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`SimHooks.stepTiming()` hangs when called from a callback registered with `SimDeviceSim.registerValueChangedCallback()` if another `SimDeviceSim` has been created
Describe the bug
SimHooks.stepTiming()
hangs when called from a callback registered with SimDeviceSim.registerValueChangedCallback()
if another SimDeviceSim
has been created.
To Reproduce
Run the following test (which uses an ADXRS450_GyroSim
as an example of a SimDeviceSim
):
package frc.robot;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeoutException;
import edu.wpi.first.hal.HAL;
import edu.wpi.first.hal.SimDevice;
import edu.wpi.first.hal.SimDevice.Direction;
import edu.wpi.first.wpilibj.ADXRS450_Gyro;
import edu.wpi.first.wpilibj.TimedRobot;
import edu.wpi.first.wpilibj.Timer;
import edu.wpi.first.wpilibj.simulation.ADXRS450_GyroSim;
import edu.wpi.first.wpilibj.simulation.SimDeviceSim;
import edu.wpi.first.wpilibj.simulation.SimHooks;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.Timeout;
import static org.junit.jupiter.api.Timeout.ThreadMode.SEPARATE_THREAD;
public class RobotTest {
@BeforeEach
void setup() {
assert HAL.initialize(500, 0);
}
@AfterEach
void shutdown() throws Exception {
HAL.shutdown();
}
@Test
@Timeout(value = 15, threadMode = SEPARATE_THREAD) // Kill the test after 15 seconds
void doesNotHang() throws InterruptedException, TimeoutException, ExecutionException {
// Create a simulated device that can be used to step the robot's timing.
SimDevice device = SimDevice.create("TimeDevice");
device.createDouble("simTime", Direction.kInput, 0.0);
SimDeviceSim deviceSim = new SimDeviceSim("TimeDevice");
deviceSim.registerValueChangedCallback(deviceSim.getDouble("simTime"),
(name, handle, direction, value) -> {
double secsBehind = value.getDouble() - Timer.getFPGATimestamp();
if (secsBehind > 0) {
System.out.println("Calling stepTiming() should not hang");
SimHooks.stepTiming(secsBehind);
System.out.println("stepTiming() returned"); // Never printed
}
}, false);
try (TimedRobot robot = new TimedRobot() {
@SuppressWarnings("resource")
ADXRS450_Gyro gyro = new ADXRS450_Gyro();
@Override
public void robotInit() {
}
@Override
public void robotPeriodic() {
if (Timer.getFPGATimestamp() > 5.0) {
endCompetition();
}
}
ADXRS450_GyroSim gyroSim = null;
@Override
public void simulationInit() {
// Adding the following line causes SimHook.stepTiming() to block in the simTime
// callback.
gyroSim = new ADXRS450_GyroSim(gyro);
}
@Override
public void simulationPeriodic() {
if (gyroSim != null) {
// This isn't necessary to produce the problem, but it should also work.
// Using the current timestamp here just to ensure we always get a new number.
gyroSim.setAngle(Timer.getFPGATimestamp());
}
}
@Override
public void close() {
gyro.close();
super.close();
}
}) {
// Start the robot on separate thread
CompletableFuture<Void> competition = CompletableFuture.runAsync(() -> {
robot.startCompetition();
});
// Wait a couple secs to be sure it is running and then pause it
Thread.sleep(2000);
SimHooks.pauseTiming();
// Emulate an external simulator telling it to step the robot time
// forward to 10 seconds. This doesn't need to be async to produce
// the problem, but more accurately represents our use case.
CompletableFuture.runAsync(() -> {
deviceSim.getDouble("simTime").set(10.0);
}).join();
// Wait for the robot to finish (which should occur as soon as the robot time is
// > 5.0 seconds).
competition.join();
}
}
}
Expected behavior
The test should pass (after only 2-3 seconds). Instead, it hangs in the call to SimHooks.stepTiming()
(until the test times out after 15 secs).
Desktop (please complete the following information):
- OS: Linux, Fedora Linux 38 (Workstation Edition)
- Project Information:
Project Version: 2024.3.1
VS Code Version: 1.85.1
WPILib Extension Version: 2024.3.1
C++ Extension Version: 1.19.1
Java Extension Version: 1.30.0
Java Debug Extension Version: 0.57.2024041008
Java Dependencies Extension Version 0.23.6
Java Version: 17
Java Location: /home/brettle/wpilib/2024/jdk
Vendor Libraries:
WPILib-New-Commands (1.0.0)
Additional Context
The test above uses a ADXRS450_GyroSim
but the problem also occurs with a new SimDeviceSim
associated with a new SimDevice
.