Fix race in isQueueBlocked.

- Sequence is as follows :
Enqueue returning event , blocked on user event.
clFinish.

There are 2 additional threads:
- one is calling updateExecutionStatus in a loop on returned
event
- one is calling setUserEventStatus on parent user event

In such case virtual event may be submitted but task count will
not be assigned.

Change-Id: Ia097bd59b276cc9213945c476cf289398b8f5934
Signed-off-by: Mrozek, Michal <michal.mrozek@intel.com>

unit_tests/event/user_events_tests_mt.cpp

@@ -107,3 +107,41 @@ TEST_F(EventTests, givenUserEventBlockingEnqueueWithBlockingFlagWhenUserEventIsC
     EXPECT_EQ(CL_SUCCESS, retVal);
     t.join();
 }
+
+TEST_F(EventTests, givenoneThreadUpdatingUserEventAnotherWaitingOnFinishWhenFinishIsCalledThenItWaitsForCorrectTaskCount) {
+
+    std::unique_ptr<Buffer> srcBuffer(BufferHelper<>::create());
+    std::unique_ptr<char[]> dst(new char[srcBuffer->getSize()]);
+    for (uint32_t i = 0; i < 100; i++) {
+
+        UserEvent uEvent;
+        cl_event eventWaitList[] = {&uEvent};
+        int sizeOfWaitList = sizeof(eventWaitList) / sizeof(cl_event);
+        cl_event returnedEvent = nullptr;
+
+        std::atomic_bool go{false};
+
+        std::thread t([&]() {
+            while (!go)
+                ;
+
+            uEvent.setStatus(CL_COMPLETE);
+        });
+
+        auto retVal = pCmdQ->enqueueReadBuffer(srcBuffer.get(), CL_FALSE, 0, srcBuffer->getSize(), dst.get(), nullptr, sizeOfWaitList, eventWaitList, &returnedEvent);
+        EXPECT_EQ(CL_SUCCESS, retVal);
+
+        std::thread t2([&]() {
+            castToObject<Event>(returnedEvent)->updateExecutionStatus();
+        });
+
+        go = true;
+
+        clFinish(pCmdQ);
+        EXPECT_EQ(pCmdQ->latestTaskCountWaited, i + 1);
+
+        t.join();
+        t2.join();
+        clReleaseEvent(returnedEvent);
+    }
+}