[SYCL] E2E test for host task scheduling fix

SYCL/Basic/host_task_depends.cpp

@@ -0,0 +1,31 @@
+// RUN: %clangxx -fsycl -fsycl-targets=%sycl_triple %s -o %t.out
+// RUN: %CPU_RUN_PLACEHOLDER %t.out
+
+#include <sycl/sycl.hpp>
+
+using namespace sycl;
+using namespace sycl::access;
+
+void test() {
+  queue Q;
+  std::shared_ptr<std::mutex> Mutex(new std::mutex());
+  Mutex->lock();
+  {
+    auto E = Q.submit([&](handler &CGH) {
+      CGH.host_task([=]() { std::lock_guard<std::mutex> Guard(*Mutex); });
+    });
+    // Host task should block kernel enqueue but not cause dead lock here
+    Q.submit([&](handler &CGH) {
+      CGH.depends_on(E);
+      CGH.single_task([=]() {});
+    });
+  }
+  // Unblock kernel execution
+  Mutex->unlock();
+  Q.wait();
+}
+
+int main() {
+  test();
+  return 0;
+}