Do not try default_context on Windows yet

Author: oleksandr-pavlyk

dpctl/tensor/_dlpack.pyx

@@ -33,12 +33,18 @@ from .._backend cimport (
 )
 from ._usmarray cimport usm_ndarray
 
+from platform import system as sys_platform
+
 import numpy as np
 
 import dpctl
 import dpctl.memory as dpmem
 
 
+cdef bint _IS_LINUX = sys_platform() == "Linux"
+
+del sys_platform
+
 cdef extern from 'dlpack/dlpack.h' nogil:
     cdef int DLPACK_VERSION
 
@@ -159,7 +165,10 @@ cpdef to_dlpack_capsule(usm_ndarray usm_ary) except+:
     ary_sycl_device = ary_sycl_queue.get_sycl_device()
 
     try:
-        default_context = ary_sycl_device.sycl_platform.default_context
+        if _IS_LINUX:
+            default_context = ary_sycl_device.sycl_platform.default_context
+        else:
+            default_context = None
     except RuntimeError:
         # RT does not support default_context, e.g. Windows
         default_context = None
@@ -328,7 +337,10 @@ cpdef usm_ndarray from_dlpack_capsule(object py_caps) except +:
         device_id = dlm_tensor.dl_tensor.device.device_id
         root_device = dpctl.SyclDevice(str(<int>device_id))
         try:
-            default_context = root_device.sycl_platform.default_context
+            if _IS_LINUX:
+                default_context = root_device.sycl_platform.default_context
+            else:
+                default_context = None
         except RuntimeError:
             default_context = dpctl.SyclQueue(root_device).sycl_context
         if dlm_tensor.dl_tensor.data is NULL: