[SYCL] fix for flaky ~event failure in Win unit tests (#19762)

Windows shutdown/teardown doesn't have the exact same timing as on
Linux, and even more in the the unit tests which are statically compiled
( so no DllMain() call, which means no space between the calls to
`shutdown_early()` and `shutdown_late()` ). Here we remove a race
between the platform deletion in the mock and the win shutdown. This
fixes a flaky failure we are seeing in a couple of the unit tests.

---------

Signed-off-by: Chris Perkins <[email protected]>

Author: cperkinsintel

sycl/unittests/context_device/DeviceRefCounter.cpp

@@ -5,6 +5,7 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
+#include <detail/global_handler.hpp>
 #include <gtest/gtest.h>
 #include <helpers/UrMock.hpp>
 #include <sycl/sycl.hpp>
@@ -31,6 +32,7 @@ static ur_result_t redefinedDeviceReleaseAfter(void *) {
 TEST(DevRefCounter, DevRefCounter) {
   {
     sycl::unittest::UrMock<> Mock;
+    EXPECT_EQ(DevRefCounter, 0);
 
     mock::getCallbacks().set_after_callback("urDeviceGet",
                                             &redefinedDevicesGetAfter);
@@ -41,6 +43,12 @@ TEST(DevRefCounter, DevRefCounter) {
     sycl::platform Plt = sycl::platform();
 
     Plt.get_devices();
+    EXPECT_NE(DevRefCounter, 0);
+    // This is the behavior that SYCL performs at shutdown, but there
+    // are timing differences Lin/Win and shared/static that make
+    // it not map correctly into our mock.
+    // So for this test, we just do it.
+    sycl::detail::GlobalHandler::instance().getPlatformCache().clear();
   }
   EXPECT_EQ(DevRefCounter, 0);
 }

sycl/unittests/helpers/UrMock.hpp

@@ -596,6 +596,16 @@ template <sycl::backend Backend = backend::opencl> class UrMock {
 
     sycl::detail::ur::initializeUr(UrLoaderConfig);
     urLoaderConfigRelease(UrLoaderConfig);
+
+    // We clear platform cache for each test run, so that tests can have a
+    // different backend. This forces platforms to be reconstructed (and thus
+    // queries about UR backend info to be called again) This also erases each
+    // platform's devices (normally done in the library shutdown) so that
+    // platforms/devices' lifetimes could work in unittests scenario. In SYCL,
+    // this is normally done at shutdown, but between Win/Lin and static/shared
+    // differences, there is no correct parallel in the ~UrMock destructor.
+    // Instead we do it here. Simple and clean.
+    detail::GlobalHandler::instance().getPlatformCache().clear();
   }
 
   UrMock(UrMock<Backend> &&Other) = delete;
@@ -606,14 +616,8 @@ template <sycl::backend Backend = backend::opencl> class UrMock {
     // these between tests
     detail::GlobalHandler::instance().prepareSchedulerToRelease(true);
     detail::GlobalHandler::instance().releaseDefaultContexts();
-    // clear platform cache in case subsequent tests want a different backend,
-    // this forces platforms to be reconstructed (and thus queries about UR
-    // backend info to be called again)
-    //
-    // This also erases each platform's devices (normally done in the library
-    // shutdown) so that platforms/devices' lifetimes could work in unittests
-    // scenario.
-    detail::GlobalHandler::instance().getPlatformCache().clear();
+    // the platform cache is cleared at the BEGINING of the mock.
+
     mock::getCallbacks().resetCallbacks();
   }