments.

Diff:
---
 libgomp/plugin/plugin-nvptx.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/libgomp/plugin/plugin-nvptx.c b/libgomp/plugin/plugin-nvptx.c
index ec103a2f40b..390804ad1fa 100644
--- a/libgomp/plugin/plugin-nvptx.c
+++ b/libgomp/plugin/plugin-nvptx.c
@@ -1040,9 +1040,17 @@ goacc_profiling_acc_ev_free (struct goacc_thread *thr, void *p)
 static bool
 nvptx_free (void *p, struct ptx_device *ptx_dev)
 {
-  /* Assume callback context if this is null.  */
-  if (GOMP_PLUGIN_acc_thread () == NULL)
+  CUdeviceptr pb;
+  size_t ps;
+
+  CUresult r = CUDA_CALL_NOCHECK (cuMemGetAddressRange, &pb, &ps,
+				  (CUdeviceptr) p);
+  if (r == CUDA_ERROR_NOT_PERMITTED)
     {
+      /* We assume that this error indicates we are in a CUDA callback context,
+	 where all CUDA calls are not allowed (see cuStreamAddCallback
+	 documentation for description). Arrange to free this piece of device
+	 memory later.  */
       struct ptx_free_block *n
 	= GOMP_PLUGIN_malloc (sizeof (struct ptx_free_block));
       n->ptr = p;
@@ -1052,11 +1060,11 @@ nvptx_free (void *p, struct ptx_device *ptx_dev)
       pthread_mutex_unlock (&ptx_dev->free_blocks_lock);
       return true;
     }
-
-  CUdeviceptr pb;
-  size_t ps;
-
-  CUDA_CALL (cuMemGetAddressRange, &pb, &ps, (CUdeviceptr) p);
+  else if (r != CUDA_SUCCESS)
+    {
+      GOMP_PLUGIN_error ("cuMemGetAddressRange error: %s", cuda_error (r));
+      return false;
+    }
   if ((CUdeviceptr) p != pb)
     {
       GOMP_PLUGIN_error ("invalid device address");