test(userspace/falco): add tests for atomic signal handler

Signed-off-by: Jason Dellaluce <jasondellaluce@gmail.com>

unit_tests/falco/test_atomic_signal_handler.cpp

@@ -0,0 +1,131 @@
+/*
+Copyright (C) 2023 The Falco Authors.
+
+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 ASSERTd 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 <gtest/gtest.h>
+#include <future>
+#include <thread>
+#include <vector>
+#include <memory>
+#include <chrono>
+ 
+#include <falco/atomic_signal_handler.h>
+#include <falco/logger.h>
+
+TEST(AtomicSignalHandler, lock_free_implementation)
+{
+	ASSERT_TRUE(falco::atomic_signal_handler().is_lock_free());
+}
+
+TEST(AtomicSignalHandler, handle_once_wait_consistency)
+{
+	constexpr const auto thread_num = 10;
+	constexpr const auto thread_wait_sec = 2;
+	constexpr const auto handler_wait_sec = 1;
+
+	// have a shared signal hander
+	falco::atomic_signal_handler handler;
+
+	// launch a bunch of threads all synching on the same handler
+	typedef struct
+	{
+		bool handled;
+		uint64_t duration_secs;
+	} task_result_t;
+	std::vector<std::future<task_result_t>> futures;
+	std::vector<std::unique_ptr<std::thread>> threads;
+	for (int i = 0; i < thread_num; i++)
+	{
+		std::packaged_task<task_result_t()> task([&handler, &thread_wait_sec]{
+			auto start = std::chrono::high_resolution_clock::now();
+			task_result_t res;
+			res.handled = false;
+			while (!handler.handled())
+			{
+				if (handler.triggered())
+				{
+					res.handled = handler.handle([&thread_wait_sec]{
+						std::this_thread::sleep_for (std::chrono::seconds(thread_wait_sec));
+					});
+				}
+			}
+			auto diff = std::chrono::high_resolution_clock::now() - start;
+			res.duration_secs = std::chrono::duration_cast<std::chrono::seconds>(diff).count();
+			return res;
+		});
+		futures.push_back(task.get_future());
+		threads.emplace_back();
+		threads[i].reset(new std::thread(std::move(task)));
+	}
+
+	// wait a bit, then trigger the signal handler from the main thread
+	auto total_handled = 0;
+	auto start = std::chrono::high_resolution_clock::now();
+	std::this_thread::sleep_for (std::chrono::seconds(handler_wait_sec));
+	handler.trigger();
+	for (int i = 0; i < thread_num; i++)
+	{
+		// we need to check that all threads didn't quit before
+		// the handle() function finished executing
+		futures[i].wait();
+		threads[i]->join();
+		auto res = futures[i].get();
+		if (res.handled)
+		{
+			total_handled++;
+		}
+		ASSERT_GE(res.duration_secs, thread_wait_sec);
+	}
+
+	// check that the total time is consistent with the expectations
+	auto diff = std::chrono::high_resolution_clock::now() - start;
+	auto secs = std::chrono::duration_cast<std::chrono::seconds>(diff).count();
+	ASSERT_GE(secs, thread_wait_sec + handler_wait_sec);
+
+	// check that only one thread handled the signal
+	ASSERT_EQ(total_handled, 1);
+}
+
+TEST(AtomicSignalHandler, handle_and_reset)
+{
+	auto do_nothing = []{};
+	falco::atomic_signal_handler handler;
+
+	ASSERT_FALSE(handler.triggered());
+	ASSERT_FALSE(handler.handled());
+	ASSERT_FALSE(handler.handle(do_nothing));
+
+	handler.trigger();
+	ASSERT_TRUE(handler.triggered());
+	ASSERT_FALSE(handler.handled());
+
+	ASSERT_TRUE(handler.handle(do_nothing));
+	ASSERT_TRUE(handler.triggered());
+	ASSERT_TRUE(handler.handled());
+	ASSERT_FALSE(handler.handle(do_nothing));
+
+	handler.trigger();
+	ASSERT_TRUE(handler.triggered());
+	ASSERT_FALSE(handler.handled());
+	ASSERT_TRUE(handler.handle(do_nothing));
+	ASSERT_TRUE(handler.triggered());
+	ASSERT_TRUE(handler.handled());
+	ASSERT_FALSE(handler.handle(do_nothing));
+
+	handler.reset();
+	ASSERT_FALSE(handler.triggered());
+	ASSERT_FALSE(handler.handled());
+	ASSERT_FALSE(handler.handle(do_nothing));
+}