gpu: add cvar MPIR_CVAR_GPU_HAS_WAIT_KERNEL

Add cvar MPIR_CVAR_GPU_HAS_WAIT_KERNEL to supply yaksa_init with info
hint "yaksa_has_wait_kernel". With the hint, yaksa should avoid code
that may potentially dead lock with a wait kernel.

src/include/mpir_gpu.h

@@ -28,6 +28,18 @@
         and we do not query the buffer type internally because we assume
         no GPU buffer is use.
 
+    - name        : MPIR_CVAR_GPU_HAS_WAIT_KERNEL
+      category    : GPU
+      type        : int
+      default     : 0
+      class       : none
+      verbosity   : MPI_T_VERBOSITY_USER_BASIC
+      scope       : MPI_T_SCOPE_ALL_EQ
+      description : >-
+        If set to 1, avoid allocate allocating GPU registered host buffers
+        for temporary buffers. When stream workq and GPU wait kernels are
+        in use, access APIs for GPU registered memory may cause deadlock.
+
 === END_MPI_T_CVAR_INFO_BLOCK ===
 */
 

src/mpi/datatype/typerep/src/typerep_yaksa_init.c

@@ -404,7 +404,13 @@ void MPIR_Typerep_init(void)
     yaksa_info_keyval_append(MPII_yaksa_info_nogpu, "yaksa_gpu_driver", "nogpu", 6);
 
     if (MPIR_CVAR_ENABLE_GPU) {
-        yaksa_init(NULL);
+        yaksa_info_t info = NULL;
+        if (MPIR_CVAR_GPU_HAS_WAIT_KERNEL) {
+            yaksa_info_create(&info);
+            yaksa_info_keyval_append(info, "yaksa_has_wait_kernel", "1", 2);
+        }
+
+        yaksa_init(info);
     } else {
         /* prevent yaksa to query gpu devices, which can be very expensive */
         yaksa_init(MPII_yaksa_info_nogpu);