Merge "add base::WaitForPropertyCreation" (22a64b3a) · Commits · e / os / android_system_core

base/include/android-base/properties.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -66,6 +66,12 @@ bool WaitForProperty(const std::string& key,
		const std::string& expected_value,
		std::chrono::milliseconds relative_timeout);

		// Waits for the system property `key` to be created.
		// Times out after `relative_timeout`.
		// Returns true on success, false on timeout.
		bool WaitForPropertyCreation(const std::string& key,
		std::chrono::milliseconds relative_timeout);

		} // namespace base
		} // namespace android

base/properties.cpp

+29 −7

Original line number	Diff line number	Diff line
		@@ -108,8 +108,10 @@ static void DurationToTimeSpec(timespec& ts, std::chrono::nanoseconds d) {
		ts.tv_nsec = ns.count();
		}

		using AbsTime = std::chrono::time_point<std::chrono::steady_clock>;

		static void UpdateTimeSpec(timespec& ts,
		const std::chrono::time_point<std::chrono::steady_clock>& timeout) {
		const AbsTime& timeout) {
		auto now = std::chrono::steady_clock::now();
		auto remaining_timeout = std::chrono::duration_cast<std::chrono::nanoseconds>(timeout - now);
		if (remaining_timeout < 0ns) {
		@@ -119,13 +121,16 @@ static void UpdateTimeSpec(timespec& ts,
		}
		}

		bool WaitForProperty(const std::string& key,
		const std::string& expected_value,
		std::chrono::milliseconds relative_timeout) {
		// Waits for the system property `key` to be created.
		// Times out after `relative_timeout`.
		// Sets absolute_timeout which represents absolute time for the timeout.
		// Returns nullptr on timeout.
		static const prop_info* WaitForPropertyCreation(const std::string& key,
		const std::chrono::milliseconds& relative_timeout,
		AbsTime& absolute_timeout) {
		// TODO: boot_clock?
		auto now = std::chrono::steady_clock::now();
		std::chrono::time_point<std::chrono::steady_clock> absolute_timeout = now + relative_timeout;
		timespec ts;
		absolute_timeout = now + relative_timeout;

		// Find the property's prop_info*.
		const prop_info* pi;
		@@ -133,14 +138,25 @@ bool WaitForProperty(const std::string& key,
		while ((pi = __system_property_find(key.c_str())) == nullptr) {
		// The property doesn't even exist yet.
		// Wait for a global change and then look again.
		timespec ts;
		UpdateTimeSpec(ts, absolute_timeout);
		if (!__system_property_wait(nullptr, global_serial, &global_serial, &ts)) return false;
		if (!__system_property_wait(nullptr, global_serial, &global_serial, &ts)) return nullptr;
		}
		return pi;
		}

		bool WaitForProperty(const std::string& key,
		const std::string& expected_value,
		std::chrono::milliseconds relative_timeout) {
		AbsTime absolute_timeout;
		const prop_info* pi = WaitForPropertyCreation(key, relative_timeout, absolute_timeout);
		if (pi == nullptr) return false;

		WaitForPropertyData data;
		data.expected_value = &expected_value;
		data.done = false;
		while (true) {
		timespec ts;
		// Check whether the property has the value we're looking for?
		__system_property_read_callback(pi, WaitForPropertyCallback, &data);
		if (data.done) return true;
		@@ -152,5 +168,11 @@ bool WaitForProperty(const std::string& key,
		}
		}

		bool WaitForPropertyCreation(const std::string& key,
		std::chrono::milliseconds relative_timeout) {
		AbsTime absolute_timeout;
		return (WaitForPropertyCreation(key, relative_timeout, absolute_timeout) != nullptr);
		}

		} // namespace base
		} // namespace android

base/properties_test.cpp

+22 −0

Original line number	Diff line number	Diff line
		@@ -150,3 +150,25 @@ TEST(properties, WaitForProperty_timeout) {
		// Upper bounds on timing are inherently flaky, but let's try...
		ASSERT_LT(std::chrono::duration_cast<std::chrono::milliseconds>(t1 - t0), 600ms);
		}

		TEST(properties, WaitForPropertyCreation) {
		std::thread thread([&]() {
		std::this_thread::sleep_for(100ms);
		android::base::SetProperty("debug.libbase.WaitForPropertyCreation_test", "a");
		});

		ASSERT_TRUE(android::base::WaitForPropertyCreation(
		"debug.libbase.WaitForPropertyCreation_test", 1s));
		thread.join();
		}

		TEST(properties, WaitForPropertyCreation_timeout) {
		auto t0 = std::chrono::steady_clock::now();
		ASSERT_FALSE(android::base::WaitForPropertyCreation(
		"debug.libbase.WaitForPropertyCreation_timeout_test", 200ms));
		auto t1 = std::chrono::steady_clock::now();

		ASSERT_GE(std::chrono::duration_cast<std::chrono::milliseconds>(t1 - t0), 200ms);
		// Upper bounds on timing are inherently flaky, but let's try...
		ASSERT_LT(std::chrono::duration_cast<std::chrono::milliseconds>(t1 - t0), 600ms);
		}