discovery fix

Inspectron.Epson/Queue/PrintServer.cs

@@ -6,7 +6,9 @@ public class PrintServer
     private readonly IPrintService _printService;
     private readonly ILogger _logger;
     private readonly ConcurrentDictionary<string, PrinterQueue> _printerQueues;
-    private readonly ReaderWriterLockSlim _printDiscoveryLock = new();
+    private readonly SemaphoreSlim _printDiscoveryLock = new(1, 1);
+    private int _readerCount = 0;
+    private readonly object _readerCountLock = new();
 
     public PrintServer(IPrintService printService, ILogger logger)
     {
@@ -19,23 +21,58 @@ public class PrintServer
     /// <summary>
     /// Acquires a read lock for print operations. Multiple print operations can run concurrently.
     /// </summary>
-    public void EnterPrintLock() => _printDiscoveryLock.EnterReadLock();
+    public void EnterPrintLock()
+    {
+        _logger.LogDebug("Entering print lock");
+        lock (_readerCountLock)
+        {
+            _readerCount++;
+            if (_readerCount == 1)
+            {
+                _printDiscoveryLock.Wait();
+            }
+        }
+        _logger.LogDebug("Entered print lock");
+
+    }
 
     /// <summary>
     /// Releases the read lock after a print operation completes.
     /// </summary>
-    public void ExitPrintLock() => _printDiscoveryLock.ExitReadLock();
+    public void ExitPrintLock()
+    {
+        _logger.LogDebug("Exiting print lock");
+        lock (_readerCountLock)
+        {
+            _readerCount--;
+            if (_readerCount == 0)
+            {
+                _printDiscoveryLock.Release();
+            }
+        }
+        _logger.LogDebug("Exited print lock");
+    }
 
     /// <summary>
     /// Acquires a write lock for discovery operations. This blocks until all print operations complete
     /// and prevents new print operations from starting.
     /// </summary>
-    public void EnterDiscoveryLock() => _printDiscoveryLock.EnterWriteLock();
+    public async Task EnterDiscoveryLockAsync()
+    {
+        _logger.LogDebug("Entering discovery lock");
+        await _printDiscoveryLock.WaitAsync();
+        _logger.LogDebug("Entered discovery lock");
+    }
 
     /// <summary>
     /// Releases the write lock after discovery completes.
     /// </summary>
-    public void ExitDiscoveryLock() => _printDiscoveryLock.ExitWriteLock();
+    public void ExitDiscoveryLock()
+    {
+        _logger.LogDebug("Exiting discovery lock");
+        _printDiscoveryLock.Release();
+        _logger.LogDebug("Exited discovery lock");
+    }
 
     public void RegisterPrinter(string printerIp)
     {