[Misc] Prevent SemaphoreSlim overflow

Release is unsafe when also using Cancellation, so add a check to whether or not we actually hold the lock. A simplified check might be checking for the CurrentCount on the semaphore, but the intent is clearer this way.

Bug 45085 - Semaphore overflow in XS on Windows

1 files changed, 8 insertions, 5 deletions

diff --git a/main/src/core/MonoDevelop.Ide/MonoDevelop.Components.MainToolbar/FileSearchCategory.cs b/main/src/core/MonoDevelop.Ide/MonoDevelop.Components.MainToolbar/FileSearchCategory.cs
index eae4e86ec8..9d6b8b959a 100644
--- a/main/src/core/MonoDevelop.Ide/MonoDevelop.Components.MainToolbar/FileSearchCategory.cs
+++ b/main/src/core/MonoDevelop.Ide/MonoDevelop.Components.MainToolbar/FileSearchCategory.cs
@@ -104,17 +104,20 @@ namespace MonoDevelop.Components.MainToolbar
 		public override Task GetResults (ISearchResultCallback searchResultCallback, SearchPopupSearchPattern pattern, CancellationToken token)
 		{
 			return Task.Run (async delegate {
-				List<Tuple<string, string, ProjectFile>> files;

-				//This lock is here in case user quickly types 5 letters which triggers 5 threads

-				//we don't want to use all CPU doing same thing, instead 1st one will create cache, others will wait here

-				//and then all will use cached version...

+				List<Tuple<string, string, ProjectFile>> files;
+				//This lock is here in case user quickly types 5 letters which triggers 5 threads
+				//we don't want to use all CPU doing same thing, instead 1st one will create cache, others will wait here
+				//and then all will use cached version...
+				bool locked = false;
 				try {
 					await allFilesLock.WaitAsync (token);
+					locked = true;
 					files = allFilesCache = allFilesCache ?? GenerateAllFiles ();
 					if (token.IsCancellationRequested)
 						return;
 				} finally {
-					allFilesLock.Release ();
+					if (locked)
+						allFilesLock.Release ();
 				}
 
 				var matcher = StringMatcher.GetMatcher (pattern.Pattern, false);