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fix(driver-twincat): resolve Medium code-review finding (Driver.TwinCAT-009)

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Swap _devices and _tagsByName to ConcurrentDictionary so ShutdownAsync
Clear() no longer races concurrent TryGetValue calls; store ProbeTask
on DeviceState and await it in ShutdownAsync before disposing the client
and gate, eliminating the probe-disposal race.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Joseph Doherty
2026-05-22 10:43:35 -04:00
parent 40aa27b64b
commit 98d8df4adf
2 changed files with 23 additions and 4 deletions
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25
src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT/TwinCATDriver.cs
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@@ -20,8 +20,13 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
private readonly ITwinCATClientFactory _clientFactory;
private readonly ILogger<TwinCATDriver> _logger;
private readonly PollGroupEngine _poll;
private readonly Dictionary<string, DeviceState> _devices = new(StringComparer.OrdinalIgnoreCase);
private readonly Dictionary<string, TwinCATTagDefinition> _tagsByName = new(StringComparer.OrdinalIgnoreCase);
// ConcurrentDictionary so ShutdownAsync (Clear) and ReadAsync/WriteAsync/SubscribeAsync
// (TryGetValue) don't race — plain Dictionary is not safe for concurrent read+write
// (Driver.TwinCAT-009).
private readonly ConcurrentDictionary<string, DeviceState> _devices =
new(StringComparer.OrdinalIgnoreCase);
private readonly ConcurrentDictionary<string, TwinCATTagDefinition> _tagsByName =
new(StringComparer.OrdinalIgnoreCase);
private DriverHealth _health = new(DriverState.Unknown, null, null);
public event EventHandler<DataChangeEventArgs>? OnDataChange;
@@ -76,7 +81,8 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
{
state.ProbeCts = new CancellationTokenSource();
var ct = state.ProbeCts.Token;
_ = Task.Run(() => ProbeLoopAsync(state, ct), ct);
// Store the task so ShutdownAsync can await it (Driver.TwinCAT-009).
state.ProbeTask = Task.Run(() => ProbeLoopAsync(state, ct), ct);
}
}
_health = new DriverHealth(DriverState.Healthy, DateTime.UtcNow, null);
@@ -104,9 +110,19 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
_nativeSubs.Clear();
await _poll.DisposeAsync().ConfigureAwait(false);
// Cancel every probe loop and await its task before disposing the client + gate so the
// loop can never touch a disposed object. (Driver.TwinCAT-009: ShutdownAsync previously
// cancelled ProbeCts but did not await the task before calling DisposeClient.)
foreach (var state in _devices.Values)
{
try { state.ProbeCts?.Cancel(); } catch { }
if (state.ProbeTask is Task pt)
{
try { await pt.ConfigureAwait(false); }
catch (OperationCanceledException) { /* expected — probe loop exits on cancel */ }
catch { /* other probe errors are not fatal to shutdown */ }
}
state.ProbeCts?.Dispose();
state.ProbeCts = null;
state.DisposeClient();
@@ -526,6 +542,9 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
public HostState HostState { get; set; } = HostState.Unknown;
public DateTime HostStateChangedUtc { get; set; } = DateTime.UtcNow;
public CancellationTokenSource? ProbeCts { get; set; }
/// <summary>The running probe-loop task — awaited by <see cref="TwinCATDriver.ShutdownAsync"/>
/// so the loop cannot touch a disposed client (Driver.TwinCAT-009).</summary>
public Task? ProbeTask { get; set; }
public void DisposeClient()
{