Retire runners that are cancelled before they start

MediaBrowser.Controller/LibraryTaskScheduler/LimitedConcurrencyLibraryScheduler.cs

@@ -191,12 +191,14 @@ public sealed class LimitedConcurrencyLibraryScheduler : ILimitedConcurrencyLibr
 
                 // Keyed on its own stop source, because cancelling that is what reaches the linked
                 // source the runner waits on. Cancellation does not travel the other way.
+                // Started without the runner's own token: a task cancelled before it is scheduled
+                // never runs its body, so it would never take itself out of _taskRunners again.
                 _taskRunners.Add(
                     stopToken,
                     Task.Factory.StartNew(
                         ItemWorker,
                         (stopToken, combinedSource),
-                        combinedSource.Token,
+                        CancellationToken.None,
                         TaskCreationOptions.PreferFairness,
                         TaskScheduler.Default));
             }

tests/Jellyfin.Controller.Tests/LibraryTaskScheduler/LimitedConcurrencyLibrarySchedulerTests.cs

@@ -65,7 +65,7 @@ namespace Jellyfin.Controller.Tests.LibraryTaskScheduler
         /// so a shutdown has to reach them. It does not travel from the linked source back to the one
         /// the cleanup cancels, which is what made them immortal.
         /// </summary>
-        /// <returns><placeholder>A <see cref="Task"/> representing the asynchronous unit test.</placeholder></returns>
+        /// <returns>A <see cref="Task"/> representing the asynchronous unit test.</returns>
         [Fact]
         public async Task ApplicationStopping_RetiresRunners()
         {
@@ -88,7 +88,7 @@ namespace Jellyfin.Controller.Tests.LibraryTaskScheduler
         /// The cleanup used to be a one shot: it never released the scheduling slot it took, so
         /// every runner spawned after the first pass stayed around for the lifetime of the server.
         /// </summary>
-        /// <returns><placeholder>A <see cref="Task"/> representing the asynchronous unit test.</placeholder></returns>
+        /// <returns>A <see cref="Task"/> representing the asynchronous unit test.</returns>
         [Fact]
         public async Task Enqueue_RetiresIdleRunnersAfterEveryOperation()
         {
@@ -110,7 +110,7 @@ namespace Jellyfin.Controller.Tests.LibraryTaskScheduler
         /// Disposing used to sit out the rest of the cleanup grace period, holding up shutdown for
         /// up to a minute.
         /// </summary>
-        /// <returns><placeholder>A <see cref="Task"/> representing the asynchronous unit test.</placeholder></returns>
+        /// <returns>A <see cref="Task"/> representing the asynchronous unit test.</returns>
         [Fact]
         public async Task DisposeAsync_DoesNotWaitOutTheGracePeriod()
         {