USVM test for multithreaded alloc & free

Allocation and free entry-points USVM entry-points should be threadsafe as they
may be used in a threaded manner.

Stresses the bug found in the USVM emulation layer bashbaug/SimpleOpenCLSamples#165

Author: EwanC

test_conformance/SVM/CMakeLists.txt

@@ -29,6 +29,7 @@ set(${MODULE_NAME}_SOURCES
     test_unified_svm_setarg.cpp
     test_unified_svm_map_unmap.cpp
     test_unified_svm_execinfo.cpp
+    test_unified_svm_threading.cpp
 )
 
 set_gnulike_module_compile_flags("-Wno-sometimes-uninitialized -Wno-sign-compare")

test_conformance/SVM/test_unified_svm_threading.cpp

@@ -0,0 +1,111 @@
+//
+// Copyright (c) 2026 The Khronos Group Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "unified_svm_fixture.h"
+#include <cinttypes>
+#include <memory>
+#include <thread>
+
+void worker(USVMWrapper<cl_int>* mem, cl_int* alloc_ret, cl_int* free_ret)
+{
+    *alloc_ret = mem->allocate(4);
+    *free_ret = mem->free();
+}
+
+struct UnifiedSVMThreadedAllocFree : UnifiedSVMBase
+{
+    UnifiedSVMThreadedAllocFree(cl_context context, cl_device_id device,
+                                cl_command_queue queue, int num_elements)
+        : UnifiedSVMBase(context, device, queue, num_elements)
+    {}
+
+    cl_int run() override
+    {
+        for (cl_uint ti = 0; ti < static_cast<cl_uint>(deviceUSVMCaps.size());
+             ti++)
+        {
+            log_info("   testing SVM type %u\n", ti);
+
+            auto mem = get_usvm_wrapper<cl_int>(ti);
+            const unsigned num_threads = 10;
+            std::vector<std::thread> threads;
+            std::vector<std::pair<cl_int, cl_int>> ret_codes(num_threads);
+
+            for (int i = 0; i < num_threads; ++i)
+            {
+                cl_int& alloc = ret_codes[i].first;
+                cl_int& free = ret_codes[i].second;
+                threads.push_back(
+                    std::thread(worker, mem.get(), &alloc, &free));
+            }
+
+            for (auto& thread : threads)
+            {
+                thread.join();
+            }
+
+            for (const auto& [alloc_ret, free_ret] : ret_codes)
+            {
+                test_error(alloc_ret, "USVM allocation failed");
+                test_error(free_ret, "USVM free failed");
+            }
+        }
+
+        return CL_SUCCESS;
+    }
+};
+
+REGISTER_TEST(unified_svm_threading_alloc_free)
+{
+    if (!is_extension_available(device, "cl_khr_unified_svm"))
+    {
+        log_info("cl_khr_unified_svm is not supported, skipping test.\n");
+        return TEST_SKIPPED_ITSELF;
+    }
+
+    cl_int err;
+
+    clContextWrapper contextWrapper;
+    clCommandQueueWrapper queueWrapper;
+
+    // For now: create a new context and queue.
+    // If we switch to a new test executable and run the tests without
+    // forceNoContextCreation then this can be removed, and we can just use the
+    // context and the queue from the harness.
+    if (context == nullptr)
+    {
+        contextWrapper =
+            clCreateContext(nullptr, 1, &device, nullptr, nullptr, &err);
+        test_error(err, "clCreateContext failed");
+        context = contextWrapper;
+    }
+
+    if (queue == nullptr)
+    {
+        queueWrapper = clCreateCommandQueue(context, device, 0, &err);
+        test_error(err, "clCreateCommandQueue failed");
+        queue = queueWrapper;
+    }
+
+    UnifiedSVMThreadedAllocFree Test(context, device, queue, num_elements);
+    err = Test.setup();
+    test_error(err, "test setup failed");
+
+    err = Test.run();
+    test_error(err, "test failed");
+
+    return TEST_PASS;
+}