LibGpiodDriver handle TaskCanceledException in Dispose (#1825)

src/System.Device.Gpio.Tests/LibGpiodDriverTests.cs

@@ -54,5 +54,22 @@ namespace System.Device.Gpio.Tests
                 controller.ClosePin(InputPin);
             }
         }
+
+        [Fact]
+        public void UnregisterPinValueChangedShallNotThrow()
+        {
+            using var gc = new GpioController(GetTestNumberingScheme(), GetTestDriver());
+            gc.OpenPin(InputPin, PinMode.Input);
+
+            static void PinChanged(object sender, PinValueChangedEventArgs args)
+            {
+            }
+
+            for (var i = 0; i < 1000; i++)
+            {
+                gc.RegisterCallbackForPinValueChangedEvent(InputPin, PinEventTypes.Rising | PinEventTypes.Falling, PinChanged);
+                gc.UnregisterCallbackForPinValueChangedEvent(InputPin, PinChanged);
+            }
+        }
     }
 }

src/System.Device.Gpio/System/Device/Gpio/Drivers/LibGpiodDriver.cs

@@ -339,7 +339,7 @@ namespace System.Device.Gpio.Drivers
                     typeOfEventOccured = e.ChangeType;
                 }
 
-                WaitForEventResult(cancellationToken, eventHandler.CancellationTokenSource.Token, ref eventOccurred);
+                WaitForEventResult(cancellationToken, eventHandler.CancellationToken, ref eventOccurred);
                 RemoveCallbackForPinValueChangedEvent(pinNumber, Callback);
 
                 return new WaitForEventResult

src/System.Device.Gpio/System/Device/Gpio/LibgpiodDriverEventHandler.cs

@@ -12,24 +12,26 @@ namespace System.Device.Gpio.Drivers
     {
         private const int ERROR_CODE_EINTR = 4; // Interrupted system call
 
-        private static string s_consumerName = Process.GetCurrentProcess().ProcessName;
+        private static readonly string s_consumerName = Process.GetCurrentProcess().ProcessName;
 
         public event PinChangeEventHandler? ValueRising;
         public event PinChangeEventHandler? ValueFalling;
 
-        private int _pinNumber;
-        public CancellationTokenSource CancellationTokenSource;
-        private Task _task;
-        private bool _disposing = false;
+        private readonly int _pinNumber;
+        private readonly CancellationTokenSource _cancellationTokenSource;
+        private readonly Task _task;
+        private bool _disposing;
 
         public LibGpiodDriverEventHandler(int pinNumber, SafeLineHandle safeLineHandle)
         {
             _pinNumber = pinNumber;
-            CancellationTokenSource = new CancellationTokenSource();
+            _cancellationTokenSource = new CancellationTokenSource();
             SubscribeForEvent(safeLineHandle);
-            _task = InitializeEventDetectionTask(CancellationTokenSource.Token, safeLineHandle);
+            _task = InitializeEventDetectionTask(_cancellationTokenSource.Token, safeLineHandle);
         }
 
+        public CancellationToken CancellationToken => _cancellationTokenSource.Token;
+
         private void SubscribeForEvent(SafeLineHandle pinHandle)
         {
             int eventSuccess = Interop.libgpiod.gpiod_line_request_both_edges_events(pinHandle, s_consumerName);
@@ -103,8 +105,17 @@ namespace System.Device.Gpio.Drivers
         public void Dispose()
         {
             _disposing = true;
-            CancellationTokenSource.Cancel();
-            _task?.Wait();
+            _cancellationTokenSource.Cancel();
+
+            try
+            {
+                _task.GetAwaiter().GetResult();
+            }
+            catch (TaskCanceledException)
+            {
+                // ignore cancellation exception
+            }
+
             ValueRising = null;
             ValueFalling = null;
         }